Histology

Muscle fascicle

A group of fibers surrounded by a thicker connective tissue sheath, the perimysium

Cell death

Apoptosis: programmed cell death Oncosis/necrosis: accidental death caused by pathological processes

Plasma cells

Are derived from B cells They have an eccentrically placed nucleus, contain abundant amounts of RER, and have a well-developed Golgi. Produce antibodies (immunoglobulins)

Fenestrated without diaphragms

Are found in the glomeruli of kidneys and allow passage of larger products (i.e. proteins)

Interstitial lamellae

Are remnants of concentric lamellae previously comprising osteons that were worn away in the remodeling process Interspersed between complete Haversian systems

Perineurium

Connective tissue and flattened epithelial cells that surrounds each bundle (fasicle) of nerve fibers. Cells are joined by tight junctions to provide a barrier to passage of most macromolecules (blood nerve barrier)

Eosinophil

Considered a transient cell in CT since under normal conditions, it is seen only in the intestinal tract. Involved in parasitic infections and allergic reactions. Cytoplasm is filled with electron-dense granules that contain major basic protein, which is toxic to parasites. These granules appear bright orange-red and account for the eosinophilia of the cytoplasm. The nucleus is typically bi-lobed.

Spongy or cancellous bone

Consists chiefly of trabeculae with relatively large spaces between them

Dura mater (pachymeninges)

Dense irregular connective tissue. There is an epidural space above and a subdural space below.

Osteogenesis

During fetal life and early childhood bone forms in 2 ways: 1. Intramembraneous bone formation 2. Endochondral bone formation

Intramembraneous bone formation

During the 2nd month of embryonic life, osteoprogenitor cells and then osteoblasts develop from a bed of mesenchymal connective tissue. The osteoblasts lay down osteoid, which becomes calcified; irregular bony plates and trabeculae form around primitive marrow spaces, and later compact bone forms externally. Occurs in frontal and parietal bones, and parts of the mandible, maxilla, occipital, and temporal bones.

Alveoli

Each alveoli wall usually lies between 2 neighboring alveoli and is called an inter-alveolar septum. An alveolar septum consists of 2 thin squamous epithelial layers between which lie capillaries, fibroblasts, elastic and reticular fibers, and macrophages. The inter-alveolar septum may contain 1 or more pores known as the pores of Kohn. These pores connect neighboring alveoli and can equalize pressure or allow collateral circulation when an alveolus is blocked.

Cells of connective tissue

Fibroblast, macrophage, mast cell, eosinophil, lymphocyte, plasma cell

Microvilli

Fingerlike projections on the apical surface of cells, increase surface area of cells up to 25X, common on epithelial cells but especially on absorptive cells where it has a thick glycocalyx, MICROVILLI + GLYCOCALYX = BRUSH BORDER, core of actin filaments linked by other proteins, actin filaments extend into the body of the cell where they form a network, the terminal web

Adaptation of skeletal muscle

Fusion of myoblasts form multinucleate cell myotube syncytia, which synthesize contractile proteins to become mature fibers; once cell (fiber) is formed no further division occurs; cell can enlarge (hypertrophy) in response to exercise or hormones or atrophy in response to inactivity, injury, loss of innervation, or malnutrition; undifferentiated progenitor cells (satellite cells) lie in connective tissue adjacent to mature fibers and may proliferate and fuse to become new fibers

Eosinophils

Generally contains a bi-lobed nucleus. The secondary (specific) granules stain bright orange (eosinophilic) and contain a dense filamentous core of major basic protein (MBP). Circulate about 8 hours. They are increased in some parasitic infections, in allergic responses, to a variety of stimuli including pollen, and some drug reactions. Major basic protein- kills parasitic worms

Lymphocyte

Involved in the immune response and found throughout the body in CT. B lymphocytes and T lymphocytes cannot be differentiated from each other in tissue without special stains. Nucleus is round or slightly oval, taking up the majority of the cell and is heterochromatic. A thing rim of blue cytoplasm may be visible. They predominate in loose CT of the respiratory and GI tracts where they protect against invasion by bacteria and foreign parasites.

Heart

Is a pump for blood and the bulk of tissue is striated, involuntary cardiac muscle which can undergo hypertrophy (thickening), atrophy (thinning), necrosis (damage-induced cell death) and apoptosis (programmed cell death). There are 4 valves in the heart, tricuspid (right AV), mitral (left AV), and semilunar (pulmonary artery and aorta). Valves are folds of endocardium covered by endothelium. Tricuspid and mitral valves are thicker than semilunar and all contain lymphatics, blood vessels, and a central connective tissue core. Heart is supported in the chest cavity by dense collagenous and elastic connective tissue fibrous skeleton.

Hyperplastic obesity

Increase in the number of adipocytes

Keratins

Intermediate filament in epithelium; terminate in desmosomes and sites of cell-cell adhesion, bundles visible under the light microscope called tonofilaments

Glial fibrillary acidic proteins

Intermediate filament in glial cells and give cells mechanical strength

Vimentin

Intermediate filament in mesenchyme; attach nucleus to plasma membrane

Desmin

Intermediate filament in muscle; provides framework for the attachment of contractile proteins

Neurofilaments

Intermediate filament in neurons; interpret support for neuron processes and maintaining gel state of cytoplasm

Sarcoplasmic reticulum (SR)

Internal membrane network; no connection with the extracellular space; does make junctional complexes with T tubules forming triads in skeletal, and dyads in cardiac; takes up and releases calcium to regulate contraction

Nucleolus

Rich in rRNA and protein. All protein components synthesized in the cytoplasm and imported. 3 basic components seen by EM: 1. Nucleolar organizer DNA: base sequences coding for rRNA 2. Pars fibrosa: densely packed ribonucleoprotein fibers, primary transcripts of rRNA genes 3. Pars granulosa: 15-20nm granules representing maturing ribosomes

Fibroblast

Responsible for formation and maintenance of all types of fibers and ground substance. 2 morphological types: 1. Active fibroblast has a large oval nucleus, prominent nucleolus, and abundant eosinophilic cytoplasm 2. Resting fibroblast is smaller, spindle-shaped, and has a slender elongated dark nucleus. Cytoplasm is indistinct. In dense CT, nuclei tend to be oriented in the direction of the collagen fibers.

Lymphoid tissue

Reticular cells and reticular fibers make up the supporting network T cells: mediate cellular immunity (maturation site is the thymus) B cells: mediate humoral immunity through production of antibodies

Bone marrow

Richly vascularized connective tissue which specializes in production of all the formed elements of blood

Conduction system pathway

SA node (pacemaker) to AV node via Bundle of His, then out to left and right anterior and posterior bundle branches, which goes to Purkinje fibers and Purkinje cells.

Arachnoid

Simple squamous epithelium that is avascular. Sends down fibrous trabeculae into the subarachnoid space to connect the subarachnoid space to connect the arachnoid with the pia mater.Subarachnoid space is filled with CSF and communicates with the ventricles of the brain; it also contains blood vessels (subarachnoid hemorrhage). Arachnoid villi perforate through the dura mater, allowing CSF to flow into venous sinuses.

Androgens and estrogens

Sex steroids that stimulate osteoblast activity and deposition of bony matrix. This bone growth results in closure of epiphysis and increased thickness of all bones.

Hematopoiesis

The process of blood cell renewal Gestational hematopoiesis occurs in 3 stages: 1. Mesoblastic phase (2 weeks-2 months): wall of yolk sac 2. Hepatic phase (6 weeks- birth): liver 3. Myeloid phase (2 1/2 months- birth): bone marrow

Holocrine secretion

entire cell with its secretory products is released into the lumen of the acinus or associated duct Examples: sebaceous glands, ovary, testes

Primary ossification center

1. Beginning at about 2 months of gestation, bone begins to replace hyaline cartilage primordia, occurring in the center of the cartilage primordium - called the diaphysis 2. Due to changes in the local environment, osteoprogenitor cells of the perichondrium switch from making chrondorblasts to making osteoblasts, resulting in the laying down of a bony collar surrounding the cartilage model. 3. Perichondrium is now a periosteum 4. Chondrocytes in the center of the cartilage begin to degenerate, resorbing their matrix and causing an enlargement of the lacunae. 5. Calcium deposits form in the matrix and the cartilage becomes calcified. 6. Blood vessels and osteoprogenitor cells from the periosteum invade the center of the cartilage and the enlarged lacunar spaces, transforming them into marrow spaces. 7. Osteogenic cells multiply and become osteoblasts 8. Osteoblasts begin to lay down osteoid, resulting in a well developed endosteum 9. With calcification, the osteoid is turned to mineralized bone and the osteoblasts are immobilized as osteocytes

Capillaries

1. Continuous: no holes in the endothelium 2. Fenestrated: has holes in the endothelium 3. Sinusoidal or sinusoids: large with big holes in the endothelium Are formed from tiny branches of the arterioles, the metarterioles, which are surrounded by a discontinuous layer of smooth muscle, and constriction of the metarterioles helps regulate blood flow in tissues. In some tissues there are arteriovenous anastomoses that allow blood to empty directly into venules from the arterial side, so that when vessels in the anastomoses contract, all the blood passes directly and rapidly straight through. The number of anastomoses and richness of capillary network is directly related to the metabolic rate of the tissue. For example, the liver, a highly synthetic and detoxification organ, has a vast capillary network.

