Chapter 7 In Class: Bone Tissue
Achondroplastic dwarfism results from a failure of cartilage growth. Activity in which two zones is impaired?
(2)cell proliferation and (3)hypertrophy?
Be able to explain/interpret calcitriol synthesis (slide 40)
(hormone that regulate Ca levels in the body) -calcitriol is a form of vitamin D produced by sequential action of the skin, liver, and kidneys -acts on bones, kidneys and small intestine to raise blood calcium levels and promote resorption 1. epidermal keratinocytes use UV light and convert steroid (cholesterol) to pre vitamind D3. transport protein to blood 2. liver add OH to molecule , turn it into calcidiol 3. Kideny adds OH , turn calcidiol to calcitriol
Tendons
(not part of the skeletal system proper) tough connective tissue connecting muscle to bone
Where, in a bone organ, are osteogenic cells found (endosteum? periosteum?)?
****in the endosteum and inner layer of the periosteum. ***
What are the potential consequences of low calcium levels (hypocalcemia)?
-Excessive excitability of the nervous system -Leads to muscle tremors, spasms, or tetany (inability to relax a muscle)
Which of these two pathologies, Osteogensis imperfecta and Rickets, is related to dietary calcium deficiency, and which is related to a congenital deficiency in the ability to synthesize collagen?
-Osteogenesis imperfecta: collagen deficiency, bones become brittle (congenital) -Rickets: calcium deficiency, bones become soft (flexible), usually due to a vitamin D deficiency **See textbook for additional information
Be able to explain/interpret calcitriol action (slide 41)
-calcitriol raises blood calcium levels in three ways (predominantly by increasing calcium absorption by the small intestines) 1) increase Ca+ absorption by small intestine 2)increase ca+ from skeleton. 3) weakly promotes reabsorption of ca+ by kideny , less calcium is lost in urine.
What are the extracellular components of osseous tissue and what are they composed of?
-organic matrix: ground substance and collagen fibers -inorganic matrix: mineral salts
Bone anatomy ID structures (slide 10)
-shaft-diaphysis -expanded portions of tissue at the ends (proximal and distal epiphysis) -metaphysis: where the diaphysis meets the epiphysis; includes the growth zone -epiphyseal line: where the growth plate was before the bone finished growing and ossified -medullary cavity: hollow space in the middle (spongy bone inward but as the bone developed spongy bone dissolved to house marrow)
Slipped capital femoral epiphysis
-the epiphysis and diaphysis of the femur have "slipped" out of their normal position to each other -fractures are normal in young kids (predisposed) because of the growth plate (weaker area of tissue)
Bone develops through the process of osteogenesis (ossification) in one of two ways
1) Intramembranous Ossification - direct developmenet 2)Endochondral Ossification - indirect development
Be able to explain/interpret parathyroid hormone (PTH) action (slide 42)
1) PTH bines to receptor on osteoblast, stimulate to secrete RANKL => raise bone resorption and osteoclas population => more resorption 2) PTH promotes ca+ reabsorption by kidney (less lost in urine , more urinary pshophate excretion) 3)PTH prmotes final step of calcitriol synthesis in kideny 4)inhibits collagen synthesis by reducing osteoblast activity -> inhibit bone deposition.
What bone surfaces are sheathed with endosteum (a reticular connective tissue)?
