1. The study Of bones is osteolgy.
2. Bone is externally covered by a thick white fibrous tissue called periosteum.
3. Bone is internally composed of calcified matrix and cells.
4. Bone matrix is called ossin.
5. Bone cells are called osteocytes. They are found in Lacunae.
6. An osteoblast cell is surrounded by newly formed matrix and becomes osteocyte.
7. Osteoblasts synthesize the matrix
8. Osteoblasts are involved in the resorption and remodeling of bone tissue.
STRUCTURE OF COMPACT BONE:
1. The compact bone has dense matrix.
2. The long bones of the arms and legs are compact bones.
3. The outer surface of the bone is covered by a tough vascular connective sheath called periosteum.
4. The inner surface of the bone is lined by endosteum,
5. The compact bone contains a central marrow cavity.The marrow cavity contains yellow bone marrow.
6. The matrix, in between the periosteum and endosteum contain collagen fibres. The fibres are arranged in lamellae.
7. Inner circumferential lamellae are located around the bone marrow cavity, and outer circumferential lamellae are located immediately beneath the periosteum.
8. Between the two circumferential lamellae several structural units called osteons or Haversian systems are arranged around and parallel to the marrow cavity.
• Haversian systems are the structural units of bone
• Each haversian system consists of a haversian canal.
• Haversian canal is surrounded by concentric lamellae.
• Between the lamellae, many lucanae are present.
• Each lucana encloses one osteocyte.
• The cytoplasmic processes of osteocytes extend into minute radial canals called canaliculi.
• Canaliculi connect lacunae with one another and with haversian canal.
• The haversian canais communicate with bone marrow cavity, the periosteum and another through transverse or oblique volkmann’s canals.
• Blood vessels, lymphatic vessels and nerves from the surface of the bone reach haversian canals through valkmann’s canals.
• A haversian canal, surrounding concentric lamellae and lacunae are collectively called a haversian system or osteon.
T.S OF BONE
CHEMICAL COMPOSITION OF BONES:
Of the dry weight of bone:
In organic substances(65%)
– calcium phosphate 85%
– calcium carbonate 10%
– chlorides, fluroides of calcium and magnesium 5%
and collgen fibres.
o The major mineral is calcium phosphate in the form of hydrxyapatite crystals.
o The major organic substance is collagen.