Membrane specialization of cardiac muscle

1. Macula adherens (desmosomes) usually at perpendicular region of the intercalated disc 2. Fascia adherens: ends of actin filaments anchor into "felt-like" mat on membrane (Macula adherens and fascia adherens are mechanical junctions) 3. Gap junction (nexus)- low resistance electrical coupling between 2 cardiac cells, where the wave of depolarization is transmitted from cell to cell in a cable fashion

Muscle types

1. Skeletal: striated, usually strong, quick, discontinuous voluntary contractions 2. Cardiac: striated, strong, quick, involuntary contraction 3. Smooth: nonstriated, weak, slow involuntary contraction *Skeletal and cardiac muscles are BOTH striated, but cardiac fibers branch *Postion of nuclei: smooth and cardiac are centrally located, skeletal on the periphery *Skeletal and cardiac have long fibers; smooth muscle has individual, distinct cells.

T lymphocytes

3 primary subpopulations: 1. T helper cells: secrete cytokines that coordinate cell-mediated as well as humoral immunity, are CD4+ 2. T suppressor/cytotoxic cells: function in the killing of virus-infected cells, are CD8+ 3. T regulatory cells: capable of preventing immune response to self-antigens, are CD4+/CD25+

Troponin

3 subunits TnT- binds to tropomypsin TnC- binds calcium TnI- inhibits actin-myosin interaction One troponin complex binds to one tropomyosin molecule, which in turn spans 7 G-actin molecules

Isogenic cell nest

A cluster of chondrocytes resulting from division of a mature chondrocyte into daughter cells

Ground substance

A colorless, transparent mixture of proteins found between cells and fibers of connective tissue. High viscosity contributes to its role as a lubricant and a physical barrier to penetration by bacteria. Composed of glycosaminoglycans (GAGs), proteoglycans, and glycoproteins.

Blood

A fluid connective tissue constituting about 7% of our total body weight (about 5L). The primary components are plasma, erythrocytes, leukocytes. If an anticoagulant is added, blood can be sedimented into 3 distinct layers due to different densities of elements: rbc > wbc > plasma. The lowermost layer (45% of the blood volume) consists of erythrocytes. Above this region is a grayish white layer (buffy coat) which represents the platelets, lymphocytes, and granulocytes (about 1-2% volume). Plasma is the top layer.

Basal lamina

A sheet-like extracellular structure at the basal surface of epithelial cells where they contact the subjacent connective tissue; visible by EM as an electron dense layer called the lamina densa; lamina densa contains type VII collagen and laminins; an electron lucent layer may be present at 1 or both sides of the lamina densa called the lamina rara

Bipolar neuron

A single axon and dendrite arise at opposite poles of the cell body. Found as sensory neurons in the ear/vestibular system, in the retina

Appendix

A small, dinger, like blind pouch projecting off the secum of the large intestine. Contains numerous lymphoid nodules in the mucosa and submucosa.

Lacuna

A space in the cartilage occupied by a chondrocyte

Lymph flow

Afferent lymphatic vessel --> subcapsular sinus --> cortical (intermediate) sinuses --> medullary sinuses --> efferent lymphatic vessels Vessels contain 1 way valves to assure flow of lymph into the proper direction

Lymph nodes

Afferent lymphatic vessels enter the LN along the convex surface of the capsule. Efferent lymphatic vessels leave the LN at the hilum. Arteries enter and veins leave the node via the hilum. Dense CT capsule that sends CT septae or trabeculae into the node. Reticular cells and reticular fibers form a supporting meshwork that extends thought the parenchyma. The parenchyma consists of diffuse and nodular lymphoid tissue and is separated into an inner and outer cortex and medulla. Main function is to filter lymph before it returns to the circulatory system. Activated B cells migrate to the germinal center of follicles and begin dividing to give rise to lymphoblasts. Lymphoblasts give rise to plasma cells and memory B cells.

Secondary ossification center

After birth, the distal ends of the cartilage primordial, called epiphyses, undergo ossification separately from the diaphysis via a similar process. Central chondrocytes degenerate, large spaces form, and cartilage matrix calcifies. Osteogenic vascular buds break into these ends, converting the center into bone marrow spaces line by endosteum. In the secondary ossification center this critical zone of cartilage remains throughout childhood and puberty, and is called the epiphyseal plate.

Residual body

After digestion most soluble material diffuses out of the secondary lysosome. Indigestible material remains in vaculor structures= residual bodies. End products of both auto- and heterophagy is often a yellow pigment, lipofuscin, which increases with age

Proteoglycans

All GAGs except those composed of hyaluronic acid can be covalently bound to a protein core to form proteoglycans. Molecules are 80-90% carbohydrate and attract water to form a gel. Give support to the connective tissue matrix, and act as binding sites for growth factors and signaling molecules.

Neurons

All neurons have a cell body and a variable number of processes, including at least 1 axon that transmits impulses away from the cell body, and usually one or more incoming processes called dendrites. 3 types: bipolar, pseudounipolar, multipolar

Peripheral Nervous System (PNS)

All outlying nervous tissue (nerve fibers and ganglia)

Cell body

Also called the soma or perikaryon and consists of the nucleus and cytoplasm.

Pseudostratified columnar epithelium

Although it appears stratified, it is composed of only 1 cell layer of columnar cells. ALL cells touch the basement membrane even though they do not all reach the luminal surface, typically have cilia on apical surface Function: protection; secretion and absorption; lubrication Location: lining of trachea, bronchi, nasal cavity, ductus deferens, and parts of the epidydmis

Nerve fibers

An axon or collection of axons, plus any surrounding sheaths of ectodermal origin.

Endoplasmic Reticulum (ER)

Anastomosing network of interconnecting channels and sacs formed by a continuos membrane which encloses a space called the cisterna 1. RER: prominent in cells specialized for protein secretion 2. SER: lack ribosomes and appears smooth and glandular; is associated with steroid hormone and phospholipid synthesis, degradation of some hormones Specialized SER in muscles called sarcoplasmic reticulum (SR)- sequestration and release of calcium during contraction/relaxation

Erythrocytes (RBCs)

Anucleate acidophilic cell. In addition to the nucleus, the mature erythrocyte also loses its Golgi apparatus, centrioles, ER, and most of its mitochondria. Bulk of the cytoplasm consists of the iron-carying pigment hemoglobin. Shape is a biconcave disk to achieve max SA to cytoplasmic volume ratio. Has a life span of ~120 days in the circulation. The major physiologic role is oxygen and CO2 transport.

Z line

At the end of sarcomere; contains actin binding protein, actinin; bisects each I band

Circumferential lamellae

At the outer periphery of compact bone, several layers of bone are oriented parallel to the free surface

Epithelial cells

Avascular; have specialized junctions; demonstrate polarity- apical modifications and basement membrane; exhibit rapid cell turnover; functions include: protection, secretion of mucus, hormones, and enzymes, absorption of material, selective permeability, transportation of particulates and mucus along surfaces, sensory perception

Myelinated fibers

Axons that become myelinated are generally larger than 1 micro meter in diameter. Myelin is deposited just beyond the axon hillock and continues to near the region of termination of the axon. The membranes of the Schwann cell wrap around the axon several times and fuse to form a myelin sheath. The sheath is interrupted by gaps called nodes of Ranvier which represent the spaces between adjacent Schwann cells along the length of the axons. A Schwann cell can only myelinate a single axon.

Hemidesmosomes

Basal structure and is half a desmosome, anchor cell by type VII collagen to the subjacent basal lamina, proteinacous plaques in these structures contain many integrins

Intermediate junctions (Zonula adherens)

Basal to tight junctions; actin filaments arising from the terminal web insert into electron dense plaques on the surface of junctional membranes

Capsule

Basophilic cartilage matrix immediately surrounding each lacuna

Auerbach's plexus

Between the 2 external smooth muscle layers to help in the peristaltic movement of the gut to move food boluses along.

Myeloid tissues

Blood forming tissues identified as the "red marrow" of bones

Systemic (bronchial) system

Bronchial arteries branch from the aorta and thus carry blood at systemic pressure. Bronchial arteries have smaller lumens and thicker walls than pulmonary arteries. Their walls contain a distinct elastic lamina and a muscular media.

Muscle

Bundle of fascicles surrounded by a thick, connective tissue epimysium. Muscle grouped as broad sheets (rectus abdominis), or in bundles (biceps), or in circular arrays (obiscularis iris, anal and urinary sphincters)

Ependymal cells

CNS only. Cuboidal epithelia cells lining the ventricles and central canal of the spinal cord. Cilia and microvilli on apical surface. Form barrier between brain and CSF. Also found in the choroid plexus. Ependymal cells that line choroid plexus produce CSF.

Astrocytes

CNS only. Large, oblong nucleus with stellate processes; contains abundant glycogen and unique intermediate filaments called glial fibrillary acid protein (GFAP); gives structural support to neural tissues by binding neurons to capillaries and to the pia mater. This is accomplished by expansion of their distal processes to form "perivascular feet" on blood vessels; function as part of the blood-brain barrier; form scar tissue. 2 types 1. Fibrous astrocyte: present in white matter, not much branching of the fibers 2. Protoplasmic astrocyte: present in gray matter, highly branched

Microglia

CNS only. Smaller than other structures in the CNS with dense, elongated nucleus. Not usually seen in normal brain tissue. The phagocytic cell of the CNS and involved in inflammation and repair. These cells are the primary site of HIV-1 infection in the CNS.

Oligodendrocytes

CNS only. Smaller than the astrocyte, with small, round dense nucleus and clear cytoplasm. Does not contain glycogen or GFAP. Responsible for myelination in the CNS. One cell can myelinate several axons.

