Definitions

Axial skeleton

Bones forming axis or centre of the skeleton (bones of head, neck, vertebrae and tail)

Apendicular skeleton

Regions attached to axial skeleton (bones of fore and hind limb)

Visceral bobes

Bones that develop in the soft tissues away from the rest of the skeleton

Chondral ossification

Ossify from cartilage precursor

Found in load bearing areas

Have specific fail/fracture configurations

Membranous ossification

Ossify directly from mesenchymal cells (scapula)

Fracture configuration like ice breaking

Long bones

Cylindrical shape

Column provides strength flared bone ends

Resist compressive force

Flat bones

Thin flat bones

Act as soft tissue attachments and protect underlying tissues

Ribs and scapular are examples

Sesamoid bone

Provide additional strength and reduce wear over joints

Protect tendons over bony prominence

Redirect course of tendon

Attachment for tendon

Weight bearing function

Short bones

Many sides, similar dimensions throughout

Found in groups that act to transmit and disseminate forces through joint

One surface is always non articulate for ligament attachment

Carpal bones are an example

Pneumatic bones

Bones which contain air spaces

Paranasal sinuses

Irregular bones

Irregular shape

Various jutting processes for muscle and ligament attachment

Vertebral bones

What do we need a skeleton for?

Structural support

Protection of vital organs against trauma

Locomotion act as levers to affect movement

Mineral ion store

What're the limitations of bones?

Limited growth potential-can only grow from ends

Get more brittle with age

They're rigid

Cortex

Tube of solid bone

Medulla

Central cavity filled with marrow

What's the cortex made of?

Compact/cortical bone

What're the bone ends made of?

Spongy cancellous bone

Diaphysis

Middle area of bone column

Metaphysis

Flared region of bone

Epiphysis

Rounded end of bone

Osteoid

Ground substance in which collagen I fibres are embedded

Synthesised by osteoblasts

Secreted onto existing bone surfaces

What is found in osteoid?

90% collagen type I

10% water containing glycoproteins, proteoglycans etc

What's mineralisation?

Process by which calcium phosphate is produced by osteoblasts and laid into the bone matrix

Woven bone

Haphazard collagen

Found in young animals and repairs

Rapid mineralisation

Lamellar bone

Thin layers of osteoid within which collagen fibres run parallel

Structurally superior to woven bone

Osteoblasts

Derived from mesenchymal stem cells

Synthesise and secrete osteoid

Active in mineralisation process

Osteocytes

Scattered in matrix

Interconnected by dendritic processes

Derived from osteoblasts

Reside within lacunae which're connected by canaliculi

Long lived

Maintain matrix

Osteoclasts

Responsible for bone resorption

Large cells, multiple nuclei

Release protons creating acid environment-demineralisation

Secrete proteases-destroy organic matrix

Derived from bone marrow

what is embryology

the branch of biology that deals with the formation, early growth and development of living organisms