The Integumentary System

1. The Integumentary System

2. I. What is the Integumentary System? • The organ system that consists of the skin and its derivatives (sweat & oil glands, hair, nails). • Dermatology is the medical specialty for the diagnosis and treatment of disorders of the integumentary system.

3. II. Basic Functions of the Skin • Protection from: • Mechanical damage (bumps & cuts) • Chemical damage (acids & bases) • Thermal damage (heat/cold) • Bacteria • UV radiation • Desiccation (drying out) • Temperature regulation (sweat glands- cool body) • Excrete urea (sweat eliminates salts and other wastes) • Synthesize Vitamin D (from sunlight) • Immunity (protects against germs) • Sensory reception (touch, heat, pain, pressure)

4. III. What are the major characteristics of the skin? • Largest organ of the body • Waterproof, stretchable, washable, and permanent- automatically repairs all cuts, rips, and burns and is guaranteed to last for a lifetime. • Area of about 2 square meters (22 square feet) and weighs 10-11 pounds • Pliable yet tough

5. 3 major layers of the skin • 1. Epidermis (epi- upon) • Composed of stratified squamous epithelial tissue • Lacks blood vessels: no blood supply • 2. Dermis- underlies the epidermis • Composed of fibrous connective tissue • Good supply of blood • 3. Hypodermis (not considered skin) • Made of adipose (fat) tissue underneath the skin • Stores fat, anchors skin to muscle below, protects against injury

7. Epidermis Dermis

8. A. Cells of the Epidermis • 1. Keratinocytes: • Produce keratin= fibrous protein that provides protection • Formed in the deepest layer of the epidermis (stratum basale) pushed upward by new cells underneath. • Top layer (stratum corneum)= dead, scalelike structures

9. 2. Melanocytes: • Produce melanin= pigment (yellow/brown/black) that gives us skin color • Shields DNA from UV radiation (protects against skin cancer) Melanocyte

10. B. Layers of the Epidermis • Stratum basale: deepest layer of the epidermis, undergoes rapid cell division. • Stratum spinosum: intermediate (middle) layer, contain spiny shaped keratinocytes. • Stratum corneum: outermost layer 20-30 cells thick of dead keratinized cells. • Dandruff • Average person shed 40 pounds of these cells in their lifetime. • Everything you see on a human is dead! * Yes, the skin, hair, and nails we see are made of dead keratin cells.

12. A. Layers of Dermis • 1. Papillary Layer: • Upper part of dermis • Contains Dermal papillae= peg-like projections • Free nerve endings • Touch receptors (Meissner’s corpuscles) • Increase gripping ability on fingers and toes • Friction ridge patterns= fingerprints

13. 2. Reticular Layer: • Deepest skin layer • Dense, fibrous connective tissue • Contains blood vessels, sweat & oil glands, pressure receptors (Pacinian corpuscles), and white blood cells.

14. V. What are the major appendages of the skin? • Sweat glands • Sebaceous glands • Hair • Nails

15. 1. Sweat Glands • Two Types: • I. EccrineSweat Glands: releases sweat (99% water, salts, Vitamin C, antibodies, wastes) • Abundant on palms, soles of feet, forehead, • Aids in evaporative cooling • II. Apocrine Sweat Glands • Sweat + fatty substances + proteins milky/yellowish • With bacteria= body odor • Activated at puberty sexual sweat gland?

17. 2. Sebaceous Glands • Secretes oil (called sebum) into the hair follicle • Waterproofing skin • Soften and lubricates hair and skin • Kills bacteria

18. 3. Hair (PILI) • 2 main regions: hair root and hair shaft • Project from follicles in dermis • Consists of dead, keratinized cells