L15 Skeletal Cartilage

Question 1

Where are chondrocytes found?

Answer 1

They occupy lacunae in cartilage

Question 2

Why does cartilage heal slowly?

Answer 2

Cartilage is poorly vascularised, exchange of nutrients/waste occurs by diffusion

Question 3

Cartilage is derived from which embryonic layer?

Answer 3

Mesoderm

Question 4

The mesoderm gives rise to the mesenchyme. What develops from the mesenchyme?

Answer 4

Cartilage

Bone

Fibrous tissue

Question 5

What separates cartilage from surrounding tissues?

Answer 5

Perichondrium

There are 2 layers:

1) outer fibrous irregular CT layer
2) inner cellular layer

Question 6

What are the 3 major types of cartilage?

Answer 6

Hyaline cartilage

Elastic cartilage

Fibrocartilage

Question 7

Hyaline is the most common type of cartilage, what is the matrix made of?

Answer 7

Densely packed collagen fibres form a translucent matrix.

Question 8

Where can hyaline cartilage be found?

Answer 8

Connecting the ribs and sternum

Nasal cartilages and respiratory tract

Articulate cartilage (joints)

Question 9

Where can you find elastic cartilage?

Answer 9

External flap of outer ear

Epiglottis

Larynx

Question 10

What makes elastic cartilage so resilient and flexible?

Answer 10

The matrix contains many elastic fibres

Question 11

What are the general uses of fibrocartilage?

Answer 11

Resist compression

Absorb shock

Prevent bone-to-bone wear

Question 12

Where can fibrocartilage be found?

Answer 12

Between spinal vertebrae

Between public bones in pelvis

Around/within some joints and tendons

Question 13

What are the two mechanisms of cartilaginous growth?

Answer 13

Interstitial growth (cartilage grows from within by chondrocyte division)

Appositional growth (new layers added to the surface, fibroblasts increase matrix)

Question 14

What is endochondral ossification?

Answer 14

Development of bones from hyaline cartilage model. Bone replaces existing cartilage.

Begins near middle of shaft (primary ossification centre)

Centre of epiphyses (head) calcify (secondary ossification centre)

Forms weight bearing bones, such as femurs and vertebrae

Question 15

What bones are formed by intramembranous ossification?

Answer 15

Flat bones (mandible, face bones, skull, clavicle)

Question 16

How does intramembranous ossification occur?

Answer 16

Bone develops from the mesenchyme or connective tissue.

Mesenchyme cells cluster and secrete matrix

Calcification occurs: Stem cells differentiate into osteoblasts

Ossification begins (ossification centre)

1st spongy bone forms, then remodelling takes place to form compact bone.

Question 17

Blood is supplied to the bones via the __1__ artery, and __2__ and __3__ vessels.

Answer 17

1) nutrient
2) metaphyseal
3) periosteal

Question 18

What are the six bone types?

Answer 18

1) Long bones (e.g. femur, humerus)
2) Short bones (e.g. carpals, tarsals)
3) Flat bones (e.g. parietal, ribs, scapula)
4) Irregular bones (e.g. vertebrae, pelvis)
5) Sesamoid bones (e.g. kneecap)
6) Sutural bones

Question 19

Which cells occupy lacunae in bone?

Answer 19

Osteocytes

Question 20

How do osteoclasts regulate serum levels of calcium and phosphate?

Answer 20

Secrete acids and proteolytic enzymes to dissolve bone matrix (osteolysis)

Question 21

What is osteopenia?

Answer 21

Thinning and weakening of the bones as they age. Caused when osteoclast activity overtakes osteoblasts activity and can lead to osteoporosis.