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A464-Test 3
lecture 16
66
Anatomy
Undergraduate 4
03/28/2011

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Term
cartilage
Definition
tissue that is comprised of highly organized ECM
Term
what does firm consistency of cartilage allow it to do?
Definition
bear mechanical stress without distortion
Term
where is cartilage found?
Definition
lining joints, tendons and ligaments, airway (nose, larynx, trachea, bronchus)
Term
functions of cartilage (4)
Definition
1. support airways, ligaments
2. shock absorption of joint surfaces
3. smooth movement of joint surfaces
4. bone growth
Term
what is cartilage matrix made up of? (3 things)
Definition
1. glycosaminoglycans and proteoglycans (50%)--made up of hyaluronic acid and chondroitin sulfate
3. glycoproteins (5-10%)
4. collagen (type II) (40%)
Term
staining of cartilage matrix
Definition
light--hard to discern because it is in much smaller fibrils than other tissues
Term
EM striations of collagen are masked by interactions with what?
Definition
proteoglycans
Term
very long hyaluronic acid molecules run parallel to what two things?
Definition
collagen fibers and proteoglycans (arranged perpendicular to collagen fibril fiber bound directly to it)
Term
perichondrium
Definition
dense regular CT covering of cartilage
Term
what is perichondrium comprised of?
Definition
type I collagen and fibroblast-like cells
Term
what does perichondrium do for cartilage?
Definition
since it is highly vascularized, it provides nutritional support for cartilage b/c cartilage does not have blood vessels within it
Term
cells of cartilage (3 types)
Definition
-mesenchymal precursor (fibroblast-like) cells
-chondroblasts
-chondrocytes
Term
mesenchymal precursor cells
Definition
-fibroblast-like
-found in perichondrium
-differentiates into chondroblasts
Term
chondroblasts
Definition
-in inner surface of perichondrium
-secretes matrix
-H&E basophilic cytoplams, euchromatic nucleus
-differentiates into chondrocytes
Term
chondrocytes
Definition
-within cartilage
-secrete smaller amounts of matrix, maintain cartilage
-represent terminal differentiated cell in this lineage
Term
lacunae
Definition
nest where chondrocytes are trapped
Term
two types of growth in cartilage
Definition
1. interstitial growth
2. appositional growth
Term
interstitial growth
Definition
cell division of chondrocytes in lacunae
Term
appositional growth
Definition
differentiation of cells from the perichondrium (much more important type of growth)
Term
types of cartilage (3)
Definition
1. hyaline
2. fibrocartilage
3. elastic
Term
hyalin cartilage
Definition
-found in airways, at ends of bones at joints, growth plate
-smooth appearing matrix
-cells present in rounded lacunae typically surrounded by more intensely stained matrix
-has a perichondrium
Term
fibrocartilage
Definition
-found in tendons and ligaments, intervertebral disks
-cartilage alternating with thick layers of dense type I collagen
-chondrocytes often found in rows
-no perichondrium
Term
elastic cartilage
Definition
-found in eustachian tubes, larynx, epiglottis, pinnae of ear
-has abundant elastic fibers in cartilage matrix
-visualized with typical elastin fiber stains
-cells in rounded lacunae
-has a perichondrium
Term
bone
Definition
specialized form of CT, comprised mainly of calcified ECM
Term
functions of bone (3)
Definition
-mechanical support
-locomotion
-metabolic reservoir of minerals (calcium)
Term
what is the ECM component of bone
Definition
osteoid
Term
osteoid
Definition
-represents 50% of dry weight of bone
-produces lightweight, stress-resistant scaffold of bone
Term
components of osteoid
Definition
-type I collagen fibers
-proteoglycans
-glycoproteins
Term
what is the mineral component of bone?
Definition
-crystals of hydroxyapatite Ca10(PO4)6(OH)2
Term
what produces the hardness of bone?
Definition
crystals of hydroxyapatite
Term
what is the mineralization process of bone
Definition
-bone cells do a number of things that lead to increased concentration of calcium and phosphate in the environment leads to precipitation or crystallization of hydroxyapatite
Term
gross anatomy types of bone (3)
Definition
-long bone
-compact bone
-cancellous trabecular, spongy bone
Term
compact bone
Definition
-found on outside of bones
-appearing intact, solid
Term
cancellous trabecular, spongy bone
Definition
-spicules found in the middle of bones
Term
epiphysis
Definition
primarily cancellous bone with a thin layer of compact bone
Term
diaphysis
Definition
majority of compact bone
Term
medullary cavity/marrow cavity
Definition
-where precursors to blood and mesenchymal cells formed, filled with fat in adults
Term
periosteum
Definition
external surface
Term
endosteum
Definition
lines marrow cavity
Term
histologic types of bone (2)
Definition
1. primary bone (woven bone)
2.secondary bone (lamellar bone)
Term
primary bone (woven bone)
Definition
-first bone to appear in embryonic tissue
-remodeled to secondary bone (very little present in adults)
-randomly distributed collagen fibers
-lower mineral content
-high number of cells
Term
secondary bone (lamellar bone)
Definition
-term comes form microscopic appearance of ground sections that show concentric layers of material
-haversian system or osteon: structural unit upon which lamellar bone is based
Term
haversian system or osteon
Definition
structural unit upon which lamellar bone is based
-composed of: haversian canal, lamellae, cancliculi, volkman's canals, interstitial lamellae
Term
haversian (central) canal
Definition
-in middle of osteon
-has blood vessels and nerves, lymphatics
Term
lamellae
Definition
layers of bone with cells/osteocytes in lacunae
-multiple lamellae with collagen fibers at right angles to one another
Term
canaliculi
Definition
-small pores that connect cells in the lamellae.
