Exam 1: Cartilage

Question 1

Cartilage characterisitcs

Answer 1

A type of connective tissue

Embryonic origin - mesenchyme

Avascular tissue

Slow at healing

Question 2

Cartilage functions (4)

Answer 2

Tensile and compressive strength

flexible and resilient to deformations

Structural support for soft tissues

Distribution and dissipation of stresses

Question 3

Extracellular matrix components

Answer 3

Type II collagen

Elastin fibers

Ground substance

Question 4

Why isn’t collagen type I seen in histological sections

Answer 4

Reflexive index similar to that of ground substance

Question 5

Ground substance

Answer 5

Sulfated glycosaminoglycans (GAG)

Hyaluronic acid

Water

Question 6

ECM characteristics

Answer 6

Inhomogeneous distribution of GAG

When stained, it is separable into pale and darkly areas

Question 7

Interterritorial matrix

Answer 7

Pale part of EMC

Low GAG

Question 8

Territorial matrix

Answer 8

Darkly part of ECM

High GAG

Question 9

Cells of cartialge

Answer 9

Chondroblasts - reside in perichondrium and produce ECM

Chondroblasts trapped in EMC (in lacunae) mature into chondrocytes

Question 10

Perichondrium

Answer 10

Peripheral layer of vascularized, dense, irregular connective tissue that surrounds hyaline and elastic cartilage

Question 11

Layers of perichondrium

Answer 11

Outer fibrous layer - Type I collagen fibers, fibroblasts, blood vessels, nerves

Inner chondrogenic layer - undifferentiated mesenchymal cells –> differentiate into chondroblasts that secrete external cartilage matrix

Question 12

What types of cartilage lack a perichondrium

Answer 12

Articular hyaline cartilage

Fibrocartilage

Question 13

Hyaline cartilage

Answer 13

Most common type

Forms most of developing skeleton (endochondral ossification)

Contains fine type II and type III (reticular) collagen fibers

Firm but flexible structural support

May calcify with age

Question 14

Isogenous groups

Answer 14

In hyaline cartilage

2-4 chondrocytes in small clusters within same lacunae due to cell division

Question 15

Where is hyaline cartilage found

Answer 15

Embryonic bone templates
Growth plate
Articular cartilage
Larynx
Tracheal rings
Bronchi
Costal cartilage
Nose

Question 16

Zones of articular hyaline cartilage

Answer 16

1. Superficial zone - elongated and inactive chondrocytes, collagen parallel to joint surface
2. Middle/transitional zone - spherical chondrocytes, collagen aligned randomly
3. Deep/radial zone - chondrocytes in columns, collagen vertical (perpendicular?) to joint surface
4. Tidemark - interface between calcified and non calcified cartilage layers
5. Calcified cartilage zone - collagen insert into calcified cartilage, transition to bone

Question 17

Hyaline cartilage - growth plate

Answer 17

Responsible for interstitial growth

Question 18

Zones of growth plate

Answer 18

1. Reserve cartilage zone
2. Cell proliferation zone -
3. Cell hypertrophy/maturation zone
4. Calcification zone
5. Bone deposition zone

Question 19

Growth plate - Reserve cartilage zone

Answer 19

Resting chondrocytes

Type II collagen randomly oriented

Closest to epiphyseal end and high oxygen tension (near epiphyseal blood supply)

Question 20

Growth plate - Cell proliferation zone

Answer 20

Chondrocytes divide, creating columns of flattened lacunae

Collagen form longitudinal septa (walls) in between lacunae

Question 21

Growth plate - Cell hypertrophy / maturation zone

Answer 21

Low oxygen tension - chondrocytes stop dividing and start hypertrophying

Cartilage walls between lacunae are thinning

Question 22

Growth plate - Calcification zone

Answer 22

Mineral deposited in collagen matrix between chondrocytes columns

Cartilage calcified (only temporary support)

Question 23

Growth plate - Bone deposition zone

Answer 23

Chondrocytes die and horizontal walls between lacunae breakdown

Osteoblasts arrive and start to deposit osteoid on calcified cartilage, creating primary spongiosa

Closest to metaphyseal end

Question 24

Growth plate - metaphysis

Answer 24

Osteoblasts deposit concentric lamellae which will create secondary spongiosa (trabeculae)

Concurrently, chondroclasts remove the temporary mineralized cartilage

Question 25

Groove of Ranvier

Answer 25

Contributes chondrocytes to growth plate for growth in diameter (appositional growth)

Prone to damage

Question 26

Ring of LaCroix

Answer 26

Provides mechanical support for weak bone-cartilage interface of the growth plate

Protects Groove of Ranvier from damage

Question 27

Growth plate - formation of cortex

Answer 27

Similar to what happens in intramembranous ossification

Spongiosa close to perimeter of bone continues to ossify and becomes cortex

Question 28

Growth plate fusion

Answer 28

Cycle of chondrocyte divisions and hypertrophy pushes reserve cartilage toward epiphysis and so the bone elongates

When reserve cartilage depleted, bone stops elongating and growth plate is closed –> fused

Question 29

In what animal does the growth plate never fuse

Answer 29

Rodents - grow throughout life

Question 30

Elastic cartilage characteristics

Answer 30

Similar structure to hyaline cartilage, plus branching elastic fibers

Very flexible

Continues growing throughout life

Affected by gravity

Question 31

Where is elastin cartilage found

Answer 31

Areas of high movement

Epiglottis
Larynx
Ear pinna
Auditory tube

Question 32

Fibrocartilage characteristics

Answer 32

Alternating layers of hyaline cartilage matrix (collagen type II) and dense connective tissue (collagen type I)

Collagen fibers oriented in direction of stress

Provide tensile and compressive strength

Resist deformation

Lacks perichondrium