Chapter 5: The Integumentary System

Overview and Functions

The integumentary system consists of the skin and its associated structures. It serves as the body's first line of defense and performs several vital functions.

• Functions: Protection, sensation, temperature regulation, excretion, vitamin D synthesis, and prevention of water loss.

• Key Structures: Epidermis, dermis, hypodermis, hair, nails, sebaceous and sudoriferous glands.

Skin Structure and Tissue Types

• Epidermis: Outermost layer, composed mainly of stratified squamous epithelium.

• Dermis: Middle layer, contains dense irregular connective tissue, blood vessels, nerves, and glands.

• Hypodermis (Subcutaneous Layer): Deepest layer, primarily adipose tissue for insulation and energy storage.

Factors Affecting Skin Color

• Melanin: Pigment produced by melanocytes; more melanin results in darker skin.

• Carotene: Yellow-orange pigment from diet.

• Hemoglobin: Oxygenated blood gives a pinkish hue.

• Other Factors: Disease states (e.g., jaundice, cyanosis) can alter skin color.

Glands of the Skin

• Sebaceous Glands: Secrete sebum (oil) to lubricate skin and hair; associated with hair follicles.

• Sudoriferous (Sweat) Glands: Two types:

  • Eccrine glands: Widely distributed, regulate temperature via sweat.

  • Apocrine glands: Found in axillary and genital areas, become active at puberty.

Skin Cancer

• Types: Basal cell carcinoma, squamous cell carcinoma, melanoma.

• Comparison: Basal cell is most common and least dangerous; melanoma is least common but most dangerous.

• ABCDE Rule: Used to identify melanoma:

  • Asymmetry

  • Border irregularity

  • Color variation

  • Diameter > 6mm

  • Evolving shape or size

Burns

• First-degree: Only epidermis affected; redness, mild pain.

• Second-degree: Epidermis and part of dermis; blisters, more severe pain.

• Third-degree: Full thickness (epidermis, dermis, and deeper tissues); may be painless due to nerve damage.

Chapter 6: The Skeletal System

Functions of the Skeletal System

The skeletal system provides structure, protection, movement, mineral storage, and blood cell production.

• Support: Framework for the body.

• Protection: Shields vital organs (e.g., skull protects brain).

• Movement: Acts as levers for muscles.

• Mineral Storage: Stores calcium and phosphorus.

• Blood Cell Production: Hematopoiesis in red bone marrow.

Classification of Bones

• Long bones: e.g., femur, humerus.

• Short bones: e.g., carpals, tarsals.

• Flat bones: e.g., skull, ribs.

• Irregular bones: e.g., vertebrae.

• Sesamoid bones: e.g., patella.

Bone Tissue Types and Structure

• Compact bone: Dense, forms outer layer; provides strength.

• Spongy bone: Porous, found at ends of long bones and inside flat bones; contains red marrow.

• Osteon (Haversian system): Structural unit of compact bone.

• Periosteum: Membrane covering bone surface.

Bone as an Organ

• Bone is a dynamic tissue composed of cells (osteocytes, osteoblasts, osteoclasts), matrix, and mineral deposits.

• It functions in support, protection, and metabolic regulation.

Bone Formation and Growth

• Endochondral ossification: Bone develops from cartilage (most bones).

• Intramembranous ossification: Bone develops from fibrous membranes (e.g., skull bones).

• Process: Involves osteoblasts (build bone) and osteoclasts (break down bone).

Calcium Regulation

• Parathyroid hormone (PTH): Increases blood calcium by stimulating osteoclasts.

• Calcitonin: Lowers blood calcium by inhibiting osteoclasts.

• Feedback Mechanism: Negative feedback maintains calcium homeostasis.

Bone Repair and Diseases

• Bone Repair: Involves hematoma formation, fibrocartilaginous callus, bony callus, and remodeling.

• Diseases:

  • Osteoporosis: Decreased bone mass, increased fracture risk.

  • Osteomalacia: Softening of bones due to vitamin D deficiency.

  • Rickets: Osteomalacia in children, leading to bone deformities.

Chapter 7: The Axial and Appendicular Skeleton

Divisions of the Skeleton

• Axial skeleton: Skull, vertebral column, rib cage.

• Appendicular skeleton: Limbs and girdles (pectoral and pelvic).

Cranial and Facial Bones

• Cranial bones: Enclose the brain (e.g., frontal, parietal, temporal, occipital).

• Facial bones: Form the face (e.g., maxilla, mandible, zygomatic).

Vertebral Column

• Regions: Cervical (7), thoracic (12), lumbar (5), sacrum, coccyx.

• Curvatures: Cervical and lumbar (concave), thoracic and sacral (convex).

• Functions: Protects spinal cord, supports head, attachment for ribs and muscles.

Girdles and Development

• Pectoral girdle: Clavicle and scapula; attaches upper limbs.

• Pelvic girdle: Hip bones; attaches lower limbs.

• Developmental Aspects: Bones grow and ossify from infancy through adolescence; fontanelles in infant skulls allow for growth.

Summary Table: Divisions of the Skeleton