1)lines inner marrow cavity, 2)all the honeycombed surfaces of spongy bone 3)lines the canal system in compact bone
Give a 1-2 sentence synopsis for each major skeletal function: support movement protection electrolyte balance acid-base balance blood formation
1. Support. Bones of the limbs and vertebral column support the body; the mandible and maxilla support the teeth; and some viscera내장 are supported by nearby bones. 2. Protection. Bones enclose and protect the brain, spinal cord, heart, lungs, pelvic viscera, and bone marrow. 3. Movement. Limb movements, breathing, and other movements are produced by the action of muscles on the bones. 4. Electrolyte balance. The skeleton stores calcium and phos- phate ions and releases them into the tissue fluid and blood according to the body's physiological needs. 5. Acid-base balance. Bone tissue buffers the blood against excessive pH changes by absorbing or releasing alkaline phosphate and carbonate salts. 6. Blood formation. Red bone marrow is the major producer of blood cells, including cells of the immune system
Two types of osseous tissue and how to ID them
1. compact bone: dense osseous tissue 2. cancellous (spongy) bone: loosely organized latticework osseous tissue
Be able to explain/interpret bone growth processes and 5 growth zones (slide 29)
1. zone of reserve cartilage: resting hyaline cartilage 2. zone of cell proliferation: chondrocytes multiplying and lining up in rows of small flattened lacunae 3. zone of cell hypertrophy: cessation of mitosis, enlargement of chondrocytes and thinning of lacuna walls (increase in size) 4. zone of calcification: temporary calcification of cartilage matrix between columns of lacunae 5. zone of bone deposition: breakdown of lacuna walls, leaving open channels, death of chondrocytes, bone deposition by osteoblasts forming trabeculae of spongy bone
Name the periosteum's two layers and give the function of each
1.outer fibrous layer: tough, outer layer of collagen, some collagen fibers continuous with tendons and penetrate into the bone matrix as perforating fibers. The periosteum thus provides strong attachment and continuity from muscle to tendon to bone. 2. inner osteogenic layer: bone-forming cells = growth of bone and healing of fractures
Label the boxes as either compact or spongy bone. (slide 7)
1st box: dense compact bone, perimeter of the length of the bone 2nd box: spongy bone (further down to the bone hollowed out with marrow)
osteogenic cell, osteoblast, osteocyte, osteoclast
4 types of bone cells
Endosteum
A thin layer of reticular connective tissue, which 1)lines internal marrow cavity 2) covers all the honeycombed surfaces of sponge bones 3) lines the canal system in compact bone. the marrow spaces amid the spongy bone are called ____
intramembraneous ossification
Appositional growth , thickening and widening, occurs by ____ ____ at the bone surface. New osteons are formed, and circumferential lamellae are deposited.
Be able to give a 1-2 sentence synopsis (interpretation) of each of the stage of endochondral ossification shown on slide 24. At what stage does osteoclast activity begin?
At stage 3. 1. early hyaline cartilage model (pericardium layer_fibrous conduit blasts, cartilage growth) 2. formation of primary ossification center (via cell death), bony collar and periosteum "appositional growth"-added girth to structure 3. vascular invasion formation of primary marrow cavity (filled with spongy tissue), and appearance of secondary ossification center. Osteclasts arrive and hollow out cavity osteoclasts dissolve calcified cartilage remnant-enlarging marrow cavity 4. bone at birth, with enlarged primary marrow cavity and appearance of secondary marrow cavity in one epiphysis 5. Bone of child; with epiphyseal plate at distal end (form between the two ossification centers); elongation of bone occurs in the growth zone at the plate 6. adult bone with single marrow cavity and closed epiphyseal plate
Osteoclasts are multi-nucleate -why (developmentally speaking)?
Because each osteoclasts is formed by the fusion of several stem cells.
How do osteocytes in an osteon receive nutrients and eliminate waste?
Blood goes into further out sheets of tissue, indirect communication through cytoplasmic processes allows for cells near the central canals to receive blood indirectly. -perforated canal: allows blood vasculature between the central canals of osteons
What is the primary function of osteoclasts?
Bone-dissolving cells
What are the two main principal ions involved in crystallization, and how do they arrive? What are they delivered to the extracellular matrix of osseous tissue?
Calcium and phosphate crystallization fibers as hydroxyapatite (frystalization of fiber) 1) lay down collagen fiber 2) fiber become encrusted with minerals -> harden matrix 3)Hydroxyapatite crystal form when it reaches critical value (solubility product) 4) most tissues have inhibitors to prevent this calcified, but Osteoblast neuralize inhibitor -> allow salt precipicate in bone matrix 5) Few crystals attract more calcium and phosphate from solution -> calcified
What is more flexible cartilage or bone? Why?
Cartilage osseous tissue (bone) = connective tissue hardened by deposition of calcium phosphate and other mineral. (mineralizationg and calcification) = hard and inflexible
The EC matrix of spongy bone is arranged in lamellae(thin memebrane), like compact bone, but there are few osteons(like compact bone), which are unnecessary-why are osteons unnecessary in spongy bone?
Central canals are not needed here because no osteocyte is very far from the marrow.
Be able to label compact bone and spongy (cancellous) bone on the x-ray (slide 2)
Compact: pure white Spongy: thread-like white lattice work *built same way, organized differently
What is "diploe" and what protective function does it serve, as an individual experiences force trauma to the skill?
