Skeletal System Overview

Study Notes

Types of Bones in the Human Body
- Long bones (e.g., femur, humerus) provide leverage for movement, featuring a shaft and two ends for strength.
- Short bones (e.g., carpals, tarsals) located in wrists and ankles offer stability and weight-bearing support.
- Flat bones (e.g., skull) protect vital organs; irregular bones (e.g., vertebrae) have specific shapes for specialized functions.

Diaphysis
- The shaft of a long bone, mainly dense cortical bone, offering strength and resistance to bending and torsion.
Epiphyses
- Ends of long bones primarily comprised of cancellous bone, essential for joint formation and covered in articular cartilage for smooth movement.
Epiphyseal Plate
- Cartilaginous growth area in developing bones, facilitating longitudinal growth; calcifies in adults into the epiphyseal line.
Articular Cartilage
- Smooth, avascular tissue on joint surfaces that reduces friction and absorbs shock for pain-free movement.

Osteoblasts
- Bone-forming cells that secrete collagen and proteins, essential for ossification and bone growth.
Osteocytes
- Mature bone cells within the matrix, maintaining tissue by regulating mineral concentrations and responding to mechanical stress.
Osteoclasts
- Large, multinucleated cells involved in bone resorption, breaking down tissue, releasing minerals, and enabling bone remodeling.

Cortical Bone
- Provides strength and support to skeletal structure.
Cancellous Bone
- Porous structure that facilitates hematopoiesis and rapid remodeling, serving as a site for blood cell production.

Osteon (Haversian System)
- The basic functional unit of cortical bone, consists of concentric layers of bone matrix surrounding a central canal housing blood vessels and nerves.
Trabeculae
- Lattice-like framework in cancellous bone that offers strength while maintaining lightness.
Periosteum and Endosteum
- Tough outer membrane (periosteum) covers bones; endosteum lines internal cavities, both containing vessels and cells vital for growth and repair.

Red Bone Marrow
- Found in flat bones and epiphyses, responsible for hematopoiesis, producing red blood cells, white blood cells, and platelets.
Yellow Bone Marrow
- Located in the medullary cavity of long bones, comprises fat cells and serves as an energy reserve, convertible to red marrow under specific conditions.
Blood Supply
- Bones receive blood via periosteal, nutrient, and metaphyseal arteries, supporting bone metabolism, nutrient supply, and waste removal.

Osteogenesis
- Bone formation initiates prenatally, continuing through adolescence, involving mesenchymal stem cell differentiation into osteoblasts.
Bone Remodeling
- Continuous process of old bone tissue removal by osteoclasts and replacement by osteoblasts, ensuring strength and mineral balance.

Physical Activity
- Regular weight-bearing and resistance exercises are essential for stimulating bone formation and increasing density.
Dietary Needs
- Calcium (1000-1200 mg/day) and Vitamin D (600-1000 IU/day) are vital for bone health, alongside adequate protein for matrix maintenance.
Hormonal Influence
- Parathyroid hormone (PTH) and calcitonin manage calcium levels; sex hormones contribute significantly to bone metabolism and density.