Bio 530 Module 2 Lectures

elastic cartilage

Elastic cartilage provides flexibility of our ears and the larynx.

hyaline cartilage

From mesoderm Avascular Surrounded by a perichrondrium Proteoglycan aggregates dominant in the matrix Type II Collagen Articular cartilage, respiratory tract

eosinophil

Life Span 8 - 12 days Bi-lobed Nucleus Specific Granules (strongly acidopilic) Crystalline core contains major basic protein (MBP) & eosinophil cationic protein (ECP) External part of granule contains phosphotase, lipase, peroxidase, RNAase Functions are: anti-parasites via MBP and ECP by binding and disrupting parasite membrane role in allergies via MBP destroys antigen- antibody complexes MBP - basophil/mast cell release of histamine Eosinophils can be easily recognized because they have a nucleus that only has two lobes and specific granules that are brightly pink. Eosinophils accumulate in sites where antigen-antibody complexes have accumulated. In airway reactions involving asthma, the connective tissue of the trachea and bronchi will contain a large accumulation of eosinophils. If a patient has a parasitic infestation of the intestine, eosinophils will accumulate in the tissue below where a tape worm may be attached to the lining of the intestine.

two types of cartilage cells

Chondrocytes Chondroblasts

two parts of perichondrium

Chondrogenic Fibrous

CNS glial cells: oligodendogliocytes

Small cells Few processes Aligned in rows between axons Form myelin around several axons Myelin is formed in segments, one segment per oligodendrocyte Oligodendroglial cells are small with few processes. The processes are connected to several axons around which these cells formed concentric layers of cell membrane to make myelin, the lipid rich covering of axons. Oligodendrocytes are only found in the CNS. They are the counter-cells of Schwann cells that make myelin in the peripheral nervous system. The difference is mainly that one oligodendrocyte myelinates several axons whereas Schwann cells only myelinate one axon. Note the Node of Ranvier. The myelin of axons is in segments approximately 1 mm long. Between the segments the axon is not covered with myelin. This is the node of Ranvier.

summary

Bone tissue presentation began with illustrations of the distribution of long bones and short bones in the body. Next the cells in bone tissue, the osteoblast, the osteocyte and the osteoclast were presented. The architecture of compact (dense) and cancellous (spongy)bone was illustrated. The functional role of osteons in a long bone was illustrated and explained.

what percentage of immature neutrophils at the band stage are found in normal peripheral blood

3%

the range of leukocyte count in total blood cell count is

3.5 to 10.5 billion/liter

what fraction of hyaline cartilage is occupied by water

60-80%

chondroblasts

A chondroblast is a cell which originates from a mesenchymal stem cell. Chondroblasts that become embedded in the matrix are called chondrocytes. They lie in the space or lacunae present in the groups of two or more. The groups are formed by division of a single parent cell. Groups of chondrocytes are called cell nests or isogenous cell groups. They have euchromatic nuclei and stain by basic dyes.

pericellular matrix

A deeply basophilic zone of cartilage matrix only 1-3 micrometers wide that surrounds chondrocytes.

distribution of smooth muscle

DIGESTIVE TRACT DUCTS OF GLANDS RESPIRATORY PASSAGES URINARY & GENETAL TRACT ARTERIES AND VEINS PILIERECTOR MUSCLES IRIS & CILIARY BODY UTERUS BLADDER STOMACH Smooth muscle plays a very important role in many locations in many organs. Smooth muscle cells are innervated by nerves of the autonomic nervous system so that the nerve fibers leading to smooth muscle cells are unmyelinated, small nerve fibers that conduct nerve impulses slowly.

megakaryocyte thrombopoeisis bone marrow megakaryocyte

Megakaryocytes are the source of platelets (thrombocytes). Megakaryocytes are the largest cells in the bone marrow. Here you see one of them within the circle. When we see the megakaryocyte at higher magnification, it can be seen that it has a very large nucleus. The cell is polyploidal, meaning that the nucleus has at least 64 times the normal amount of DNA. Normally our cells contain 2n chromosomes (23 pairs = 46 chromosomes). Megakaryocytes have 64n chromosomes (46 x 64 = 2944 chromosomes). The nucleus contains multiple nucleoli. All this is necessary to maintain the large amount of cytoplasm and direct the process of forming platelets. Platelets are created first by segmentation of the megakaryocyte cytoplasm, and then fragments break off, becoming individual platelets as we shall see in the next slide.

blood components

Protein-rich matrix Water - 91-92% Protein - 7-8% Albumins, globulins & fibrinogen Other solutes Electrolytes - Na+, K+, Ca+, Mg+, Cl+, HCO3-, PO43-, SO42- Urea, uric acid, creatine,

select the identity of this cell from the image

monocyte

PNS

motor and sensory nerves

composition of nervous tissue

neurons (parenchyma)- cell body with nucleus processes often long polarized transmit impulses glial cells (stroma)- cell body with nucleus processes (short) not polarized do not transmit impulsesun

immature bone

osteocyte

which of the following is the name of unmineralized bone matrix

osteoid

which type of collagen does a chondroblast forming hyaline cartilage matrix secrete

type 2

autonomic ganglia

Location Beside spinal cord & within organs Function Cell bodies of autonomic neurons providing maintenance of nerve fibers

sensory ganglia

Location Posterior root ganglion Function Cell bodies of sensory neurons providing maintenance nerve fibers

what is the estimated number of blood formed elements that are released from the bone marrow and destroyed by the spleen each day in the average adult

100,000,000,000

which of the following is the life span of an erythocyte

120 days

how many types of cartilage are there

3

eosinophils

Always a two lobed nucleus and large eosinophilic granules Unlike neutrophils, mature eosinophils always have a nucleus that has only two lobes (segments). Note that the cells appear like bags of pink marbles. That is the look of an eosinophil.

axon diameter and myelin thickness

Tissue In this cross-section of a collection of nerve fibers, a wide range of axon diameter and myelin sheath thickness can be seen. Round clear non-stained areas are seen surrounded by a black rim. The clear round spaces are where the axons are located and the black rims are the myelin sheath of each nerve fiber. The lipid in the myelin stains black as a result of reacting with the stain which, in this case, was osmium tetroxide. All somatic peripheral nerves have such a diameter range.

identify this cell

basophilic erythroblast

CNS

brain and spinal cord

multipotent

cell can differentiate into multiple but a limited number of cell types. For example, the hemocytoblast of bone marrow that can develop into several types of blood cells, but cannot develop into brain cells or other types of cells.

a sarcomere begins and ends with an I band

false

which of the following is not present in serum

fibrinogen

which of the following is the potency of a hemocytoblast

multipotent

identify this cell

neutrophilic myelocyte

which of the following nerve tissues forms myelin in the central nervous system

oligodendroglial cell

intramembranous bone formation

osteoblasts arise in connective tissue from mesenchyme cells osteoblasts secrete bone matrix forming bone spicules osteoblasts continue to secrete matrix and many become entrapped resulting in woven lamellae that form spicules of bone flat bones of the skull and the mandible are examples of bones forming by this method So now, we see the flow of development from mesenchymal cells giving rise to osteoblasts beginning to secrete bone matrix that eventually results in the formation of bone spicules as shown in the lower left histological specimen stained with hematoxylin and eosin. Temporal, occipital, parietal, frontal bones of the skull and the mandibular (jaw) bones are some of the bones that form by this method.

which of the following blood components transport glucose

plasma

which of the following blood components transports albumin

plasma

choose the correct identification of the tissue specimen

smooth muscle tissue

hyaline cartilage is found in which of the following

the nose

a blastema forms as one of the stages of intramembranous bone formation

true

branching cells and intercalated discs are unique features of cardiac muscle cells

true

sarcomeres are present in skeletal and cardiac muscle cells, but not in smooth muscle cells

true

the schwann cell makes the myelin that surrounds a peripheral myelinated neuron

true

the zone of hypertrophying cartilage cells is one component of the epiphyseal plate

true

one drop of blood is equal to how many cubic millimeters

1

A group of nerve fascicles is shown wrapped in epineurium

A part of one fascicle is shown stained with trichrome to emphasize collagen. This illustrates the collagen of endoneurium surrounding each nerve fiber.

terminally differentiate cell

A terminally differentiate cell has no potency. It cannot differentiate into another cell type ..as in skin cells, liver cells, skeletal muscle cells etc.

autonomic ganglion cells

Autonomic ganglia are similar to sensory ganglia except for the fact that the neurons are multipolar. They differ in their location in the body and the fact that the neuron cell body nuclei are located, not in the center of the cell body, but displaced in an eccentric position.

basophil

Life Span - few hours to 2 days Bilobed Nucleus - large granules obscure nucleus Specific Granules (basophilic) Eosinophilic chemotactic factor Heparin, Histamine and Peroxidase Functions are Back up mast cells' by secreting histamine & heparin In inflammation secrete leukotrienes causing slow contraction of smooth muscle Migrate to connective tissue via adhesion molecules The basophil is a very rare cell, present in the circulating blood at less than one if you counted 100 white blood cells. Of the leukocytes, these cells have the least presence and how much they function is questionable. Their function and structure overlaps that of mast cells. Recall that mast cells reside in the connective tissue frameworks of organs and subcutaneous tissue adhering close to the outside of small blood vessels. The function of these minority white blood cells is suggested to join the mast cells in secreting histamine and heparin and to affect smooth muscle in blood vessels to cause them to dilate admitting more blood into tissues in the case of inflammation.

A totipotent

cell can divide and produce all the differentiated cells in an organism, including extraembryonic tissues.

oligopotent

cellcandifferentiateintoafewcelltypes.Forexample,vascular stem cells can become both endothelial and smooth muscle cells.

unipotent

cellcandifferentiateintoonlycelltype.Forexamplestemcellsinthe skin and liver can only develop into either skin or liver cells, respectively.

anisocytosis denotes erythrocytes with abnormal shape

false

blood

platelet leuokocyte erythrocyte oxygenated blood deoxygenated blood

what is the function of canaliculi

small channels containing osteocyte processes and tissue fluid

which of the following is true regarding platelets

they are without a nucleus they contain microtubules they are fragments of megakaryocytes

spinal cord

white matter surrounds gray matter

epiphyseal plate zones

zone of reserve cartilage zone of proliferation zone of hypertrophy zone of calcified cartilage zone of resorption and bone deposition

epiphyseal plate zones

zone of reserve cartilage zone of proliferation zone of hypertrophy zone of calcified cartilage zone of resorption and bone deposition The histology of the epiphyseal plate reveals zones of different morphology reflecting different function. The zone of reserve cartilage supplies the stem cells that feed into the zone of proliferation. The zone of proliferation is like the chondrogenic perichondrium. These cells are continuously dividing but only in one plane that is parallel to the longitudinal axis of the forming bone. This is the activity that increases the length of a bone. As more and more chondrocytes are created, they are pushed into the next zone where the chondrocytes no longer divide but they enlarge (become hypertrophied). The next zone is where the matrix of the cartilage calcifies. Shortly after the cartilage matrix calcifies, chondroclasts (similar to osteoclasts) remove part of the calcified matrix. Remnants of the calcified cartilage matrix forms a template for osteoblasts to migrate to and begin to secrete bone matrix. This results in the formation of spicules and trabeculae of bone in the diaphysis so that the lengthening provided by the proliferating chondroblasts in the zone of proliferation is now made permanent.

three parts of cartilage matrix

Capsule (pericellular) Territorial Interterritorial

Three types of cartilage

Hyaline Fibrous Elastic

cartilage

Cartilage is a specialized connective tissue. It is composed of cells, fibers and ground substance. There are three types of cartilage - hyaline, fibrous and elastic.

compact bone

Cortical bone, synonymous with compact bone, is one of the two types of osseous tissue that form bones. Cortical bone facilitates bone's main functions: to support the whole body, protect organs, provide levers for movement, and store and release chemical elements, mainly calcium. As its name implies, cortical bone forms the cortex, or outer shell, of most bones. Again, as its name implies, compact bone is much denser than cancellous bone, which is the other type of osseous tissue. Furthermore, it is harder, stronger and stiffer than cancellous bone. Cortical bone contributes about 80% of the weight of a human skeleton. The primary anatomical and functional unit of cortical bone is the osteon.

surface structure rbc platelet and white blood cell

This scanning electron micrograph shows clearly the difference in size and surface texture of an erythrocyte, a platelet and a leukocyte. The RBC is designed to be flexible with a large surface area because of its biconcave disc shape. The platelet is much smaller and clearly can send out processes from its surface. The leukocyte is rounded with many small projections. Leukocytes, when they escape from the blood stream into the tissues to perform their function, can become very mobile. They can undergo dramatic changes in shape to send foot processes (pseudopods) to grab onto collagen fibers in the tissues and literally pull themselves around to migrate to where they are needed to engage and neutralize bacteria, viruses or other foreign bodies

which is not a feature of a neutrophil

has acidophilic granules

hematopoiesis

is the process of formation of the formed elements - erythrocytes, leukocytes and platelets of blood. In the adult it takes place in the bone marrow. Hematopoiesis has several components: 1) erythropoiesis- the formation and maturation of erythrocytes 2) leukopoiesis - the formation and maturation of leukocytes 3) Thrombocytopoiesis - the formation of platelets

skeletal striated muscle cells

long multinucleated cells and nuclei located just inside cell membrane

in general cartilage tissue is derived from the cells of which germ layer in the trilaminar disc of the embryo

mesoderm

which of the following degrades resorbs bone matrix

osteoclast

which of the following is a multinucleated cell

osteoclast

what is the mature bone cell called

osteocyte

which of the following is true about the size of formed elements of blood

platelet diameter is 2 to 4 micrometers

what is the expected range of the number of erythrocytes in one drop of blood

4-6 million

Canaliculi

Canaliculi are microscopic canals between the various lacunae of ossified bone. The radiating processes of the osteocytes project into these canals. These cytoplasmic processes are joined together by gap junctions. Osteocytes do not entirely fill up the canaliculi. The remaining space is known as the periosteocytic space, which is filled with periosteocytic fluid. This fluid contains substances too large to be transported through the gap junctions that connect the osteocytes, including calcium and phosphate ions.

monocytes

Here are six examples of monocytes. One key identifying feature is the presence of vacuoles in the cytoplasm. Also, in addition to the nucleus being large, it is usually indented, and stains lighter than the nuclei of the other leukocytes. Also, the nuclei in all six of these cells appears like the surface of the brain, the cerebrum. That is the dark areas look like gyri and the light areas look like sulci as in the cerebral cortex of the brain. This is a morphological feature that is unique to monocytes.

Lamellae

Successive layers of calcified bone matrix about 3-7 micrometers thick, formed by osteoblasts as the result of successive waves of appositional growth in bone. They are maintained by osteocytes.

Lacunae

The Lacunæ are situated between the lamellæ, and consist of a number of oblong spaces. In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots. Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle. Lacunae are connected to one another by small canals called canaliculi. A lacuna never contains more than one osteocyte.

mature bone

interstitial lamellae, osteocyte, resoption canal, osteoclasts, osteon, concentric lamella

ganglion

is a collection of cell bodies of neurons located outside of the central nervous system

Cancellous 'spongy' Bone

Cancellous bone, synonymous with trabecular bone or spongy bone, is one of two types of osseous tissue that form bones. Compared to compact bone, which is the other type of osseous tissue, it has a higher surface area but is less dense, softer, weaker, and less stiff. It typically occurs at the ends of long bones, proximal to joints and within the interior of vertebrae. Cancellous bone is highly vascular and frequently contains red bone marrow where hematopoiesis, the production of blood cells, occurs. The primary anatomical and functional unit of cancellous bone is the trabecula. Its Latin name is substantia spongiosa or substantia spongiosa ossium.[1] The words cancellous and trabecular refer to the tiny lattice-shaped spicules that form the tissue.

