Anatomy and Physiology: Chapter 6 - Osseous Tissue

Overview

• Focus on skeletal system and bone tissue.
• Skeletal system includes bones, cartilage, ligaments, and connective tissues.
• Functions: support, mineral storage (mainly calcium), lipid storage, blood cell production, protection, leverage.

Bone Classification

• Sutural Bones: Small, flat, irregular bones in skull sutures.
  • Not present in everyone.
  • Can vary in size.
• Irregular Bones: Complex shapes; examples include vertebrae and pelvic bones.
• Short Bones: Boxy shape; examples include carpal and tarsal bones.
• Flat Bones: Thin with parallel surfaces; examples include skull bones and sternum.
• Long Bones: Long and slender; examples include humerus and femur.
• Sesamoid Bones: Small, round, flat; found near joints, e.g., patella.

Structure of Long Bones

• Diaphysis: Shaft with compact bone; contains marrow cavity.
• Epiphysis: Ends of the bone; contains spongy bone.
• Metaphysis: Where diaphysis and epiphysis meet; includes growth plate or epiphyseal line.
• Articular Cartilage: Thin cartilage covering joint surfaces.

Bone Composition

• Bone Matrix: Made of calcium salts and collagen.
  • Provides strength and slight flexibility.
• Calcium Phosphate: Main component; interacts to form hydroxyapatite.

Bone Cells

• Osteogenic Cells: Stem cells dividing to produce osteoblasts.
• Osteoblasts: Immature cells producing new bone matrix.
• Osteocytes: Mature bone cells maintaining bone tissue.
• Osteoclasts: Absorb and remove bone matrix.

Bone Tissue Organization

• Osteons: Units of compact bone, contain central canals with blood vessels.
  • Central Canal: Contains blood vessels.
  • Lamellae: Layers of bone matrix.
  • Canaliculi: Narrow passageways for nutrient exchange.

Types of Bone Tissue

• Compact Bone: Dense; strong; supports weight.
• Spongy Bone: Porous; handles stress from multiple directions.

Bone Membranes

• Periosteum: Outer cover, protective, aids growth and repair.
• Endosteum: Lines marrow cavity, active in growth and repair.

Bone Development

• Ossification: Formation of bone, includes calcification.
  • Endochondral Ossification: Bone replaces cartilage model.
    • Involves primary and secondary ossification centers.
  • Intramembranous Ossification: Bone develops in dermis; forms flat bones.

Bone Growth and Remodeling

• Bone Remodeling: Continuous process with osteocytes, osteoblasts, and osteoclasts.
• Stress and Exercise: Strengthen bone; lack of activity weakens it.

Nutritional and Hormonal Influence

• Calcium and Phosphates: Essential for bone health.
• Calcitriol and Vitamin D3: Aid calcium absorption.
• Hormones: Growth hormone, sex hormones, parathyroid hormone, and calcitonin regulate bone growth and calcium levels.

Calcium Homeostasis

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

Fracture Healing

• Steps: Fracture hematoma, callus formation, spongy bone formation, compact bone formation.

Age-Related Changes

• Osteopenia: Reduced bone mass, common after age 40.
• Osteoporosis: Severe bone mass loss, affects function; common post-menopause.

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Conclusion

• Chapter 6 covers bone tissue, structure, function, growth, and remodeling, setting the stage for understanding the axial skeleton in Chapter 7.