- Osteocyte: Mature bone cell
- Osteoblast: Responsible for creating new bone
- Osteoclast: Responsible for removing old/dead bone cell
Bones are specialised connective tissue so it is made up of standard componants:
- Ground Substance/ Matrix: A solid matrix made up of calcium phosphate.
- Cells: Osteocytes
- Fibres: Collagen for stregnth and resiliance.
Made up in concentric circles (like a tree trunk) known as Lamellae arranged around a central Haversian Canal that contains nerves, blood vessels and lymphatic vessels. Osteocyes are positioned within Lacunae within lamella.
There are 2 types of bone tissues:
- Compact / Cortical Bone:
- Has tightly packed Haversian systems
- Strong and dense
- Found in cortex (outer edge)
- Cancellous / Spongy Bone:
- Lighter than compact bone
- Made up of bars called trabeculae
- Found at end of long bones and core of others
- Support: Scaffold of the body and houses sensory organs.
- Locomotion: Skeletal muscles attach to the bones and pull on them for movement.
- Protection: Form a protective cage for vital organs.
- Storage: Calcium is stored within the bones.
- Haematopoiesis: Blood cells are produced withing the bone marrow.
Classification and Examples
- Long : Humerous, Ulna, Femur, Tibia, Phalanges
- Short : Carpal and Tarsal Bones
- Irregular : Vertebrae
- Flat : Scapula, Pelvic bone, Ribs
- Sesamoid : Patella , Fabellae
- Pneumatic / air filled : Frontal bone, Maxillary bone, some long bones in birds
Components of Long Bones
Diaphysis : Main shaft of bone
Epiphysis : Ends of bone
Metaphysis : Where diaphysis and epiphysis meet. Growth plate in young animals
Articular Cartilage : Hyline cartilage that covers ends of bones
Periosteum : Membranous structure that surrounds outer surface of the bone
Nutrient Foramen : Small hole where blood vessels enter the bone
Cortex : Outer region of compact bone
Medulla : Central cavity of bone, filled with bone marrow
Endochondral: Occurs in all bones except flat bones
- Occurs in diaphysis (primary ossification centre)
- Osteoblasts replace cartillage with bone (develops outwards)
- Secondary ossification centres develop in epiphysis (develops outwards towards diaphysis)
- Osteoclasts reabsorb centre of bone forming medullary cavity
- 2 bands of cartilage forms between diaphysis and epiphysis forming growth plates
- When cartilage is replaced with bone, no further growth occurs
Intramembranous: Occurs in flat bones only