Haversian Canal

Haversian canals (sometimes Canals of Havers, named after British physician Clopton Havers) are a series of tubes around narrow channels formed by lamellae. This is the region of bone called compact bone. Osteons are arranged in parallel to the long axis of the bone. The Haversian canals surround blood vessels and nerve cells throughout the bone and communicate with osteocytes in lacunae (spaces within the dense bone matrix that contain the living bone cells) through canaliculi. This unique arrangement is conducive to mineral salt deposits and storage which gives bone tissue its strength. In mature compact bone most of the individual lamellae form concentric rings around larger longitudinal canals (approx. 50 µm in diameter) within the bone tissue. These canals are called Haversian canals. Haversian canals typically run parallel to the surface and along the long axis of the bone. The canals and the surrounding lamellae (8-15) are called a Haversian system or an osteon. A Haversian canal generally contains one or two capillaries and nerve fibres.

intramembranous ossification

Intramembranous ossification is one of the two essential processes during fetal development of the mammalian skeletal system by which bone tissue is created. Unlike endochondral ossification, which is the other process by which bone tissue is created, cartilage is not present during intramembranous ossification. It is also an essential process during the natural healing of bone fractures and the rudimentary formation of bones of the head.

the pyramidal cells

Let's take a closer look at a pyramidal cell, one of the motor neurons located in the cerebral cortex. The left image is stained with Luxol Blue & Neutral Red showing two cell bodies of pyramidal neurons, one in which the light stained euchromatic nucleus with a dark blue stained nucleolus is visible. The blue stained structures outside of the neurons are axons that are myelinated. Lipid stains blue with this stain. The drawing on the right is how a pyramidal neuron would look if a specimen were stained with silver. Note the two axon processes and several dendrites The small lines on the dendrites represent sites of synaptic connections. For each neuron in the CNS there can be from 1,000 to 10,000 synaptic connections. With 100 billion neurons and up to 100 trillion synapses in the CNS, it is obvious that our CNS is designed for communication.

x rays of bone reveal epiphyseal plate

X-rays appear white in areas where bone has the highest density with lesser density in bone with less mineral. Where cartilage is present, the x-rays pass through pretty much uninhibited and therefore, those areas appear dark. Note the epiphyseal plates, several of which are indicated by the white arrows. These growth areas (epiphyseal plates) are not closed and therefore, in this individual, growth in the length of bones is still taking place. If growth had ceased, the epiphyseal plate would not exist. It would be replaced with a light line indicating a higher density of mineral - now properly named the epiphyseal line. Observe in the x-ray on the right of two long bones that are articulating. Notice the difference in the appearance in the x-ray between cancellous and compact bone.

a cell that can differentiate into any of the three embryonic germ layers is ectoderm, mesoderm, or endoderm is named

pluripotent cell

cardiac striated muscle cells

shorter branched cells with one nucleus and nuclei located near center of each cell

smooth muscle cells

tapered cells with one nucleus and nuclei located near center of each cell

bone marrow aspirate or biopsy

A large needle is inserted up to 1 cm through the bone cortex into the marrow If a smear is need, then an aspirate of about 2 cc is withdrawn If a biopsy is needed, then a cutting needle is used and a chunk of marrow is removed for making a histological section When an analysis of bone marrow histology is required, a sample is taken from either the sternum or the iliac crest. A large needle is used and must be inserted about 1 cm into the bone marrow. The needle has to pass the hard bone cortex. There are two methods of examining the bone marrow. One is in a smear similar to a blood smear and the other is in a histological section. If the examination will be in a smear, then about 2 cc of bone marrow is withdrawn. A portion of the sample is squeezed from the syringe onto a glass slide and smear is made. If the examination requires a look at the histological architecture of the bone marrow, then, a cutting needle is used to remove a core or chunk of bone marrow. The tissue is then fixed and processed to section and stain. The next slide shows a sample of bone marrow prepared in this manner.

bone is a reservoir for calcium

A very large store for calcium - bone is about half crystalline calcium salts (hydroxyapatite/bone mineral) Calcium is removed from storage by cells that eat away bone & put its salts back into solution Calcium is put into storage by cells that make bone and build in the calcium salts Calcium is obtained and conserved by calcium in the diet; absorbed in the gut; not lost by the kidneys into the urine Calcium blood levels are maintained by hormones & other factors (e.g. vitamin D, cytokines) As a living organ, bone serves as a storage site for calcium, yet calcium can be readily retrieved from bone, ifneeded.

CNS glial cells: macroglia

Astrocytes Protoplasmic gray Matter Short branched processes Fibrous White matter Straight processes Astrocyte Function Regulate metabolite Contribute to blood- brain barrier This slide illustrates the Macroglia, i.e. the large glial cells consisting of astrocytes of which there are two kinds, protoplasmic and fibrous. Astrocytes have their processes touching neurons and processes on one side and blood vessels on the other side. They regulate metabolite exchange between the blood and the cytoplasm of the neuron. This arrangement contributes to what is called the blood-brain barrier. The other component of the blood-brain barrier is the capillary and its tightly joined endothelial cells. The tight junctions function to only allow exchange between blood and brain cells to go through the endothelial cell by special transporting proteins. More detail of this barrier will be presented in the lecture on the cardiovascular system. Protoplasmic astrocytes are located mostly in the gray matter while fibrous astrocytes are located mostly in the white matter.

hyaline cartilage matrix

Capsule or pericellular matrix- C Surrounds single chondrocytes Highest density of ground substance & is basophilic Territorial matrix - TM Surrounds isogenous groups Less ground substance with less basophilia Interterritorial matrix - IM Region of matrix between isogenous groups Least basophilic due to higher density of collagen There are three regions recognizable in the matrix of hyaline cartilage. Overall the matrix appears smooth hence the name hyaline which means glassy or glass like. Although collagen fibers are present, they are small and masked by the matrix. The staining result in the matrix in a given specimen may vary from the ideal due to fixation quality and the technical perfection of the staining procedure. The description of the different regions is based on ideal staining. The matrix that immediately surrounds a single chondrocyte is known as the capsule or pericellular matrix, C. It has the highest density of proteoglycans and therefore, is highly basophilic The matrix that surrounds isogenous groups has a lower concentration of ground substance and therefore, it is less basophilic. This region is known as territorial matrix, TM. The matrix between the isogenous groups is even less basophilic and is known as the interterritorial matrix, IM. Observe the lower part of the image. The shift from basophilic to acidophilic is due to a higher density of the collagen in the fibrous perichondrium, the tissue that surrounds the cartilage. Note that just above the fibrous perichondrium, there is more basophilia due to cartilage matrix being secreted by chondroblasts in the chondrogenic perichondrium. The dotted arrow shows the direction of maturity from chondroblasts to young chondrocytes with the most mature chondrocytes in the middle of this specimen.

endoneurium, perineurium, epineurium

Endoneurium: loose connective tissue around individual nerve fiber Perineurium: specialized ct of nerve fascicle providing a blood-nerve barrier Epineurium: dense irregular ct surrounding fascicles

summary

First, intramembranous bone formation was described and illustrated. Then how bone remodeling occurs was explained. The anatomy of a long bone was presented to show where the epiphyseal plates are located in a long bone. Endochondral bone formation was described and illustrated. The zones of an active epiphyseal plate were presented and the histology of the different zones was described and illustrated. The closure of the epiphyseal plate in a bone that has stopped growing was presented. Abnormal bone growth resulting in dwarfism and gigantism was explained and illustrated. Finally, two examples of abnormal bone matrix were presented.

blood clotting

Formation of a clot Intrinsic -small tears in endothelium exposing plasma/platelets to basal lamina Extrinsic -vessel is punctured & blood is exposed to tissue protein (collagen) Fibrinogen Dissolved in plasma and adsorbed in glycocalyx of platelets Platelets release thromboplastin that converts prothrombin to thrombin Complex cascade of factors convert prothrombin to thrombin Thrombin is a protease that acts on fibrinogen to convert it to fibrin The clot is a feltwork of fibrin, platelets and blood cells Blood clotting is a complex process. This slide presents the essential steps in the process. Platelets perform a critical and very important role in clotting. Clotting is a protective mechanism in two ways -1) to plug tiny defects or tears in the endothelium lining the body's blood vessels and 2) to prevent loss of blood if a blood vessels is cut or torn. The first mechanism is intrinsic. It involves platelet aggregation at the site of a small tear in the endothelium. Platelets aggregate and plug the defect until the endothelial cells can proliferate, migrate to the site and repair the defect. The second mechanism is extrinsic. It involves the platelets also, but instead of a platelet aggregate plugging the large defect, platelets release factors (one of which is thromboplastin) that cause the conversion of prothrombin in the plasma to thrombin. Thrombin, a protease, then acts on fibrinogen in the plasma and also fibrinogen adsorbed to the platelet cell membrane. Thrombin converts fibrinogen to fibrin, a fibrillar protein, that is cross-linked into a complex network that entraps platelets, erythrocytes and leukocytes. And thus, a clot is formed that prevents loss of blood. Clotting can be harmful when the process is activated by the rupture of an atherosclerotic plaque in a coronary artery. The result is blockage of blood flow to heart tissue leading to a heart attack.

a demyelination diseases

Multiple Sclerosis Myelin is damaged Oligodendrocytes are destroyed Disease is Episodical Symptoms Vision impairment Weak muscles Lack coordination Loss of bladder and bowel control Treatment Interferon injections Steroidinjections No known cure There are several diseases that affect myelin. Multiple Sclerosis is one of them. The function of myelin can be ascertained, in general, by noting the symptoms of this disease, namely a reduced capacity to move muscles whether they be skeletal or smooth. The specimen on the right is stained for the lipid that is in myelin. A large region of the spinal cord is lacking myelin surrounding its axons in the white matter. As an insulator myelin is critically important in the propagation of the impulse down or up an axon. Multiple Sclerosis symptoms are episodical, that is they may come and go, but there is no known cure and the disease slowly progresses. Injections of interferon and steroids seem to help. Spinal Cord of Human stained with lipid stain formyelin. Notethelightregionononeside. Myelin has been lost.

blood formed elements turned over

On the order of 100 billion formed elements of blood are released each day from the red bone marrow. Blood cells are formed in the red bone marrow Hematopoiesis- the term for formed elements formation An equal number of blood cells are destroyed each day in the spleen. The next few slides will present the histology of bone marrow and hematopoiesis Recall that the formed elements of blood are erythrocytes, leukocytes and platelets. These are the components of blood that are developing each day in the red bone marrow, about 100 billion / day. The name of this developmental process is called hematopoiesis. First, this lecture will describe and illustrated the histology of bone marrow followed by the various components of hematopoiesis.

functions of blood

Plasmatransports Electrolytes, proteins & hormones Glucose, amino acids & lipids Dissolved oxygen & carbon dioxide Erythrocytes transport oxygen & some carbon dioxide Leukocytes migrate into tissues Neutrophils- capture & destroy bacteria Eosinophils - neutralize parasites Basophils - release vasoactive substances Monocytes - are precursors to connective tissue macrophages and other phagocytic cells in the body Platelets function to seal leaks in vessels and participate in clottting monocyte basophil neutrophil eosinophil lymphocyte Plasma is 92% water in which a variety of solutes are dissolved. Electrolytes help maintain optimal pH. Proteins such as albumin help maintain the osmolarity of blood. Glucose and amino acids are carried to tissue cells. Cholesterol and other lipids are transported in the plasma. Erythrocytes transport most of the oxygen and it is complexed with hemoglobin, although a little oxygen is transported dissolved in plasma. Most of the carbon dioxide is transported in plasma as carbonic acid. Leukocytes perform a variety of functions and all of the functions occur outside of the blood vessels. Blood only serves as a transporter of leukocytes. Finally, platelets perform the essential function of sealing small leaks in vessels and participate in the clotting process.

staining a peripheral blood smear

Procedure Air dry smear and then fix in absolute methanol Stain with Wright's stain, a stain made by mixing methylene blue dye with eosin in a methanol diluent Results Basic components of the cell, such as hemoglobin or certain inclusions or granules, will unite with the acidic portion of the stain, eosin, and are said to be eosinophilic (acidophilic); red blood cells and the granules of eosinophils stain red. Acidic cell components, such as nucleic acids, reactive cytoplasm, etc. take up the basic dye components, methylene azure; nuclei and the granules of basophils stain blue. Quality Control pH must be carefully controlled through the use of a buffer of 6.4-6.7. If the pH is too acidic the stain will take on a pinkish tint, and nuclear structures will be poorly stained. A basic pH will cause all intracellular structures, nuclei, etc. to be blue-black in color, with poorly defined structure. al Blood After a blood smear is made the cells are fixed by either air drying or immersion in absolute methanol. Wright's stain is the stain of choice. It is named after James Homer Wright who devised the stain in 1902 as a modification of the Romanowsky stain. Romanowsky and another investigator, Malakowsky, were the first to mix eosin and methylene blue in an aqueous solution but the dyes were unstable. Wright and others added methanol to the dye mixture resulting in stability and a routine stain that is still used today. Any basophilic structure (holding an anionic charge) will react with the mixture resulting in blue color and any eosinophilic structure (holding a cationic charge) will react to produce a red color. Red blood cells and granules of eosinophils stain red. Nuclei and granules of basophils stain blue. Certain granules in neutrophils that have become reactive will stain blue / azure. Also, remnants of ribosomes from the developing red blood cell will stain blue. Other variations of staining exist such as basophilic blue staining granules in the platelet.

summary

This lecture began by highlighting the turnover of blood cells, defining stem cell potency levels and the histology of bone marrow. Next, hematopoiesis was defined and the location in the body where this process is occurring. The phases of hematopoiesis were presented. Then, Erythropoiesis, the formation of erythrocytes, was explained and the steps were illustrated. Granulopoiesis followed next with explanations and illustrations of the steps in the process of the development of a granulocyte. Finally, the role of the megakaryocyte in the formation of platelets was explained and illustrated.

summary

This lecture began by presenting an overview of the general structure of striated skeletal, striated cardiac and smooth muscle cells. Next, the striated skeletal muscle cell internal architecture was presented in which the details of the sarcomeres, the repeating units in myofibrils was presented. Then, the architecture of skeletal muscle that is designed to facilitate the conduction of an excitation impulse was presented. Skeletal muscle was then described and presented as a tissue. Cardiac muscle structure was presented, including the location of intercalated discs, the physical and chemical connecting structure between cardiac muscle cells. Smooth muscle was contrasted with cardiac and skeletal muscle in the fact that these cells have no striations but yet can contract and use myosin and actin to accomplish their function without a sarcomere structure.

summary

This lecture began by presenting the appearance of whole blood freshly drawn from a vein and an artery showing the contrast between oxygenated and deoxgenated blood. The components of blood were then presented as plasma, the buffy coat and the packed red blood cells in a sample of blood that was treated with an anticoagulant and centrifuged. Next the morphology and features of erythrocytes were presented. Following that, the morphology and features of leukocytes were presented. Finally, several methods for determining the total blood count and differential blood count were presented along with a few examples of the changes brought about by disease related to blood cell numbers and morphology.

summary

This lecture began with an explanation of the difference between and the location of the central and peripheral nervous systems. Next the general composition of nerve tissue was presented emphasizing the neuron as the functional (parenchymal) cell and the glial cell as the supporting (stromal) cells. The various types of neurons were presented. Somatic Peripheral Nerve Tissue was then presented that included the construct of a single nerve fiber and a nerve with its connective tissue wrappings of endoneurium, perineurium and epineurium. Next the way in which a central and peripheral nerve fiber is myelinated was presented. This was contrasted to unmyelinated autonomic nerve fibers. Then the histology of sensory and autonomic ganglia was presented. Finally, neurons and supporting cells of the Central Nervous System were presented that included the pyramidal cell of the cerebral cortex, the motor neuron of the spinal cord.

analysis of a patients blood cell count

Total Blood Cell Count Counting formed elements in a known blood volume Manually with a hemocytometer Automated with a "Coulter" counter Results expressed in # cells / Liter Differential Leukocyte Count % of each type of leukocyte determined Manually by tabulating # different cells in 100 cell Automated with a "Coulter" counter that not only counts cells but determines size, volume, concentration of hemogloblin Thus, whether carried out manually or by automation, two variants of blood cell analysis can be carried out. One is the total blood cell count. The total blood cell count is literally counting all of the blood cells, including platelets, in a known volume and expressing the result in the number of cells per liter of blood. The other analysis is to tabulate the white blood cells in a known volume of blood and express the results in percent of the total count represented by each of the leukocytes. This is a differential leukocyte count. The next slide will present the normal ranges of the white cells in a differential leukocyte count.

histology of bone marrow

Yellow Marrow Consists of fat cells and blood vessels Red Marrow Consists of Stem cells Developing RBCs Developing WBCs Megakaryocytes Platelet developing cells Blood vessels Large thin walled diameter - sinusoids Reticular cells that secrete factors influencing blood cell development

sarcomere is relaxation and contraction

*Key concept is that during contraction neither filament changes length but the sarcomere shortens in length because thick and thin filaments slide past each other This slide illustrates the shortening of a sarcomere when a muscle contracts. It is the combined shortening of thousands of sarcomeres connected end to end that result in muscle contraction and movement. Actin filaments are anchored in the z discs, one group of actin filaments at one end, and another group at the other end of a sarcomere. The myosin filaments are suspended and kept in an organized 3 dimensional array by special proteins at the M line in the middle of the H zone. When contraction occurs due to interaction of thin and thick filaments, the length of the sarcomere decreases because thin and thick filaments slide past each other. Neither filament changes in length.