Cranium = two layers of compact bone enclosing middle layer of spongy bone. This spongy layer in the cranium is _______. -force is dissipated/dispersed throughout the lattice work of the spongy tissue "shock absorber and protect inner layer of compact bone. -A moderate blow to the skull can fracture the outer layer of compact bone, but the ______ may absorb the impact and leave the inner layer of compact bone unharmed. Both surfaces of a flat bone are covered with periosteum, and the marrow spaces amid the spongy bone are lined with endosteum.
What is the underlying cell-molecular cause of hypercalcemia?
Inhibit sodium channels from opening because excess calcium causes a larger charge difference across the membran
The ruffled border of osteoclasts faces the bone-what is the function significance of this orientation and of the ruffled border?
It increases the cell surface area and enhances the efficiency of bone resorption.
Long Bones
Movement = > these bones function importantly as levers acted on by skeletal muscle (radius, ulna, femur, tibia, fibula etc, humerus)
Are osteocyte cells mitotic?
NO
What are the potential consequences of hypercalcemia?
Nerve and muscle cells are less excitable than normal causing depression of the nervous system, muscle weakness, emotional disturbances
Are osteoblast cells mitotic?
No, no miotic
Hypocalcemia causes "excitability" - why ie what is the cell/molecular explanation with respect to neurons and muscle cells and their voltage-gated sodium channels?
Not enough calcium to counteract the negative glycoproteins they usually mask; the calcium channels open more easily and stay open longer allowing sodium to enter the cell too freely
cells, fibers, and ground substance
Osseous tissue is connective tissue that consists of
Do osteogenic cells remain mitotically active, and if so, to what type of bone cells do they give rise to?
Osteoblast (bone forminc cells)
How do osteocytes function in bone remodeling?
Osteocytes are strain sensors. When a load is applied to the bone, it produces a flow in EC fluid and lacunae. This stimulates the sensory primary cilia on the osteocytes and induces the cells to secrete signals that regulate bone remodeling - adjustment in bone shape and density to adapt to stress.
Give the structural relationships between lacunae, canniculi, osteocytes
Osteocytes reside in lucunae (tiny cavity) which are interconnected by channels "canaliculi"
What is the functional significance of the cytoplasmic processes of osteocytes that lie in the canniculi?
Osteocytes reside in tiny cavities called lacunae, which are interconnected by slender channels called canaliculi (CAN-uh-LIC-you- lye). Each osteocyte has delicate cytoplasmic processes that reach into the canaliculi to contact the processes from neighboring osteocytes. Some of them also contact osteoblasts on the bone surface. Neighboring osteocytes are connected by gap junctions where their processes meet, so they can pass nutrients and chemical signals to one another and pass their metabolic wastes to the nearest blood vessel for disposal.
How does bone function in homeostatic control of pH?
Phosphate help to correct acid-base imbalance in the body fluid. acid breaks down minerals and releases carbonate and phosphate ions into blood--if you break down calcium carbonate ions, bicarbonate is released--which is a buffer also get rid of CO2
How does the pathology arteriosclerosis relate to mineral deposition?
Results from calcification of the arterial walls "hardening of the arteries"
Be able to explain/interpret calcitonin action (slide 43)
Secreted when blood calcium is too high and needs to be lowered • Inhibits osteoclasts -> less bone resorption • Stimulates osteoblasts to deposit Ca into skeleton
Bone injury types
Simple fracture Comminuted fracture Open fracture: completely broken *healing of a fracture usually occurs as long as the blood supply and cells of the endosteum and periosteum survive
Critical value (and significance)
Solubility product - Hydroxyapatite crystals form only when product of calcium and phosphate concentration in tissue fluid reaches that point.
How to osteocytes function in homeostasis of bone density and blood levels of calcium and phosphate ions?
Some resorb bone matrix and others deposit it, so they contribute to the homeostatic maintenance of both bone density and blood concentrations of calcium and phosphate ions
Stress and fractures stimulate osteogenic cells to multiply more rapidly and quickly generate increased numbers of osteoblasts: what is the function significance of this-how is this adaptive?
Stress and fractures stimulate osteogenic cells to multiply more rapidly and quickly generate increased numbers of osteoblasts, which reinforce or rebuild the bone.
Example of form of dense regular connective tissues (2)
Tendon, ligament (cords of fibrous tissue; regular (parallel to one another))
What is the function of: articular (hyaline) cartilage?
