Types of Bone Tissue
1. Compact bone
80% skeletal is compact bone. More bone matrix, less space.
2. Spongy bone/ Cancellous bone
20% is spongy bone. Less bone matrix and more space.
1. Compact Bone Tissue/ Cortical bone
Compact bone forms the hard external layer of all bones.
Very hard and dense.
Compact bone tissue consist of units called osteons or haversian system.
Has concentric ring structure.
Function
1. It provide protection and strength to bone.
2. It helps long bone resist stress of weight placed on them.
Provide levers for movement.
Store and release chemical elements mainly calcium.
Support whole body.
Structure of Compact Bone
Bone contains cylinders of calcified bone known as osteons/ haversian systems.
Haversian System/ Osteons
Central canal with it's surrounding lamellae, lacunae, osteocytes and canaliculi forms an osteon.
1. Central canal/ haversian canal
Inside each osteon is a space, called central canal.
In the center of osteon are central canal, longitudinal channels that contain blood vessels, nerves, and lymphatic vessels.
2. Concentric lamellae layer
Osteons are made up of concentric layer of lamellae of bone.
Lamellae are articular layer or rings of hard, calcified bone matrix that surround a common center, central canal.
Lacunae
Lamellae contains lacunae or little spaces which contains osteocytes or bone cells.
Canaliculi
Small channels (canaliculi) radiate from lacunae to osteonic canal to provide passageway through hard matrix.
Canaliculi route is for nutrients and oxygen to reach osteocytes and wastes to diffuse away.
Facilitating movement of material from cell to cell.
Perforating canal/Volkmann's canals
Perforating canal are small channel's, which are empty spaces that allow blood vessels, lymph vessel and nerve from periosteum enter into bone.
Perforating canals are not enclosed by concentric canal.
Interstitial lamellae
The area or space between osteons contains or occupies by interstitial lamellae. Interstitial lamellae are fragments of older osteons, that have been partially damaged during bone replacement.
Circumferential lemellae
Outer surface of compact bone are covered by circumferential lamellae which are flat plates that extend around bone.
2. Spongy bone tissue/ Cancellous
Spongy bone consist web like arrangement of marrow filled spaces separated by thin bone is called trabeculae.
3. Trabecular
Spongy bone consist of interconnecting plates of bone is called trabeculae.
Trabeculae consist several lamellae.
Osteocytes located between the lamellae.
Osteocytes lie in lacunae.
Radiating from lacunae are canaliculi.
Space between trabeculae of some bone are filled with red bone marrow which produce blood cell.
Osteocytes in trabeculae receive nourishment directly from blood circulating through bone marrow.
Function
1. Responsible for production of red blood cell.
2. Provide greatest strength with least weight.
Cancellous bone consist of spongy, porous, bone tissue that is filled with red bone marrow.
Mostly concentrated in hip bone, skull, vertebrae, ribs, pelvis
Spongy bone is lighter than compact bone, reducing weight of skeleton.
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