Cartilage And Bone

Question 1

Hyaline cartilage

only chrondrocytes

Answer 1

Matrix
- proteoglycans
- hyaluronic acid
- type II collagen
the hyaluronate proteoglycan aggregates are bound to the fine collagen matrix fibres
in foetal development it is the precursor model of the bones which later calcify (ossify)
Sited at articulating surfaces, parts of the rib cage, nose, trachea, bronchi and larynx

Question 2

Elastic cartilage

chondrocytes and elastin

Answer 2

matrix like that of hyaline cartilage with the addition of many elastic fibres and elastic lamellae
- does not calcify
- external ear (pinna)
- external acoustic meatus (ear canal)
- epiglottis
(White spaces often seen in section - as chondrocytes fall out during processing)

Question 3

Fibrocartilage

chondrocytes and fibroblasts

Answer 3

abundant type I collagen fibres in addition to the matrix material of hyaline cartilage
- no surrounding perichondrium
- intervertebral discs
- menisci of the knee
Has the resilience to act as a shock absorber and to resist shearing forces

Question 4

Hyaline cartilage layers

Answer 4

Perichondrium
- covers the margin (either side)
- contains many elongate, fibroblast like cells which develop into chondroblasts then into chondroblasts
- dense connective tissue
Chondrocytes
- lying in cartilage extracellular matrix which they produce and maintain

Question 5

Perichondrium

Answer 5

Growth from the periphery — appositional growth

- no perichondrium at articulating surfaces

Question 6

Chondrocytes

Answer 6

• may divide and give rise to isogenous groups (interstitial growth)
• lie in a lacuna - territorial matrix

Question 7

Cartilage

Answer 7

• is an avascular tissue that consists of an extensive extracellular matrix in which lie chondrocytes (which produce and maintain the extracellular matrix)
• large ratio of glycosaminoglycan (GAGs) to type II collagen in the cartilage matrix permits the ready diffusion of substances between the chondrocytes and the blood vessels surrounding the cartilage

Question 8

Cancellous bone

Answer 8

• network of fine bony columns or plates to combine strength with lightness
• spaces filled with bone marrow (can get nutrients from the bone marrow - does not need a blood supply)

Question 9

Compact bone

Answer 9

• the external surfaces of bone

- 80% of bodies skeletal mass

Question 10

Decalcified mature bone

Answer 10

Osteocyte lacunae for, osteons around Haversian canals
- canaliculi (tiny interconnecting tunnels) - connect via gap junctions such that nutrients can be passes between osteocytes

Question 11

Bone remodelling

Answer 11

• osteoclasts reabsorb bone to remodel it

- cutting cone bore tunnels through the bone by action of osteoclasts which release H+ ions and lysosomal enzymes

Question 12

Bone fracturing

Answer 12

• bone resists fracture as it has great tensile strength
• lamella are thought to be able to slip relative to each other giving bone a degree of flexibility
  When bone breaks
• bleeding from multiple broken blood vessels
• haematoma (clot) between the broken bone ends

Question 13

Fracture repair

Answer 13

• haematoma formed in which granulation tissue arises (swelling and inflammation)
• procallus of granulation tissue is replaced by fibrocartilaginous callus in which bony trabeculae are developing (splints the break)
• ossification gives rise to a bony callus of spongy/cancellous bone (continues for about 2 months)
• cancellous bone is replaced by compact cortical bone until remodelling is complete (continues for several months)