The joint surface where one bone meets another is convered with layer of hyaline cartilage called ____ ________. Function: enable joint to move easily. (blue color on slide 10) eases joint movements with the fluid, holds airway open during respiration, moves vocal cords during speech, precursor of bone in the fetal skeleton and the growth zones of long bones of children
embryonic mesenchymal cell -> osteogenic cell -> osteoblast -> osteocyte
The order of cells that arise from embryonic mesenchymal cells
The regularity (parallel orientation of fibers) seen in ligaments makes "engineering" sense, given the forces they experience. How so?
The parallele arrangement of fibers is an adaptation to the fact that tendons and ligaments are pulled in predictable direction by musculoskeletal stresses.
Periosteum
The periosteum is a membrane that covers the outer surface of all bones, except at the joints of long bones. Function: Bone growth, remodeling, repair, bone sensitivity, nourishment This has a tough, outer fibrous layer of collagen and an inner osteogenic layer of bone-forming cells . Some collagen fibers of the outer layer are continuous with the tendons that bind muscle to bone, and some penetrate into the bone matrix as perforating fibers. The periosteum thus provides strong attachment and continuity from muscle to tendon to bone. The osteogenic layer is important to the growth of bone and healing of fractures. There is no periosteum over the articular cartilage.
(cellular components) osteoclasts, which arise from ___ stem cells
They develop from the same bone marrow stem cells that give rise to the blood cells. formed by the fusion of several stem cells, so osteoclasts are unusually large (up to 150 μm in diameter, visible to the naked eye).
T/F both tendons and ligaments are forms of dense regular connective tissue
True -1) collagen fibers are packed and leave little space 2) fibers are parallel to each other both are found in tendons 힘줄 and ligament.인대
What is the function of: red and yellow bone marrow?
Yellow: adipose tissue, fat storage, later in life in the shafts of long bones -energy storage -extensive bleeding yellow marrow can be mobilized to drive large volumes of blood synthesis Red: blood cell and platelet forming
osteoblast
are bone-forming cells. immature bone cell that secrete organic components of matrix. (ground substance and collage fibers)
osteogenic cell
are stem cells that develop from embryonic mesenchyme and then give rise to most other bone cell types. ****in the endosteum and inner layer of the periosteum. *** stem cell whose divisions produce osteoblasts
primary function of red marrow is the production of:
blood cell
Wolff's law of bone
bones change their morphology in response to environmental forces -remove or add to bony tissue to meet circumstances -mechanical stresses correct spongy bone structure **Spongy tissue adapts to force lines (adaptations: cowboys bone growth on inner sides of femurs because of force generation) --tension and compression forces are responsible for force lines
The skeletal system is composed of ____ to form a strong, flexible framework
bones, cartilage ,ligament
what are the other names for spongy bone (2)
cancellous , trabecular bone
What is bone matrix
composite material synthesized by osteoblasts 1/3 organic - flexibility , reduce brittleness (polymer, collagen) - some protein carbo complex = GAG's linked to core protein, forming proteoglycans 2/3 inorganic - resistance to force. mostly calcium phosphate (Hydroxyapatite), some calcium carnonate
Osseous tissue
connective tissue in which the extra cellular matrix is hardened by the deposition of calcium phosphate and other minerals ( through calcification or mineralization processing); (consists of cells, collagen fibers and ground substance)
cellular matrix
consists of: fibroblasts, fibrocytes, machrophages, mast cells, histiocytes
bone ( the word)
denote an organ composed of all these tissues (blood, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue) or it can denote just the osseous tissues
What role does the enzyme acid phosphatase, released by osteoclasts, play in bone resorption?
digest collagen of the bone matrix
(cellular components) Osteogenic cells, osteoblasts, and osteocytes, which arise from _____ stem cells
embryonic mesenchymal cells developing embryo, loose confederation of cells -osteogenic cells develop into osteoblasts which form bone and then become osteocytes (former osteoblasts embedded in matrix they deposited-extensions allow for separated osteocytes to communicate through mineralized tissue) *aren't close to vasculature (communication and transport via extensions)
dense connective tissue
fiber occupies more space than the cells and ground substance, closely packed in tissue section.
periosteum
flat bones are covered with
Not many of the bones of the human skeleton from through intramembranous ossification, but some do, which one?
flat bones of skull and most of clavicle (collarbone
What are the four types of bones (structure)?
flat, long, short, irregular
ground substance
fluid or semi-fluid portion of the matrix
Bone
hard, calcified connective tissue that compose the skeleton, composed in part by osseous tissue
Osteoblast cells primary function is secretory-what do they secrete?
hormone osteocalcin - stimulates insulin secretion by the pancreas, increases insulin sensitivity in adipocytes and limit the growth of adipose tissue.
