SKELETAL SYSTEM

1. Introduction to Skeletal System

The skeletal system is the framework of the body made up of bones, cartilage, ligaments, and joints.

Functions of Skeletal System

1. Support – provides body framework

2. Protection – protects vital organs

3. Movement – helps in body movement with muscles

4. Blood cell formation – hematopoiesis in bone marrow

5. Mineral storage – calcium and phosphorus

6. Fat storage – yellow bone marrow

Total bones in adult = 206 bones

2. Anatomical Position

Anatomical position is the standard reference position used to describe body parts.

Features

• Body standing upright

• Face forward

• Arms at sides

• Palms facing forward

• Feet together

• Toes pointing forward

Importance

• Provides standard direction reference

• Used in anatomy and clinical practice

• Avoids confusion in describing body parts

3. Bone – Definition

Bone is a hard connective tissue forming the skeleton.

Bone matrix contains:

• Calcium phosphate

• Collagen fibers

• Minerals

4. Structure of Bone

Parts of Long Bone

Part	Description
Diaphysis	shaft of bone
Epiphysis	ends of bone
Metaphysis	growth area
Periosteum	outer covering
Compact bone	hard outer layer
Spongy bone	inner porous layer
Medullary cavity	contains marrow

Microscopic Structure

Cells of Bone

1. Osteoblasts – bone forming cells

2. Osteocytes – mature bone cells

3. Osteoclasts – bone destroying cells

Haversian system (Osteon)

• Structural unit of compact bone

5. Types of Bones (Classification)

Type	Example	Function
Long bone	femur, humerus	movement
Short bone	carpals	stability
Flat bone	skull, sternum	protection
Irregular bone	vertebra	special function
Sesamoid bone	patella	reduce friction

6. Bone Growth and Development

Bone formation process = Ossification

Types of Ossification

1. Intramembranous ossification – flat bones

2. Endochondral ossification – long bones

Epiphyseal plate (Growth plate)

• Responsible for increase in length

• Active during childhood

Factors affecting bone growth

• Nutrition (calcium, vitamin D)

• Hormones (growth hormone)

• Exercise

• Genetics

7. Axial Skeleton

Forms central axis of body

Total bones = 80

Parts of Axial Skeleton

Part	Number of bones
Skull	22
Vertebral column	26
Ribs	24
Sternum	1
Ear ossicles	6
Hyoid bone	1

Functions

• Protect brain

• Protect spinal cord

• Protect heart and lungs

8. Appendicular Skeleton

Bones of limbs

Total bones = 126

Parts

Region	Bones
Pectoral girdle	clavicle, scapula
Upper limb	humerus, radius, ulna
Pelvic girdle	hip bone
Lower limb	femur, tibia, fibula

9. Differences between Axial and Appendicular Skeleton

Feature	Axial	Appendicular
Location	central axis	limbs
Bones	80	126
Function	protection	movement
Parts	skull, ribs, spine	arms, legs

10. Nursing Importance of Skeletal System

• Understanding fractures

• Orthopedic patient care

• Posture assessment

• Mobility support

• Calcium deficiency disorders

• Osteoporosis care

• Traction and cast care

• Patient education about bone health

11. Common Disorders of Skeletal System

Disease	Description
Osteoporosis	bone weakness
Fracture	break in bone
Arthritis	joint inflammation
Rickets	vitamin D deficiency
Osteomyelitis	bone infection
Scoliosis	spinal curvature