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Cartilage And Bone Flashcards

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1
Q

Cartilage

A

.CT characterized by cells embedded in highly specialized ECM
. Found at sites requiring firm but flexible support

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2
Q

Adult distribution of cartilage in body

A

. Movable joints
. Immovable joints
. Support of structures
. Vertebral column

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3
Q

Cartilage role in skeletal development

A

Model for the development of the majority of bones and provides mechanism by which bones grow in length

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4
Q

T/F cartilage is avascular w/ no nerves

A

T

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5
Q

Composition of cartilage ECM

A 
. Collagen type II (40% dry weight)
. Aggrecan
. Hyaluronic acid polymers bind to proteoglycans noncovalently via link proteins (bundles bind to II collagen fibrils)
. Chondronectin
. Water (60-80% fresh hyaline weight)
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6
Q

Aggrecan

A

250 kD proteoglycan with side chains of chondroitin sulfate and keratin sulfate

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7
Q

Chondronectin

A

Structural glycoprotein with multiple binding sites

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8
Q

Mechanical properties (compressible and resilient) are cartilage are due to ___

A

. Presence of fibers
. Amt of anionic charge (amt of sulfate glycosaminoglycans attached to core protein)
. Amount of hydration

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9
Q

Chondroblast

A

Proliferating undifferentiated cell that begins to synthesize ECM elements

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10
Q

Chondrocyte

A

. Fully differentiated ECM-forming cells w/ reduced mitotic activity
. Embedded in ECM

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11
Q

Lacunae

A

Spaces of ECM occupied by chondrocytes

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12
Q

isogenous units (groups)

A

Groups of chondrocytes derived from same cell

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13
Q

Perichondrium

A

. CT surrounding cartilage
. Outer fibrous layer (fibroblasts, collagen II)
. Inner cellular layer (undifferentiated condrogenic precursors and chondroblasts

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14
Q

Perichondrium function

A

. Supporting tissue containing blood vessels, nerves, and lymphatics
. Inner cells participate in repair and appositional growth of cartilage

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15
Q

Cartilage formation steps

A

. Differentiation of mesenchymal cells
. Cartilage-specific collagen types, elastin, and aggrecan synthesis
. Mature matrix formation
. Accumulation of ECM (territorial and inter territorial matrix)

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16
Q

What occurs in mature matrix formation

A

. Bound water facilitates diffusion of nutrients and oxygen to cells of cartilage and confers gel-like property to the matrix

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17
Q

Mechanisms of cartilage growth

A

. Appositional: growth by cell addition to the periphery of the tissue
. interstitial: growth by division of cells w/in tissue (formation of isogenous groups)

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18
Q

Cartilage repair

A

. Limited ability to repair after injury
. Formation of repair cartilage from perichondrium (matrix of repair cartilage mixed properties of hyaline and fibrocartilage)

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19
Q

Hyaline cartilage

A

. Type II collagen
. Most common, highly hydrated matrix
. Temporary skeleton during embryonic development
. Forms epiphyseal plates until majority bone growth is done

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20
Q

Elastic cartilage

A

Type II collagen and elastin

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21
Q

Fibrocartilage

A

Type I and II collagen

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22
Q

Articulate cartilage

A

. Covers articulating bones in synovial joints

. Hyaline

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23
Q

Articulate cartilage deep lesion

A

. Bone region reached, local bleeding can occur spontaneously repairing lesion but turning cartilage from hyaline to fibrocartilage of scar tissue

