Understanding the Skeletal System: Definition, Components & Injuries

The skeletal system is the body's structural framework—206 bones (in adults) plus cartilage, ligaments, and tendons—providing support, protection, movement, mineral storage, and hematopoiesis.

Components

Division	Bones	Function
Axial (80)	Skull, vertebral column, ribs, sternum, hyoid	Protects CNS, heart, lungs; central axis
Appendicular (126)	Limbs, girdles (pectoral/pelvic)	Locomotion, manipulation

Bone Tissue & Structure

• Compact (cortical) bone: Dense outer shell; strength.
• Spongy (trabecular) bone: Porous interior; shock absorption, marrow housing.
• Periosteum: Vascular membrane; attachment, repair.
• Endosteum: Lines internal cavities.

Joints (Articulations)

• Fibrous (sutures), Cartilaginous (intervertebral discs), Synovial (freely movable: hinge, ball-and-socket, pivot, condyloid, saddle, plane).

Common Injuries & Conditions

Category	Examples	Mechanism
Fractures	Stress, compression, comminuted, open/closed	Trauma, overuse, osteoporosis
Dislocations/Subluxations	Shoulder, patella, elbow	Force exceeding ligamentous restraint
Degenerative	Osteoarthritis, DJD	Cartilage wear, inflammation
Inflammatory/Autoimmune	RA, AS, psoriatic arthritis	Immune-mediated synovitis
Metabolic	Osteoporosis, osteomalacia, Paget's	Bone density/mineralization defects
Neoplastic	Primary (osteosarcoma), metastatic	Malignant transformation
Infectious	Osteomyelitis, septic arthritis	Bacterial/fungal seeding

Diagnostic Tools

• X-ray (first-line), CT (complex fractures), MRI (soft tissue, marrow), DEXA (density), bone scan (metabolic activity), labs (Ca, PTH, Vit D, inflammatory markers).

Bone Health Essentials

• Weight-bearing/resistance exercise.
• Calcium 1000–1200 mg/day (diet > supplements).
• Vitamin D 1000–2000 IU (target 30–50 ng/mL).
• Protein, magnesium, vitamin K2.
• Avoid smoking, excess alcohol, fall risks.

The skeleton is dynamic—constantly remodeling. Invest in it daily.