Anatomy and Physiology 1 - Lecture on Bone Tissue

Overview

• Discussed Chapter 7 on bone tissue
• Introduction to the skeletal system (bones, cartilage, joints, ligaments)

Functions of the Skeletal System

• Support: Supports body structure (limb bones, vertebrae, jaw)
• Protection: Protects organs like the brain, spinal cord, heart, and lungs
• Movement: Assists in limb movements, walking, breathing
• Homeostasis: Maintains acid-base and electrolyte balance
• Blood Formation: Bone marrow produces blood cells and immune cells

Composition of Bone Tissue

• Bone is a living organ composed of osseous tissue
• Contains bone marrow, cartilage, adipose tissue, nervous tissue, and dense regular connective tissue
• Cells in Bone: Osteocytes (bone cells) are embedded in the extracellular matrix

Bone Matrix

• Composite of minerals and proteins (approx. 35% organic, 65% inorganic)
• Organic Component: Mainly collagen for flexible strength
• Inorganic Component: Calcium phosphate (hydroxyapatite) for weight-bearing strength
• Importance of both mineral and collagen components for bone strength

Classification of Bones by Shape

• Flat Bones: Thin, curved plates protecting soft organs (e.g., sternum, skull)
• Long Bones: Longer than wide, serve as levers (e.g., humerus, radius, ulna)
• Short Bones: Equal in length and width, glide across each other (e.g., wrist bones)
• Irregular Bones: Elaborately shaped (e.g., vertebrae, patella)

Types of Bone Tissue

• Compact Bone (Cortical Bone): Dense and strong, forms outer layers
• Spongy Bone (Cancellous Bone): Lattice structure, less dense, found in centers and ends of bones

Structure of Long Bones

• Diaphysis: Shaft of the long bone
• Epiphyses: Enlarged ends of the long bone
• Medullary Cavity: Central cavity containing yellow bone marrow
• Endosteum: Inner lining of the medullary cavity, role in bone repair
• Periosteum: Outer fibrous membrane (dense irregular connective tissue)

Bone Marrow

• Red Bone Marrow: Produces blood cells, found in epiphyses and flat bones
• Yellow Bone Marrow: Stores fat, found in the medullary cavity
• Red marrow can convert to yellow and vice versa if needed

Histology of Compact Bone

• Composed of osteons (structural units)
• Central Canal: Contains blood vessels and nerves
• Lamellae: Concentric layers of bone matrix and cells
• Perforating Canals: Connect osteons
• Nutrient Foramina: Allow blood vessels to enter bone

Bone Cells

• Osteogenic Cells: Stem cells that differentiate into bone and cartilage
• Osteocytes: Maintain bone matrix
• Osteoblasts: Build new bone matrix
• Osteoclasts: Break down bone matrix

Bone Remodeling

• Continuous breakdown and rebuilding of bone
• Entire skeleton remodeled approximately every 10 years
• Exercise stimulates bone remodeling (use it or lose it principle)

Bone Ossification

• Intramembranous Ossification: Formation of flat bones
• Endochondral Ossification: Formation of most other bones (long bones)

Factors Affecting Bone Growth

• Nutrition, vitamins (Vitamin D), hormones, and exercise
• Calcium is critical for many bodily functions beyond bone structure

Calcium Homeostasis

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

Bone Disorders

• Osteoporosis: Decrease in bone density, increased fracture risk
• Influenced by calcium, vitamin D, exercise, and hormonal levels

Bone Fractures

• Stress Fracture: Due to abnormal trauma
• Pathological Fracture: Due to weakened bone (e.g., osteoporosis)
• Healing involves hematoma formation, soft and hard callus formation, and remodeling

Conclusion

• Orthopedics studies bone/joint/muscle disorders
• Upcoming chapters will cover the skeletal system and joints further