-processes of osteocytes found inside here
Term
volkman's canals
Definition
-oblique canals without surrounding lamella
-permit Haversian system to communicate with other systems and the bone marrow
Term
interstitial lamellae
Definition
-in between partially remodeled Haversian systems
Term
cell of bone (4)
Definition
1. osteoprogenitor cells
2. osteoblasts
3. osteocytes
4. osteoclasts
Term
osteoprogenitor cells
Definition
-mesenchymal progenitor cells derived from bone marrow (can be similar in appearance to fibroblasts, but can also line internal surfaces of bone with appearance of squamous epithelium)
-found primarily in periosteum and endosteum
-differentiate into osteoblasts
-plays key role in bone growth w/in periosteum: appositional growth
Term
osteoblasts
Definition
-secrete matrix that becomes bone
-H&E basophilic cytoplasm bone matrix-synthesizing cell found only on surface of bone
-EM abundant ER
-found in rows, have appearance of epithelium
-differentiate into osteocytes
Term
osteocytes
Definition
-responsible for maintenance of mineralized bone
-it is an osteoblast trapped inside a lacuna w/in bone
-relatively inactive, but required for bone to be maintained
-transduces signals in response to mechanical strain
-H&E-condensed nucleus weaker staining cytoplasm EM-less ER and Golgi
-connected to other osteocytes and ultimately blood supply by thin dendrite-like cytoplasmic processes that extend through the canaliculi
-at contact site, two cells are gap junctions
-this is terminally differentiated cell in the lineage
Term
osteoclast
Definition
-degrades bone matrix, responsible for bone resorption
-derived from macrophages, fusion of several cells
-H&E-large multinucleated cells found along bone surface
-EM: cytoplams of osteoclasts are full of vesicles-Golgi, secretory vesicles, 1 degree lysosomes
Term
howships lacunae
Definition
depressions of bone where osteoclasts are found
Term
structure/function of osteoclasts
Definition
-at margins, tightly adhered to bone matrix
-will produce a ruffled border where acid and lysosomal enzymes (collagneases) are secreted to breakdown the mineralized and organic portions of the bone respectively
Term
remodeling of bone (bone turnover)
Definition
-10% of bone is destroyed and replaced in 1 year in adults
-based on paracrine signaling relationship b/t osteoclasts and osteoblasts
-osteoblasts produce factors that recruit, stimulate, proliferate, and activate osteoclasts
-remodeling liberates bound growth factors
-factors lead to proliferation of osteoprogenitor cells, differentiation of these to osteoblasts, increased synthesis of matrix by osteoblasts
-balanced system where bone destruction stimulates bone formation
Term
osteoporosis
Definition
disease of decreased bone density that affects the entire skeleton
Term
in whom is osteoporosis most commonly found?
Definition
post menopausal women
Term
what does decreased bone density lead to?
Definition
multiple fractures
Term
why is osteoporosis common in post-menopausal females?
Definition
reduced levels of estrogen, which controls the factors that stimulate production and activation of osteoclasts. also stimulates apoptosis of osteoclasts. also may be needed for cells to become osteoblasts.
Term
what does osteoporosis mean in terms of bone density?
Definition
amount of mineralized bone reduced within the skeleton
Term
how does estrogen affect osteoblasts?
Definition
it inhibits the production of cytokines and growth factors that recruit and activate osteoclasts
Term
how does estrogen affect osteoclasts?
Definition
leads to rapid apoptosis
Term
how does lack of estrogen affect the process of bone remodeling?
Definition
more cytokines and growth factors are produced by teh osteoblasts, which leads to more long-living osteoclasts that in turn leads to more bone destruction that is not balanced by high rates of bone formation
Term
what would be an ideal treatment for osteoporosis, what is the limitation of that treatment?
Definition
estrogen replacement therapy, leads to breast cancer
Term
what kind of growth do osteoprogenitor cells play a key role in?
Definition
appositional
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