articular cartilage histology

-articular surface -tangential -transitional -radial lage Now let's look at the histology of the special type of hyaline cartilage known as articular cartilage. First, observe that H&E staining of articular cartilage reveals that it is more acidophilic than ordinary hyaline cartilage. The reason for this is that articular cartilage contains significantly more collagen fibers than ordinary hyaline cartilage, yet it is not fibrous cartilage because it still has that hyaline or glassy look.., not a fibrous look. In the diagram on the right, you see the zones of cartilage where the tangential or gliding zone has collagen fibers arranged parallel to the surface and the chondrocytes are flattened. The next deeper zone is the transitional zone in which the collagen fibers are more randomly arranged where the chondrocytes are round. The deepest zone is the radial zone in which the collagen fibers are arranged vertically or at right angles to the surface. The arrangement of the collagen in articular cartilage enables the cartilage to be somewhat spongy to absorb force, yet providing a smooth surface for one bone to articulate upon another. Originally, the thickness of the articular cartilage was achieved by intersititial growth. Once the adult thickness is reached no more growth takes place and articular cartilage cannot regenerate because there is no perichondrium.

hyaline cartilage functional properties

-avascular -permeable (conducts nutrients and water) -flexible but weight bearing (resistance to compression) -elasticity and resiliency -resistance to shear forces -slippery (low friction at articular joints) -poor regenerative capacity -chondrocytes, fibers, collagen type 2, lacunae, isogenous groups, Ground Substance (hyaluronic acid, chondroitin sulfate, keratan sulfate, 60-70% H2O) Hyaline, fibrous and elastic cartilage all lack blood vessels, otherwise known as avascular. Nutrition diffuses into the cartilage tissue from surrounding blood vessels. The matrix is permeable so nutrition can reach the cells within the cartilage matrix. Observe that the matrix consists mainly of fibers composed of collagen type II and proteoglycan aggregates made up of glycosaminoglycan molecules on a backbone of hyaluronic acid. Within this matrix are chondrocytes, the cartilage cell that secreted the components of the matrix. They become entrapped in their own secretions as cartilage is formed. Each chondrocyte resides in a tiny cavity known as a lacuna. Many chondrocytes are associated in groups called isogenous groups. Each of these cells was derived from a single chondrocyte or chondroblast by mitosis. The process is called interstitial growth of cartilage (i.e. growth from within). Hyaline cartilage is flexible but not as elastic as elastic cartilage. Hyaline cartilage is found at the ends of long bones where it provides a smooth surface with weight bearing properties. It is found in the wall of the trachea and bronchi where it functions to maintain the opening of these airways.

hyaline cartilage architecture

-lacuna -isogenous group -proteoglycan monomer -collagen type 2 -chondrocyte -hyaluronic acid This drawing illustrates the components of hyaline cartilage - the cells, the fibers and the ground substance. Chondrocytes, the cells of cartilage, are shown within the matrix that they secreted. After the matrix is secreted, if the chondrocyte were removed, a space would remain and that space in which the chondrocyte resides is called a lacuna (plural - lacunae). The proteoglycan aggregates provide the main mass of the cartilage matrix. The proteoglycan monomers consist of around 200 molecules of chondroitin sulfate or keratan sulfate bound to a protein core. Each proteoglycan monomer is fastened to the very large hyaluronan molecule by a link protein. Cartilage matrix is about 60-70% water due to the high water adsorbing capacity of the proteoglycan aggregates. Chondrocytes only account for up to 5 % of the mass and collagen accounts for around 15% of the mass.

osteoarthritis stages

1. bone 2. cartilage 3. thinning of cartilage 4. cartilage remants 5. destruction Osteoarthritis is a common degenerative condition of the joints. The condition is partly genetically inherited, but may occur without any family history and simply be due to 'wear and tear'. Arthritis can also develop within a joint as a consequence of previous injury to the joint. As arthritis develops within a joint, the articular cartilage (the very smooth layer of cartilage that covers the surfaces of the bones on either side of a joint) wears away and becomes rough. This eventually results in exposed areas of bone, where the bones on either side of the joint start to rub and grate against each other, eventually leading to bone loss and deformity

differential white blood cell count

A complete blood count is the total number of leukocytes in a defined volume of blood. The normal range is 3,500 to 10,500 per microLiter (3.5 - 10.5 billion per Liter). In contrast to the complete blood count is the Differential WBC Count, often abbreviated as the Diff Count. This is determined by counting and categorizing at least 100 leukocytes in a peripheral blood smear to determine the percent of the total cells represented by the different leukocytes. The differential count can be done manually with a microscope and a blood smear or, it can be determined automatically with a Coulter Counter. When this is done, the normal range for neutrophils is 54-62 %. The normal range for eosinophils is 1-3 %. The normal range for basophils is 0 - 0.75 %. The normal range for lymphocytes is 25-33 % and the normal range for monocytes is 3-7 %. At any one time there can be up to 5% of the neutrophils that are band cells - having just been released from the bone marrow. Obviously, the compartment having the highest percentage of cells is the neutrophil compartment.

endoneurium, perineurium, epineurium

A group of nerve fascicles is shown wrapped in epineurium

accessory proteins and filament alignment

A sarcomere measures 2 - 3 microns in length in a relaxed muscle cell. It may be stretched to more then 4 microns and, during extreme contraction, may be reduced in length to as little as 1 micron. Tissue Within the myofibril and within each sarcomere segment, there is also a structural framework made up of non-contractile filamentous proteins that keep the actin filaments in line and regulate their length. Nebulin (colored blue) extends from the z disk along the length of an actin filament. It acts like a template to regulate the length of the actin filament. This is one nebuin molecule for each actin filament. Titin (colored brown) is a molecule that extends from the Z disk to the M Line. Titin filaments are anchored at both at the Z disc and the M line. Their function is to maintain the central position of the thick filaments in the sarcomere. Titin generates passive tension through elastic extension when the sarcomere is stretched. In a relaxed muscle cell, the sarcomeres are from 2 - 3 microns in length. They may be stretched to more than 4 microns and, in extreme contraction, may be reduced to 1 micron in length. Stretching a muscle before contraction, i.e. loading the muscle, actually increases the range of action of the muscle.

lymphocyte

Although lymphocytes and monocytes are classified as agranulocytes, this does not mean that you will not find any granules in the cytoplasm. Small azurophilic granules are present and these are lysosomes. Macrophages have more of these than lymphocytes. What is not present are specific granules that are large and have specific substances in them unique to the cell types as in neutrophils, eosinophils and basophils. Lymphocytes always have a round or slightly indented nucleus. Functionally, there are three subtypes of lymphocytes: 1) B lymphocytes (small), 2) T lymphocytes (large) and 3) Natural Killer cells (large). B lymphocytes mature in the bone marrow and migrate to lymph nodes. They represent the least percentage of circulating lymphocytes. More detail about T and B cells will be presented in the lectures presenting lymphoid organs. Lymphocytes do vary in size ranging from 6 to 18 microns in diameter. As is the case for all leukocytes, lymphocytes must migrate out of the blood stream in order to perform their functions.

articular cartilage

Articular cartilage is a variant of hyaline cartilage and it serves to form a smooth surface where two bones articulate (move upon one another). Two bones at a joint have been cut so that the relationship between the bone and cartilage can be seen. Observe that the white hyaline cartilage covers the surface of both bones providing a smooth surface for articulating (hence the term, articular cartilage). There is no perichondrium covering the surface of this cartilage which means that this cartilage cannot regenerate as is the case of cartilage in other sites of the body like the ear, nose and airways. Arthritis, chronic inflammation of a joint, will eventually lead to destruction of the cartilage. With swelling as a result of the inflammation, the smooth articulating surfaces are now thinner than normal or, even destroyed completely, resulting in pain upon movement. The next two slides will illustrate the stages and histopathology of osteoarthritis.

stem cells and their potency

Blood cells arise and develop from precursor cells in the bone marrow called stem cells. Stem cell denotes a cell that can differentiate into a specialized cell type. Potency denotes how many cell types can arise from a certain stem cell. The purpose of this slide is to list and define stem cells of varying potency so that the activity in the bone marrow can be understood in reference to the global function of cellular development and differentiation. Even though this is a well accepted scheme of the level of potency, the stem cell research field is rapidly discovering how to modify terminally differentiated cells, like skin or liver cells, so that they can differentiate into multiple cell types. This is beyond the scope of this course.

plasma vs serum

Blood drawn from a vein & no anticoagulant added Blood Clot forms & supernatant is serum Blood drawn, into tube containing an anticoagulant Blood Clot is a network of fibrin entrapping the formed elements of blood If blood is drawn from a vein into a tube and allowed to set it will form a blood clot. The normal clotting time for human blood is 5 - 15 minutes (time to the beginning of the formation a clot). The blood clot is formed after fibrinogen, a soluble plasma protein, is converted to fibrin. Fibrin is then cross-linked by a clotting factor, thrombin, and a meshwork of fibrin is formed that entraps the formed elements of blood. With fibrinogen now extracted from the plasma the fluid supernatant above the blood clot is known as serum. Serum contains everything that plasma does except it lacks fibrinogen. Compare this depiction of a test tube containing clotted blood with a tube containing a blood sample drawn into a tube that contained an anticoagulant such as sodium citrate or heparin.

composition of blood

Blood is made up of: Plasma Water, proteins, hormones, salts Cells Erythrocytes (lack nuclei) Leukocytes (various shaped nuclei) Cell fragments Platelets (thrombocytes) One drop* of blood contains 4 - 6 million erythrocytes 3,500 - 10,500 leukocytes 150,000 - 450,000 platelets *1drop=approx.1mm3 (1mL) ral Blood Blood is another specialized connective tissue. It is a connective tissue with a liquid extracellular matrix. Plasma is composed of water, proteins, hormones and salts. The cells are erythrocytes (red blood cells) and leukocytes (white blood cells). Erythrocytes do not have nuclei but leukocytes do have nuclei. Cell fragments are present that are much smaller than the blood cells; these are platelets. Observe the two drops of blood. The one on the left is blood from an artery that contains more oxygen than the one on the right that came from a vein. When hemoglobin, the main substance of erythrocytes, is saturated with oxygen the color is bright red. A drop of blood is approximately 1 mm3 (1 microLiter) and contains up to 6 million erythrocytes, 10,500 leukocytes and 450,000 platelets. So, blood is a fluid that has a certain viscosity that is greater than water and contains a suspension of cells and fragments of cells.

bone formation

Bone formation occurs by two methods - intramembranous and endochondral. One occurs independent of cartilage and the other occurs in close association with hyaline cartilage. Bone formation (also commonly called ossification) begins in-utero and continues until the epiphyseal plates close in the early 20's of adult life. It involves two steps; 1) matrix consisting of fibers and ground substance is secreted by osteoblasts followed by 2) the incorporation of mineral into the matrix. The result is a hard and strong tissue that forms a wide variety of bones of the human body.

bone

Bone is the hard supporting tissue that is used to make the very many bones of the skeleton: small, large; long, short; flat, rounded The term bone can be used to mean a tissue which is the main topic of this lecture, or, the term can mean an organ. The bones of our body are organs because they are composed of parts contributed to by the 4 basic tissues; epithelium- lining blood vessels, muscle - forming constrictor and dilator smooth muscle of the arteries, nerves providing sensations of pain etc in bone, and connective tissue forming various components of bone as an organ. Bone tissue forms the various types of bone organs such as small, large, long, short, flat and rounded, each serving an important function as a part of the skeleton.

the striated cardiac muscle cell

Cardiac Striated Muscle Cells Short branched cells with one nucleus Nuclei located near center of each cell Intercalated discs that connect cells Intercalated discs indicated by arrows Striated cardiac muscle cells have a large amount mitochondria and myoglobin that gives them a deep red color as you can observe in the small photograph (upper left) of a fresh heart taken at autopsy and cut open. The light micrograph stained with hematoxylin and eosin illustrates the branched cells with centrally located nuclei in each cell. The arrows indicate three intercalated discs that are located at the junction between cardiac muscle cells. Cardiac muscle cells depend upon being connected end to end to function in cardiac contractions. Cardiac muscle cells are striated but the striations do not show up as dramatically as they do in skeletal muscle cells. In this lecture, we will focus just on the cardiac muscle cell. The heart, the organization of cardiac muscle tissue and the cells involved in the conducting of the impulse to initiate each cardiac contraction, will be presented in the lecture on the heart.

blood disease terms

Certain disease states are defined by an absolute increase or decrease in the number of a particular type of blood cell. This table lists the blood cell types and the terms used to denote either an increase or decrease in their number. The suffix cytosis or philia is used to denote an increase in number whereas the suffixes -ia, blastopenia, or -cytopenia denote a decrease in number. For granulocytes, the term agranulocytosis is used to denote a very low number of granulocytes, less than 100 granulocytes per microliter (less than 100,000 granulocytes per liter) compared to a normal number of at least 3,500 granulocytes per microliter or 3.5 x 109 per Liter (3.5 billion cells per Liter). If you are curioius, each term that is underlined has a hyperlink to 'Wikipedia' where you can learn more (You will not be tested on the pathological terms).

endochondral bone formation

Endochondral bone formation implies that the formation is associated with cartilage (hence chondral in the name of the process). The first step is that mesenchymal cells in the area where a bone will form differentiate into chondrocytes. The chondrocytes multiply and secrete matrix in a genetically determined pattern that creates a model for the future bone made out of hyaline cartilage. Next, the cells surrounding the body of the cartilage model transform into osteoblasts and form a bony collar composed of compact bone. This greatly reduces any diffusion of nutrients and oxygen into the cartilage mass inducing the cartilage to first become mineralized, so the cartilage calcifies. Next, the bony collar is invaded by blood vessels. The channels for growth of vessels into the calcified cartilage are created by the action of bone destroying cells called osteoclasts. Accompanying the vessels are osteoprogenitor cells that produce osteoblasts that set about secreting bone matrix upon a template that consists of remnants of the calcified cartilage. This is known as the primary center of ossification occurring in the shaft or diaphysis of the future bone. At this stage, the secondary ossification centers appear in the epiphyses at either end of the developing bone. Cartilage remains between the two epiphyses and the diaphysis. The last stage is a definitive stage in which the diaphysis continues to grow in width by appositional growth and in length by interstitial growth because the cartilage cells in the epiphyseal plates (EP) divide in the longitudinal plane only. The next slide will illustrate and explain the histology and function of the epiphyseal plate region of a developing bone. cartilage anlage periosteal collar compact bone calcified cartilage invasion by blood vessels primary center of ossification spongy bone subperiosteal intramembranous ossification growth in diamter spongy bone bone is growing in length due to proliferation of cartilage cells in the epiphyseal plates

erythrocyte structure detail

Erythrocyte content Volume = 90 femtoliters (fL) 30 picograms (pg) of hemoglobin Acidophilic due to net positive charge on hemoglobin Biconcave Shape maintained by Interaction between integral and peripheral membrane proteins Integral proteins are Glycosalated and express blood group antigens Peripheral proteins are mainly spectrin and actin Lets look at the structure of an erythrocyte. The drawing on the right of an erythrocyte shows the dimensions of the biconcave disc. Hemoglobin makes up the main mass of the erythrocyte. There are about 30 pg (a picogram is 10-12 gram) of hemoglobin in each erythrocyte. Hemoglobin carries a net positive charge and therefore, the erythrocyte is acidophilic, reacting strongly with dyes like eosin. The volume is very small, about 90 fL (a femptoliter = 10-15 Liter). The shape of the erthryocyte is maintained by the interconnection between integral membrane proteins and cytoplasmic proteins such as actin and spectrin. Energy and a critical salt concentration in the plasma is required to maintain the biconcave shape. A protein, ankyrin, anchors the lattice of peripheral proteins to the lipid bi-layer of the cell membrane by its interaction with the integral membrane protein band 3 and band 4.2. The mechanism of the maintenance of the normal biconcave disc shape of an erythrocyte is not completely understood but it is clear that it involves glucose and a source of ATP. Erythrocytes produce the energy carrier ATP from glucose by a glycolysis pathway that ends with lactic production. Furthermore, red blood cells do not have an insulin receptor and thus, their glucose uptake is not regulated by insulin. In other words, erythrocytes produce energy without using oxygen (anaerobic metabolism) and glucose is the molecule that is used to make ATP. Thus, the biconcave disc shape is maintained without robbing any of the oxygen we breathe that is needed by our other cells.

hemocytoblast proerythroblast basophillic erythroblast polychromatophillic erythroblast orthochromatophillic erthyroblast nuclear extrusion reticulocyte RBC

Erythropoiesis begins with a multipotential progenitor cell, that transforms first into a cell that shows the beginning of the hemoglobin factory (the free ribosomes). This is the proerythroblast. Further development and increase of ribsosomes causes a significant increase in cytoplasmic basophilia - the basophilic erythroblast. Then, as hemoglobin first begins to appear a mixture of acidophilia (pink due to hemoglobin) and basophilia (ribosomes) develops and this cell is called the polychromatophilic erythroblast. The next stage continues hemogloblin synthesis by ribosomes but the main event is that the nucleus is becoming inactive, condensing and therefore stains very dark. This is the orthrochromatophilic erythroblast (named for the ortho or more typical true color -pink of the cytoplasm). In the next stage, the nucleus is extruded from the cell and this transformation results in the cell called the 'reticulocyte' (another name for this cell is the basophilic erythrocyte because of the ribosomes remaining in the cell). The bluish basophilic cast remains in the cytoplasm for a few days until the cell matures into the definitive erythrocyte.

fibrous cartilage

Fibrous cartilage provides a 'padding' between our vertebra and also aids in firmly connecting one vertebra with another. Fibrous cartilage also plays an important role in the joint that fastens the two halves of our pelvic bone, providing a limited movement flexible joint. The meniscus of the knee and where the Achilles tendon inserts into our heel bone are also sites where fibrous cartilage is found.

