Anatomy and Physiology 1: Chapter 6 - Osseous Tissue

Introduction to the Skeletal System

• Bone as a Tissue: Understanding bone as a tissue helps in understanding the skeletal system.
• Components: Bones, cartilage, ligaments, and other connective tissues.
• Functions of the Skeletal System:
  • Support
  • Storage of Minerals and Lipids: Mainly calcium and fat in yellow bone marrow.
  • Blood Cell Production: In red bone marrow.
  • Protection: E.g., rib cage for heart/lungs, skull for brain.
  • Leverage: Bones act as levers for muscles.

Classification of Bones

• By Shape:
  • Sutural Bones: Found between flat bones of the skull, not present in everyone.
  • Irregular Bones: Complex shapes, e.g., vertebrae.
  • Short Bones: Small and boxy, e.g., carpal bones.
  • Flat Bones: Thin and flat, e.g., skull bones, sternum.
  • Long Bones: Long and slender, e.g., humerus, femur.
  • Sesamoid Bones: Small, round, flat, e.g., patella.

Structure of a Long Bone

• Diaphysis: The shaft, contains compact bone and marrow cavity.
• Epiphysis: Ends of the bone, contains spongy bone.
• Metaphysis: Where diaphysis and epiphysis meet.
• Articular Cartilage: Found at joints.

Bone Tissue Structure

• Compact Bone: Dense, made of osteons.
• Spongy Bone: Trabecular bone, porous structure.

Bone Composition

• Matrix: Collagen fibers and calcium salts.
• Bone Cells:
  • Osteocytes: Mature bone cells in lacunae, maintain matrix.
  • Osteoblasts: Produce new bone matrix.
  • Osteogenic Cells: Stem cells producing osteoblasts.
  • Osteoclasts: Resorb bone matrix, important for homeostasis.

Bone Formation and Growth

• Ossification: Bone formation, includes calcification.
• Endochondral Ossification: Bone development from cartilage, primarily for long bones.
• Intramembranous Ossification: Formation from mesenchymal tissue.

Bone Remodeling and Homeostasis

• Includes: Osteocytes, osteoblasts, and osteoclasts for renewal.
• Nutritional Needs: Calcium, phosphorus, vitamins D, C, A, K, and B12.
• Hormonal Regulation: Growth hormone, sex hormones, parathyroid hormone, and calcitonin.

Calcium Homeostasis

• Parathyroid Hormone (PTH): Increases blood calcium levels.
• Calcitonin: Decreases blood calcium levels.

Bone Health and Disorders

• Fractures: Breaks can be compound or simple.
• Repair Process: Involves formation of hematoma, callus, and bone remodeling.
• Bone Density Reduction with Age: Osteopenia and osteoporosis.
• Osteoporosis: Severe bone mass loss, more common post-menopause.

Conclusion

• Overview of bone functions, structures, and health.
• Transition to the axial skeleton in the next chapter.