Fast Skin Facts The average adult has 21 square feet of skin (2 sq m) which weighs 7lb (3.2 kg) and has approximately 300 million skin cells. The average adult has 21 square feet of skin (2 sq m) which weighs 7lb (3.2 kg) and has approximately 300 million skin cells. On average each square half inch of skin contains: On average each square half inch of skin contains: 10 hairs, 15 sebaceous glands, 100 sweat glands, 3.2 feet (1m) of tiny blood vessels Skin is thickest on the palms & soles (1.2mm to 4.7mm) and thinnest on the lips and around the eyes. Skin is thickest on the palms & soles (1.2mm to 4.7mm) and thinnest on the lips and around the eyes. Every skin cell on your body is shed and replaced about every days but can be much quicker in some skin diseases such as psoriasis. Every skin cell on your body is shed and replaced about every days but can be much quicker in some skin diseases such as psoriasis. An average of 40 kilos of skin is shed during a lifetime An average of 40 kilos of skin is shed during a lifetime

Integumentary System Consists of Consists of skin skin hair hair glands glands nails nails Largest organ of the human body the Largest organ of the human body the Skin accounts for 16% of the bodies mass! Skin accounts for 16% of the bodies mass!

Functions 1. Protection Disease (micro-invaders) Disease (micro-invaders) Loss of fluids Loss of fluids Physical injury Physical injury UV Light UV Light 2. Regulation of Temp Sweat Sweat Insulation Insulation Blood supply Blood supply 3. Communication Receptors Receptors Hot/cold Hot/cold Pain Pain Touch Touch

4. Vitamin D Production Calcium absorption Calcium absorption For bones For bones For muscle contraction For muscle contraction 5. Excretion of Wastes sweat sweat Functions

Subcutaneous (Hypodermis) Dermis Epidermis Dermis Skin Cross Section

Epidermis The epidermis is divided into two layers, dead and living cells. Dead Living

Living cells of the epidermis replicate, pushing their way towards the surface. Living cells of the epidermis replicate, pushing their way towards the surface. The cells flatten and the organelles The cells flatten and the organelles disintegrate. disintegrate. Eventually the living cells of the Eventually the living cells of the inner epidermis become the dead, inner epidermis become the dead, tough, waterproof, and flexible tough, waterproof, and flexible outer layer. outer layer.

As the living cells replicate they produce two proteins As the living cells replicate they produce two proteins Keratin: tough protective protein Keratin: tough protective protein Melanin: pigment Melanin: pigment

Localized loss of melanocytes (the cells that produce melanin)

Differences in melanocyte density leads to variation in skin color

Dermis blood vessels nerve endings glands sense organs smooth muscles hair follicles. Epidermis

Skin Cross Section

Two major types Sweat glands Eccrine- thin and watery Apocrine- thick, kicks in at puberty Sebaceous glands Sebum- an oil that coats the surface of the skin flexibility and waterproofing Hair Follicle

Subcutaneous tissue Layer of fat Layer of fat Insulation Insulation Food reserve Food reserve

Nails grow rapidly from the nail root. During cell division the nail root fills with keratin producing a plate-like nail. Fingernails grow 4 times faster than toe nails with an average rate of 3 millimeters per month.

Functions of Integumentary system. Functions of Integumentary system. The layers of the skin. The layers of the skin. Various components of the epidermis and dermis, including the nails. Various components of the epidermis and dermis, including the nails.