Osteoprogenitor Cell

Flattened or spindle-shaped cells which differentiate from mesenchymal cells. They have slightly acidophilic cytoplasm, a flattened nucleus. They are cells that divide under appropriate bone formation influence and the resulting cells differentiate into osteoblasts. Thus they are a source of osteoblasts. They lie close to the surface of bone in the osteogenic layer of the perichondrium and reside in the endosteum.

summary

For this course, all cartilage is derived from mesoderm. All three cartilage tissues do not contain any blood vessels. Cartilage receives nutrition by diffusion from blood vessels nearby. Hyaline (except for articular hylaine cartilage) and elastic cartilage are surrounded by a perichondrium that contains cells that can add to the cartilage tissue, but fibrocartilage does not have perichondrium. Notice that only hyaline cartilage has matrix that is dominated by ground substance. Both fibrocartilage and elastic cartilage have collagen or elastic fibers as the dominant component of the matrix. Hyaline cartilage is the tissue that covers the ends of bones that articulate with one another, the articular cartilage. Fibrous cartilage makes up the structure of intervertebral discs, the meniscuses of the knee, the sternum-clavicle joint and the pubic symphysis. Elastic cartilage constitutes the core tissue of the external ear, the epiglottis and the auditory tube.

platelet structure detail and four zones

Four Zones Peripheral zone microtubules glycogen microtubules membrane channel Platelets do not have nuclei Cell membrane with thick coat of glycoproteins - receptors Structural zone Microtubules, myosin, actin-binding proteins arranged circumferentially beneath cell membrane - maintains platelets disc shape Organelle zone Mitochondria, peroxisomes, glycogen and granules that contain function in vessel repair and platelet aggregation Membrane zone Two types of membrane channels that regulate calcium concentration within the platelet al Blood The colored inset is a high magnification snapshot of RBCs and one platelet. All that can be resolved with the light microscope is a blue center (the granulomere) and a lighter halo (the hyalomere) surrounding the blue center. Platelets contain a variety of substances that are involved in platelet aggregation and the clotting of blood. Note the different zones of the platelet structure that can only be resolved with an electron micrograph - the peripheral zone consisting of the cell membrane with its glycoprotein coat, the structural zone consisting of microtubules and microfilaments that maintain its shape, the organelle zone that contains mitochondria, perioxisomes, glycogen and granules containing important substances for facilitating clotting and the membrane zone consisting of membrane channels that regulate calcium concentration in the platelet.

fibrocartilage

From mesoderm Avascular Lacks a perichondrium Type I collagen fibers dominant in very little ground substance Intervertebral discs, meniscuses of the knee, sternum-clavicle joint, pubic symphysis

elastic cartilage

From mesoderm Avascular Surrounded by a perichondrium Matrix is dominated by elastic fibers with some collagen type II External ear, epiglottis and auditory tube

erythrocyte homeostasis

Hematopoiesis It is important that a balance of new cells and removal old blood cells be achieved. This is homeostasis. An equal number of erythrocytes are released from the bone marrow and destroyed by the spleen each day. The synthesis in the bone marrow by erythropoiesis is highly regulated. It takes about 10 days to make an erythrocyte. When they are released, they are still immature with some free ribosomes. The reticulocytes account for about 1% of circulating erythrocytes. Within 2 days they mature and remain in the circulation for up to 120 days. When red blood cells become too stiff the cell coat molecules change and macrophages in the spleen recognize this. They are removed from the circulation, digested and the amino acids of hemoglobin and iron are recycled and used again. Note the huge number that are released each day and an equal number destroyed by the spleen in order to maintain homeostasis of the red blood cell population. It is hard to imagine that nearly 2 million erythrocytes enter the circulation every second and 2 million are removed and destroyed.

hyaline cartilage

Hyaline cartilage (aka "Gristle") consists of a slimy mass of a firm consistency, but of considerable elasticity and pearly bluish color. Hyaline cartilage plays an important role in preventing the collapse of airways of the respiratory tract, nose through bronchi. Hyaline cartilage also covers the surface of bones at joints to provide a smooth surface for articulation.

Bone tissue preparation

If a bone sample is to be sectioned and stained for examination in the microscope, the specimen must be fixed and then submerged in a weak acid for a time in order to remove the calcium salt. This renders the tissue soft so that it can be processed and stained for histological examination. The result is illustrated here in the top illustration. Another way of preparing bone is to cut the bone with a diamond wheel or wire saw into slices approximately 0.5 mm thick and then hand grind the section to a thickness between 75 - 150 microns. By comparing the two photographs, you can see that the layered structure of bone and small canals within the bone called canaliculi can be better seen in the lower photograph of a ground bone section. A modification of the ground bone method is used routinely now to examine bone implants for compatibility. Decalcified Bone Specimens Bone is fixed in formalin and then decalcified in a weak acid Ground Bone Specimens Sections of bone are ground to 75-150 micron thickness, no staining

decalcified

If the mineral is removed from bone by treating it with an acid solution the bone can be literally tied in a knot. This demonstrates that the mineral gives the bone hardness and brittleness. The fibrous component of the matrix, collagen, gives the bone strength and integrity of structure. You can see the bone substance remains when decalcified but it becomes flexible.

bone marrow smear specimen

In conclusion, a look at the cells in a bone marrow smear will serve as a reminder of what is going on in the bone marrow. The cells indicated by the letter E are in various stages of erythropoiesis. The 3 large cells indicated by the letter E are basophilic erythroblasts. Observe the cell marked with E in the lower left of the sample. This is the stage of erythropoiesis when the nucleus is being extruded; the orthochromatophilic erythroblast. Immediately after this stage the anucleated cell is diffusely basophilic and it is the reticulocyte. The cells indicated by the letter L are in various stages of leukopoiesis. The one in the extreme upper left of the sample is a mature neutrophil, the one in the middle is a metamyelocyte and the one in the extreme right of the sample is a eosinophilic myelocyte. The pink staining areas are occupied by red blood cells that have lost their nuclei and are ready to be released from the marrow.

thrombopoiesis

In this drawing, made to illustrate the megakaryocyte as seen in an electron microscope, you can see the demarcation lines created by a three-dimensional system of clefts about 15 - 20 nm wide that subdivide the cytoplasm of the megakaryocyte. It is at these clefts that the fragments of cytoplasm are broken off and thus forming platelets. In other words, the platelets detach from the cell along these demarcation channels....analogous, in a sense, to "tearing along the dotted line".

leukocyte homeostasis

Leukocytes are formed in the bone marrow and this process is called granulopoiesis. It takes up to 14 days for a neutrophil to develop from its stem cell. When the cells are released into the circulation a small percentage are immature band cells. The neutrophil, typical of the granulocytes, only stays in the circulation up to 4 days and then migrates into the tissues eventually dying. When you consider that 7,000 WBCs are released and destroyed each second in a person weighing 70 kg, it is clear that our tissues are very active all the time.

monocyte

Life Span - several months Large non-lobated indented nucleus No Specific Granules Cytoplasm lightly basophilic with vacuoles & azurophilic granules that are lysosomes Functions are: Become macrophages: phagocytosis of leftovers of damaged tissues with assistance of lysosomal enzymes coordination of defense and repair via cytokine antigen presentation to other cells Cell of origin for connective tissue macrophages, Langerhans cell of epidermis, microglia cells of CNS, Kupffer cells of the liver, osteoclasts of bone, dendritic cells of lymph nodes and alveolar macrophages of the lung The monocyte is the largest in diameter of the white blood cells. In addition to this unique property, monocytes often have an indented nucleus and vacuoles in their cytoplasm. When monocytes leave the blood stream and move into the tissues, they perform their function of phagocytosis. Macrophages normally are very low in number in the connective tissues. A chronic infection in a local area will attract monocytes from the blood and they will ingest bacteria and cellular debris from acute infection such as dead neutrophils. If tissue is damaged and necrosis occurs, they will remove the dead tissue. Monocytes also can become osteoclasts, a cell that removes bone tissue, a topic taken up in the histology of bone.

neutrophil

Life Span in Circulating blood averages 12 hours Activated neutrophils in tissue live up to 2 days Multi-lobed Nucleus 2 - 7 lobes (increases with cell age) Specific Granules (salmon color) type IV collagenase, phospholipase Azurophil Granules (azure color) myeloperoxidase Functionsare: bacterialkillingviafree radicals and lactoferrin phagocytosisofbacteria,then destruction via acid hydrolases found in lysosomes diameter 12-15 microns The neutrophil is named so because its granules are neutral staining, neither pink nor blue. Specific granule refers to the granule that secretes a substance specific to that type of cell. Non-specific granules mostly are lysosomes and are also referred to in light microscopy as azurophilic granules. Neutrophils escape from post-capillary venules in inflammation. The secretory products of their specific granules perform important functions in neutralizing bacteria, a function for which they are designed. The mechanism of antibacterial activity of lactoferrin is by its ability to strongly bind iron. Iron is essential to support the growth of pathogenic bacteria. Collagenase, elastase and alkaline phosphatase, break down any tissue barrier in the way of attacking the bacteria. In an acute infection, if systemic, the count of neutrophils in the blood increases significantly.

adult bone tissue types compact dense A and cancellous spongy B

Mature bone, i.e., fully formed adult bone, is classified as either compact or cancellous. The image on the right is a section through a fixed and dried femur where it articulates with the ilium at the hip joint and socket. The frame A is enlarged on the left. Compact bone at this level of magnification is solid, i.e. no spaces. In contrast, observe the enlargement of frame B. This is cancellous or spongy bone. It is seen at this level of magnification to be composed of a network of thin bone plates that are called spicules. When the spicules are oriented parallel and running in a longitudinal plane, they are larger and are called trabeculae. On the next slide, cancellous bone histology will be illustrated and explained.

the striated skeletal muscle cell

Multinucleated cell / fiber Each cell connected to tendon 100 or more nuclei per cell A morphological syncytium Striations Light = I band bisected by z line Dark = A band bisected by H zone Repeating Unit - The Sarcomere 2-3 microns in relaxed muscle Z line/discs are the boundaries Structure-functional unit of skeletal muscle cells / fibers A striated muscle cell is connected at both ends by special adhering junctions to a tendon. It is a multinucleated cell with 100 or more nuclei per cell / fiber. This is correctly referred to as a morphological 'syncytium', - prefix syn means together, suffix - cytium refers to cells. Literally, it means many cells into one cell. In fact, that is exactly how the skeletal muscle cell comes into being in the developing embryo and fetus. Myoblasts first form and many myoblasts fuse to form a single cell with many nuclei. The term cell and fiber can be used interchangeably. The cell is shaped like a fiber, i.e. longer than wide. The cell diameters can range from 50 to 100 microns or more. A magnified portion of the skeletal muscle fiber stained with hematoxylin and eosin and observed in a light microscope reveals light and dark bands crossing the cell perpendicular to the cell's long axis. These are the I (light staining) and A (dark staining) bands. The I band is transected by a line that is called the Z line and the A band is transected by a light staining area called the H zone. Examination of the striations of the muscle cell in a transmission electron microscope reveals that the A band is electron dense and the I band is less dense or electron lucent. Two Z discs (in 3D disc, in 2D line) can be seen to be placed in the middle of the I bands. I bands are composed of thin filaments made up of actin and the A bands contains both actin filaments and thicker filaments made up of myosin. Skeletal muscle stains predominantly pink with an H&E stain. The basic proteins, myosin and actin, react with the acid dye -eosin.

neutrophil in inflammation

Neutrophils respond to bacteria in tissues by Migrating out of blood vessels into tissues First step in migration is slowing of neutrophil and binding to the endothelium as illusrated here........... Next step is passing through the endothelium, a process known as diapedesis - literally putting a foot (pseudopod) through as illustrated here....... Finally the neutrophil encounters a bacteria, disables it, takes it into its cytoplasm by a process known as phagocytosis as illustrated here..... All leukocytes must leave the blood stream in order to perform their functions. This action of leaving the blood by passing through the endothelial (epithelial) lining of blood vessels is called diapedesis. Chemicals from bacteria cause capillary lining cells to express molecules (selectins) that are specific for leukocytes such as neutrophils. Neutrophils then via molecules expressed at their surface (ligands) bind to the selectins. This slows the neutrophil as it rolls along the lining intermittantly sticking. Then, adhesion molecules (ICAMs intercellular adhesion molecules) are expressed by the lining cells (endothelial cells). These molecules bind to integrins (integral membrane proteins) of the neutrophil which stops the cell from circulating. Then, the neutrophil secretes a chemical to temporarily dissolve the tight junction between endothelial cells and it passes from the blood vessel into the surrounding tissue. This is called diapedesis (dia = through and pedesis from pede - foot.....literally, putting a foot or pseudopod through). The neutrophil (shown here in the electron micrograph) was caught in the act of protruding a pseudopod through the lining of a small blood vessel. Finally, the neurtrophil encounters a bacteria, disables it by secreting superoxides, a bacteria killing molecule, and lactoferrin that binds Fe essential for bacteria binding to cells and then takes the bacteria into its cytoplasm by a process known as phagocytosis after which the neutrophil dies. When great numbers accumulate at the site of an infection, their corpses create a yellow substance known as pus. Pus is eventually cleaned up by tissue macrophages that were derived from monocytes. You may wish to pause the lecture and click on the link at the bottom of this slide that will take you to an excellent animation of this entire process created and produced at Harvard University. When you access the website, you can just sit back and watch the animation or, you can click the advance button to jump to certain sections.

longitudinal and cross section of profiles of cardiac muscle cells

Note that the nucleus of a cardiac muscle cell does not extend the entire length of the cell. Therefore, when cross-sections are viewed some profiles will not include a nucleus. Also, the profiles are irregular in shape as some profiles are of the branches that run obliquely between two adjacent muscle cells. The dark thick lines in the longitudinal view drawing are meant to represent intercalated discs

osteoarthritis histopathy

Observe on the left the appearance of normal articular cartilage, especially the tangential or gliding layer that is smooth. Now compare this with the abnormal, arthritic cartilage on the right where the tangential layer is fragmented. It is quite apparent that this arthritic cartilage would not provide a smooth gliding articular surface.

Osteoblast

Osteoblasts (from the Greek words for "bone" and "germ" or embryonic) are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are sophisticated fibroblasts that express all genes that fibroblasts express, with the addition of the genes for bone sialoprotein and osteocalcin. Osteoblasts produce osteoid, which is composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of the osteoid matrix. Zinc, copper and sodium are some of the many minerals produced.

