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Cartilage and Bone
1. Cartilage:
organ=Cartilage tissue+perichondrium
1) structure of cartilage tissue
---cell: chondrocyte
---cartilage matrix
① chondrocyte:---Structure: LM
embedded in cartilage lacuna
peripheral cells: --small and immature --single and flattened
central cell: --large and mature, --round and in group of 2-8 cells --small and round nucleus --basophilic cytoplasm --EM: rich in RER and Golgi complex
*isogenous group: several cells locates in one lacuna, which are derived from a single(same) parent cell
② Cartilage matrix
---ground substance: proteoglycan:
--same to loose CT --there are more chondroitin sulfate distributed
at the periphery of cartilage lacuna---called as cartilage capsule(basophilic) water
---fiber: type and number of fiber depends on the type of cartilage
2) Classification: according to the fiber
a. Hyaline cartilage: less collagenous fibrilarticular surface, rib cartilage, trachea and bronchi
b. Fibrous cartilage:large amount of collagenous fiber bundles cells are small and lessintervertebral disc, symphysis pubis
c. Elastic cartilage:
large amount of elastic fiber
external ear, epiglottis
3) perichondrium
two layers:
---out layer: contain more fiber-protection
---inner layer: more cells-osteoprogenitor cell(fusiform in shape)
4) growth of cartilage---interstitial growth:
inner chondrocyte proliferation→ produce fiber and matrix.immature cartilage
---appositional growth:osteoprogenitor cell→chondroblast → chondrocyte → produce fiber and matrix.growing and mature cartilage
2.Bone---consists of bone tissue, periosteum and
endosteum, bone marrow
1) Bone tissue
① Cells:
a. osteoprogenitor cell: stem cell
---structure:
fusiform, small
ovoid nucleus
slight basophilic cytoplasm
exist in periosteum and endosteum
---function: differentiated into osteoblast and chondrocyte
b. osteoblast: ---structure: LM:
single layer of cuboidal or low columnar cell
round nucleusbasophilic cytoplasmlocated on the surface of bone tissue
EM:
fine processes
rich in RER, Golgi complex
---function:
ⅰ.synthesize bone collagen fiber and ground
substance-osteoid
ⅱ.release matrix vesicle:
0.1um in diameter
membrane-coated
function: promote calcification
c.osteocyte ---structure:
flattened cell with multiple long thin processes
located in bone lacuna and bone canaliculus
basophilic cytoplasmadjacent cells connect in bone
canaliculus by gap junctions---function:
Maintain bone matrix
d. osteoclast
---structure: LM: multinuclear large cell, 30-100um 6-50 nuclei acidophilic cytoplasm located at peripheral part of bone
EM: ruffled border-processes light zone: --under the ruffled border
--microfilament primary lysosome, pinosome and secondary lysosome RER, mito. and Golgi
---function: dissolve and absorb bone matrix
②Bone matrix
---organic matter:
bone collagen fiber -collagenous fiber (type I collagen)
ground substance:
glycosaminoglycan
---inorganic matter: bone salts
Hydroxyapatite crystal: Ca10(PO4)6(OH)2
pin-shaped
longitudinal arranged
*bone lamella: bone matrix arranged in layers at different direction
2) Architacture of long bone Long bone is an organ, made up of b
one tissue(shaft and epiphyses), periosteum and endosteum, bone marrow
① shaft: consists of compact bone
a. circumferential lamella: /outer concentrically-arranged /inner around inner surface of bone
b. Haversian system (osteon):
/cylindric structure, 3-5mm
/central canal: N, BV, CT
/Haversian lamella: 4-20 layers
c. interstitial lamella:
/irregular lamella
/remnant of Haversian
or circumferential lamella
*perforating canal:
/transverse canal
/connect with Haversian canal
② epiphyses: composed of spongy bone
---trabeculae:
formed by parallelly-arranged lamella
form a spongy-liked network
---Bone marrow: hemopoietic tissue
③ periosteum and endosteum: CT membrane
---periosteum: DCTouter layer:more fiber bundles
form perforating fiberinner layer:
rich in BV, N and osteoprogenitor cells---endosteum: thin, a layer of osteoprogenitor cell
and CT---function: provide nutrition and osteoblast for bo
ne growth and repairing
3) osteogenesis
Self study!