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Histo > Cartilage > Flashcards

Cartilage Flashcards

1
Q

Cartilage Fxns

A

Bearing mechanical stresses without permanent distortion

Smooth surface of joints which facilitates gliding motion of bones (articular cartilage)

Enhances shock absorption capabilities

Cartilage is also essential for the development and growth of long bones

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2
Q

Cartilage Components

A 
Chondrocytes/chondroblasts
Collagen
Hyaluronic Acid
Proteoglycans
Glycoproteins
Elastin-high levels occur in elastic cartilage
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3
Q

Cartilage characteristics

A

Cartilage has a firm, gel-like consistency

GAGs provide ionic bonding with collagen fibers and with water

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4
Q

3 types of Cartilage

A

Hyaline – predominately type II collagen

Elastic cartilage – type II collagen and elastin

Fibrocartilage – predominately type I collagen and lesser amounts of type II collagen

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5
Q

How does cartilage receive nutrients?

A

Cartilage is avascular tissue

Derives nutrient supply via diffusion of substances from adjacent tissues:
Perichondrium
Synovium – (articular joints)

Cartilage has no lymphatic vessels

Cartilage has no neural innervation

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6
Q

Perichondrium

A

Dense CT that surrounds hyaline cartilage (except articular cartilage and fibrocartilage)

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7
Q

Perichondrium Fxn

A

Essential for growth and maintenance of cartilage (provides new chondrocytes)

Contains: nerves, arteries, lymphatics, fibroblasts, type I collagen

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8
Q

Chondrocytes

A

Main cell of cartilage

“Lives” within cavities (lacunae) and are surrounded by matrix

Actively synthesize and secrete ECM molecules

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9
Q

Chondroblast

A

Immature chondrocytes that exist outside of lacunae (perichondrium)

Differentiate into chondrocytes once they are within lacuna

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10
Q

Somatomedin C

A

Hormone produced by liver that stimulates chondrocyte proliferation

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11
Q

Chondrocyte Fxn

A

dependent on proper hormonal balance

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12
Q

ECM synthesis by chondrocytes is increased by:

A

Growth hormone
Thyroxin (T4 thyroid hormone)
Testosterone

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13
Q

ECM synthesis by chondrocytes is decreased by:

A

Cortisone, hydrocortisone (corticosteroids), estrogen

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14
Q

ECM fibers: Collagen

A

Type I and Type II
Type I collagen, main fiber of fibrocartilage

Type II collagen, main fibril in hyaline cartilage
Is present only in fibril form
Fibrils do not aggregate into collagen fibers and/or bundles

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15
Q

ECM fibers: elastic fibers

A

Main fiber type of elastic cartilage, with lesser amounts of Type II collagen

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16
Q

ECM: Ground Substance

A

Glycosaminoglycans (GAGs)
Hyaluronic acid
Proteoglycans
Glycoproteins (Chondronectin)

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17
Q

Glycosaminoglycans (GAGs)

A

Chondroitin-4 sulfate, chondroitin-6 sulfate, keratan sulfate

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18
Q

Hyaluronic acid

A

GAG; responsible for formation of PG aggregates in articular cartilage, main component of synovial fluid

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19
Q

Proteoglycans

A

Up to 200 PGs can be bound to hyaluronic acid and to link proteins to form PG aggregates

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20
Q

Glycoproteins (Chondronectin)

A

Promotes adherence of chondrocytes to collagen in ECM

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21
Q

Hyaline Cartilage (articular cartilage)

A

Walls of bronchi, larynx, trachea
Costal cartilage of ribs
Epiphyseal plate of long bones

22
Q

Elastic Cartilage

A

Auricle of ear, auditory tube

Nose, epiglottis

23
Q

Fibrocartilage

A

Intervertebral disc, symphysis pubis

24
Q

Hyaline Cartilage in embryos

A

serves as a temporary skeleton that is gradually replaced by bone

25
Q

Hyaline Cartilage in adults

A

serves as articular cartilage and as sites for growth of long bones at the epiphyseal plates

26
Q

Matrix Characteristics of Hyaline Cartilage

A

Type II collagen is embedded in a firm, hydrated gel of proteoglycan aggregates and glycoproteins

27
Q

Proteoglycans consist of the GAGs:

A

Chondroitin 4-sulfate, chondroitin 6-sulfate, keratan sulfate

28
Q

Hyaline Cartilage: Structure

A

Proteoglycan aggregates
—Hyaluronic acid + proteoglycans
PG aggregates bind collagen
The GAGs bind water which increases firmness and enhances shock absorption capacity

29
Q

Elastic Cartilage Components

A

PGs
GAGs
Type II collagen
—Similar components to hyaline cartilage
Elastic fibers
—Abundant network of elastic fibers in ECM