Periosteum

Periosteum is a membrane that lines the outer surface of all bones,except at the joints of long bones. Endosteum lines the inner surface of all bones. Periosteum consists of dense irregular connective tissue. Periosteum is divided into an outer "fibrous layer" and "osteogenic layer". The fibrous layer contains fibroblasts, while the osteogenic layer contains progenitor cells that develop into osteoblasts. These osteoblasts are responsible for increasing the width of a long bone[3] and the overall size of the other bone types. After a bone fracture the progenitor cells develop into osteoblasts and chondroblasts, which are essential to the healing process.

erythrocyte

RBC diameter = isocytosis Normal = 6 - 8 μm (avg. 7.8) = isocytosis Disease causes diameters outside of this range and is called anisocytosis RBC shape Normal is a biconcave disc In blood smears the center is thinnest and therefore takes less stain Disease causes abnormal shapes as seen in this cell - a Poikilocyte (if >10% of cells like this, then Poikilocytosis RBC diameter < 6 μm is a microcyte; rbc diameter > 8 μm is a macrocyte al Blood Erythrocytes (RBCs) can now be examined for whether they have a normal shape and whether they fall within the normal size (diameter) range- 6- 8 micrometers (isocytosis). The term for diameters outside of this range is anisocytosis. The normal shape of an erythrocyte is that is a disc with two concave surfaces - a biconcave disc. The center where the concavities exist is very thin and thus, when viewed from either side one red blood cell will be much lighter stained in its center than at the edge where the cell is thicker. The condition of abnormally shaped erythrocytes is called poikilocytosis. Learning the terms for variation in shape, poikilocytosis, and variation in size, anisocytosis is important because various diseases affect these aspects of the erythrocyte. For example, in sickle cell anemia the RBC is sickle-shaped and in microcytic anemia, the average diameter of the red blood cell is less than 6 microns. The life span of an erythrocyte is 120 days. Red blood cells older than 120 days are removed by the spleen as new ones are released from the bone marrow.

the sarcomere of striated muscle cells

Sarco means flesh and mere denotes a small segment or part. So, sarcomere is a segment of the flesh where flesh denotes muscle. Specifically, the sarcomere is a repeating unit of structure of the myofibril. Each muscle cell is composed of myofibrils - the profiles at the cross- sectioned end of this muscle cell drawing represents myofibrils. Whereas a single striated skeletal muscle cell diameter is anywhere from 40 - 100 microns or more (if world class strength training), a single myofibril a illustrated here 0.5 or less in diameter. Myofibrils are very long, reaching as long as the muscle cell and connected at either end to tendon tissue at the z-discs. Thus, the repeating unit called a sarcomere is actually the repeating unit of the myofibril. The myofibril content is composed of two proteins - myosin and actin that are formed into filaments - the thin and thick filaments. As you can see in this scheme, the thick and thin filaments are interlaced end to end so that they overlap. The thin filaments interact with the globular head portion of the thick filaments. The interaction is like a ratchet in which the z discs are brought closer together with each myosin head - actin filament engagement. The whole process is calcium and ATP (as the energy source) dependent.

two examples of abnormal bone matrix are scurvy and rickets.

Scurvy vitamin C deficiency improper collagen synthesis (hydroxyproline) weakness in epiphyseal plate, diaphysis Rickets (most often Vit. D3 deficiency) calcium deficiency in children incomplete bone matrix calcification spicules distort under strain: bone deformation results Scurvy is caused by a vitamin C deficiency. The underlying problem in scurvy is improper collagen synthesis, leading to weak bones. The underlying cause of rickets is a calcium deficiency which leads to incomplete bone matrix calcification. This problem is so important in children because active bone growth occurs in this part of life. Spicules are distorted under strain and bone deformation results.

the smooth muscle cell

Smooth Muscle Fiber (Cell)- spindle shaped Smooth muscle cells are long and tapered. Two terms are used to describe the shape - fusiform or spindle shaped. The nucleus lies in the center of each cell but does not reach either end of the cell. When a cross-section of smooth muscle is viewed, not all profiles contain a nucleus because of this fact.

smooth muscle contraction

Smooth muscle cells have filaments of actin and myosin. The The Smooth Muscle Cell Return to outline TEM- Longitudinal Section Smooth Muscle Fiber- Transverse Section dense bodies Smooth Muscle Contraction Mechanism α actinin-containing dense bodies actin filaments anchor into the dense bodies composed of alpha l actin, the Z disc like material, located at the cell membrane and e entire cytoplasmic area is occupied by muscle proteins with some reserved for smooth endoplasmic reticulum, mitochondria 2 and stored glycogen. However, in smooth muscle cells, this is not the case. There are no myofibrils and therefore, the sarcomeric pattern does not exist. This illustration of the 3 morphological change, brought about by smooth muscle contraction, is as it would appear in a single isolated muscle cell, distributed throughout the cytoplasm. Observe that the bipolar myosin filaments are interposed between the actin filaments like in skeletal muscle, except the density of myosin and actin filaments is much lower. In skeletal muscle cells, almost the not anchored to thousands of other muscle cells to form a functional syncytium. There is, in the intact human, a deformation but it is not this severe. Indeed, however, contracted smooth muscle cells in-situ do exhibit a cork-screw shaped nucleus. Relaxed smooth muscle cells can be recognized in tissue sections because their nuclei are elongated fusiform shaped. Smooth muscle cells require only 10% of the energy that is required to have successful contraction in striated muscle cells.

how is myelin formed

Somatic (Body) motor and sensory peripheral nerve fibers are insulated with a wrapping of the cell membrane of a Schwann cell. The drawing illustrates the relationship between a Schwann cell and the axon of a peripheral nerve fiber that is being myelinated. The Schwann cell wraps its cell membranes around the axon in concentric layers forming an end structure that resembles a 'jelly roll'. The light micrograph appearing in the center is a tissue section showing several myelinated nerve fibers stained with H&E. Note the axon and Schwann cell nucleus within a thin rim of Schwann cell cytoplasm. The clear or lightly stained region between the thin rim of acidopjlic Schwann cell cytoplasm and the axon is the myelin sheath. Examination of a cross-section of a myelinated axon in an electron micrograph would reveal the structure as seen in this electron micrograph. You can observe the myelin as the dark electron dense band around the axon. In the light micrograph, the lipid was dissolved during processing so that the myelin sheath is seen as a lightly stained region between the axon and the rim of Schwann cell cytoplasm where its nucleus is located. The next slide presents a narrated animation of the myelination of a peripheral nerve axon.

coulter counter results: scatterplot

The Scatterplot got its name from the plotting of the distribution of the different formed elements in two dimensions based on size and density of each formed element. At a glance, an experienced cytotechnician or hematologist could see if any population of cells deviated in size or volume. The size of white cells is determined by volume and plotted. Notably in this scatterplot are monocytes, lymphocytes and neutrophils. To the right of the scatterplot are two graphs. The upper one shows the distribution of 105 billion RBCs by volume in femptoliters. The normal average is around 90 fL. The lower graph shows the distribution of platelets by volume. The average volume of platelets is around 8 fL. Now, look under White Blood Cell Results where you can see the total white cell count as 10,600 / microLiter (or 105 billion / Liter). Then, note the differential WBC count in percent and absolute number / microliter. Now, look under Red Blood Cell Results where you can see the numbers of RBCs as 4.54 million per microliter (or 454 trillion / Liter). Then, under that are the values for hematocrit, mean rbc volume, mean rbc hemoglobin, mean rbc hemoglobin concentration, distribution of rbc width. Finally the number of platelets / microliter and the average volume of a platelet is given.

muscle cell types

The basic architectural differences between the three types of muscle cells that make up muscle tissues are presented in this slide. Skeletal muscle has multiple nuclei (as many as 100 or more) in each cell (placed just under the cell membrane). Skeletal muscle cells are shaped like cylinders. The cytoplasm shows striations that run perpendicular to the cell's long axis. In this photomicrograph of a skeletal striated muscle specimen, you can see dark and light bands- called A and I bands respectively. Cardiac muscle is composed of branched cells that have centered nuclei that are box shaped (rectangles). There is only one nucleus per cardiac muscle cell. The cells are connected end to end with special junctions called intercalated discs. Cardiac muscle cells have striations but they are much fainter than skeletal muscle as you can see in the photomicrograph of a specimen of cardiac muscle tissue. Smooth muscle cells have fusiform (tapered) nuclei in the center of a fusiform (tapered) shaped cell. Each smooth muscle cell has only one nucleus. The cytoplasm has no striations as you can see in the specimen on the right. These cells were named for their smooth look in contrast to the striated cells. Thus, there are two main types of muscle cells forming muscle tissue - striated and smooth. There are two subtypes of striated muscle -striated skeletal that is the makeup of the named muscles of the body that attach to bones and move them, and striated cardiac muscle that makes up the main mass of the heart and some of the large veins that attach to the heart. Smooth muscle is found in the wall of most blood vessels, the wall of the gastrointestinal tract, the uterus, the urinary bladder and many more small and large hollow organs that require a regulation of the diameter of their lumens.

lecture focus is nerve tissue

The focus of this lecture will be on the composition of nervous tissue and how it differs in composition in the central vs. the peripheral nervous system. It is not within the scope of this lecture to present, describe and discuss the brain, spinal cord, and peripheral nerves as organs. The brain is a very complex organ consisting of 100 billion neurons and a myriad of supporting cells all organized into architecture and connected by synapses (of which there are 100 trillion) to enable humans to function in being aware of their surroundings and to move within the environment. The spinal cord is complex with tracts consisting of the processes of neurons that provide the conduction of neural stimuli to travel from the body to the brain and from the brain to the body. The peripheral nervous system is composed of a myriad of named nerves that will not be presented in this lecture. Even each peripheral nerve, e.g., the sciatic or median nerve, is an organ consisting of the 4 basic tissues. The next slide will compare the Central to the Peripheral to the Autonomic Nervous System.

making of a peripheral blood smear

The histological structure of blood cells is traditionally studied using a microscope to view and magnify a blood smear. The appropriate term is a peripheral blood smear because it is made with a drop of blood taken from a peripheral body site like the ear lobe or finger. This slide illustrates the stepped involved in the preparation of a blood smear. The goal of this procedure is to create a single layer (monolayer) of blood cells on the glass slide. Two slides are required. After making a small nick (using a lancet) in either the ear lobe or finger, a drop of blood is collected on one of the glass slides. With this slide held and placed on a solid surface, the second slide is held at a 45 degree angle and slid on the first slide until it just touches the drop of blood. For a brief moment, the blood is allowed to spread along the interface between the two slides and then pulled away from the drop in a smooth motion. The result is a blood smear. The monolayer of cells will be found near the end or tail of the smear as indicated in this slide.

bone marrow

The histological structure of bone marrow is a mix of sinuses carrying blood that serve as an exit point for developing blood cells and platelets that are mature enough to function, cords of hematopoietic tissue that consists of stem cells and the developing blood cells and supporting cells that secrete hormones that facilitate and direct the formation of blood cells. In the adult, human hematopoietic tissue is located in the sternum, the crest of the iliac bone and the proximal and distal ends of long bones like the femur and humerus. Hematopoietic tissue is red and thus, is called the 'red marrow'. The other compartment of the marrow of our bones is composed of adipose tissue and is called the yellow marrow.

bands and segs

The nucleus of a young neutrophils is band shaped. Older neutrophils have segmented nuclei (lobated); the older the neutrophil the more lobes. This slide presents the variation in neutrophil morphology related to age. A less developed or, sometimes referred to as a more juvenile form of the neutrophil is a neutrophil whose nucleus is shaped like a band. Neutrophils are formed in the bone marrow. The very young ones have a nucleus that is band shaped. Sometimes these young cells get into the blood stream in numbers sufficient to detect, usually because of the response of the blood to a bacterial infection by recruiting neutrophils into the tissue. This slide gives you practice on detecting the difference between a young (band) neutrophil and an older (with a segmented nucleus) neutrophil. These cells live hours in the blood stream and days (up to 4 days) in the tissues. The older the neutrophil, the more segments (lobes) to its nucleus. To determine whether a neutrophil is a band or seg, one method is to determine whether there are any strands or filaments connecting segments (lobes) of the nucleus. The presence of such a strand makes a cell a seg. Examining the examples of each type in this slide should give you ample reinforcement of how to differentiate a seg from a band neutrophil.

haversian system

The osteon, or Haversian system, is the fundamental functional unit of much compact bone. Osteons, roughly cylindrical structures that are typically several millimeters long and around 0.2mm in diameter,[1] are present in many of the bones of most mammals, birds, reptiles, and amphibians.

perichondrium

The perichondrium is the tissue that surrounds cartilage. It is composed of dense connective tissue with chondrogenic cells next to the cartilage. •. Components of the Perichondrium •Inner part •Chondrogenic •Cells that become chondrocytes •Outer part •Fibrous •Collagen fibers & fibroblasts lage The term perichondrium literally means around cartilage - it is the tissue that immediately surrounds cartilage. Observe this image of a specimen of hyaline cartilage. Note the chondrocytes that occupy most of the mass of the cartilage specimen with a layer of tissue surrounding called the perichondrium. Cartilage can grow by two mechanisms. Cells in the chondrogenic layer of the perichondrium divide which increases the size of the cartilage at the perimeter. This is called appositional growth (applying new growth to the surface of cartilage). Cells within the formed cartilage matrix can still divide and thereby increase the mass of the cartilage from within. This is called interstitial growth (growth from within the cartilage). The frame encloses a portion of the perichondrium and it is shown enlarged at the right. The perichondrium that surrounds the cartilage has two components that serve to enclose the cartilage and provide precursor cells to chondrocytes. The inner part is chondrogenic containing the cartilage precursor cells. The outer part is fibrous composed of dense connective tissue that makes a compact wrapping.

platelets

The term thrombocyte is a synonym for platelet. Platelets can be seen, examined and assessed in a peripheral blood smear. Note that a platelet can be observed here but as the image suggests, this photograph was taken in a region of the blood smear other than the monolayer as evidenced by the stacking of RBCs. Here in this image, you observe the two regions within a platelet; a center that is basophilic containing granules, the granulomere, and an outer aspect that is stains pink, the hyalomere. Platelets are composed of three principal components: membrane structures, microtubules, and granules. Platelet plasma membrane with its external coat of the glycocalyx, and submembrane structures mediate responses to platelet stimulation and express specific antigenic characteristics. The surface glycoproteins variously serve as receptors, facilitate platelet adhesion and contraction, and determine expression of specific platelet antigens and antigens shared with other formed elements. One of the several functions of platelets is to control and stop micro-bleeds that occur when the endothelial lining of blood vessels is torn thus exposing collagen and initiating a sticking of platelets to seal the micro-tear.

basinophils

The top left image is what a basophil appears like most of the time when encountered in a peripheral blood smear where the smear is examined in an area other than the monolayer. The cell is not flattened enough to appreciate its histology. The other six examples serve to illustrate cells examined in the region of the monolayer. Note that you can see that the nucleus has two lobes like the eosinophil by examining the two cells on the left. Many times, as in the two cells on the right, the nucleus is obscured by the basophilic granules. We have now concluded a study of the histology of the three granulocytes; neutrophils, eosinophils and basophils. Next, the histology and function of the agranulocytes, lymphocytes and monocytes, will be presented.

lymphochytes

These examples will reinforce the distinguishing features of a lymphocyte. No segmentation of the nucleus, relative to the other leukocytes, relative small cells, and a sparse amount of cytoplasm..........and no specific granules. Examine closely the lymphocytes in the upper right and middle left frames where you can see the non-specific azurophilic granules. (These are lysosomes that are present in all white blood cells to a greater or lesser degree, thus not specific to any cell). Can you find the platelets? Look in the middle left, lower middle and lower right frames.

hematopoiesis overview

This chart displays the cell lineage (or you might say ancestry) of the formed elements of blood. Hematopoietic stem cells are multipotent stem cells. These multipotent hematopoietic stem cells are the ancestors to all the blood cell types, including myeloid (monocytes and macrophages, neutrophils, basophils, eosinophils, erythrocytes, megakaryocytes/platelets, dendritic cells), and lymphoid lineages (T-cells, B- cells, NK-cells). Hematopoietic stem cells constitute 1 in 10,000 cells in bone marrow tissue. This lecture will focus on 1) erythropoiesis - the development of erythrocytes, 2) granulopoiesis - the development of leukocytes that have specific granules, the granulocytes (neutrophils, eosinophils and basophils), and 3) thrombocytopoiesis, the development of platelets (alias thrombocytes). The development of the different kinds of lymphocytes, lymphopoiesis, will be included in the lecture on the lymphoid organs. Recent studies indicate that, in addition to hematopoietic stem cells, the marrow contains mesenchymal stem cells that can differentiate under appropriate conditions into adipocytes, liver cells, osteoblasts, and many other cell types in the body. This is an active field of research. The most recent report is that stem cells have been harvested from the soft tissue (the pulp) inside of extracted adult teeth.

neutrophil count in disease

This slide depicts the various types of neutrophils and which are more prevalent in a normal sample compared to a sample of blood from a patient with infection, leukemia, or pernicious anemia. The concept of shift to the left and shift to the right came from the fact that these different stages in the development and maturity of the neutrophil in a count were tabulated just in this way. So, the normal picture is in the middle with the most frequent type of neutrophil being the ones with nuclei having three lobes. As you can see in pernicious anemia, you have lots of old cells having 5 or more lobes in the nucleus, so this is a shift to the right. In contrast, in mild infection, you have an increased percentage of band cells (less mature) and in a more severe infection there will be even more of the immature cells like metamyelocytes, myelocytes, promyelocytes. In cases of myelogenous leukemia, all of these cells will be present in addition to many myeloblasts.

