skeletal

• The area where two or more bones meet is the joint
• Rigid strong bones – for bearing weight and is the major supporting tissue of the body.
• • Cartilage – provides a firm yet flexible support within certain structures (ex. nose and external ears).
• Ligaments – are strong bands of fibrous connective tissue that attach to bone and hold them together
• Protection - The hardness of the bone contributes to its ability to protect the vital organs of the body from injury (ex.cranial bones protect the brain).
• Movement - Skeletal muscles attach to bones by tendons. When muscles contract, they pull on bones and together they produce movement
• 1. Storage

  • Fat is stored in the internal cavities of bones. 
  • Stores several minerals especially calcium and phosphorus.
  • Important in maintaining homeostasis of minerals in the blood with minerals stored in the bone are released in response to body’s demand.
• Blood cell production (hematopoiesis) - Many bones contain cavities filled with bone marrow that gives rise to blood cells and platelets
• OSTEOLOGY - The study of bone structure and treatment of bone disorder.
• BONE OSSIFICATION (OSTEOGENESIS) - It refers to the formation of bone by osteoblast.
• Intramembranous Ossification

  • A process of bone development from fibrous membrane.
  • It is involved in the formation of the flat bones of the skull, the mandible and clavicles.
• Endochondral Ossification

  • A process of bone development from hyaline cartilage.
  • All of the bones of the body, except for the flat bones of the skull, mandible and clavicles are formed through
• Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center
• Osteoblast begin to secrete  osteoid, which is mineralized within few days
• Trapped osteoblasts become osteocytes
• • accumulating osteoid is laid down between embryonic blood vessels, which form a random network. The result is a network (instead of lamellae) of trabeculae.
• Vascularized mesenchyme condenses on the external face of the woven bone and becomes the periosteum.
• • Trabeculae just deep to the periosteum thicken, forming a woven bone collar that is later replaced with mature lamellar bone.
• Spongy bone (diploe), consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow.
• Appositional Growth - It refers to the formation of new bone on the surface of existing bone.
• • Appositional growth results as osteoblasts deposit new bone matrix on the surface of bones between the periosteum and the existing bone matrix.
• Appositional Growth - Responsible for the increase in width or diameter of long bones and most growth of other bones.
• Endochondral Growth - It refers to the growth of cartilage in the epiphyseal plate and its eventual replacement by bone.
• Endochondral Growth - Responsible for the increase in the length of the bone.
• Endochondral Growth - Bones continue to grow in length until early childhood, the rate of growth is controlled by hormones.
• Bone Remodeling

  • It involves the removal of old bone by cells called osteoclast and the deposition of new bone by osteoblast.
  • It occurs in all bone.
• • Remodeling is responsible for:

  1. Bone growth
  2. Changes in bone shape
  3. Adjustment of bone to stress
  4. Bone repair
  5. Calcium ion regulation
• 1. Resorption – during which osteoclasts digest old bone.
• 1. Reversal – when mononuclear cells appear on the bone surface.
• Formation – when osteoblasts lay down new bone until the resorbed bone is completely replaced.
• Bone Repair (Healing) - A process in which a bone repairs itself following a bone fracture.
• When a bone is broken, a clot forms in the damaged area.
• • Callus forms, the zone of tissue repair between the two bone fragments.
• Osteoblasts enter the callus and form cancellous bone.
• The cancellous bone is slowly remodeled to form compact bone and the repair is complete.
• Bone serves as the major storage site for calcium
• • The movement of calcium in and out of bone helps determine blood calcium levels.
• • Calcium moves into bone as osteoblasts build new bone.
• • Calcium move out of bone as osteoclasts break down bone.
• Calcium homeostasis is maintained by parathyroid hormone and calcitonin