Untitled Quiz

Bone Functions

• Provides structural support for the body, acting as a framework.
• Protects vital organs, such as the brain, heart, and lungs.
• Facilitates movement by interacting with muscles.
• Serves as a storage site for minerals, primarily calcium and phosphorus.
• Involved in hematopoiesis, the production of blood cells.

Bone Tissue

• Classified as connective tissue.
• Composed of cells, fibers, and matrix.
• Cells include:
  • Osteogenic cells: bone stem cells
  • Osteoblasts: bone-forming cells
  • Osteocytes: mature bone cells
  • Osteoclasts: bone-destroying cells
• Fibers are primarily collagen, providing tensile strength.
• Matrix is composed of calcium phosphate salts, imparting compressive strength.

Chemical Composition of Bone

• Contains approximately 1/3 organic compounds.
• Organic compounds include cells and collagen, contributing to bone's tensile strength.
• Contains approximately 2/3 inorganic compounds, primarily calcium phosphate in the form of hydroxyapatites.
• Inorganic compounds contribute to bone's compressive strength.
• Calcification: the process of hardening the bone matrix by depositing calcium phosphate.

Types of Bone Tissue

• Compact bone: Solid, dense bone tissue found in the outer layer of bones.
• Spongy bone (Cancellous bone): Porous bone tissue with interconnected spaces, found in the interior of bones.

Microscopic Structure of Compact Bone

• Composed of lamellae (concentric layers) arranged in osteons (Haversian systems).
• Contains osteocytes (mature bone cells) housed within lacunae (small cavities) within the lamellae.
• Features canaliculi (tiny canals) that connect lacunae and allow for nutrient and waste exchange.

Red Bone Marrow

• Located within the spongy bone.
• Responsible for blood cell formation (hematopoiesis).

Parts of a Long Bone

• Diaphysis: the shaft or central region of a long bone.
• Epiphysis: The ends of a long bone.
• Metaphysis: The region between the diaphysis and epiphysis.
• Periosteum: A fibrous membrane covering the outer surface of bone, containing blood vessels and nerves.

Bone Development (Ossification)

• Intramembranous ossification: Bone develops directly from mesenchymal tissue.
  • Occurs in skull bones and clavicles.
• Endochondral ossification: Bone develops from a cartilage model.
  • Occurs in most bones of the skeleton, excluding skull bones and clavicles.

Bone Growth in Length

• Occurs at the epiphyseal plate (growth plate).
• Growth plate consists of four zones:
  • Resting cartilage cells
  • Zone of proliferation
  • Zone of hypertrophy
  • Zone of calcification
• Bone growth in length ceases when the epiphyseal plate closes.

Bone Remodeling

• Continuous process of bone deposition (bone formation) and bone resorption (bone breakdown).
• Osteoblasts are responsible for bone deposition.
• Osteoclasts are responsible for bone resorption.
• Remodeling is influenced by various factors, including vitamins, hormones, and mechanical stress.

Factors Affecting Bone Remodeling

• Vitamins: Vitamins A, C, and D play crucial roles in bone health.
• Hormones: Growth hormone, thyroid hormone, and sex hormones influence bone growth and remodeling.
• Mechanical stress: Exercise and physical activity stimulate bone deposition and increase bone density.
• Calcium levels: Bone remodeling helps regulate blood calcium levels.

Regulation of Blood Calcium Levels

• Bone plays a crucial role in maintaining blood calcium homeostasis.
• Hypercalcemia: High blood calcium levels.
• Hypocalcemia: Low blood calcium levels.

Mechanisms of Calcium Homeostasis

• Parathyroid hormone (PTH): Increases blood calcium levels by stimulating osteoclast activity, increasing calcium absorption in the kidneys, and promoting vitamin D synthesis.
• Calcitonin: Lowers blood calcium levels by inhibiting osteoclast activity and stimulating bone deposition by osteoblasts.

Osteoporosis

• A condition characterized by decreased bone density and increased bone fragility.
• Occurs when bone resorption exceeds bone deposition.
• Increased risk of fractures.