30
Q

Fibrocartilage Characteristics

A

Tissue characteristics of dense CT and hyaline cartilage
Abundant collagen type I fibers
—Collagen fibers form irregularly sized bundles
Fibers align parallel to direction of stress
Lesser amount of type II fibrils
NO perichondrium

31
Q

IV Disks: Fibrocartilage Annulus Fibrosus

A

Composed of multiple layers of fibrocartilage

Collagen fibers oriented at 90º angles between each layer

32
Q

IV Disks: Fibrocartilage Nucleus pulposus

A

Composed of type II collagen and hyaluronic acid

Replaced with fibrocartilage during aging and/or injury

33
Q

Interstitial Growth (inside of)

A

Mitotic division of pre-existing chondrocytes within lacuna

“Additional” chondrocytes secrete matrix to increase the mass of cartilage tissue:

34
Q

Interstitial Growth occurs where?

A

Epiphyseal plates to increase length of long bones

Within articular cartilage

Embryonic stages of cartilage formation

35
Q

Appositional Growth

A

Differentiation of fibroblast cells of the perichondrium into chondroblasts

The new chondroblasts secrete ECM to produce additional matrix material which adds to thickness of the cartilage

Important process for bone healing and for growth of mature cartilage (elastic cartilage, hyaline cartilage)

36
Q

Articular cartilage is what type of cartilage?

A

Hyaline

Contains a specialized network of type II collagen fibrils and high level of hydrated GAGs

37
Q

Where do you find articular cartilage?

A

covers bony surfaces of synovial jts

38
Q

What does articular cartilage do for these joints?

A

Provides shock absorption and smooth gliding surfaces for joints

39
Q

How does articular cartilage get nourishment?

A

Nourished by intermittent compression that allows cartilage to expel and imbibe synovial fluid

40
Q

Articular Cartilage alignment

A

Type II Collagen Alignment

Fibrils have variable alignment depending on their location within the articular cartilage

41
Q

Tangential Zone

A

Closest to joint surface

Fibrils oriented parallel to joint surface

42
Q

Transitional Zone

A

Fibrils oriented at an angle with respect to joint surface

43
Q

Radial Zone

A

Deepest zone

Fibrils oriented perpendicular to joint surfaces

44
Q

Aging and Articular cartilage

A

With increase in age, cartilage degenerates

45
Q

Acute Activity and Articular Cartilage

A

Normal loading and unloading increases nutrient exchange and waste removal

Joint space increases with exercise (intermittent loading)
Articular cartilage “puffs up” with uptake of fluid

Aids in shock absorption

Following cessation of activity, joint space returns to normal size

46
Q

Chronic Training and Articular Cartilage

A

Physical activities maintain nutrient exchange in articular cartilage

The benefit of training for articular cartilage is dependent on proper training that limits joint stresses
i.e. proper footwear, even/soft running surface, assistive devices (orthotics)

Excessive mechanical stress to joints may speed up the process of articular cartilage degeneration

47
Q

Immobilization and Articular Cartilage

A

Immobilization necessarily reduces intermittent compression of the joint surfaces

Without normal physiologic movement, the normal nutrient supply is interrupted

Cartilage is not well supplied with nutrients, creating cartilage atrophy

With prolonged immobilization, structural degeneration of cartilage can occur due to prolonged lack of nutrient delivery and waste removal

48
Q

Corticosteroids and Articular Cartilage:: RA or OA

A

Anti-inflammatory properties of corticosteroids reduces inflammation, pain and progression of articular cartilage damage

Corticosteroids can inhibit chondrocyte proliferation, ECM synthesis and type II collagen deposition by chondrocytes 
Repetitive injections (and chronic administration for other inflammatory pathologies) can have deleterious affects on the integrity of articular cartilage
49
Q

DJD (OA)

A

Break down of articular cartilage

“Wear and tear” arthritis

Often accompanied by calcification of damaged cartilage and excess bone formation (i.e. bony spurs)

50
Q

OA (DJD) three stages

A

3 stages:

fibrillation, fissuring, eburnation

51
Q

Regenerative Capacity of Cartilage

A

Damaged cartilage does not regenerate, but is able to repair with scar tissue

Existing chondrocytes in the cartilage proliferate and deposit ECM
Scar tissue contains greater amounts of type I and type III collagen and disorganized ECM of PGs and GAGs

Repair (scar) tissue is sub-optimal in functional characteristics (less compression/shear resistance)

Repair tissue is less able to withstand joint forces and therefore is prone to be damaged

52
Q

Regenerative Capacity of Cartilage

A

Damaged cartilage does not regenerate, but is able to repair with scar tissue

Existing chondrocytes in the cartilage proliferate and deposit ECM
Scar tissue contains greater amounts of type I and type III collagen and disorganized ECM of PGs and GAGs

Repair (scar) tissue is sub-optimal in functional characteristics (less compression/shear resistance)

Repair tissue is less able to withstand joint forces and therefore is prone to be damaged

Histo (12 decks)

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