Cardiac muscle contraction

Cardiac contraction occurs without direct nerve stimulation, but VIA an initiating wave of depolarization that originates at sino-atrial (SA) node and travels through the conductive pathway cells (AV node, Bundle of His and Purkinje fibers) to the contractile cells of the myocardium Heart rate affected by autonomic innervation of the SA node and of other regions by the vagus nerve, as well by hormones such as adrenaline; contractile activities dependent on neighboring cell depolarizations (intercalated discs)

Components of conducting system

Cartilage (primarily hyaline): from C shaped rings to irregular rings and small plaques, prevents collapse of the walls Collagen fibers Elastic fibers: tend to be oriented longitudinally in this area Smooth muscle: from trachea to alveolar ducts, contraction reduces diameter of tubes and restricts airflow

Macrostructure of cardiac muscle

Cells joined by specialized electro-mechanical junctions the intercalated disks; branching; connective tissue is interspersed throughout, but no distinct fasicular structure; no direct innervation, although autonomic nerves do travel in myocardium; dense vascularization due to substrate and oxidative demands of the myocardium

H band

Central region of A band which contains only myosin thick filaments; width decreases during contraction; "heller"-light

Neutrophils

Characterized by a prominent nucleus segmented into 2-5 lobes. Most numerous of the WBCs in an adult. Contains 2 major types of granules: specific (secondary) and azurophilic (primary) granules. Neutrophils just released from the bone marrow often have a band-shaped nucleus and are known as bands. Half life in blood is only 6-8 hours, 1-4 day lifespan. Are the 1st line of defense against microorganisms, especially bacteria. They are active phagocytes. The bone marrow will release more neutrophils in response to stimuli such as bacterial infection, tissue necrosis, etc.

Continuous capillary

Characterized by absence of fenestrae (holes). Common in muscle, connective tissue, exocrine glands, and nervous tissue. Normal to see pinocytotic vesicles on both surfaces of endothelial cells, responsible for transport of macromolecules

Loose (Areolar) connective tissue (cellular and acellular)

Characterized by delicate, loosely arranged collagen with abundant ground substance and cells of all types (most numerous are fibroblasts and macrophages). All fiber types are present and it is well vascularized. Is designed for flexibility and is not very resistant to stress and is found: sheaths around blood vessels and lympahtics; serosal lining of the peritoneal and pleural cavities; below epithelial surfaces such as the lamina propria of the GI and respiratory tracts, and in areas of the dermis; submucosa of the GI tract; glands Distinguishing feature: more cells than in mesenchyme

Compact bone

Characterized by primarily bone substance, with small spaces. There is a transition from spongy to compact bone that is intermediate in appearance and difficult to assign to either category. Most bone contains variable amounts of outer compact and inner spongy bone.

Chromatin

Coiled strands of DNA bound to basic proteins (histones) Heterochromatin: electron dense and appears as coarse clumps in electron microscope or basophilic clumps by light microscopy, composed of unexpressed DNA Euchromatin: less coiled portions of chromosomes and visible as finely dispersed granular material, site of active transcription

Dense regular connective tissue

Collagen fibers predominate HOWEVER, the collagen fibers are all arranged in one direction, providing protection against prolonged stress exerted in 1 direction. Distribution: tendons (join muscle to bone) and ligaments (join bone to bone)

Dense irregular connective tissue

Collagen fibers predominate. The fibers are arranged in bundles oriented in 2 or more directions and without a definite structure. Compared with loose CT, this type of CT is less flexible, but much more resistant to stews. Found in the dermis of skin, wall of vagina, periosteum, perichondrium

Fibers of connective tissue

Collagen, reticular, and elastic fibers

Bone remodeling

Compact bone is always being resorbed and replaced with new compact bone as follows: 1. Osteoclasts from the marrow move into the area of the compact bone to be replaced 2. They absorb bone in what are called resorption tunnels 3. Irregular outlines and the presence of osteoclasts lining their borders distinguish resorption tunnels from Haversian systems. 4. These tunnels contain blood vessels, osteoprogenitor cells, and osteoblasts that proceed to lay down concentric lamellae from the outside to the inside of the tunnel, where a central canal is left 5. These osteons develop through the progressive filling in of a tunnel with successive lamellae of bone.

Golgi apparatus

Completes post-translational modification of proteins, packages and directs them to their ultimate destination cis face (convex) receives vesicles from RER and proteins are released in vesicles from the trans face (concave)

Desmosomes (Macula adherens)

Complex disk-shaped structures at the surface of one cell directly opposite an identical structure on an adjacent cell, on cytosolic sides tonofilaments converge and form hair-pin loops near the dense plaques of the desmosomes, plaques contains many proteins including vimetin desmin and cadherins, rows of desmosomes lie basal to the intermediate junctions of absorptive or secretory epithelial cells, the more friction a cell is exposed to the more desomosomes it will have

Blood-air barrier

Components include: 1. Surface and cytoplasm of the alveolar cells 2. Fused basal laminae of the alveolar cells and the capillary endothelial cells 3. The cytoplasm of the endothelial cells

Connective tissue

Composed of cells embedded in an extracellular matrix (ECM). Composed of ground substance, fibers, and tissue fluid. The variation in the cells and components of the ECM determines the different types of connective tissue throughout the body. Functions in a wide variety of supportive and protective roles.

White pulp of spleen

Composed of diffuse and nodular lymphoid tissue, primarily lymphocytes. The PALS parallels the course of the central arteries. The PALS are primarily T-lymphocytes. Lymphoid nodules or follicles may be present. Like lymphoid follicles in the lymph node, these are composed chiefly of B-lymphocytes. Germinal centers with mantle zones (B-cells) and marginal zones (B and T cells) maybe be present and result in the formation of large nodules known as splenic nodules or Malpighian corpuscles.

Elastic cartilage

Composed of elastic fibers in the matrix, in addition to type II collagen. The thickness of the fibers permits them to be resolved with LM therefore appearing fibrous (easily seen with specialized stains such as elastin or silver staining). Elastic fibers allow more flexibility, allowing bending. Elastic cartilage is always associated with a perichondrium. Locations: external ear, auditory tube, epiglottis

Lymph node medulla

Composed of medullary cords separated by medullary sinuses that contain lymph, lymphocytes and macrophages Medullary cords contain primarily B-lymphocytes, macrophages, plasma cells, and reticular cells. Major site of phagocytosis and immunoglobulin synthesis.

Collagen fibers

Composed of the protein collagen and are important components of tissues that require rigidity, flexibility, and strength. Synthesized by fibroblasts, chondroblasts, osteoblasts, smooth muscle, endothelial and epithelial cells. It is the most abundant protein in the body. Synthesis: In the RER, polypeptide chains (pro collagen), are transported outside the cell, and cleaved by proteases to yield tropocollagen. Tropocollagen molecules spontaneously assemble into collagen fibrils, which are very long and thin and cannot be seen with LM. Fibrils further crosslink to form collagen fibers that can be seen with LM, especially as larger collagen bundles.

Elastic fibers

Composed of the structural protein elastin, and the glycoprotein fibrillin that organizes elastin into fibers. The presence of elastin allows the fibers to stretch in response to tension (unlike collagen fibers). Contains 2 unique amino acids, desmosine and isodesmosine. Often interwoven with collagen fibers and found in elastic vessels like the aorta and large arteries. In the walls of larger blood vessels, elastin forms sheets known as elastic laminae; stain thicker than reticular fibers

Fibrocartilage

Composed of type I collagen in the matrix in addition to type II collagen . Type I fibers can be seen swirling through the matrix, sometimes forming bundles. Found in high stress areas where strength is necessary, as at the attachments for bone and muscle. A perichondrium is NEVER associated with fibrocartilage. Locations: intervertebral disks (annulus fibrous), pubic symphysis, intersections of tendons with lateral aspects of articular cartilage, temporomandibular joint articular surface.

Lymphatic circulation

Composed of vessels that remove excess extracellular fluid (lymph) from spaces between tissues and return it to the cardiovascular system. NOT PRESENT IN THE CNS. Lymph passes through lymph nodes where antigens are concentrated and presented to lymphocytes, ultimately leading to an immune response. Lymph enters lymph node through afferent lymphatics and leaves via efferent lymphatics. Some lymphocytes will remain in the B-dependent or T-dependent areas of the lymph node. Lymphatic vessels empty into the thoracic duct which joins the venous system at the junction of the internal jugular and subclavian veins. Lymphocytes transiting through blood regain entry into the lymphatic system via postcapillary venules (high endothelial venules, HEVs) in the paracortex of lymph nodes. This recirculation of lymphocytes involves all lymphatic tissue except the thymus and bone marrow. Most lymphocytes are involved in active immunologic surveillance.

Intra-alveolar septum

Consists of 5 main cell types: 1. Capillary endothelial cells- very thin and non-fenestrated 2. Type I alveolar (squamous) pneumocytes- 97% of the alveolar surface 3. Type II pneumocytes- release pulmonary surfactant 4. Interstitial cells- including fibroblasts and mast cells 5. Alveolar macrophages or Dust cells- often contain large amounts of carbon and dust

Endosteum

Consists of a thin layer of cells that line the inner part of bone along the marrow cavity, purely osteogenic in function

Respiratory portion

Consists of alveolar ducts, sacs, and pores Gas exchange occurs between the alveolar and capillary lumen, across the squamous epithelium of alveolar pneumocytes and the capillary endothelium.

Glycoproteins

Contain a protein core and carbohydrates; however the protein component predominates and the carbohydrate moiety is branched not linear. Function in the adhesion of cells to each other and to the fibers of the extracellular matrix Fibronectin- made by fibroblasts and mediates normal cell adhesion and migration Laminin- made by epithelial cells and mediates adhesion of these cells to the underlying basement membrane Integrins- transmembrane proteins on cells that serve as the receptor sites for gylcoproteins. One end binds to proteins in the ECM, the other end attaches to actin microfilaments in the cell. The process is mediated by intracellular proteins: paxillin, vinculin, talin

Lymphocytes

Contain a single, deeply-stained, spherical nucleus which can have a slight indentation. Are an important part of the immune system. 2 major subtypes are T and B cells. Plasma cells are derived from B cells.

