PRACTICAL ROADMAP OSTEOGENESIS TN Augustine

OSTEOGENESIS

• Intramembranous ossification – Development of bone

directly from mesenchyme

• Endochondral ossification – Bone develops ON a

hyaline cartilage model – This thus requires

chondrogenesis – the growth and development of cartilage) – to take place initially.

The growth and development of bone

INTRAMEMBRANOUS OSSIFICATION

• Slide 110 Foetal skull (late)

Note: – Vascular mesenchyme – Osteoblasts secreting osteoid – Osteoblasts trapped in mineralising osteoid. They will

thereafter be known as osteocytes – Once the osteoid is fully mineralised it is known as

bone – Mixed spicules containing both osteoid and bone

Foetal Skull (early) Slide 109

Spicules of osteoid and

bone

Mesenchyme

Foetal Skull (early)

Developing epidermis

Capillary

Osteocyte in lacuna

Developing hair follicle

Bone

Spicule of developing

bone

Foetal Skull (early)

Arteriole Mesenchyme

Osteocytes in lacunae

Venule

Bone

Osteoid Osteoblasts

Note: – The pale eosinophilical osteoid – The more basophilic mineralised osteoid = bone

INTRAMEMBRANOUS OSSIFICATION • Slide 109 Foetal skull (early) • Slide 110 Foetal skull (late)

Note:

– The further development of the mesenchyme and the epidermis

– Osteoblasts secreting osteoid – Osteocytes trapped in lacunae within the mineralised

osteoid – The coalescing of mixed spicules of osteoid and bone – The development of marrow cavities

Foetal Skull (late) Slide 110

Spicules of developing bone

coalescing

Hair follicle

Endosteal cells

Osteoid Developing marrow cavity

Foetal Skull (late)

Osteocytes in lacunae Osteoblasts

Bone

ENDOCHONDRAL OSSIFICATION

Note: – Requires a hyaline cartilage model upon which osteoid

is laid down and mineralised • The hyaline cartilage model develops via chondrogenesis

ENDOCHONDRAL OSSIFICATION

• Slide 52 Foetal knee Note:

– The developing femur, patella and tibia. – The developing synovial cavity – The surrounding tissues

Endochondral Ossification

Developing femur

Developing tibia

Developing patella

Developing synovium

Developing articular cartilage

Endochondral Ossification

Developing femur Developing

patella

Secondary ossification centre

Endochondral Ossification

Developing femur

Secondary ossification centre

Hyaline cartilage

Zonation associated with endochondral ossification

Endochondral Ossification

Zone of cell rest

Zone of hypertrophy

Zone of cell proliferation

Zone of calcified cartilage

Zone of resorption

Osteoid

Endochondral Ossification

Hypertrophied chondrocytes

Calcified cartilage

Haematopoeitic cells

Osteoblasts

Calcified cartilage

Endochondral Ossification

Osteoblasts

Osteoid

Osteoclasts

Use your gross anatomy knowledge to identify developing: a) Muscle groups

and muscles b) Ligaments c) Bones