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24
Q

What occurs in arthritis

A

. cartilage ECM is degraded

. Articulate surface is lost

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25
Chondrosarcoma
Malignant tumor derived from cartilage cells
26
Osteosarcoma
Malignant tumor derived from osteoblasts
27
Bone
. rigid CT w/ limited flexibility | . ECM has Ca and P
28
T/F Bone is avascular
F, it is highly vascular
29
Bone features
. Metabolically active . Ca and P reservoir (99% Ca in body) . undergoes remodeling (turnover)
30
How is bone formation and remodeling controlled?
Local paracrine regulators (bone morphogenic proteins and fibroblast growth factor) and hormones in bloodstream (growth hormone, thyroid hormone, estrogen), diet and muscle activity
31
Osteoblasts
. Bone forming cells . Produce osteoid . Control bone matrix mineralization . Located on bone surfaces (endosteum and periosteum)
32
Osteoid
``` Collagen 1 (90% osteoid) Proteoglycans ```
33
Osteocalcin
Stimulated by vitamin D, required for bone mineralization
34
Parathyroid hormone (PTH) in bone
. Activates synthesis of factors in osteoclasts differentiation (macrophage colony-stimulating factor M-CSF, and RANKL
35
Osteocytes
. Mature bone cells (osteoblasts trapped in Matrix) . Inactive (has PTH receptors for osteolysis of perilaunar bone) . No cell division . Detect mechanical stress on bone >maintain bone matrix
36
Osteoclasts
. Bone resorbing cells . Multinucleted giant cells derived from monocytes . Located at bone resorption sites . PTH stimulates them when released from low Ca blood levels . Calcitonin receptors dec. activity to dec. Ca blood levels . HaveRANK receptors for RANKL
37
Osteoblast origin
Mesenchymal stem cells
38
Mesenchymal stem cells give rise to what cells?
Osteoprogenitor cells, adipocytes, fibroblasts, and myoblasts
39
Osteoclasts origin
. Mononueclear hemopoietic progenitor cells .differentiation stimulated by factors produced by osteoblasts . Osteoclasts undergo apoptotic death when bone resorption is completed
40
Bone matrix
. Organic matter (35-50% dry weight) embedded in calcified inorganic matrix (50-65% weight) . Type I collagen, proteoglycans, bone proteins . Ca hydroxyapatite (major inorganic), Mg, K, Na, Na2CO4, and citrate
41
What are the bone specific proteins?
Osteocalcin, osteopontin, and osteonectin
42
What does Ca hydroxyapatite do?
. Association w/ collagen makes bone hard and resistant | . Makes bone Ca reservoir
43
How does mineralization of bone matrix occur?
. Osteoblasts synthesize organic parts and control mineralization . Vit. D3 regulates levels of osteocalcin that binds to hydroxyapatite
44
Ectopic mineralization
. Formation of hydroxyapatite in osteoid-like ECM outside of bone . Occur in muscle pathologies (myositis ossificans)
45
Bone resorption
. Carbonic anhydride II in osteoclasts produces carbonic acid . H ions from acid transported via ruffled border to ECM between osteoclasts and bone . Acid causes bone decalcification and Ca enters blood stream . Degradation of organic matrix components via hydrolytic enzymes
46
Matrix metalloproteinases
Hydrolytic proteins that degrade organic matrix components in bone resorption
47
What regulates osteoclasts activity?
Calcitonin, Vit. D3, regulatory molecules made by osteoblasts
48
T/F Maturation of osteoclasts doesn’t always occur in contact with bone
F, it always needs contact of bone
49
Woven bone
. Primary bone tissue . Immature, initially formed tissue . Irregular arrangement of type I fibers
50
Laminar bone
. Mature bone tissue | . Regularly arranged types I fibers forming lamellar
51
Cortical bone
. Compact . 80% total bone mass . Made up of osteons (Haversian systems) surrounding Haversian canal
52
Osteon
Parallel bony columns with concentric bony lamellae
53
Haversian canal
Central canal containing blood vessels, lymph, and nerves
54
Cancellous/trabecular bone bone
. Spongy bone . Interconnected trabeculae (honeycomb) . Forms interior of bones, end of long bones adjacent to bone marrow cavity . Prominent in vertebrae, carpal, and hip bones
55
Woven bone remodeling to lamellar bone
. Osteoclasts remove bone matrix and osteoblasts lay down lamellae of bone gradually forming osteons
56
How are osteons oriented?
In the line of stress exerted on bone | . Parallel to longitudinal axis in long bone
57
How do osteocytes communicate??
. Cell extensions in canaliculi (small channels) | . No cellular communication between adjacent osteons
58
Volkmann’s canals
. Canals for vascular connections that anastomose w/ vessels in bone marrow and periosteum
59
Internal remodeling of bone
. Osteon undergoes cyclic remodeling from central canal outward (centrifugal direction) followed by lamellar formation (centripetal direction . Central canal never closes
60
Interstitial lamellae
Remnants of previous lamellae
61
How are inner and outer surfaces of compact bone organized?
Inner and outer circumferential lamellae
62
Regional anatomy of long bone
. Epiphysis: end of long bone w/ epiphyseal growth plate . Metaphysis: neck of bone . Diaphysis: shaft of long bone w/ compact bone
63
Flat bones of skull
. 2 layers compact bone plates separated by diploe
64
Diploe
Spongy bone layer in flat bones of skull
65
Endosteum
Lines internal surface of bone adjacent to marrow cavity
66
Ostegenesis imperfecta
Mutations in collagen gene resulting in abnormal collagen production resulting in weak bones
67
Osteoporosis
. Inc. bone resorption w/o reformation
68
Primary osteoporosis
. Post-menopausal low estrogen levels . Type I early postmenopausal: loss of trabeculae bone . Type II postmenopausal: loss fo trabecular and cortical bone
69
Secondary osteoporosis
. From disease or medication . 50% men that have osteoporosis is from this . Caused by chronic corticosteroid use
70
Osteomalacia
. Progressive softening and bending of bones | . Defect in mineralization of osteoid from lack of Vit. D or renal tubular dysfunction
71
Rickets (juvenile osteomalacia)
Defect in mineralization of cartilage in growth plate
72
Tetracycline
. Antibiotic that can stain teeth | . Binds to Ca in teeth (don’t use when pregnant)
73
Periosteum
. Inner cellular (osteogenic) layer and outer fibrous layer . Forms bone during circumferential growth of diaphysis . Highly vascularized and contains sensory nerves

Histology (22 decks)

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