Bone growth and development

Question 1

Describe the structure and function of bone development

Answer 1

Happens in the embryo
2 types: intramembranous & endochondral which both replace connective tissue template

Question 2

Describe the structure and function of intramembranous

Answer 2

Sheets of mesenchymal cells
Differentiation to osteoblasts in centres of ossification merge to form trabecular bone that is remodelled
Remaining mesenchyme makes bone marrow and periosteum

Question 3

Describe the structure and function of endochondral

Answer 3

Blood supply to shaft of bone causes osteoblast differentiation
Cartilage growth plate remains to allow the bone to lengthen
- Long bones

Question 4

Describe the process and function of bone remodelling

Answer 4

Remodelled through osteocytes, osteoblasts and osteoclasts
Adjusts to stresses and strains
Responds to micro fractures and wear & tear

Question 5

What are the factors of an increase of bone turnover

Answer 5

Change in function
New demands (running, tennis etc)
Repair of fractures
Disease (e.g Pagets disease)

Question 6

Describe the role of the growth plate in long bone growth

Answer 6

Epiphyseal end for proliferation
Chondrocytes mature and die then replaced by bone at diaphyseal end

Question 7

Explain step by step the process of bone metabolism

Answer 7

Parathyroid hormone (PTH) increases blood calcium levels and regulates phosphate by releasing calcium from bone and stimulating vitamin D.

Stimulating Vitamin D will help the uptake of calcium in the gut and increase calcium and phosphate reabsorption from bone (increased osteoclast, decreased osteoblast activity)

Calcitonin decreases blood calcium levels by inhibiting osteoclast activity and reducing calcium absorption in kidney

Question 8

Explain the process step by step of bone fracture and repair

Answer 8

1. periosteum breached, blood clot forms
2. then replaced by vascular collagenous tissue
   new osteoprogenitor cells arise Fromm mesenchymal cells
   neutrophils and macrophages phagocytose the haematoma and necrotic debris
3. on external callus, cartilage bridges the fracture
   on internal callus, woven bone bridges fracture in cavity and is both fully established by 3rd week
4. full replacement of lamellar bone
   some residual fibrosis