Functions and Components of the Skeletal System

Functions of the Skeletal System

• Support: Provides framework for the body.
• Protection: Protects vital organs such as the brain, heart and lungs.
• Movement: Allows for movement through joints, tendons, and ligaments.
• Storage: Stores minerals like calcium and phosphorus, and adipose tissue in marrow cavities .
• Blood Cell Production : Bone marrow produces red blood cells, white blood cells, and platelets.

Components of the Skeletal System

• Bone: Hard, rigid connective tissue consisting of organic and inorganic materials.
• Cartilage: Flexible connective tissue without blood vessels or nerves, found in joints, nose, trachea, and ears.
• Tendons: Connective tissue that attaches muscles to bones.
• Ligaments: Connective tissue that connects bones to other bones.

Types of Cartilage

• Hyaline Cartilage: Most common type, found in joints, nose, trachea, and ribs.
• Fibrocartilage: Strongest type, found in intervertebral discs and menisci.
• Elastic Cartilage: Most flexible type, found in the ear and epiglottis.

Cartilage Cell Types

• Chondroblasts: Immature cells that are responsible for producing the cartilage matrix.
• Chondrocytes: Mature cells that maintain the cartilage matrix and reside within lacunae (small cavities).

Bone Histology

• Bone Matrix: Consists of both organic components like collagen and proteoglycans, and inorganic components like hydroxyapatite (calcium phosphate crystals)

Bone Cells

• Osteochondral Progenitor Cells: Bone stem cells that can differentiate into other bone cell types.
• Osteoblasts: Bone-building cells that secrete matrix components.
• Osteocytes: Mature bone cells that maintain the bone matrix.
• Osteoclasts: Bone-destroying cells that resorb bone tissue.

Bone Development

• Intramembranous Ossification: Bone formation that occurs directly within embryonic connective tissue membranes, forming flat bones like skull bones.
• Endochondral Ossification: Bone formation that occurs within a cartilage model, forming long bones and most other bones in the body.

Bone Growth

• Growth in Length: Occurs at the epiphyseal plate, a region of cartilage growth at the ends of long bones.
• Growth in Width: Occurs at the periosteum, a fibrous membrane that covers the outer surface of bones.

Factors Affecting Bone Growth

• Nutrition: Calcium, phosphorus, vitamin D, and vitamin C are essential for bone growth.
• Hormones: Growth hormone, thyroid hormone, estrogen, and testosterone play important roles in bone growth.

Calcium Homeostasis

• Parathyroid Hormone (PTH): Increases blood calcium levels.
• Calcitriol: Increases blood calcium levels by stimulating intestinal absorption of calcium.
• Calcitonin: Decreases blood calcium levels by inhibiting osteoclast activity.

Bone Remodeling

• Basic Multicellular Unit (BMU): A group of osteoclasts and osteoblasts that work together to remodel bone tissue.
• Osteon: The functional unit of compact bone, formed by the process of bone remodeling.

Bone Repair

• A complex process involving several stages, including inflammation, soft callus formation, hard callus formation, and bone remodeling.

Abnormal Spinal Curvatures

• Scoliosis: Abnormal lateral curvature of the spine.
• Kyphosis: Exaggerated thoracic curvature of the spine, often referred to as "hunchback."
• Lordosis: Exaggerated lumbar curvature of the spine, often referred to as "swayback."

Bone Disorders

• Rickets: A condition in children caused by a deficiency of vitamin D, leading to soft and weak bones.
• Osteomalacia: A condition in adults caused by a deficiency of vitamin D, leading to soft and weak bones.
• Osteomyelitis: A bone infection typically caused by bacteria.
• Osteoporosis: A condition characterized by low bone density, making bones weak and brittle.

Diagnostic Tests for Skeletal System Disorders

• Blood Tests: Can be used to measure calcium levels, alkaline phosphatase, C-telopeptide, P1NP, 25-hydroxyvitamin D levels, and vitamin C levels.