Bone Growth

Question 1

What is woven bone

Answer 1

Immature disorganised bone, collagen deposited in basket like weave because bone is rapidly formed

Question 2

What does decalcified bone look like in HE staining

Answer 2

Ecm stains pink with he because basic

Question 3

How do osteocytes regulate response of bone to mechanical response (coordination)

Answer 3

Osteocytes reside in lacunae. They have thin cell processes that extend from lacunae into canaliculi allowing intercellular communication

Question 4

Describe process of bone remodelling

Answer 4

Osteoclasts attach to mineralised bone matrix, excavate small pits on bone surface, releasing bone collagen and minerals into circulation. Osteoblasts are recruited to newly resorbed areas on bone where they deposit new collage. After resting phase during which bone is mineralised, remodelling cycle begins again

Question 5

2 time spaced doses of auto fluorescent tetracycline and calcein binding. What does smudgy result suggest

Answer 5

Deficient or delayed mineralisation

Question 6

Function of bone

Answer 6

Mechanical: rigidity for attachment of muscles
Protection: support and protect organs
Vessel
Chemical: homeostasis
Hemapoiesis: blood regeneration
Mesenchymal: stem cells

Question 7

Describe osteoblasts

Answer 7

Cuboidal cells found where there is active bone formation. Basophilic cytoplasm. Rich in alkaline phosphatase and RER. Derived from mesenchymal cells.

Form and mineralise ECM. Deposit osteoid on mineralising front. Deposit collagen in parallel and concentric layers to form mature lamellar bone. Synthesise proteoglycans and bone proteins eg osteopontin, proteoglycan, osteocalcin

Question 8

Features of osteoclasts

Answer 8

Large motile, multinucleated. Formed from mononuclear/macrophage cells.

Ruffled border to increase surface area in contact with bone matrix. Many lysosomes. Tight seal, binds to bone surface via integrins. Clear zone (organelle free) around cell membrane). Lie in Howship’s lacunae