Seromucous (mixed) secretion

Contains both types of secretory cells; cell morphology- seromucous acini are often organized as mucous acini capped by serous demilunes ("half moons")

Skeletal muscle

Contraction is parallel to orientation of fibers. Strength, endurance and fine control dependent on number, size, and type of innervation. Pink-red color of muscle due to blood supply and myoglobin content. Contractile force transmitted to bone or other muscle via myotendonal junctions, then connective tissue tendons. Unlike other skeletal muscles, contraction of the diaphragm is involuntary.

Centrioles

Cylindrical bodies of short microtubules. Each centriole is composed of 9 sets of microtubules arranged in triplets

Skeletal muscle events in depolarization

Depolarization spreads outward over sarcolemma and down into T-tubules initiating cascade: At the triad, depolarization is "sensed" by the SR via "dense feet"-->stored calcium in SR is released through channels into sarcoplasm-->sarcoplasmic calcium increases from resting and calcium binds to TnC causing conformational change--> troponin change alters tropomyosin to uncover actin--> myosin head-ATP interacts with actin--> myosin head activated, hydrolyzes ATP--> ratcheting of attached myosin head pulls actin into A band--> Z-Z distance decreases as sarcomere shortens (I band decreases and A band constant)--> cyclic repeats of myosin-ATP formation, ATP hydrolysis, and contraction until full contraction of sarcomeres-->uptake of calcium by SR--> muscle relaxes

Plasma cell

Derived from B lymphocyte. Function in the synthesis of antibodies and are most numerous in sites prone to invasion by bacteria and foreign substances. Large oval cells with an eccentrically placed nucleus. Cytoplasm stains basophilic due to large amount of RER. Prominent Golgi situated near the nucleus, resulting in a light-staining area of the cytoplasm known as a "hot". Often looks like it has a clock face.

Respiratory epithelium

Does not mediate gas exchange but functions to cleanse, moisten and warm air before it enters the lungs The # of goblet cells, along with the amount of ciliated epithelium and cartilage, decrease as the conducting tubes gradually proceed into respiratory system while the amount of smooth muscle and elastic fibers progressively increases Ciliated, pseudostratified columnar epithelium consists of 5 cell types: 1. Ciliated columnar cells- most abundant 2. Mucos goblet cells- contain polysaccharide rich mucous droplets 3. Brush cells- many microvilli on apical surface, sensory receptors 4. Basal (short) cells- give rise to other cell types by mitosis 5. Small granule cells- contain numerous dense granules and form part of diffuse neuroendocrine system Ciliated, pseudostratified columnar epithelium transitions to simple columnar to simple squamous epithelium in the alveoli. Ciliated cells continue beyond the goblet cells, preventing accumulation of mucous

Fiber

Each fiber is an elongate, multi-nucleate cell; from embryonic fusion of 100's of myoblasts. Each fiber is surrounded by thin layer of connective tissue, the endomysium, synthesized primarily by fibroblasts.

Skeletal muscle innervation

Each fiber receives electrical stimulation via branch of a motor neuron; each motor neuron can innervate up to 100 muscle fibers; combination of the neuron and muscle fibers is termed the motor unit; stimulation of the motor nerve results in contraction in all or none response of all of its muscle fibers; the strength, speed, and duration of contraction are dependent on: type of skeletal muscle, number of motor units stimulated, frequency of stimulation

Contractile event of the skeletal muscle

Each skeletal muscle fiber innervated by 1 motor neuron via the motor end plate (neuromuscular junction); at nerve terminus, ACH is stored in numerous synaptic vesicles; nerve impulse produces fusion of vesicles in nerve terminal with nerve presynaptic membrane; ACH discharged into synaptic cleft and binds to receptor on muscle postsynaptic membrane resulting in sodium influx and depolarization

Origin of nerve tissue

Ectoderm->neural plate->neural groove->neural tube-> CNS Neural crest cells: neurons of sensory ganglia, neurons of sympathetic and parasympathetic ganglia, Schwann cells, satellite cells, chromaffin cells of adrenal medulla, melanocytes of epidermis, pia mater and arachnoid, odontoblasts

Lymphoid tissues

Elements of the larger lymphatic system (lymph nodes, Peyer's patches, tonsils)

Ganglia

Encapsulated groups of neurons and associated glial cells and connective tissue

3 layers of heart

Endocardium: inside- a thin layer of endothelium Myocardium: middle- a thick layer of striated muscle Epicardium: outer- a thin layer of squamous endothelium Layers are attached to each other by connective tissue

Formed elements (blood cells) in blood

Erythrocytes (red blood cells): occupy about 40-45% of the total blood volume Leukocytes (white blood cells) and platelets: together make up about 1-2% of the total blood volume

Hypertrophic obesity

Excessive accumulation of fat in unilocular tissue cells that become larger than usual. Usual mechanism of obesity.

Microplicae

Fold like extensions of cytoplasm present on luminal epithelial cells in places like the cornea, esophagus, and renal collecting ducts; increase surface area and the adherence of surface fluid layers

Fat cells (adipocytes)

Found in aggregates of varying sizes, constituting adipose tissue. Adipose tissue accounts for 20-25% of the weight of women, 15-20% of the male's weight. 2 separate categories of adipocytes which differ in distribution, histological appearance, and function: 1. white adipose tissue 2. brown adipose tissue

Gap junctions

Found in most tissues along the lateral membranes of cells, gap junction protein units called connexins- these form hexamers with hydrophilic pores in the center (connexons), connexons project through plasma mebrane and join in mirror symmetry with connexons in adjacent cells, site of exchange between cells for electrical coupling and cell-cell communication

Meissner's plexus

Found in submucosa (include Meissners corpuscle) to help in neuromuscular signalling and food debris propulsion

Fenestrated with diaphragms

Found in tissue where specific products are required to pass from synthesizing organs into the blood. The thyroid is one example where transport of thyroid hormones occurs. Capillaries are nestled between follicles.

Primary cilia

Found on virtually every cell. They are non-motile and have no central pair of microtubules and lack dyne in (9+0 arrangements)

Pacinian corpuscle

Found under the skin in places where pressure sensing is needed, such as in the bottom of the foot. Located in deep dermis or subcutis of weight-bearing and sensitive areas. Ovoid; resembles a cut onion. Contains a terminal afferent nerve fiber which loses its myelin after entering the corpuscle, and has supporting (laminar) cells thought to be Schwann cells

Blood-brain barrier

Functional barrier composed of endothelial cells with tight junctions, their basement membranes, and astrocyte foot processes.

Distribution of white & gray matter

Gray matter contains neurons, dendrites, the initial portion of unmyelinated axons, and glial cells. White matter contains myelinated axons, a few unmyelinated fibers, glial cells, but NO neurons. The non-neuron compartment is often collectively referred to as neuropil. Brain: gray matter forms the cerebral and cerebellar cortex; white matter lies beneath. Aggregates of neurons (known as nuclei) may form islands within white matter Spinal cord: white matter is peripheral; gray matter forms a central "H" shaped structure containing the central canal

Nerves

Group or bundles of nerve fibers. Covered by connective tissue.

Appositional growth

Growth due to division and differentiation of chondroblasts on the outer surface. Cartilage is added to the periphery. Occurs in perichondrium. Osteoprogenitor cell--> chondroblast--> chondrocyte--> outer matrix

Interstitial growth

Growth due to division of pre-existing, medially located chondrocytes, adding matrix to the inner mass of the cartilage. This process does NOT require chondroblasts. Occurs in the early phases of cartilage formation, in the epiphyseal plates (growth increasing length of long bones) and within articular cartilage

Basophils

Has a nucleus containing 2-3 lobes which are difficult to see because of the large, dark staining specific granules. Least numerous WBC in peripheral blood. It is mainly the secretory cell which mediates the hypersensitivity reaction.

Mucous connective tissue

Has an abundance of ground substance with a large number of collagen fibers and few cells (mostly fibroblasts). It is the principal component of the umbilical cord, Wharton's jelly.

Spongy bone

Has little mass and consists of peninsulas of bone (trabeculae; spicules) that project into the marrow cavity with its nutritive vasculature. Depressions seen along a trabeculum may contain a large, multinucleate cell called an osteoclast and the depression is a Howship's lacuna. The osteoclast is responsible for the dissolution of bone- its activity is increased by parathyroid hormone and diminished by calcitonin

Venules

Have a very thin, low cuboidal to squamous endothelium (wall), minimal tunica media (maybe a few smooth muscle cells and a few wisps of connect tissue), and an ill-defined adventitia that blends with the surrounding fibrous connective tissue.

Major types of collagen

I: fibers, bundles; LM; CT proper, dermis, bone, dentin, tendon, ligaments, fibrocartilage; resistance to force, tension and stretch II: fibrils; TEM; cartilage, intervertebral disc; resistance to pressure III: fibrils, very thin fibers (Reticular fibers); special stains (argyrophilic); loose CT (along with type I collagen), reticular tissue (organ stroma, perivascular CT), laminar reticularis; maintenance of structure in expansible organs and tissues IV: not visible; special stains; basal lamina (lamina densa); support of delicate structures VII: not visible; TEM; dermal-epidermal junctions; attach lamina densa to underlying connective tissue (lamina reticularis)

Chondroblast

Immature cartilage cell, always located on the periphery (perichondrium- dense irregular CT) of the cartilage

Microfilaments (Actin filaments)

Important in defining cell shape, motility, and movement of organelles; microfilaments form the terminal web in the apical cytoplasm of some epithelial cells; intimately associated with contractile process

Adaptation of smooth muscle

In response to increased demand cells can hypertrophy (increase in the size of cells); smooth muscle can also undergo hyperplasia (increase in the number of cells) by cell division

Choroid Plexus

In roof of 3rd and 4th ventricles and walls of lateral ventricles. Composed of "fibrovascular" core of loose connective tissue and blood vessels covered by specialized ependymal cells. These cells contain microvilli and cilia on their apical surface. Main function is to produce cerebrospinal fluid. CSF passes from ventricles to subarachnoid space and then enters the venous circulation via the arachnoid villi.