drawn blood samples

This slide illustrates the difference in the physical appearance of blood in arteries compared to veins. The test tubes contain blood that was withdrawn from an artery and a vein and immediately put into capped tubes that contained an anticoagulant such as sodium citrate to prevent the blood from clotting. One of the important functions of blood is to transport oxygen via the arterial blood vessels from the lung to cells and return carbon dioxide via the venous blood vessels from cells to the lung. Oxygen is bound to hemoglobin in red blood cells and that complex renders arterial blood bright red. Venous blood has less oxygen complexed with hemoglobin because oxygen is released for use by cells and the resulting color is dull red to blue. (Only a small percentage of carbon dioxide is bound to hemoglobin for transport; the majority of it is transported as bicarbonate ions in the plasma). It is interesting to note that blood that has hemoglobin bound to carbon monoxide forms a complex known as carboxyhemoglobin, as in carbon monoxide poisoning, resulting in a cherry-red blood color. It is extremely difficult to reverse the binding of carbon monoxide to hemoglobin and that is why exposure to carbon monoxide is life threatening.

intercalated discs in cardiac muscle cells

Three components: Fascia Adherens, Desmosomes, and Gap Junctions As illustrated in this drawing, an intercalated disc is a connection between two cardiac muscle cells where the cells interweave themselves to provide a significant surface area for attachment and ion flow between cells. There are two components in the intercalated disc, the fascia and macula adherens, that fasten one cardiac muscle to another physically so that force can be transmitted through a chain of cells. The other component is the gap junction that provides a way for ions to flow between cells so that stimulus to contract can be propagated along a chain of cells. The electron micrograph below illustrates a part of one intercalated disc. Note that they occur at the Z line at the end of both cells. Note how the intercalated disc zig zags, as indicated by the dotted line. This electron micrograph only shows about 7 or 9 myofibrils running parallel to one another, so this view is only part of a cardiac muscle cell. The electron micrograph to the right clearly shows more detail and you can see that the intercalated disc is in the middle of the I band where the Z line is located. Cardiac muscle cells function together as if they were one giant cell. This is due to the gap junctions and the coordinated functional population of cells is known as a functional syncytium.

phases of hematopoeisis

Three overlapping phases: Primordial (prehepatic) Phase: 3rd - 6th wk in-utero Blood islands in yolk sac for primitive erythroblasts Hepatosplenothymic phase: 6th wk - 6th month in-utero Liver & spleen make granular leucocytes, platelets & RBCs Spleen & Thymus make lymphocytes Medullolymphatic (definitive) phase: begins 3rd month, in-utero, hematopoiesis shifts to bone marrow and lymphoid tissue. By 5th month Medullary tissue of bone marrow is the primary site of hematopoiesis. In adult human, hematopoietic tissue ('red bone marrow') can be found in the marrow of all vertebra, ribs, clavicles, distal and proximal ends of long bones and the ilial crest of the iliac bone. There are several phases of hematopoiesis as defined by the tissue in which the process occurs. First, in the early embyro, it is taking place in the yolk sac, next, from the 6th week to the 6th month in the fetus it takes place in the liver and spleen and finally, in the newborn and adult it takes place in red bone marrow of vertebra, the sternum, ribs, clavicles, proximal and distal parts of long bones and the iliac crest of the iliac bone. Note that during in-utero development the timing frames of the three phases overlap.

peripheral nerve tissue: somatic

Tissue First some terminology clarification. Observe the terms dorsal and ventral root in the lower left drawing of a cross-section of the spinal cord. For human anatomy, it is better to use the term posterior for dorsal and anterior for ventral. The cell body of a motor neuron is located in the anterior part of the gray matter (butterfly shaped region) of the spinal cord. Its axon, surrounded by myelin, leaves the spinal cord via an anterior root and becomes part of a spinal nerve. Note at this point that an axon surrounded by myelin is a nerve fiber and a nerve is composed of many nerve fibers. The connective tissue wrappings that surround nerve fibers, wrap nerve fibers in bundles and surround the bundles and the entire nerve are called endoneurium, perineurium and epineurium, respectively. Observe the pathway of the sensory nerve from the pressure sensing receptor, the Pacinian corpuscle in the dermis of the skin, through the posterior root ganglion, posterior root and into the gray matter of the spinal cord where a synapse occurs between the terminal end of the sensory neuron and the dendrites of the motor neuron. The motor neuron axon process then emerges from the spinal cord via the anterior root and courses through a nerve until it reaches a skeletal striated muscle cells where a special terminal ending called the motor end plate makes it possible for the nerve impulse to initiate a chemical response in the muscle leading to contraction. We will now describe the architecture of a nerve fiber in detail.

organization of a muscle as an organ

Tissue Skeletal muscle tissue is composed of striated skeletal muscle cells the structure of which we now understand. For muscle tissue to be useful in moving one bone in relation to another at a joint, it must be organized and include blood vessels and nerves. This figure illustrates how an anatomically recognized muscle like the biceps, an organ, is constructed. The smallest building material resolvable with a light microscope is the skeletal muscle cell, also commonly referred to as a myofiber because the cell is shaped like a fiber, i.e., longer than it is wide and not tapered at the ends. Note the terms followed by the < signs at the bottom of this slide. One of your most important things to learn is the proper name and size of the components of a skeletal muscle beginning with one of it smallest units, the myofibril (recognizable only in an electron micrograph). Here is a cross-section of striated skeletal muscle stained with a trichrome stain that demonstrates the collagen of the endomysium and the perimysium. Observe and study the endomysium, perimysium and epimysium in this slide. These are the wrappings of connective tissue in a skeletal muscle that organizes the cells ultimately into a gross anatomical muscle.

smooth muscle in tubes with peristalsis

Tissue Smooth muscle, as a tissue is composed of smooth muscle cells connected physically by fascia adherens and desmosomes; and chemically, by gap junctions. The cells form sheets or layers in tubular organs, like in the blood vessels and the gastrointestinal tract. They function in arterioles in a coordinated way to regulate the diameter of the lumen to either increase or decrease the flow of blood. In the gastrointestinal tract, the smooth muscle cells are arranged in the outer part of the wall as you see in the light micrograph on the right where there are outer (longitudinal) and inner (circular) muscle layers. Waves of contraction move down the GI tract to move digesting food. These waves are called peristalsis.

the neurophil

Tissue The neuropil is a region between neuronal cell bodies in the gray matter of the brain and spinal cord (i.e. the central nervous system). It consists of a dense tangle of axon terminals, dendrites and glial cell processes. It is where synaptic connections are formed between branches of axons and dendrites. Observe in the specimen on the left, stained with hematoxylin and eosin, that the region between nuclei of neurons and glial cells the tissue stains eosinophilic and grainy with some faint lighter staining lines. A similar area in the specimen on the right, stained with a silver stain, reveals the complex network of axons and dendrites that make up most of the substance of the neuropil. In the left specimen, a few glial cell nuclei are indicated by the clear block arrows. Observe that one nucleus is round and darkly stained and is, most likely, an oligodendrogliocyte. The other nuclei are shaped differently and are, most likely, one of the two varieties of astrocytes. In the next two slides, the detail morphology of glial cells will be presented.

spinal cord and somatic motor neuron

Tissue This slide will present the relationship between the spinal cord and a somatic motor neuron. First, observe the drawing of the spinal cord. The butterfly shaped purplish region is the gray matter where cell bodies of neurons and the unmyelinated segments of axons are located. The lighter surrounding region of the spinal cord is the white matter where the myelinated processes of neurons are located (no cell bodies in the white matter). A somatic motor neuron is one that innervates skeletal muscle. Its cell body lies in the gray matter and its axon processes emerges from the spinal cord, is immediately now a myelinated axon. The axon process emerges in the anterior spinal nerve root and joins with other neuron processes in the spinal nerve. The posterior root of a spinal nerve contains axons of sensory nerve fibers. The axon process of the motor neuron extends to a skeletal muscle where its impulse causes the muscle to contract. Now observe the gray matter. If the boxed in area is enlarged and viewed in a specimen that was prepared by taking a sample of the gray matter, smearing it on a glass slide and staining it with a basic stain like toluidine blue. The result is that you can see the neuron cell body and its processes. In the higher magnification, you can clearly see the neuron processes. This is possible because you are looking at the whole neuron that was squashed on the slide, not sectioned. Note the nucleus and the very darkly stained nucleolus. If the tissue were prepared by embedding in paraffin, sectioned and then stained, the neuron would appear as it does in the right image. This is a tissue section. Note that you can only make out the beginning of the processes because the tissue section only presents a part of the neuron, not the whole.

bone is a living organ

Tissues in the Organ- Bone Epithelial Tissue Lining blood vessels Connective Tissue Bone tissue Reticular tissue in marrow Articular Cartilage Muscle Tissue Smooth muscle in arteries Nerve Tissue Periosteal nerves - pain Nerves of arteries & arterioles While we are focusing in this lecture on bone as a tissue, it should be recognized that when bone tissue, a specialized connective tissue, is combined with epithelial, muscle and nerve tissues an organ is formed that is living and dynamic. The dynamics of living bone include making new blood cells and serving as a flexible reservoir for calcium. Bones are hard and strong. As you learn about histology of bone you will appreciate what tissue components make bone hard and strong. articular cartilage, epiphyseal artery, metaphyseal artery, periosteal arteries, nutrient artery, compact bone, epiphysis, metaphysis, diaphysis

triads

Triads are unique to skeletal muscle. Two triads are illustrated in this slide. They are located in this specimen at the Z-line. However, in skeletal muscle, triads are located at the junction of the A & I Band, which provides two triads for each sarcomere. (this is a specimen of frog skeletal muscle having triads at the z line. Cardiac muscle has diads (one transverse tubule and one dilated cisterna of sarcoplasmic reticulum at the z line. Tissue In this slide, you see the close relationship between the T-tubule (transverse tubule) and two dilated ends of the sarcoplasmic reticulum running through the muscle between and surrounding the myofibrils. This relationship of one T-tubule and two terminal cisternae of the sarcoplasmic reticulum is called a triad. The triad in skeletal muscle of humans is located at the A and I band junction. This electron micrograph is of a specimen of frog muscle where you can see the location of the triad is at the Z line. Try to visualize how extensive the invaginated sarcolemma is to be represented throughout the muscle over and over like this. The surface area contact between the two membrane systems is very extensive. The transmission of the action potential (depolarization of the sarcolemma) from the cell surface to all points within the cell is almost instantaneous. The instantaneous release of calcium to be available to displacement of troponin C so that actin is available to bind to myosin.

coupling and excitation of contraction

What is the architecture that enables a single muscle cell to coordinate the contraction of all its sarcomeres, or in other words, how is the coupling of excitation and contraction accomplished? In this 3 dimensional drawing, you can observe the special structural invaginations of the sarcolemma called transverse tubules that carry an action potential deep inside the muscle cell. At the level of the A and I band junction, there is a close relationship between two sacs (terminal cisterna) of sarcoplasmic reticulum and a transverse tubule. The action potential is conveyed at these sites to the sarcoplasmic reticulum which causes the release of calcium. The speed at which the electrical impulse reaches the innermost part of the muscle cell is very fast. Due to the fact that the T tubules penetrate deep and throughout the cell, the spread of the excitation happens quite uniformly. The calcium causes a deformation of the actin molecule so that binding sites for the myosin heads are exposed. Once the myosin head is bound to the actin filament, the energy to contract is supplied by ATP. More details of the excitation of a skeletal muscle fiber by motor nerve stimulation and the coupling of that action potential via the transverse tubules and the sarcoplasmic reticulum to the contraction of the sarcomere is not in the scope of this course.

blood components

al Blood If one takes a sample of blood, treats it with an agent to prevent clotting (either sodium citrate or heparin) and spins it in a centrifuge, the red cells settle to the bottom and the white cells & platelets settle on top of them forming the buffy coat that is white because white cells and platelets do not contain any pigment. The 'straw-colored' plasma that contains no cells becomes the supernatant. Plasma makes up between 53-58%ofthevolumeoftheblood. The composition of plasma includes proteins dissolved in water and other substances such as electrolytes, urea, glucose, lipids, amino acids, oxygen, carbon dioxide, nitrogen, hormones and enzymes. The formed elements are the cells and cell fragments (RBCs, WBCs & Platelets). Important data to collect in a blood sample is the complete blood count, which is the number of formed elements of each kind per liter of blood (International Unit). Leukocyte range in International Units (IUs) is 4.3-10.8 x 109 cells (billions) per liter. Platelet range in IUs is 150-450 x 109 (billions) per liter. RBC range in IU is 4.2-5.9 x 1012 cells (trillions) per liter. It should be clear that the formed element present in the greatest number is the red blood cell, followed by a lesser number of platelets and the least number is the leukocyte. The fraction occupied by the red cells is called the hematocrit. Normally it is 45%. A value lower than 42% is a sign of anemia.

which of the following is is the location of the periosteal collar in bone formation

around the diaphysis of a cartilage model

cerebral cortex neurons with silver stain

astrocytes pyramidal cells

sensory ganglion

axons cell bodies capsule This is a histological section through the long axis of a posterior root sensory ganglion. Note that there are more rounded profiles or cell bodies in the peripheral region than in the center of the ganglion. The sensory nerve fibers pass through the center of the ganglion, hence the paucity of cell bodies. The sensory neurons are pseudounipolar. The nerve axon comes into the ganglion from a peripheral location. While it is passing through the ganglion, the process turns at right angles to enter a cell body where it fuses with the process that is emerging from the cell body. This process will continue into the spinal cord. Note the blue stained collagen of the connective tissue wrapping the ganglion. This connective tissue would be continuous with the epineurium. Connective tissue inside would be continuations of the perineurium and endoneurium.

osteoblast

bone forming cell Single nucleus, basophilic cytoplasm rich in RER Secretes collagen and facilitates calcium influx Location: surface bone that is increasing in size The osteoblast is always at a bone surface when it is performing its function of secreting the elements of the bone matrix, i.e. collagen fibers and proteogylcans.

osteocyte

bone maintenance cell Single nucleus, less basophilia than osteoblast Facilitates influx and reflux of calcium Can secrete matrix in response to external stimulus Embedded within the bone matrix Cytoplasmic processes reach those of other osteocytes The osteocyte is a more stable cell that resides within the matrix that it has secreted. Osteocytes are physically and chemically connected to each other at the ends of their processes.

osteoclast

bone resorption removal cell Multinucleated with an acidophilic cytoplasm Secretes collagenase to remove collagen Produces Carbonic Acid, the protons of which remove the mineral Ruffled cell border facing bone The osteoclast brings about the dissolution of bone matrix, i.e. the bone is resorbed. It secretes collagenase that disassembles collagen and protons that act as an acid to breakdown the mineral.

skeletal muscle fibers

can be red muscle, red fibers, white muscle or white fibers Skeletal muscle cells vary in the amount of glycogen, oxidative enzymes and muscle (myofibrillar) ATPase. Several skeletal muscle fiber types have been characterized by using a combination of histochemical reactions for these components. (There is extensive literature on this) . There are basically two main types, type I and II. Type I appear red because they have so much myoglobin (called slow twitch - meaning the muscle reacts slower than fast twitch) and Type II are white because they have little myoglobin but lots of glycogen (called fast twitch because they respond to a stimulus very rapidly). Note the analogy to chicken muscle with which we are all familiar. The leg meat is red and when cooked it is dark, consisting of cells with lots of mitochondria. The breast meat is white and light when cooked, consisting of very few mitochondria but lots of glycogen. Chickens can run fast for a much longer distance than they can fly. White fast twitch fibers fatigue easily because the glycogen stored in the cell depletes rapidly. If any of you listening has hunted ducks, you know that the breast muscles of ducks are very red containing a very high density of myoglobin and mitochondria. Ducks can fly for very long distances. Their breast muscles have great endurance.

the key event that is under the direct influence of growth hormone that begins the process of closure of the epiphyseal plate is which of the following

cartilage cell stops dividing

closure of the epipyseal plate

cartilage proliferation stops and bone eventually fuses The drawing illustrates a long bone in which all of the growth has ceased in the epiphyseal plates. Observe the two epiphyses at the top of this bone and see the epiphyseal lines that represent where the active plates were located. Now the epiphyses have fused with the diaphysis in a solid bone. Growth hormone maintains an active proliferation of chondroblasts in the proliferationzoneoftheepiphysealplate. Whenthe levels of growth hormone decrease significantly in early adult life (varies from late teens to early 20s), the proliferation of cartilage ceases and the cartilage present at that time is all converted into bone. The transformation histologically looks like this. Note the zones are visible in the histological specimen of the an active epiphyseal plate at the top and at the bottom, the bone is in the process of fusion. Once cartilage proliferation ceases the bone no longer grows in length. Thus, increase in height of the individual ceases.

pluripotent

cell can differentiate into any of the three germ layers- ectoderm, mesoderm or endoderm.

