10. Bone physiology Flashcards
What is Bone?
- Connective tissue with collagen framework
- with Ca2+, PO43- (Hydroxyapatites (ca10(po4)6(oh)2).
- Non static : reabsorbed, formed, constant Remodeling
Bone is NON-STATIC
constant Remodeling, respond to stress and strains
Function of Bone
- Structure and shape
- Protect vital organs
- Movement, locomotion, support against gravity
- Hemopoisis: bone marrow
- Mineral storage and homeostatsis: Ca2+, po4 3_ homeostasis
Calcium Metabolism
Absorption, secretion rapid exchange (exchangeable) accretion reabsorption (stable bone) reabsorption (glomerular filtrate)
Exchangeable (with ECF) vs Stable Bone
100 mmol, 27200mmol
Phosphorus Metablism
- intestinal absorption
- renal absorption
FGF23
Fibroblast growth Factor (decrease 1,25(OH)2D production, Na phosphate cotransporter
Na12a2c
Na Phosphate cotransporters (increase renal, intestinal absorption)
Osteon
basic structural unit of COMPACT BONE
consists of:
- Haversian canal
-concentrically arranged Lamellae
central vascular channel surrounded by Harvesian canal.
each osteon surrounded by concentric layers of mineralised bone
Cortical Bone (between periosteum and marrow) 80%
Compact bone
- Osteoblast Precursor Cells
- Osteoblast
- Osteoid
- Calcified Bone matrix
- Osteocytes
- surface of existing matrix (around periosteum and precursor)
Trabecular Bone
20% skeletal, 80% of surface
- in Epiphyseal + metaphysical region of long bones, interior of short bone
- bundles of short, parallel strands of bone fused together
- less dense, more elastic, rigid, looks spongy
- forms interior scaffolding to help maintain bone shape despite compressive force
- high turnover rate
Haversian Canal
-Blood vessel
- nerve
bone pain when compressed
Bone type (4 classifications)
Architecture: spongy/compact
structure: woven/lamellar
histogenesis: endochondral/intramembranous
shape: flat/long
woven Bone
temporary non-lamellar, lower mineral content
Osteoid (Uncalcified Bone Matrix)
90-95% collagen fibres
Ground substance:
- ECF
- Glycoproteins
- proteoglycans ( chondroitin sulfate, hyaluronic acid)
- Vit K dependent protein (osteoclatin)
site for nucleation of HYDROXYAPATITE CRYSTALS
Cortical Bone function and structure
80% of skeletal mass protective outer shell slow turnover rate high resistance to bending, torsion -adjacent/overlapping Osteon/Harvesian Systems
Cancellous Bone function
Trabecular Bone
- nutrients diffuse from ECG to trabeculae
Collagen strand + deposition of Ca2+ and PO43-
BONE
Bone cell 1: Osteoprogenitor cell
below periosteum and endostium -
give rise to:
- Osteoblasts
- Osteoclasts
Bone cell 2: Osteoblast cels
Bone formation - form matrix of bone tissue
Bone cell 3: Osteocytes
mature osteoblast - maintain matrix of bone tissue
Bone cell 4: Osteoclasts
Bone breaker - resorption of bone
Development origin of Bone cells
- Haemopoietic stem cell (bone marrow) -> monocytes -> pre-osteoclasts -> OSTEOCLAST
- Mesenchymal stem cell -> pre-osteoblast -> OSTEOBLAST ( also gives rise to bone lining cells)