Short Bones
in their articulation with other bones, these bones facilitate a limited gliding motion (triquetral, carpals, tarsals)
Endochondral bone
is preceded by a hyaline caritlage model that is replaced by osseous tissue.
osteocytes
mature bone cell that maintains the bone matrix
osteoclast
multinucleats cell that secrets acid and enzymes to dissolve bone matrix
in adults, the major function of yellow marrow is:
no longer produces blood, fatty--in the event of severe or chronic anemia, it can transform back into red marrow and resume its hemopoietic fucntion
Where, in a bone organ, are osteoblast cells found, and to what type of bone cells do they give rise to?
on the bone surface under the endosteum and periosteum. give rise to Osteocytes - trapped in matrix and deposited.
Where, on a bone organ, do osteoClasts (bone dissolving cells) reside?
on the bone surfaces or some reside in pits called resorption bays (Howship lacunae) that they have etched (engraved) into the bone surface
What is the function of: nutrient foramina?
opening in bone to allow blood vessels to enter the bone to bring in oxygenated blood and remove non oxygenated blood -accommodated by vessels and arteries -lots of metabolic activity services by vascular
The term "bone" differs from "osseous tissue". How so?
osseous tissue: ossified, bony tissue bone: osseous tissue and the other tissues (blood vessels, bone marrow, cartilage, adippose tissue, nerous tissue, and fibrous tissue)
What bone surfaces are sheathed with periosteum, and which are not?
outer surfaces of all bones not the inner surfaces or the hyaline(articular) cartilage
Mineral resorption
process of dissolving bone. releases minerals into the blood and makes them available for others use.
Cartilage (연골)
relatively stiff connective tissue with a flexible rubbery matrix; shape and support the nose, ears and partially enclose the larynx (voice box), trachea (windpipe) and thoracic cavity
Be able to give a 1-2 sentence synopsis of each of the four stage of intramembranous bone development (slide 22)
sheet/membrane of mesenchymal tissue (highly vascularized, diff. into osteoblasts_secrete tissue_EC matric) high activity near blood vessels; convert to osteoblasts and bony tissue 1. osteiod tissue being formed, deposited into embryonic mesenchyme (limit space for blood vessels) 2. calcification of osteoid tissue and entrapment of osteocytes 3. honeycomb of spongy bone with developing periosteum 4. filling of space to form compact boen at surfaces, leaving spongy bone in the middle (trabecula with marrow in the middle) *cross section of the skill bone = figure 7.7
lacunae
small cavities in bone that contain osteocytes
What is the function of the perforating fibers of the outer periosteum layer and how are they organized to meet this function?
some collagen fibers of the outer layer are continuous with the tendons that bind muscle to bone, and some penetrate into the bone matrix as perforating fibers.The periosteum thus provides strong attachment and continuity from muscle to tendon to bone.
Osteons
the basic structural unit of compact bone -each osteon consists of a central canal and it's concentric lamellae -each lamella consists of EC matrix, with embeded osteocytes -central canals connect via perforating (Volkman's) canals, both of which are lined with endosteum
endosteum
the marrow spaces amid the spongy bone are lined with
BONE MARROW: within long bones, in what two areas is marrow located?
the spaces amid the 1)trabeculae of spongy bone, 2)the larger central canals
Be able to circle the epiphyseal line in the adult femur on slide 25.
the thin line near the top of the bone
Flat Bones
these bones are thin plates, many of which serve a protective function (temporal,scapula, rib bones, skul, sternum)
Irregular Bones
these bones have varied structures and roles-many bones of the body fall into this classification (vertebra) -"catch all"
Understand appositional bone growth (slide 31)
thickening and *widening*, occurs by intramembranous ossification at the bone surface -new osteons are formed and laid down in concentric layers under the periosteum-circumferential lamellae are deposited -new osteon layering as well *enclosing the blood vessel/vasculature=central canal being created for the new osteons (created on the edges)
Ligaments
tough connective tissue connecting bone to bone (stabilize joints)
What role do osteoclasts and surface receptors for calcium ions on osteoclasts play in triggering mineral resorption?
• surface Receptors for calcium respond to falling levels of calcium in the tissue fluids • Mineral resorption is carried out by osteoclasts trigger in osteoclasts, produce HCl and dissolve the tissue "resorption bays" -crystal dissolution releases minerals into the blood -mediated by osteoclasts in response to falling blood Ca++ levels