Central Nervous System (CNS)

Includes brain and spinal cord

Tonsils

Incompletely encapsulated aggregates of lymphoid nodules. Do not filter lymph (no afferent lymphatic vessels), their purpose is it capture antigen from airways and mouth and allow for immune response to occur.

Lacteal

It fills/absorbs fat and is found in the center of intestinal villi

Arteries/veins

Largest arteries are elastic arteries, which gradually lose elastic, retain an internal elastic lamina, and become muscular arteries. The largest veins are large muscular veins that gradually lose their muscle component and become smaller muscular veins. Both large arteries and veins possess a vasa vasorum, a network of small blood vessels in the tunica adventitia. The 3 tunics thin out, the elastic disappears and the component smooth muscle becomes less. As the veins become smaller they become less round, while arteries usually maintain a nice circular shape. Small muscular arteries have 5-10 concentric layers of smooth muscle in their tunica media while veins have a couple of smooth muscle cells in the tunica media and a large, wispy, ill-defined adventitia.

Reticulocytes

Less mature erythrocytes. RBCs released from the bone marrow into the peripheral circulation are considered reticulocytes for ~2 days. Contain residual ribonucleoprotein particles which impart a bluish hue on staining.

Smooth muscle innervation

Like cardiac muscle, smooth muscle contraction regulated by autonomic innervation; responds to hormones; contractile-activating depolarization passes from cell-to-cell- like cardiac muscle via gap junctions; contraction is slow Depolarization of SL causes an increase in sarcoplasmic calcium concentration but unlike skeletal muscle actin-myosin interaction is mediated through calmodulin, which activates myosin light chain kinase, which in turn phosphorylates the myosin light chain, permitting myosin to interact with actin; Because of diagonal arrangement of contractile apparatus in smooth muscle cells, and anchoring of fibers and intermediate filaments at dense bodies, cells become shorter and fatter in contraction No troponin regulation in smooth muscle!

Bone- general

Like cartilage, consists of cells living in lacunae, surrounded by a matrix they produce. Matrix is infiltrated with inorganic salts, making it rigid and inflexible. Like cartilage, has an outer fibrous CT compartment called the perisoteum. Unlike cartilage, is highly vascular. Unlike cartilage, has overall complex architecture, and constantly is remodeled and reshaped in response to physical stresses and mineral needs of the body. Functions for support, attachment, leverage, mineral storage, and protection of hematopoeitic tissues within marrow spaces All bone consists of cells (osteoprogenitor cells, osteoblasts, osteocytes) and a matrix containing fibers (type I collagen) and ground substance (organic and inorganic components)

Palatine tonsils

Lined by stratified squamous epithelium that forms multiple invaginations known as crypts. Contains dense collections of lymphoid nodules, many with germinal centers. Partially encapsulated at the basal surface.

Trachea

Lined with a typical respiratory epithelium. 16-20 c-shaped rings of hyaline cartilage in lamina propria keep the tube open. Fibroelastic cartilage and a bundle of smooth muscle bridge the 2 ends of the cartilage.

Meissners corpuscle

Located high in dermal papillae of palms, soles, digits, nipples, lips. Cylindrical or pear shaped. Zigzag arrangement of unmyelinated terminal afferent nerve fibers with supporting (laminar) cells thought to be Schwann cells

Peyer's patch

Located in the ileum, acts as an "inductive site" for immunity in the digestive tract. Covered with epithelium composed of M (microfold) cells.

Sterocilia

Long non-motile microvilli (actin core) found on epithelial cells of the epididymis and hair cells of the inner ear, absorptive function in epididymis and sensory function in the ear MISLEADING NAME

Tropomyosin

Long protein molecule; lies in the groove of the two entwined actin strands

Glycosaminoglycans (GAGs)

Long, non-branched polysaccharide chains consisting of repeating disaccharide units. All are sulfated, except hyaluronic acid, and have a strong negative charge.

Pia mater

Loose connective tissue, very vascular. Partially follows blood vessels that enter the brain, resulting in a perivascular space around these vessels lined by pia mater.

Red marrow cells

Macrophages- they function in phagocytosis and iron storage in bone marrow Structural cells- adipocytes, reticular cells, endothelial cells Mast cells- found throughout the connective tissue of the body

Cell nucleus

Main components are: nuclear envelope, chromatin, the nucleolus, and nuclear matrix Houses the genetic machinery and does not synthesize protein

Parathyroid hormone (PTH)

Maintains serum calcium, in part by increasing dissolution of bone and transferring calcium from bone stores to blood. Large amounts of PTH will actually cause bone destruction.

Myosin

Major component of thick filaments; shaped like golf club with 2 heads on one end; head region contains ATPase and several "light chain" proteins that help regulate interaction with actin during contractile cycle

Actin

Major component of thin filaments: globular monomeric actin molecules (G-actin) linked end to end (like a pearl necklace) to form an actin filament (F-actin); 2 actin "strands" entwine to form a thin filament

Macrophage

Make up the mononuclear phagocyte system (MPS) and are present in most organs. Derived from stem cells in bone marrow that enter the blood stream as monocytes which subsequently make their way into connective tissues and mature into macrophages. Major functions include: ingestion and digestion of foreign substances, bacteria, and old cells; storage of iron in the liver; release of inflammatory mediators, and antigen recognition and processing

Nuclei

Many, often end-to-end and located just beneath the sarcolemma

Red pulp of spleen

Massive amount of RBCs. Consists of splenic cords and sinuses. Splenic cords (cords of Billroth) are a meshwork of reticular fibers. Splenic sinuses carry venous blood and are lined by special endothelial cells. These cells are very long and flat and run parallel to the direction of the vessel. Macrophages associated with the sinusoids are highly phagocytic and function to filter out damaged cells and foreign particles.

Osteocytes

Mature bone cell is the osteocyte which does not produce new matrix but is responsible for maintaining it. Imprisoned within the surrounding matrix in a space called a lacuna. Osteocytes have long cytoplasmic processes radiating outward like tentacles. Unlike cartilage, substances cannot diffuse through the matrix of the bone. Each cell process is imprisoned in a channel in the bony matrix, called a canaliculus. Bone matrix is traversed by numerous canaliculi radiating out from lacunae. The osteocyte is derived from an osteoblast, which in turn arises from the osteoprogenitor cell. The osteoblast is primarily responsible for production of the organic matrix of bone; it becomes imprisoned in that matrix and is then called an osteocyte.

Chondrocyte

Mature cartilage cell. Lay down and maintain the surrounding matrix. Nutrition to all chondrocytes is via diffusion through the matrix

M line

Middle of H band; each myosin joined laterally to its myosin neighbor; "mittel" line = middle line

Sweat glands

Mode of secretion of sweat glands is merocrine Deep sweat glands are called apocrine Superficial sweat glands are called eccrine

Cilia and Flagella

Motiles processes covered by plasma membrane. Highly organized with microtubular core. Cilia and flagella have same core organization, 9 peripheral + 2 central pairs of microtubules = axoneme. Protein brideges (nexins) like adjacent peripheral pairs

Mononuclear white blood cells

Monocytes and lymphocytes do not have segment nuclei

Hyaline cartilage

Most abundant/ prevalent in the body. Bluish-white when fresh. Composed of fine type II collagen fibrils that are not resolvable under microscope so look glassy and homogenous under the microscope. A perichondrium may or may not be present. Locations: ala of nose, costal cartilage, respiratory tract, fetal skeleton, articular surfaces of synovial joints. Found in places that need good protection or some kind of structure.

Tight junctions (Zonula occludes)

Most apical junction, divides apical and basolateral domains

Endochondral bone formation

Most bones of the body form around and within a cartilage primordium that is very small but has the general shape it will eventually assume. Formation of primary and secondary ossification centers

Multipolar neuron

Most common. One axon with multiple dendrites. Found in brain, spinal cord, and peripheral ganglia.

I band

Mostly actin thin filaments; width decreases during contraction regularly spaced regulatory proteins, tropomyosin and troponin; troponin has 3 subunits - I, T, and C; "isotropic"- does not bend polarized light so shows up bright

A band

Mostly myosin but some actin-myosin overlap; "anisotropic"- bends polarized light, shows up as dark band, which gives striated muscle its characteristic appearance; width remains constant during contractile cycle

Bronchioles

Mucosa contains no glands or cartilage In the larger bronchioles the epithelium is ciliated pseudostratified columnar which decreases in height to become ciliated simple columnar or cuboidal epithelium in the terminal bronchioles. Within the terminal bronchioles, the epithelium also contains Clara cells. These cells have no cilia but contain secretory granules and secrete GAGs that serve to protect the epithelium. The lamina propria contains mainly smooth muscle and elastic fibers.

Stratified columnar epithelium

Multiple layer of tall cells Function: secretion, absorption, protection Location: large ducts of exocrine glands

Stratified cuboidal epithelium

Multiple layers of cuboidal cells Function: absorption and secretion Location: sweat glands and ducts, larger ducts of exocrine glands

Stratified squamous epithelium

Multiple layers of flat cells Function: protection; secretion Location: epidermis, lining of oral cavity, esophagus, and vagina

Autonomic (motor) ganglia

Multipolar neurons typically found in walls of organs (GI tract). They do have a few satellite cells associated with them, but do not have a connective tissue capsule.

