T1L9: Principles of Skeletal Systems

Question 1

Axial

Answer 1

Skull, vertebrae, ribs, sternum and hyoid bone

Question 2

Appendicular

Answer 2

Limb bones and bones of pectoral and pelvic girdle

Question 3

Bone development length

Answer 3

week 9 to 20yo

Question 4

Endochondral ossification

Answer 4

• Cartilaginous template from mesenchyme
• Template replaced by bone - osteogenesis
• Different ossification centres emerge (primary in diaphysis and secondary in epiphysis)
• Initially a bone collar is produced and this is where primary centre develops
Epiphyseal plate (growth plate) exists between diaphysis and epiphysis

Question 5

Bone growth

Answer 5

• Associated with partial reabsorption of previously laid down bone and new bone
• Long bone gradually lengthen as ossification continues
• Developing bone is penetrated by blood vessels at week 9
Maturity = epiphyseal plate abolished

Question 6

Intramembranous ossification

Answer 6

• Direct mineralisation of CT (mesenchyme)
• Cells divide and condense around capillary network
• Starting point is called primary ossification centre
• Grows radially -> fuse and replace CT
• CT that remains is penetrated by blood cells and undifferentiated mesenchyme gives rise to bone marrow
Skull mandible and clavicle

Question 7

Bone maintenance regulated by dietary intake of calcium, phosphorus, vit A/C/D

Answer 7

Vit A - bone remodelling
Vit C - CT
Vit D - Calcium absorption

Question 8

Cartilage

Answer 8

• CT
• Forms skeleton where flexibility is needed
• Avascular
Proportion of bone to cartilage changes as individual develops

Question 9

Bone

Answer 9

• Hard form of CT
• Provide ridged framework
• Vascular
Compact and spongy

Question 10

Coverings

Answer 10

CT element covers skeletal system
Except where articulation occurs
CT surrounding bone is called periosteum
CT surrounding cartilage is perichondrium

Question 11

Compact bone

Answer 11

• Covered by periosteum
• Lamella (concentric layers of inorganic matrix) laid by osteoblasts
• Lamella forms harversian canal in centre
• Haversian canal contains vascular and nerve supply
• Osteoblasts become trapped and turn into osteocytes
• Each osteocyte occupies its own lacunae
• Radiating from each lacunae are minute canals (canaliculi)
Nutrients travel in the canaliculi to the osteocyte

Question 12

Spongy bone

Answer 12

• also known as cancellous bone
• Irregular lamellae
• Has red bone marrow surrounding it
Highly vascular