Fast Skin FactsFast Skin Facts

The average adult has 21 square feet of skin (2 sq m) The average adult has 21 square feet of skin (2 sq m) which weighs 7lb (3.2 kg) and has approximately 300 which weighs 7lb (3.2 kg) and has approximately 300 million skin cells. 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 10 hairs, 15 sebaceous glands, 100 sweat glands, 3.2 feet (1m) of tiny blood vesselsfeet (1m) of tiny blood vessels

Skin is thickest on the palms & soles (1.2mm to Skin is thickest on the palms & soles (1.2mm to 4.7mm) and thinnest on the lips and around the eyes. 4.7mm) and thinnest on the lips and around the eyes.

Every skin cell on your body is shed and replaced Every skin cell on your body is shed and replaced about every 52-75 days but can be much quicker in about every 52-75 days but can be much quicker in some skin diseases such as psoriasis. 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 SystemIntegumentary System

Consists of Consists of skinskin hair hair glandsglands nailsnails

Largest organ of the Largest organ of the human body the human body the

Skin accounts for 16% Skin accounts for 16% of the bodies mass!of the bodies mass!

FunctionsFunctions1.1. ProtectionProtection Disease Disease (micro-invaders)(micro-invaders)

Loss of fluidsLoss of fluids Physical injuryPhysical injury UV LightUV Light

2.2. Regulation of Regulation of TempTemp

SweatSweat InsulationInsulation Blood supplyBlood supply

3.3. CommunicationCommunication ReceptorsReceptors

Hot/coldHot/cold PainPain TouchTouch

4.4. Vitamin D Vitamin D ProductionProduction

Calcium absorptionCalcium absorption For bonesFor bones For muscle For muscle

contractioncontraction

5.5. Excretion of Excretion of WastesWastes

sweatsweat

FunctionsFunctions

Subcutaneous(Hypodermis)

Dermis

Epidermis

Dermis

Skin Cross Section

Epiderm

is

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

Dead

Living

Living cells of the epidermis replicate, Living cells of the epidermis replicate, pushing their way towards the surface.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 As the living cells replicate they produce two proteins produce two proteins

KeratinKeratin: tough protective protein: tough protective protein

MelaninMelanin: pigment: pigment

Localized loss of melanocytes (the cells that produce melanin)

Differences in Differences in melanocyte density leads melanocyte density leads to variation in skin colorto variation in skin color

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

Epidermis

Skin Cross Section

Two major types 1. Sweat glands Eccrine- thin and watery Apocrine- thick, kicks in

at puberty

2. Sebaceous glands Sebum- an oil that

coats the surface of the skin flexibility and

waterproofing

Hair Follicle

Subcutaneous tissueSubcutaneous tissue Layer of fatLayer of fat

InsulationInsulation

Food reserveFood 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 Functions of Integumentary system.system.

The layers of the skin.The layers of the skin.

Various components of the Various components of the epidermis and dermis, epidermis and dermis, including the nails.including the nails.