Adaptation of cardiac muscle

Myocardium develops from splanchnic mesodermal cells; once formed no further division; no satellite cells so tissue has no capacity for replacement of damaged cells instead, connective tissue (fibrotic scar) replaces dead myocardial cells; myocardial cells will enlarge (hypertrophy) in response to increased vascular resistance or exercise; they will atrophy in response to decreased workload

Granulocytes

Neutrophils, eosinophils and basophils They have a segmented nucleus in the mature stage and granules in the cytoplasm.

MALT

No capsule is present. The major antibody produced by the plasma cells is IgA, which is secreted directly onto the mucosal surface. Can be further classified according to location: GALT: Gut BALT: Bronchus

Platelets

Non-nucleated flat, biconvex, round or ovoid disks Derived from bone marrow megakaryocytes Involved in hemostasis (stopping bleeding) and promote the coagulation cascade involving plasma factors to form a blood clot The formation of the platelet plug is referred to as "primary hemostasis" Deficiency of platelets is called thrombocytopenia and can result in bleeding or bruising Life span is 7-10 days

Dendrites

Numerous, short processes that become attenuated and branch with distance from the perikaryon. Provide receptor sites for axon terminals from other neurons, and carry impulses to the cell body. Ultrastructurally, contain Nissl bodies, mitochondria, neurofilaments, microtubules, and other features of the perikaryon, but no Golgi complex

Bone growth across diameter

Occurs mostly during youth. For a bone to increase in diameter, new bone is laid down by the periosteum on the outside of the preexisting compact bone. A compensatory widening of the marrow cavity must occur to prevent the bone from becoming too heavy. A small bone grows and widens by remodeling to a larger bone. Osteoclasts widen the marrow cavity by resorbing compact bone from the inner aspect of the cortex, forming trabeculae in the process.

Pseudounipolar neuron

Only one cell process arises from the cell body and then divides into 2 branches. Developmentally, begin as bipolar neurons. Functionally, one process carries impulses to the cell, while the other carries it away. Found in peripheral sensory ganglia, such as dorsal root ganglia, and in cranial ganglia

Bone matrix

Organic material - osteoid: type 1 collagen-95% of the organic portion; GAGS; glycoprotein Inorganic material (contributes 50% of the bones dry weight): hydroxyapatite crystals of calcium, phosphorus, carbonate, magnesium, fluoride, sulfate

Lymphatics

Originate in tissues as thin, closed-end vessels, with a 1 cell thick endothelium and an incomplete basal lamina. Both vessels and lymphatics contain valves. The lymphatic is very thin walled, held open against collapse by just a few smooth muscle cells and a meager number of elastic fibers. The larger vein has a substantial tunica adventitia and amount of muscle cells. The thin lymphatics converge to form 2 large trunks: the thoracic duct and the right lymphatic duct, which empty into the venous system. Lymph contained in the lymphatics is cleaned via passage through the lymph nodes. Valves are more numerous in the lymphatic system and contraction of surrounding skeletal muscle bundles aid in ensuring unidirectional flow of lymphatic fluid.

Glandular epithelium

Originates from epithelial cells Composed of parenchyma (the secretory portion and associated ducts) + stroma (the connective tissue that keeps it all together) Secretory products are synthesized intracellularly and stored in secretory granules

Haversian systems (osteons)

Osteocytes are arranged into Haversian systems in the interior of compact bone. It is a cylindrical structure. In the center is a canal filled with blood vessels. Osteocytes in their lacunae are arranged in progressively larger concentric circles around this canal. In cross sections a Haversian system appears with a central canal (Haversian canal) surrounded by 4-20 concentric lamellae. Small thread-like canaliculi can be seen traversing the lamellae, forming connections among all of the lacunae and central canals. Interstitial fluid from capillaries in the Haversian canals percolates around osteocyte processes inside the canaliculi, carrying nutrients to the most peripheral cells of the system. Each Haversian system is surrounded by an amorphous cement line. Large transverse channels may be seen cutting across Haversian systems and connecting adjacent Haversian canals, called Volkmann's canals, and containing blood vessles. Haversian systems are constantly being remodeled.

Any time bone grows, it is by laying down of new bone to preexisting surfaces (appositional growth only)

Osteocytes do not lay down new matrix or divide

Meninges

Outer coverings 1. Dura mater- thick 2. Arachnoid- blood vessels in subarachnoid space 3. Pia mater- thin

Cellular structure of skeletal muscle

Overall regular striated appearance due to registered myofibrils, in each cell or fiber; contractile elements are repeating units- sarcomeres (dark line to dark line); approx 2.2 micrometers in width; the fundamental contractile unit

Peroxisomes

Oxidize organic materials by transferring hydrogen atoms to molecular hydrogen

Satellite cell

PNS only. Small, dark nuclei. Cluster around and provide support for neuron cell bodies in peripheral ganglia.

Schwann cell

PNS only. Small, dark, flat nucleus. Responsible for myelination in the PNS. Each cell can myelinate only one axon, however each axon can be myelinated by several Schwann cells. Cytoplasm can also cover axons without myelinating them.

Pericardium (outer, fluid filled sac covering the heart)

Parietal pericardium (outer, nearest the skin): thin mesothelium that adheres to fat and connective tissue of pericardial cavity Pericardial fluid: plasma ultrafiltrate from visceral pericardium; proteinaceous in nature, lubricant for the contraction/relaxation of the heart, 15-50 cc Visceral pericardium: thin mesothelium, sometimes cuboidal, that adheres to epicardium

Mast cell

Participates in inflammatory and allergic responses through the release of mediators such as heparin, histamine, leukotrienes, and eosinophil chemotactic factor of anaphylaxis (ECF-A). Are most abundant in the skin, the GI and respiratory tracts, and around blood vessels. Cytoplasm contains numerous secretory granules (show up well with toludine blue a basic blue dye as large basophilic granules); VERY GRANULAR

Mucous secretion

Polysaccharides added to protein substrate to produce mucin (a glycoprotein). Packaged into secretory granules that become hydrated when released from the cell, to form mucus, a lubricating gel; cell morphology- typically simple columnar with flattened, basally located nucleus + apical portion containing granules; look clear

White adipose tissue

Predominant type of fatty tissue in humans. Consists of fat cells with a single large lipid inclusion- unilocular. White fat is ubiquitously distributed throughout the body, padding and insulating the organs. Functions as an energy reservoir, providing a low-weight, high calorie form of energy (relative to glycogen), without thermogenic properties. An endocrine organ involved in energy metabolism- synthesizes leptin.

Follicles

Primary: contain small B-lymphocytes Secondary: a pale central area, the germinal center. Germinal center contains activated B cells that will give rise to plasma cells. Germinal center is surrounded by a cuff of small B-lymphocytes called the mantle zone. Germinal center contains follicular dendritic cells (FDCs) which trap antigen and present them to B-cells and T cells. Tingible body macrophages can be found which are large cells whose cytoplasm contains phagocytized debris.

Erythropoiesis

Process of formation and differentiation of RBCs Under the control of a kidney-produced hormone known as erythropoietin. Proerythroblast --divides Basophilic erythroblast -- divides Polychromatophilic erythroblast -- divides Orthochromic erythroblast -- no division Reticulocyte -- no division Erythrocyte -- no division

Granulopoiesis

Process of formation and differentiation of granulocytes Is stimulated by CSF (colony stimulating factors), substances released by the macrophage/monocyte community, such as G-CSF or GM-CSF Myeloblast--divides Promyelocyte-- divides Neutrophilic, eosinophilic, or basophilic myelocyte-- divides Neutrophilic, eosinophilic, or basophilic metamyelocyte-- no division Neutrophilic, eosinophilic, or basophilic band-- no division Segmented neutrophil, eosinophil, or basophil-- no division

Thrombopoiesis

Process of formation of platelets Control is by a serum glycoprotein known as thrombopoitein Megakaryoblast- large cell with a big nucleus (4n) situated close to sinuses Megakaryocyte- a giant cell with a large polyploid nucleus (32n-64n), platelet demarcation channels very distinct, a massive protrusion of the cell penetrates a sinus and fragments into platelets Thrombocyte- final end product which circulates in the peripheral blood

Endocrine gland

Product is secreted into the bloodstream or the lymphatics. NO ducts associated with these glands. The "stalk" of connecting cells is obliterated during differentiation, so the gland consists of an "island" of cells embedded in connective tissue- NO direct connection to the surface. Closely associated with capillaries and products are called hormones.

Exocrine gland

Product is secreted via ducts onto an external or internal epithelial surface; gland remains connected to the surface by a stalk of cells (the duct) Unicellular- isolated cells in an epithelial surface, there is not duct (goblet cells in GI tract) Multicellular- clusters of cells that function as a single secretory unit. ~Without ducts- sheets of secretory cells, typically lining a surface (surface mucous cells lining the stomach) ~With ducts- this group compromises most of exocrine glands (salivary glands)

Serous secretion

Proteins packaged into secretory granules (called zymogen granules if they contain digestive enzymes); released by exocytosis; will stain pink or purple because they are making proteins; cell morphology- simple cuboidal or simple columnar. Basophilia may be present in the basal area due to large amounts of RER. Apical portion with secretory granules. In some glands, cells are pyramidal in shape and surround a small central lumen

Conducting portion

Provide a conduit through which air can travel to and from the lungs and to condition the inspired air

Functional (pulmonary) system

Pulmonary arteries are low-pressure vessels with thin walls. These vessels have an internal elastic lamina, smooth muscle, and elastic fibers. Venules originate from the capillaries and enter the interlobular septum finally leaving the lobule to follow the bronchial tree to the hilum

Sensory ganglia

Receive afferent impulses and transmit to the CNS. Neurons are pseudounipolar and surrounded by satellite cells. Entire group surrounded by a connective tissue capsule.