bone tissue composition

cells like the osteoblasts found at bone surface and the osteocytes embedded in matrix. in the matrix there is fibers, collagen type 1 that are responsible for acidophilia, also ground substance bone mineral like calcium hydroxyapatite This image is a specimen of newly formed bone stained with the hematoxylin and eosin stain. Observe the osteoblasts at the surface of the bone tissue. Observe also the osteocytes embedded in the bone matrix. These osteocytes were once on the surface of bone as osteoblasts. Osteoblasts secrete bone matrix and as a result, they surround themselves with the growing bone that is due to the accumulation of matrix. The matrix, composed of fibers and ground substance is acidophilic, staining with eosin, due to the high density of collagen. The preparation of this bone specimen included removing the mineral with the use of acid so that the specimen could be embedded in paraffin and sectioned. The mineral, if left in would be basophilic due to the calcium component of the mineral.

fibrinogen to fibrin

clotted and unclotted blood Here you see an illustration of the entrapment of red blood cells by fibrin. This is a highly magnified image produced and photographed with a Scanning Electron Microscope (an instrument that magnifies the surface of structure). Note the fibrin strands. They are very sticky as this image suggests.

maintaining skeletal muscle cell integrity

cytoskeletal protective network of a skeletal muscle cells The role of the intermediate filament, desmin, in skeletal muscle is to keep myofibrils in register to each other and to the sarcolemma All of the sarcomeres in adjacent myofibrils are kept in register which results in the typical appearance of a striated skeletal muscle cell as seen in this light micrograph. So, how is this accomplished? The adjacent myofibrils are bound to each other by special proteins at the Z discs, and ultimately, the whole entirety of the myofibrillar complex is fastened through the sarcolemma to the extracellular matrix. This is accomplished by several proteins that make up an intermediate filament complex. One of the most widely used proteins is desmin which makes up the intermediate filaments that bind to the actin binding protein (alpha-actin) of the Z disks. The drawing clearly shows this relationship. Note that Plectin assembles the desmin filaments into a network between the myofibrils. This is how the myofibrils are anchored together. Now, we need to understand how the entire complex of desmin bound myofibrils are anchored into the extra-cellular matrix. The next slide illustrates this and the cause of muscular dystrophies as well.

pyramidal cell

dendritic synapses dendrites ascending axon descending axon

smooth muscle cell TEM longitudinal section smooth muscle fiber transverse section

dense bodies When viewed with an electron microscope, it is confirmed that smooth muscle cells do not exhibit any striations. There are, however, actin and myosin filaments and Z disc like material in smooth muscle cells. The z disc like material is scattered throughout the cell and at the sarcolemma as seen as dense bodies in the right electron micrograph. On the next slide, these dense bodies in the cell and at the cell membrane are illustrated and explained in relationship to how smooth muscle cells contract and relax. TEM- Longitudinal Section Smooth Muscle Fiber- Transverse Section dense bodies

anatomy of long bone

diaphysis between growth centers epiphysis upon the growth centers epiphyseal line is the site of growth long bone articular cartilage, epiphyseal line, spongy bone, medullary cavity, nutrient foramen, endosteum, periosteum, articular cartilage, blood vessel A long bone is composed of a shaft and two epiphyses. The epiphyses are located at either end of the bone where the bone is covered with hyaline cartilage (articular cartilage). The epiphyses and diaphysis are composed of compact and cancellous bone tissue. The rectangular area is enlarged in this diagrammatic representation of the organization and orientation of the osteons in the shaft of a long bone. It is important to realize that these osteons are oriented parallel to the long axis of the diaphysis. In this way, they function similar to support pillars or columns of a building. Thus, our long bones, especially of the lower limb, accomplish the bearing of our weight by the structure and orientation of the Haversian systems (the osteons). The periosteum functions to wrap the bone with connective tissue, provide nerve fibers for pain sensation and osteoprogenitor cells for bone repair in case of breakage. The endosteum is a delicate connective tissue containing osteoprogenitor cells, that in active bone production transform into osteoblasts.

distribution of the three types of cartilage

elastic cartilage: -pinna of the ear -pharyngotympanic tube -certain laryngeal cartilages hyaline cartilage -cartilage of nose -cartilage of upper respiratory passage -costal cartilages fibrous cartilage -intervertebral discs -pubic symphysis -meniscus of knee -insertion of achilles tendon articular cartilage -pubic symphysis -meniscus of knee -insertion of achilles tendon

which of the following blood components transports oxygen

erythrocytes

a smooth muscle cell is striated, but compared to a skeletal or cardiac muscle cell, the striations in a smooth muscle cell are only just under the cell membrane

false

an isogenous group in cartilage tissue is a group of collagen fibers arranged radially around a chondrocyte

false

red marrow is found in the diaphysis of long bones

false

the hepatosplenothymic phase of hematopoeiesis is the phase where hematopoietic tissue is located in the marrow of vertebra, the ribs, clavicles, distal, and proximal ends of long bones and the ilial crest of the iliac bone

false

the histological architecture of woven bone includes osteons

false

the parts of a neuron are the axon, the dendrite, and the ganglion

false

there is one epiphysis and two diaphysis in a long bone

false

thrombocyte is a synonym for erythrocyte

false

normal bone marrow core biopsy at high power

fat cell megakaryocytes This is a specimen of bone marrow that was obtained by using a large bore needle that was inserted through the bone into the marrow. When the needle is withdrawn the needle contains bone marrow tissue. This is called a Marrow Core Biopsy. The tissue is then processed for paraffin embedding and staining with a variant of Wright's blood stain. Note the presence of fat cells. Even in red marrow, where hematopoiesis is taking place, fat cells have a presence; they just do not dominant the tissue. Note the two megakaryocytes that are indicated. These cells make platelets by breaking off small bits of their cytoplasm. If you look very carefully, you can see many cells that have u-shaped or (band-shaped) nuclei. These are band or juvenile neutrophils. Other cells have round nuclei and these cells belong to a series of cells that develop into red blood cells. So this is what hematopoietic tissue in bone marrow looks like. Another method of preparing bone marrow for study is to make a smear. This can be done with a bit of the core sample by squeezing a small bit on a cover slip and then placing a second cover slip on top at an angle to the first. The two cover slips are slid apart and this produces a smear in which the detail of the cells can be seen at high magnification similar to examination of a peripheral blood smear.

peripheral blood smear

feathered edge This is how a peripheral blood smear looks after being created. The original drop of blood can be seen on the left. From that point to the far right, the stained preparation gets lighter. That is because the number of cell layers is decreasing until just in back of the edge (called the feathered edge because it looks like a feather and is created by columns of cells being dragged out between columns where there are no cells. Just before the feathered edge is the location of cells that were deposited in a monolayer. This is the best area to examine the blood smear. Thus, when viewed in the microscope with a 100x objective lens (with a 10x eyepiece) at a magnification of 1,000x one can examine the shape, size and staining of peripheral blood cells.

osteoclasts and bone remodeling

functional secretory domain, basolateral membrane, sealing zone, bone, resoprtion lacuna, ruffled border, nuclei These light micrographs are from bone tissue that has been fixed, embedded, sectioned, and stained with hematoxylin and eosin. The bone spicule shown in the micrograph on the left is being remodeled. Note the osteoblasts on the surface of the bone indicated by the solid arrow where they are tall and are adding to the bone. Now observe the osteoclast on the lower right side of the spicule indicated by the transparent arrow. The osteoclast is resorbing bone matrix. Now observe the enlargement of this area in the upper light micrograph where you can see a pale region at the tip of the short arrow. This is a Howship's lacuna. As an osteoclast resorbs bone, it creates a tiny crater - Howship 's Lacuna. At the tip of the black arrow, you can observe the bottom of this tiny crater above which is a clear area where processes of the osteoclast interdigitate with matrix that is being dissolved. Specifically, collagen is being degraded with collagenase and by the secretion of carbonic acid, bone mineral crystals are being broken down into calcium, phosphate and water. As you can see illustrated in the drawing (lower right), the osteoclast fixes itself to the bone matrix. Properly anchored, it begins its work that soon creates the small crater. The surface interacting with the bone matrix is ruffled, i.e. large processes interdigitate with the dissolving bone matrix to increase the surface area for its action upon bone matrix.

abnormal bone growth

gigantism and dwarfism is an excess or deficiency of growth hormone during normal growth period acromegaly is when bones become thicker due to GH induced apositional growth excess growth hormone after normal growth period Human growth hormone has an effect on bone length and mass during the years leading to adulthood. Human growth hormone is described by some as the key to slowing the aging process. Before you sign up, get the facts — and understand proven ways to promote healthy aging. Growth hormone levels throughout the life of an individual vary. It is at its highest level during the growth spurt of the teen age years. There is little evidence that taking growth hormone as an adult actually slows the aging process and may do harm. Growth hormone, produced by cells in the anterior pituitary, is a major factor in causing and maintaining the proliferation of cartilage cells in the epiphysis of bones that are growing longer. . During the growth and development of childhood to early adult life, if there is too little of this hormone available, then individuals will be shorter to the extreme case of a dwarf; if too much and over a longer than normal period of time, then individuals will be unusually tall (gigantism). During adult life, after the epiphyses have closed, if excess growth hormone is produced, then bones will grow by the only method that they can and that is by appositional growth, applying new bone to the surface of existing bones. This will result in bones becoming thicker. The cause can be traced to an abnormal proliferation of acidophils in the anterior pituitary which results in excess growth hormone. The thickening of the bones, especially of the head and hands, is known as acromegaly. The common cause of acromegaly is a tumor in the pituitary of the cells that produce growth hormone - producing abnormal amounts in the adult. The treatment, if discovered early, is to remove the tumor.

leukocyte family

granulocyte agranulocyte Now we will learn about the Leukocytes. One drop of blood can contain up to 10,500 leukocytes. Leuco, also can be spelled Leuko, is a Greek term meaning white, thus its use in blood cell terminology. Leukocytes are cells of the blood, that when examined in the fresh unstained state, are white. Recall that the buffy coat in a centrifuged tube sample of blood is that thin white layer on top of the packed red blood cells and that it contains white blood cells and platelets. White blood cells belong to a family that includes cells having granules, Granulocytes and those that have no granules, Agranulocyates. Granulocytes have specific granules that are either very neutral in staining-the neutrophil, are red-the eosinophil, or are blue-the basophil, thus the neutrophil, eosinophil and basophil, respectively. Agranulocytes include two sizes of lymphocytes and the very large monocyte. One very important fact to learn is that all of these white blood cells do not perform their various functions while in the blood vessels. Blood vessels just serve to transport them. They must migrate from the blood vessels into the tissues where they perform the various functions you will learn in the next few slides.

the primary component of red bone marrow

hematopoietic tissue

the basophilic erythrocyte stage of erythocyte development is characterized by which of the following

high density of ribosomes

immature vs mature bone

immature is woven. the bone is formed in the fetus and structure appears woven. it contains high density of cells. mature bone is lamellar bone. it is cancellous spongy arranged in spicules. it is also compact arranged in osteons In the fetus when bone is first forming, the structure is like a woven rug or cloth. The structure of bone at that stage does not appear very organized as you can observe in the top drawing. In the newborn, bone begins an extensive remodeling process that produces tunnels through the woven, immature bone by the action of bone destroying cells osteoclasts and then depositing new bone with bone making cells in order to produce the pattern that you can observe in the lower diagram. You can see the concentric pattern of the layers or lamellae of bone matrix with the cells embedded in the matrix in a circumferential pattern that forms a 3 dimensional structure named an osteon. In a 2 dimensional tissue section, the osteon resembles our solar system. This lecture will provide more detail about the two types of adult bone, cancellous and compact.

muscular dystrophy

is caused by a defect in the gene for dystrophin that weakens the link between the cytoskeleton and the extracellular matrix which results in a disarray of myosin and actin filaments leading to myofiber degeneration. Study the relationship of the desmin bound myofibrils to the molecule dystrophin, the dystrophin complex and laminin 2 and you will see a continuity of molecules that connect the myofibril complex to the extracellular matrix. Dystrophin is a protein of around 430 kDaltons that forms a robust perimeter surrounding the myofibril complex. Dystrophin is then bound to a complex integral membrane protein called the dystroglycan complex which, in turn, is linked to laminin-2. Laminin-2 is anchored into the extracellular matrix via of linking fibers of the connective tissue. During muscle contraction, this complex arrangement of desmin intermediate filaments linked via dystrophin to the extra-cellular matrix keeps the muscle cell from tearing its cell membrane when contraction of the sarcomeres occurs. A defect in dystrophin, the dystroglycan complex, or laminin-2 will make the muscle cell fragile, resulting in the myofibrils becoming disoriented and eventually, the sarcolemma ruptures allowing extra-cellular calcium to rush into the cell. This initiates degeneration of the skeletal muscle cell, an event that occurs over and over in children with muscular dystrophy. This is what a specimen of muscle from a normal person would look like. It is a cross- section of the skeletal muscle showing a uniform staining and all nuclei at the edge of the cell just below the cell membrane (sarcolemma). This is what a specimen taken from a patient with Muscular Dystrophy would look like stained also with hematoxylin and eosin. Note the variable diameters of the cells, the non-uniformity in staining and that some cells have nuclei within the muscle cells. The disastrous results of the reoccurring phenomenon are delayed for a variable number of years, due to the fact that skeletal muscle cells can be replaced by regeneration of muscle fibers until the system is overwhelmed.

CNS glial cell: microglia

issue Microglia are very small cells that are analogous to macrophages in loose connective tissue. These cells have very small, flat, heterochromatic nuclei. They are derived from the blood monocyte and belong to the mononuclear phagocytic system. Microglia are a type of glial cells that are the resident macrophages of the brain and spinal cord, and thus, act as the first and main form of active immune defense in the central nervous system (CNS). Microglia constitute 20% of the total glial cell population within the brain. Microglia are constantly searching the CNS for damaged neurons, plaques, and infectious agents. The brain and spinal cord are considered "immune privileged" organs, in that they are separated from the rest of the body by a series of endothelial cells known as the blood-brain barrier, which prevents most infections from reaching the vulnerable nervous tissue. In the case where infectious agents are directly introduced to the brain or cross the blood-brain barrier, microglial cells must react quickly to decrease inflammation and destroy the infectious agents before they damage the sensitive neural tissue. Due to the unavailability of antibodies from the rest of the body (few antibodies cross the blood brain barrier due to their large size), microglia must be able to recognize foreign bodies, swallow them, and act as antigen- presenting cells activating T-cells. Since this process must be done quickly to prevent potentially fatal damage, microglia are extremely sensitive to even small pathological changes in the CNS.

cerebral cortex neurons layers

issue The cerebral cortex is the gray matter that extends and covers both cerebral hemispheres of the brain (blue stained regions in this image). Inspection with the microscope of a rectangular portion of the cerebral cortex reveals multiple layers of neurons, small and large, with processes and supporting cells. The largest neurons in the cerebral cortex are the pyramidal cells and they are motor neurons that initiate movement in skeletal muscle (there is a motor neuron between these and skeletal muscle and those are the motor neurons in the spinal cord with which the axons of these pyramidal cells synapse). If a specimen is stained with silver the cell bodies and processes of the pyramidal cells can be visualized. However, if the specimen is stained with toluidine blue that stains Nissl substance, then the cell body and only a short segment of any process can be seen. The cortex of the cerebellum contains the cell with the most extensive branching of dendrites in the central nervous system - the Purkinje cell.

central nervous system

issue This slide will walk you through the steps of removing and preparing the CNS, in this case the brain, for observation, grossly and microscopically. The brain is prepared for examination by removing from the skull and sectioning in one of three planes -coronal, horizontal or sagittal as illustrated here. A mid- coronal section would start about where the arrow indicates. After removing the brain and making the mid-coronal section, the fresh, unstained specimen would look like this. Observe the gray and white regions, the gray and white matter, respectively. In this photograph of the gross brain, the gray matter looks gray and it is located outside of the white matter that appears white. The term gray may appear as grey in some texts and the literature. Traditionally, grey has been used to refer to color in nature and gray, to inanimate objects such as paint. However, today, gray is the more conventional term. The gray matter is where all of the cell bodies of the approximately 100 billion neurons are located. The white matter is where the processes of those neurons, mostly axons, are located. The axons are myelinated as demonstrated in the next specimen that was fixed and then stained for lipid that marks the location of the myelinated axons in the white matter that is stained black. The next specimen, lower right, was fixed and then stained bluish for neuron cell bodies. You can see that most of the cell bodies of the neurons are located in the gray matter. The location of the gray and white matter in the spinal cord is just the opposite of what it is in the brain. This specimen demonstrates that. It was stained with Luxol Blue and Neutral Red. The Neutral Red stains neuron cell bodies and the Luxol Blue stains myelinated nerve axons blue. You can see here that the blue stained myelin in the white matter is on the outside. On the next slide, a look into the detail of neurons in the gray matter of the brain will be undertaken.

cell ganglion cells

lipofuscin pigment Here you see several examples of sensory ganglion cell bodies within a sensory ganglion. They are pseudounipolar neurons and their most characteristic feature is that the nucleus is located in the center of each cell. The smaller cells outside of the cell bodies are satellite cells which are actually continuation of the Schwann cells and are modified to cover and insulate the cell body. Other cells would be fibroblasts and endothelial cells lining capillaries and other small blood vessels. Note the lipofuscin pigment which is a collection of residual bodies. These are accumulations of undigested organelles. The pigment increases with age. Neurons never divide. They are never renewed. The organelles are systematically renewed. Accumulation of lipofuscin pigment is somewhat indicative of aging neurons.

site of endochondral bone formation

long bone is the location of endochondral bone formation between the diaphysis and the epiphysis. after growth stops, epiphysis fuses with diaphysis, only an line is present between diaphysis and epiphysis Before we deal with the other type of bone formation, endochondral bone formation, a knowledge of the anatomy of a long bone is important to understand where this type of bone formation takes place and how, during the growth of children through the teens and early adulthood, the bones grow in length. A long bone is composed of a shaft and two epiphyses. The epiphyses are located at either end of the bone where the bone is covered with hyaline cartilage (articular cartilage). In a growing long bone, there is a dynamic structure called the epiphyseal plate where cartilage is proliferating and being replaced by bone as the bone grows in length. In this drawing, the epiphyses at both ends have fused with the diaphysis so that no more growth is possible. There is just a line called the epiphyseal line where the plate was located previously. The next few slides will illustrate the histology of endochondral bone formation in an active epiphyseal plate and then you will understand what takes place prior to the fusion of an epiphysis with a diaphysis.

