Cartilage And Bone

Question 0

Classify the three main types of cartilage, describing structural differences between them and their functions

Answer 0

Hyaline:
Collagen type - 2
Location - end of long bones, foetal skeleton, respiratory passageways
Function - firm and flexible support
Perichondrium - present
Elastic:
Collagen type - 2
Location - auditory tubes, external ear, epiglottis
Function - extra flexibility, support
Perichondrium - present
Fibrocartilage:
Collagen type - 1
Location - IV discs, meniscus, pubic symphysis
Function - very strong, resistant to stretching and compression
Perichondrium - absent

Question 1

Describe the composition of cartilage in terms of its cells and extracellular components

Answer 1

Appears in fifth week of embryonic development, avascular, chondrocytes produce extracellular matrix, originates from mesenchyme –> condenses –> chondroblasts, chondroblasts caught in matrix –> chondrocytes (lie in lacunae), surrounded by perichondrium

Question 2

Describe the characteristic features and functions of the different types of bone in the body

Answer 2

Types - long (humerus), short (carpal bones), flat (skull), irregular (pelvis), sesamoid (patellar), sutural (bones between flat bones in skull)
Features - withstand compression, dynamic, sensitive to pain
Functions - support, protection, mineral storage, haemopoiesis

Question 3

Describe the classifications of bone

Answer 3

Compact (dense) and spongy (cancellous/trabecular)

Question 4

Describe the composition of bones in terms of its cells and extracellular components

Answer 4

Osteoblasts (build), osteocytes, osteoclasts (breakdown by releasing H+ and lysosomal enzymes)
Made up of hydroxyapatite crystals for hardness, type I collagen for flexibility and tensile strength

Question 5

Describe the microstructure of compact (dense) and spongy (cancellous/trabecular) bone

Answer 5

Compact bone - 80% of body’s skeletal mass
Cancellous bone - spaces filled with bone marrow
Compact - Haversian (concentric lamellae) and Volkmann’s canals carry blood and lymph vessels and nerves, osteocytes are arranged in osteons, canaliculi connect to adjacent osteocytes
Cancellous - have osteocytes but no Haversian or Volkmann’s canals, lacunae consists of adipose and haemopoietic cells

Question 6

Explain how bone is a living tissue undergoing remodelling and repair

Answer 6

Endochondral ossification = cartilage –> bone
Intramembranous ossification = connective tissue/mesenchyme –> bone
Osteoblasts form new bone
Osteocytes are mature bone cells
Osteoclasts break down bone by releasing H+ and lysosomal enzymes - cutting cone

Question 7

Describe the cellular processes involved in bone repair following a fracture

Answer 7

1. Haemotoma formations - blood vessels in bone and peritoneum break, haemotoma forms, bone cells at fracture edge die, swelling and inflammation occur, phagocytic cells and osteoclasts begin to remove dead and damaged tissue, macrophages eventually remove clot
2. Fibrocartillaginous callus formation (fracture repair) - new blood vessels infiltrate fracture haemotoma, procallus of granulation tissue develops, fibroblasts produce collagen fibres, fibrocartillaginous matrix splints broken bone, osteoblasts invade fracture and begin bone remodelling
3. Bony callus formation (fracture repair) - new bone trabeculae begin to appear in fibrocartillaginous callus so it turns into a hard callus of cancellous bone, endochondral ossification replaces all cartilage with cancellous bone
4. Bone remodelling - callus of cancellous bone is remodelled into compact bone, osteoclasts break down bulging