Calcitonin

Secreted by parafollicular cells in the thyroid gland. Reduces bone resorption and opposes the effects of PTH. Effect is to lower blood calcium levels and decrease osteoclast activity.

Growth hormone (GH)

Secreted by the anterior pituitary. Enhances synthesis of all the CTs.

Apocrine secretion

Secretory products are released along with a portion of the apical cytoplasm Example: mammary gland (lipid portion of milk only)

Merocrine secretion

Secretory products are released by exocytosis in membrane-bound granules or vesicles. Examples: salivary glands, exocrine portion of pancreas

Zymogen

Secretory vesicle containing digestive enzymes

Perichondrium

Serves both for protection, with an outer fibrous layer, and as a source of new cartilage, the inner chondrogenic layer. The fibrous layer contains abundant type I collagen and fibroblasts. The chondrogenic layer contains Type I collagen and some fibroblasts, but also a population of stem cells called osteoprogenitor cells. Osteoprogenitor cells may become either chondroblasts and then chondrocytes in cartilage or osteoblasts and then osteocytes in bone.

Endocardium

Simple squamous epithelium, sometimes cuboidal, over a CT layer of variable thickness, the subendocardial layer (thicker in the atria than in the ventricles), containing collagen fibers, elastic fibers, and smooth muscle (same as tunica intima of vessels). Purkinje fibers associated with the conduction system are found here

Endocrine gland

Since these glands secrete hormones directly into the bloodstream, they are highly vascularized. THEY DO NOT HAVE DUCTS. The major endocrine glands are discrete glands- pituitary, thyroid, parathyroid, adrenals, pineal gland. Products released from the base of the cell

Nucleus

Single large nucleus, usually centrally placed, moves to periphery if cell is injured. Fine chromatin. Large prominent nucleolus ("owl-eye" nucleus)

Simple cuboidal epithelium

Single layer of cells of equal height and width Function: absorption and secretion; protection Location: small ducts of exocrine glands; surface of ovary; kidney tubules; thyroid follicles

Simple columnar epithelium

Single layer of cells taller than they are wide Function: absorption and secretion; protection; lubrication Location: lining of gastrointestinal system; lining of gallbladder; some large ducts

Simple squamous epithelium

Single layer of flat cells Function: exchange of gases, nutrients; barrier; lubrication Location: lining of blood vessels (endothelium), lining of body cavities (mesothelium), lining of respiratory spaces (alveoli) in the lung, Bowman's capsule in the kidney

Pharyngeal tonsil

Single lymphoid structure located in posterior nasopharynx. Lined by ciliated pseudostratified columnar epithelium (respiratory type epithelium) with occasional patches of stratified squamous epithelium. No crypts

Thymus

Site of T-cell maturation. Bilobed lymphoid organ in the mediastinum. Has a thin loose CT capsule that penetrates into the parenchyma, dividing the organ into lobules. Each lobule has a cortex and medulla. CT contains blood vessels, efferent lymphatic vessels (NO afferent lymphatics), and nerves. Essential for the development of T-lymphocytes. Most of the growth factors are thought to be produced by the epithelial reticular cells. Blood-thymus barrier: continuos, non-fenestrated endothelial cells with tight junctions + basal lamina + epithelial reticular cells; found in cortex only and prevents exposure of thymocytes to antigens

Spleen

Site of destruction of aged or abnormal red blood cells and platelets. Enclosed by fibrous dense irregular CT capsule. Prominent trabeculae extend from the capsule into parenchyma. Parenchyma composed of splenic pulp, which is further subdivided into red and white pulp. The medial surface houses the hilum through which vessels and nerves pass into and out of the spleen. Lymphatic vessels are present in only 2/3 of all spleens.

Lysosomes

Site of intracellular digestion Primary: quiescent or not involved in digestion Secondary: primary lysosome fused with a phagosome, has a heterogenous appearance (heterophagy)

Blood flow

Size of vessels diminishes through arterial circulation, and then increases back up through venous return Elastic arteries to muscular arteries (with internal elastic lamina) to muscular arteries to arterioles to metarterioles to capillaries to metarterioles to capillaries to venules to large venules to small muscular veins to large muscular veins.

Slow twitch, oxidative

Skeletal muscle Color: red Contraction: slow Metabolism: oxidative (aerobic) Substrate: fatty acids Endurance: high Blood supply: high Fiber diameter: small Mitochondria: many Lipid droplets: many Sarcoplasmic reticulum: sparse Myoglobin: high Glycogen: low Myosin ATPase: low

Fast twitch, glycolytic (FG)

Skeletal muscle Color: white Contraction: fast Metabolism: glycolytic (anaerobic) Substrate: glucose Endurance: low Blood supply: low Fiber diameter: large Mitochondria: few Lipid droplets: few Sarcoplasmic reticulum: extensive Myoglobin: low Glycogen: high Myosin ATPase: high

Azurophilic (primary) granules

Stain reddish purple (not specific like secondary granules)

Unmyelinated fibers

Small axons in the PNS are embedded in clefts of the cytoplasm of Schwann cells. Each Schwann cell can sheathe (but not myelinate) a dozen axons. In the CNS, the majority of axons are unmyelinated. The axons are not sheathed by any type of cell.

Lingual tonsils

Small, numerous lymphoid nodules at base of tongue. Covered with stratified squamous epithelium; each has a single crypt into which empty the ducts

Smooth muscle macrostructure

Smooth muscle can be in bundles or sheets, longitudinal or circular in array (blood vessels or GI system); paler than cardiac or "slow twitch oxidative" skeletal muscle (less vascularization and lower myoglobin content); endomysium is sparse except between circumferential and longitudinal layers; cells are spindle shaped resulting in the nuclei having a staggered appearance

Marrow cavity

Soft connective tissue filling the central cavities of long bones and all the spaces between bony spicules or trabeculae. Classified as red (filled with sinusoids, reticular tissue, and hematopoietic tissue in which blood cells are formed) and yellow marrow (older, less active, filled with fat)

Alveolar ducts

Squamous alveolar cells line alveolar ducts and alveoli

Monocytes

Spend about a week in blood and migrate into tissue where they become tissue macrophages or histiocytes. Contain a fairly large nucleus which is ovoid, kidney, or horseshoe-shpaed, often located in an eccentric position. Life-span is 5-8 days. They ingest (phagocytize) and remove particulate matter, tissue debris, and infectious agents.

Cellular organization of smooth muscle

Spindle shaped cells; a single central nucleus, which appears wavy if the muscle is contracted; cytoplasm is eosinophilic but difficult to see distinct cell boundaries; no striations or sarcomeres; actin and myosin bundles anchor on SL membrane dense bodies (organization is usually diagonal); SR not as distinct or well organized; NO T-TUBULES; gap junctions between cells; autonomic nerve endings

Splenic circulation

Splenic artery enters a hilum branches into trabecular arteries, which follow the trabeculae. Trabecular arteries branch repeatedly and eventually enter splenic pulp as central artery. Become ensheathed by a cuff of T lymphocytes, the periarterial lympathic sheath (PALS). Central arteries subdivide to form penicillar arterioles that eventually empty into capillaries. Capillaries carry blood to the splenic sinusoids. Blood empties from the sinusoids into pulp veins and then into trabecular veins. Trabecular veins empty into the splenic vein that exits the spleen at the hilum.

Arterioles

Still maintain a round profile, with 2-5 concentric layers of smooth muscle cells, a low cuboidal to squamous endothelium and sparse adventitia.

Transitional epithelium

Stratified epithelium found exclusively in parts of the renal system. The shape of the top layer can change based on distention of the underlying tissue. Function: ability to distend Location: urethra, bladder, ureters, renal calyces

Cellular organization of cardiac muscle

Striated appearance; myofibrils- not as organized as in skeletal muscle, so striations not as apparent; T tubules larger in diameter and invaginate at Z band; SR; t-tubule junction is dyad not triad; SR less extensive; higher mitochondrial density Intercalated disks connect cardiac muscle cells at membranes of longitudinal ends

Cortex of lymph nodes

Subcapsular sinus located immediately beneath the capsule. Empties into the medullary sinuses via the cortical (intermediate) sinuses. Outer cortex is a meshwork of diffuse lymphoid tissue with macrophages, T-lymphocytes, plasma cells, and reticular cells. Contains lymphoid nodules (follicles) composed of B-lymphocytes. Inner (or deep) cortex also called the paracortex is continuation of the outer cortex and contains diffusely arranged T-lymphocytes . Few lymphoid nodules are found. The paracortex can be identified by the presence of specialized cells called high endothelial venules- serve as the point of entry for lymphocytes from peripheral blood into LN parenchyma.

Medulla of thymus

THERE ARE NO LYMPHOID NODULES OR FOLLICLES! Contains Hassall's corpuscles. Composed of flattened epithelial reticular cells which have degenerated; they may show some keratinization. Contains a large number of epithelial reticular cells, some large immature T-lymphocytes, and macrophages

Cortex of thymus

THERE ARE NO LYMPHOID NODULES OR FOLLICLES! Immature T-lymphocytes called thymocytes are produced and accumulate in the cortex. Composed of closely packed thymocytes, epithelial reticular cells, and macrophages

Mesenchyme

The cells have a large nucleus and prominent nucleoli, the cytoplasm is barely visible; Between the cells is a large amount of ground substance with very few fibers. Mesenchyme is only present in the embryo and gives rise to all adult CT

Respiratory bronchioles

The conducting portion transitions into the respiratory portion. Walls are interrupted by numerous saccular alveoli, sites of gas exchange.