Long bone vs short bones

long bones are spongy bone, compact bone, epiphyseal line, medullary cavity short bones are metacarpals, spongy bone, compact bone Bones are organs that contain blood vessels and nerves. As you can see in the two frames illustrating long and short bones, their architecture includes a solid component that is dense and a component that looks spongy. All bones are composed of cells, fibers and ground substance similar to cartilage except that, in bones, the matrix is hard because it has a large presence of calcium in the form of hydrated calcium phosphate crystals. Note the structure of long bones - that they have a cavity in the center that contains bone marrow, that the perimeter of the bone is very dense, that, at either end, the bone shows tiny spaces with bone between that reminds one of a sponge. Long bones include bones of the arms and legs, the long bones of the hand and foot -tarsals and carpals. Observe that the structure of short bones is similar in that they are composed of both dense and spongy like bone. These are the metacarpals of the wrist, metatarsals of the ankle and the patella (knee cap). The bones of the skull are flat bones. They are constructed similar to short bones - an outer part that is compact and an inner part that is spongy.

intramembranous bone formation

mesenchyme patterning signals mesenchymal cells blood vessel bone blastema osteocytes osteoblasts bone matrix osteoid primary bone tissue mineralization osteoclast Intramembranous bone formation begins in a condensation (or gathering) of mesenchymal cells in embryonic connective (mesenchymal) tissue. Mesenchymal cells differentiate into osteoblasts. The osteoblasts organize around a central area and begin to secrete matrix in which some become embedded early in the process. This produces a structure composed of bone matrix and entrapped osteoblasts now properly named osteocytes. This structure is called a bone blastema. The next step is the influx of calcium, phosphate and water that forms crystals of calcium hydroxyapatite , Ca10(PO4)6(OH)2, that begins the process of mineralization. Now the structure is called primary bone tissue.

granulopoiesis

neutrophilic myelocyte, metamyelocyte, segmented neutrophil, The story of the formation of a granulocyte white blood cell is one of nuclear shape change and the formation of specific granules. Neutrophils, eosinophils and basophils all take the same steps with the exception that each of these cell types has different specific granules and the nuclei of mature eosinophils and basophils have only two lobes (bi-lobed nuclei). The first stage is the promyelocyte characterized by numerous azurophilic granules (lysosomes) and a nucleus with several nucleoli. The azurophilic (blue) granules in the cytoplasm are not specific and many of them will disappear as the cell proceeds in development. The next stage is characterized by the sudden appearance of specific granules, in this case of a developing neutrophil you see salmon colored areas appearing the azurophilic granules much less in number. The next stage is the metamyelocyte characterized by a nucleus that is becoming indented and more neutrophilic granules. Finally, the mature neutrophil, the segmented neutrophil has a segmented (lobed) nucleus and is full of salmon colored neutrophilic specific granules. Looking back to the promyelocyte, you may be asking "why is the nucleus tinted reddish?", a logical question because you have learned nuclei are basophilic. In the early stages of leukocyte development the histones, that make up the core protein around which DNA is wrapped, is more exposed until the DNA becomes tightly wrapped. Histone protein is basic, thus explaining the slight acidophilia. If the developing cells shown here were going to be basophils or eosinophils, basophilic or eosinophilic granules would appear at the myelocyte stage. Also, instead of segmented nuclei the nuclei of these cells would only have two lobes.

somatic peripheral nerve fiber

node or ranvier internodal segment myelin sheath axon The myelin sheath of myelinated nerve fibers is segmented. Each Schwann cell myelinates approximately a 1 mm segment of the axon. These are named internodal segments of the axon. Between the segments are regions where there is no myelin present. These are called the Nodes of Ranvier. This drawing shows the detail of a node of Ranvier where the myelin sheath terminates in the internodal segment on either side of the node exposing the plasma membrane of the axon. This specimen stained for myelin (dark blue reaction) shows the lack of myelin at the node indicated by the arrow. This architecture provides an amplification of the speed of conduction of the nerve impulse traveling along an axon. The nerve impulse 'jumps' from node to node along the myelinated axon, known as saltatory (also known as discontinuous) conduction. Voltage reversal can only occur at the nodes where the axon plasma membrane (axolemma) is exposed to the extracellular fluids where the membrane possesses a high concentration of voltage-gated sodium and potassium channels. The speed of conduction is directly related to the diameter of the axon and the thickness of the myelin sheath.

three bone tissue cells

osteoblasts, osteocytes, osteoclast

cancellous spongy bone

osteocyte lamellae osteoblasts osteoid The terms cancellous and spongy refer to the fact that the bone matrix forms a network of bone with other tissue (bone marrow) interposed between the spicules of bone. The tissue between also contains blood vessels. The image on the left shows cancellous bone as it would appear if the bone were extracted from the body and dried. Only the hard bone tissue would be left. It closely resembles a sponge. The framework of the sponge is composed of adult lamellar bone. The image on the right is how a single bone spicule (part of the framework) would appear if the bone were fixed, decalcified, sectioned and stained with hematoxylin and eosin. If you observe closely, you can just make out the layered composition of the spicule of bone. The osteocytes (bone cells) are entrapped in the acidophilic matrix and also are arranged in layers along with the lamellae. Osteoblasts are on the surface of the bone and in this specimen, they are especially robust on the lower side of the bone spicule. These osteoblasts (bone forming cells) have produced new matrix that has not yet mineralized. The lighter pink staining (acidophilic) layer at the surface of this bone spicule is the newly formed matrix that is called osteoid.

two views of an osteon

osteon 1 is a decalcified specimen and note concentric lamellae and canaliculi not visible osteon 2 is ground bone specimen and note concentric lamellae and canaliculi are readily visible lacuna, canaliculi, haversian canal This slide shows two views of an osteon. The top image is an osteon as viewed in a histological section after decalcification (removing the bone mineral) and staining with hematoxylin and eosin. The bottom image is an osteon as viewed in a section of bone not decalcified that was prepared by grinding the bone specimen until it was very thin. The dark regions are where only air is present. The dark ovoid shaped areas are the lacunae where osteocytres reside in the living bone. The dark thin lines are the canaliculi where the processes of the osteocytes reside in the living bone. The lighter parts of the specimen represent the solid bone matrix- the mineralized matrix that behaves like glass transmitting light directly rather than scattering light where air is present. Finally, in the center of the osteon is a canal appearing dark here because mostly air is present because the blood vessel it contained in the living bone has dried and shrunk.

compact (dense) bone

osteon is the building unit of dense bone osteon concentric rings of bone lamellae nutrient flow by bucket brigade passing on of minerals haversian canal with vessel The lamellae of compact bone are not arranged in parallel layers as they are in cancellous bone. The lamellae of compact bone are arranged in concentric layers that surround a canal that contains a blood vessel. The canal is called the Haversian canal. This pattern is called an osteon. The osteocytes are located in the matrix and arranged in the same concentric pattern around the vessel in layers. Osteocytes reside in little cavities called lacunae and their processes reach to each other through little canals called canaliculi. Nutrients in tissue fluid can flow from the vessel to osteocyte to osteocyte to osteocyte etc., until the outer perimeter of the osteon is reached. In this way, the outermost osteocyte can receive the oxygen and nutrients it needs to perform its function of bone matrix maintenance and regulation of calcium flux.

compact bone organization

osteons are long adn cylindrical, made up of concentrically organized bone matrix and contain a blood vessel within their haversian canals. those are lateral vessels connecting haversian blood vessels travel through volkmanns canals. The concentric lamellae and the Haversian canal that they surround constitute an osteon (also named a Haversian system). One of the Haversian systems in this diagram is drawn as an elongated cylindrical structure rising above the plane of the bone section. It consists of several concentric lamellae that have been partially removed to show the perpendicular orientation of collagen fibers in adjacent layers. Interstitial lamellae result from bone remodeling and formation of new Haversian systems. The inner and outer surfaces of the compact bone in this illustration show additional lamellae - the outer and inner circumferential lamellae - that are arranged in broad parallel layers, not concentric as in the osteons. Observe the blue colored inner and outer surfaces of the bone in this diagram. The outer surface is covered with a tissue that is similar to the perichondrium that surrounds cartilage. This tissue covering bone is called the periosteum. It consists of an outer part that is composed of dense connective tissue and an inner part that contains bone forming precursor cells - the osteoprogenitor cells. The inner surface is covered with only a cellular layer consisting also of osteoprogenitor cells called the endosteum. Observe the blood vessels in the Haverisan canals that course through the bone in the longitudinal plane and the vessels that connect between the Haversian vessels through canals called Volkmann's canals osteonal artery, collagen fibers, inner circumferential lamellae, endosteum, volkmanns canal, lamellae of bone, osteonal endosteum, haversian canal, osteocyte and lacuna, periosteum, outer circumferential lamellae, osteon

which is the most basophilic component of hyaline cartilage

pericellular matrix

the arrows indicate which of the following in the cross section of a nerve

perineurium

which of the following blood components do not migrate into tissues as part of their normal function

platelets

analysis of a blood sample

ral Blood A blood sample may be evaluated for normal/abnormal features by one of two manual methods and an automated one. A visual inspecition can be done to evaluate RBC color/light center for anemia, estimate of fewer or more cells than normal, and perform a differential WBC count on a blood smear. A device known as a hemocytometer can be used to make a quantative determination of total number RBCs & WBCs, by counting diluted sample in known volume of blood under grids of a 0.1mm deep chamber. Automated counting is used in all clinical blood labs today. Even though automated blood analysis is quick and efficient, the instruments cannot determine the shape of the red cells. Shape is very important in the diagnosis of sickle cell disease and spherocytosis that would suggest an abnormality in the cytoskeletal structure of an erythrocyte. Also, the solution used to dilute the blood samples often causes platelets to clump. The Coulter Counter counts an aggregate of platelets as one platelet. For these reasons, it is estimated that about 30% of the time, a cytological technician in a clinical blood lab will need to examine a stained blood smear under the microscope to resolve these findings. A specialist medical doctor, a hematologist, would then sign off on the cyto-technicians report.

red blood cell variants

ral Blood Erythrocytes are affected by the salt concentration of the fluid that they are in whether it be in the intact human body blood vessels or in test tube solutions. The normal concentration of salt in a solution is said to be isotonic and the RBCs are the normal biconcave discs. Erythrocytes in hypertonic solutions are star- shaped cells (crenated) that have pointed projections due to the fact that the cytoskeletal microtubules and filaments are forced into abnormal shapes. In hypotonic solutions, erythrocytes swell taking on a spherical shape. Aside from tonicity, in blood vessels, if the blood is not flowing and also not clotted, then the erythrocytes stack upon each other similar to a stack of coins. This is known as 'rouleaux formation. The average capillary is around 5.5 - 6.0 micrometers in diameter. Normal erythrocytes 7.5 micrometers in diameter. Normal erythrocytes are flexible so that they can change their shape in order to flow smoothly through the narrow capillaries. They become bullet-shaped as illustrated in this slide. There are several diseases that cause abnormally shaped erythrocytes. One is sickle cell disease in which a substitution of the amino acid, glutamine, with valine in the beta chain of hemoglobin causes a dramatic change in shape so that they look like 'sickles'. Another disease is an inherited abnormality of the protein spectrin resulting in erythrocytes shaped like spheres similar to that caused by placing them in a hypotonic solution. Erythrocytes in both of these pathological conditions are not flexible and therefore, capillaries become congested or blocked to blood flow causing local hypoxia.

blood clot

resembles a connective tissue RBCs, WBCs & Platelets entrapped in a fibrin network This is a scanning electron micrograph of a blood clot. Note the network of fibrin containing fibers. There are actually no white blood cells visible in this photograph of a clot. There are three platelets visible indicated by arrows. Platelets are 2 - 4 micrometers in diameter compared to 7.5 micrometers for red blood cells (erythrocytes).

epiphyseal plate at low magnifaction

tibia- epiphysis epiphyseal plate- hyaline cartilage This slide shows the epiphysis and part of the diaphysis of a long bone at low and high magnification. The epiphyseal plate remains functioning until the end of growth in height of a human being which is reached anywhere from late teens to early the 20s. The epiphyseal plate is under the influence of growth hormone from the pituitary gland. When growth hormone diminishes, the epiphyseal plate will be no more. Only a line of dense bone will remain.

the multipolar neuron

typical motor neuron Cell Body (perikaryon) Nissl bodies (RER) Nucleus Processes Dentrites Impulses to cell body Axons Impulses away from cell body A motor neuron illustrates the typical morphology of a multipolar neuron. It has a cell body (the so-called perikaryon - the part that surrounds the nucleus) that contains the nucleus and organelles that maintain the cell, e.g. the Nissl bodies that are composed of rough endoplasmic reticulum that synthesizes the protein component of enzymes like acetycholinesterase. Common to all neurons are processes that extend from the cell body. Most neurons have one axon, usually the longest process, that transmits impulses away from the cell body. Most neurons have many dendrites (range is from 1,000 to 10,000), shorter processes that transmit impulses to the cell body. Many neurons, but not all, have axons that have a coating of lipid called myelin that is colored yellow in the drawing. If an axon is wrapped in myelin, it is properly referred to as a myelinated axon. Myelin insulates the axon from the extracellular environment. The myelin is made by oligodendrocytes in the CNS and by Schwann cells in the PNS. Observe in the drawing that there is line drawn between the central and peripheral nervous system. While there are many, many neurons that have all of their parts within the central nervous system, there are also many neurons that have their cell bodies and part of their axonal processes in the peripheral nervous system.

autonomic nerve fibers

unmyelinated one schwann cell wraps axons but does not make a myelin sheath slow conducting found as parasympathetic and sympathetic nerve fibers in the case of autonomic nerve fibers, a single Schwann cell either wraps one axon or multiple axons of autonomic nerve fibers with no deposition of myelin. Observe the drawing that depicts one Schwann cell wrapping multiple axons. Thetransmissionelectronmicrograph below shows one myelinated axon (M) and two views of unmyelinated axons. Above is a single axon wrapped by a Schwann cell and below are multiple axons wrapped by one Schwann cell. Autonomic nerve fibers are much smaller in diameter than somatic nerve fibers so, with no myelin the conduction of the nerve impulse is very slow. This is perfectly okay because the types of cells innervated like smooth muscle cells do not need to contract rapidly and adjustments occur over time.

nucleus

when referring to cell bodies is a collection of cell bodies within the brain or spinal cord. Note carefully the distinction between a ganglion and a nucleus when referring to a collection of neuron cell bodies. In this case, the term nucleus or pleural, nuclei does not refer to the nucleus inside a cell. In the brain and spinal cord, there are concentrations or grouping of cell bodies in specific locations and these are appropriately referred to as 'nuclei' such as the red nucleus of the basal ganglia or the intermedio-lateral nucleus of the spinal cord gray matter.

choose the correct identification of the muscle structure indicated by the arrow

z line disc