1. The Integumentary System
HLTAP301A

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

3. 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

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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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