The Integumentary System HLTAP301A

The integumentary system Consists of the skin, accessory organs and subcutaneous tissue below the skin

The integumentary system Functions of skin Keeps harmful substances out and retains electrolytes and water Protects internal structures Acts as a waste removal system Synthesises vitamin D Sensory role Regulates body temperature

Skin Structure Considered an organ Epidermis Dermis Study of skin is dermatology

Skin Epidermis Thin outer layer Composed of stratified Squamous epithelium Avascular Cells are continually being replaced, produces millions of cells per day Contains keratin which waterproofs the skin About 500ml/day of water is lost through skin

Skin Dermis Located under the epidermis Dense fibrous connective tissue Contains collagen and elastin fibres that make the dermis strong and stretchable Thickness varies depending on location Accessory structures such as hair, nails and some glands are in dermis Blood vessels, nerves and some muscle tissue also located here Nerves detect pain, temperature and pressure

Skin Subcutaneous layer Dermis lies on this layer Composed of loose connective tissue and adipose tissue Helps insulate the body Anchors the skin to underlying structures Some areas have no subcutaneous tissue, like the knuckles on your hand

Skin Can absorb many chemicals This is good when drugs need to be given. Called transdermal patches Can be used to detect allergens when they are injected Can also absorb toxins

Skin Skin colour In the epidermal layer are cells called melanocytes These cells secrete melanin The more secreted, the darker the skin Moles are common but when they change they can become a melanoma Cyanosis occurs when blood is poorly oxygenated Embarrassment causes skin to redden Fear can cause skin to whiten

Accessory structures of skin Hair Main function is to sense insects before they sting us Some body parts are hairless, such as palms and soles, lips and nipples In some areas hair plays important role such as eyebrows and lashes, nasal hairs Growth is influenced by the hormones oestrogen and testosterone Excessive growth is called hirsutism

Hair Chief parts are the shaft and the root Colour determined by genes Arrector pili muscle is attached to hair follicle and contracts to make hair stand up when cold or frightened

Accessory organs of skin Nails Thin plates of stratified squamous epithelial cells that contain keratin Found on distal ends of fingers and toes Protection

Accessory organs of skin Glands Sebaceous glands are associated with hair follicles and secrete sebum which lubricates and waterproofs the skin. Sweat glands are located in dermis and secrete sweat which aids in temperature control

Skin disorders Acne – sebaceous glands over secrete sebum Athlete’s foot – fungal Infection Boil – localised area of pus caused by staph infection Cold sore – collection of watery vesicles caused by infection with herpes simplex Cyst – saclike structure containing fluid Dermatitis – inflammation of skin Eczema – inflammatory condition Skin cancer – excessive exposure to sun

Regulation of Body temperature Heat is produced by chemical reactions in cells At rest, muscles produce 25% of heat Liver produces 25% of heat Brain produces 15% of heat Amount is affected by food consumption, amounts and types of hormones secreted, physical activity

Heat Loss Most heat loss is through skin- 80% 20% through respiration and excretion Four ways this can occur Radiation-heat lost from the body to cooler air Conduction-from body in contact with cooler object Convection-lost by movement of air currents Evaporation-occurs when a liquid becomes gas

Heat Loss Normal body temp is between 36.2 degrees C and 37.6 degrees C Higher than normal is hyperthermia Lower than normal is hypothermia

Regulation Body’s thermostat is located in the hypothalamus in the brain With heat, blood vessels dilate allowing more blood to flow to the skin This transfers heat from the deeper body tissues This triggers sweat glands to produce sweat, which evaporates to cool the body

Regulation When body temp drops, blood vessels constrict, reducing blood flow to skin This traps blood and heat in deeper tissues, preventing heat loss Sweat glands become less active Arrector pili muscles contract, causing shivering to increase heat production