3. Biology and chemistry of bone formation

LABEL

1. Proximal epiphysis

2. Metaphysis

3. Diaphysis

4. metaphysis

5. distal epiphysis

6. nutrient artery

7. endosteum

8. medullary cavity

9. compact bone

10. periosteum

11. epiphyseal line

12. spongy bone

13. articular cartilage

What’s the metaphysis also known as during what

during growth, it’s replaced by a physis growing plate

What’s the articular cartilage do

reduces friction at joints & is shock absorbing

adjective for the periosteum

strong, dense, irregular, connective tissue

what cells does the periosteum have & what do they do

they have osteogenic progenitor cells that differentiate into osteoblasts, letting the bone thicken

what’s the periosteum it do for the bone

protects it, nourishes its tissue, assists in fracture repair

What sort of point is the periosteum

attachment point for tendons and ligaments

what’s the medullary cavity contain

bone marrow

2 types of bone marrow

red and yellow

what’s red marrow create

red blood cells, white blood cells, platelets

where’s red marrow found

in ribs, breastbone, scapulae, clavicles, pelvis, skull, vertebrae, epiphyses of long bones

what’s made in yellow marrow

contains fat and connective tissue and some white blood cells

proportion of red and yellow over time & why

only red at birth, then most is replaced by yellow over time due to the decrease of erythropoietin (which regulates red cell mitosis and differentiation)

2 layers of bone

compact/cortical on the outer

spongy/trabecular/cancellous on the inside

what’s the purposes of compact bone

• provides support and protection to the spongy bone

• resists non-constant stresses produced by weight and movement

What’s compact bone made of

collagen

what’s compact bone organised into

osteons/haversian system

what’s lamellae

contracentric layers that the bone’s arranges to around the canal

what’s lacunae

spaces between layers, where osteocytes lie

which way do osteons face

the same direction along whatever lines of stress are happening rn

Does spongy bone have osteons

nah

how are lamellae in spongy bone arranged

irregular lattice of thin interconnecting struts called trabeculae

what are spaces between trabeculae filled with

marrow

what’s in each trabeculae

osteocytes w radiating canaliculi (communication stuff)

how’s spongy tissue deal with stress

the trabeculae spreads it out, angled along the lines of stress so the bone resists the stress and transfers the force without breaking

what bones is spongy > compact

short, flat & irregularly shaped bones & epiphyses of long bones.

weight of spongy bone and why’s it cool

light, making the skeleton lighter, so muscles don’t need to work as hard

what percent of bone is organic, and inorganic, and what else

22% organic, 70% inorganic, 8% water

what’s the organic stuff in bones

90% type 1 collages

also cells, non-collagenous proteins, bone proteoglycan

how’s collagen formed

triple helix, made of hydroxyapatite crystals

what’s the inorganic stuff in bone

Calcium

Phosphate

Magnesium

Sodium

Potassium

why’s water important

the compression of bone makes the water move around, relieving stress

5 bone cells

osteoblast

osteoclast

bone lining cells

osteocyte

chondrocyte

purpose of osteoblast

formation

purpose of osteoclast

resorption

purpose of bone lining cell

protection and communication

osteocyte purpose

picks up waterflow in the bone, communicating to blasts and clasts on what to do next

purpose of chondrocytes

bone growth in embryo

what happens in endochondral ossification

growth plates on long bones grow towards the centre of the bones, pushing the bone out to be longer. (hypertrophy)