Endochondral bone growth

The epiphyseal disk, maintaining itself via interstitial growth, is necessary for bone to attain its final length. The process by which bone lengthens requires a series of steps involving interstitial growth of remaining cartilage, resorption of cartilage facing the primary marrow cavity, and deposition of new bone on calcified cartilage remnants. 5 distinct zones of bone lengthening: 1. Zone of reserve cartilage (quiescence, resting zone)- little mitosis or synthesis of new cartilage here 2. Zone of cartilage cell multiplication (proliferative zone)- high mitotic activity and synthesis of new matrix here, cells align into longitudinal rows 3. Zone of cartilage cell hypertrophy- cartilage between adjacent cells become thinner as the cells and lacunae enlarge 4. Zone of cartilage calcification- cartilage matrix becomes calcified: cells die and blood vessels from the marrow cavity invade, forming tunnels. Chondroclasts nibble away at the calcified cartilage, reducing the "peninsulas" of calcified cartilage in some areas to "islands" 5. Zone of ossification- osteoblasts align spicules of remaining calcified cartilage and lay down osteoid

Blood vessels

The largest artery is the elastic artery, such as the aorta and its major branches, so called because the tunica media (middle layer) contains lots of elastic fibers (made of elastin) as well as CT and smooth muscle. The largest type of vein such as the pulmonary vein (which does NOT have lots of elastic in it, just a few for some flexibility) which is supported against collapse by lots of smooth muscle. The elastic in the artery is in the media (circular), while the muscle in the vein is in the adventitia (longitudinal). Next in size is the muscular artery, in which the elastic fibers have mostly disappeared and the media contains mostly smooth muscle. Both the artery and vein have an internal elastic lamina (IEL), a structure very evident in big, muscular arteries that have to accept large, pulsatile volumes of blood. IEL is also present in elastic arteries, but difficult to distinguish due to all the elastic fibers.

Plasma

The liquid in which peripheral blood cells are suspended. Composed of water, electrolytes, 7% plasma proteins, hormones, fats, amino acids, vitamins, carbohydrates, and lipoproteins.

Respiratory system

The mean by which, through a system of tubes, the body exchanges carbon dioxide for oxygen, which is then distributed throughout the body. 2 parts: an upper conduction portion and a lower respiratory portion

Periosteum and endosteum

The osteogenic layers are comprised of osteoprogenitor cells and osteoblasts. Osteoblasts are directly responsible for matrix production, will turn into osteocytes, and are found in actively growing bone. Osteoprogenitor cells are squamous, spindly cells that are more immature than osteoblasts and can evolve into either osteoblasts or chondroblasts. With the proper stimulus, osteoprogenitor cells become osteoblasts in highly vascularized regions, or chondroblasts in avascular regions. Tendons, ligaments, and joint capsules insert into bone by blending in with the outer fibrous layer of the periosteum and inserting into the underlying bone matrix. Their collagen fibers that are anchored in the bone tissue are called Shipley's fibers.

Epineurium

The outer layer of dense connective tissue. It surrounds several nerve bundles. Contains blood vessels and lymphatics.

Sarcolemma

The plasma membrane (outer-covering) of muscle cells; contains many ion transport proteins, ion channels and receptors; regulates flow of ions and metabolism; invaginates in striated muscle, at each Z-band in cardiac, and at A-I band junction in skeletal muscle, to form transverse tubule system; TT brings depolarization signal deep into the muscles (There is a specialized region in each skeletal muscle fuber that forms post synaptic membrane portion of the motor end plate. No such structure in cardiac or smooth muscle)

Vocal cords

The upper pair of folds are the false, or vestibular, vocal cords which are covered by typical respiratory (ciliated pseudostratified columnar) epithelium beneath which are numerous serous glands. The lower pair of folds are the true vocal cords. The true vocal cords are covered by a stratified squamous epithelium.

Myocardium

Thickest layer of the heart, composed of bundles of cardiac muscle of varying thickness, recognized by striations, intercalated discs, branched fibers and centrally located nuclei. Strands of connective tissue and some vascular tissue through it (same as tunica media of vessels).

Epicardium

Thin layer of flat to cuboidal cells, covering fibrous and adipose connective tissue; contains nerves and vasa vasorum (vessels) of both heart and of coronary vessels found in this connective tissue mass (same as adventitia of vessels)

Endoneurium

Thin layer of reticular fibers that surround individual nerve fibers

Kinetics of neutrophil production

Time to develop from myeloblast to mature neutrophil ~11 days 1. Medullary formation compartment: in the bone marrow 2. Medullary storage compartment: acts as a buffer system, capable of releasing large numbers of mature neutrophils upon demand, located in the bone marrow 3. Circulating compartment: consists of neutrophils suspended in plasma and circulating in blood vessels 4. Marginating compartment: composed of neutrophils present in blood but not circulating (are in capillaries) In the case of an acute bacterial infection, neutrophils can be recruited quickly from the marginating pool, rather than waiting for new neutrophils to be formed and/or released from the bone marrow.

Lymphatic

Tissues or organs in which lymphocytes form the major cellular component and includes the thymus, bone marrow, lymph nodes, and spleen. All lymphoid organs originate from mesoderm, EXCEPT the thymus that originates from mesoderm and endoderm

Bronchial tree

Trachea divides into 2 primary bronchi. After entering the lungs the primary bronchi give rise to lobar bronchi which supply a pulmonary lobe. There are 3 lobar bronchi in the right lung and 2 in the left. Lobar bronchi divide to give rise to smaller bronchi whose termini are the bronchioles. Each bronchiole enters a pulmonary lobule where it branches to form 5-7 terminal bronchioles.

Axons

Transmission of impulses away from the perikaryon. Although collateral branches may arise a short distance from the body, the axon is otherwise unbranched until it terminates; it is constant in diameter throughout its length. Arises from the axon hillock. This contains no Golgi complex or Nissl substance. The axoplasm contains many longitudinally oriented microtubules and neurofilaments, mitochondria and smooth ER. It never contains Nissl substance or Golgi. Surrounded by a plasma membrane called the axolemma, a protective layer of glial cells further surround this. Bidirectional transport: 1. Macromolecules and organelles made in the perikaryon are transported to the axon terminals by anterograde flow 2. Retrograde flow transports molecules (viruses and toxins included) to the cell body

3 layers of vessels (veins, arteries and capillaries)

Tunica intima: inner- akin to the endocardium Tunica media: middle- akin to the myocardium Tunica adventitia: outer- akin to the epicardium

Brown adipose tissue

Uncommon in adult humans sole purpose appears to be heat generation in mammals, in which it functions upon arousal from hibernation, survival after birth, and during cold stress. The main site of non-shivering heat production under conditions of cold stress. Brown fat is widely distributed in the first decade of life in humans, becoming confined with increasing age to deeper organs in the body such as the kidney. Lipid accumulates in each of the fat cells as many individual droplets of varying size- A MULTILOCULAR PATTERN. When lipolysis is initiated, fatty acids enter the numerous large mitochondria of these cells where oxidative phosphorylation is increased, and energy is liberated as heat. The large number of mitochondria in the cells and rich vascularity of the tissue contribute to its dark color.

Development of fat cells

Undifferentiated mesenchymal cells are transformed into lipoblasts. Lipoblasts accumulate fat and give rise to mature fat cells. When the body mobilizes a large amount of lipid, mature unilocular fat cells return to the lipoblast stage. Once adipocytes are formed, they remain throughout life and only a reduction of cell size is possible.

BAT is not WAT

Unilocular fat cell (WAT) develops from fibroblast-like precursor into a cell with multiple lipid droplets similar to those of BAT. The individual droplets then coalesce into a single lipid droplet.

Mitochondria

Very elongate, branch extensively through and around myofibrils; produce ATP for contractile proteins and membrane ion pumps; smaller mito often found under the sarcolemma, around the nuclei, mito may exist as a "reticulum" (continuous complex)

Sinusoids

Very large capillaries and have no diaphragms, numerous fenestrae (openings) and a discontinuous basal lamina. Large compounds and even cells pass through and can move in and out of these vessels. Found in liver, bone marrow, and spleen.

Basement membrane

Visible with light microscope; formed by either the fusion of 2 basal laminae or a basal laminar and a reticular laminar 1. the fusion of a basal lamina formed by an epithelial cell and a basal lamina of an endothelial cell layer, especially visible in the kidney glomerulus and in the alveoli of the lung 2. more common form of basement membrane composed of a basal lamina plus a lamina reticularis; lamina reticularis is formed by fibroblasts subjacent to the basal lamina; lamina reticularis contains fibronectin and type III collagen, type IV collagen fibrils bind the basal lamina to the subjacent collagen

Matrix composition

Water (70%), type II collagen (40% of dry weight), GAGs, and various proteins/ glycoproteins

Cytoplasm

Well developed RER and polyribosomes. Appears as clumps with H&E stains (Nissl substance). Especially prominent in large active neurons such as the motor neurons of the spinal cord. Usual organelles are present --Golgi complex, mitochondria, lysosomes. May contain pigment such as melanin or lipofuscin. Abundant microfilaments (intermediate filaments) help form the cytoskeleton of the perikaryon

Cartilage- general

Well-defined structural organization. Consists of abundant amounts of intercellular material, or matrix, produced by cells that are permanently surrounded and entrapped in the matrix. It is firm and rigid yet has some flexibility. Usually surrounded by a fibrous connective tissue- the perichondrium. Functions for support, growth of most bones, and articulation of bones. AVASCULAR