Integumentary Integumentary SystemSystem

Unit 3: Integumentary System

A&P Chapter 5

1. Integumentary 1. Integumentary SystemSystemThe Integumentary

system includes:◦Skin – largest organ of the body

◦Accessory Organs: Hair Nails

Serves to protect the viscera (internal organs) and regulate temperature

11. Structure of the 11. Structure of the SkinSkin

The skin is composed of 3 layers from superficial to deep:

1. Epidermis1. EpidermisOutermost layer of skin

Stratum Corneum – hard outermost layer of epidermis ◦Produces a protein called keratin◦Keratinization causes hardening of

dead skin cells, making skin waterproof.

Stratum Basale – produces new cells of epidermis◦Contains Langerhans cells (for

immunity) and melanocytes (make pigment to give skin color)

2. Dermis2. DermisThick layer of connective tissue containing:◦Dermal papillae – ridges that cause fingerprints and provide gripping surface

◦Collagen & elastic fibers – stretching & movement

◦Blood vessels◦Sensory Nerves◦Sebaceous Glands◦Hair Follicles

3. Hypodermis 3. Hypodermis (Subcutaneous (Subcutaneous Layer)Layer)

Deepest layer of skinComposed of loose connective tissue and adipose tissue (fat)◦Helps to store energy, insulate body, and provides protective padding

IV. Five Functions of the IV. Five Functions of the SkinSkin1. Protection• Physical barrier to disease, dirt,

and UV radiation• Bacteria and other invaders are

prevented entry by the top dead layer of skin and the acidic, oily secretion from sebaceous glands (sebum).

2. Regulates Water 2. Regulates Water LossLossKeratinization of the dead skin

outer layer also prevents water from entering or leaving the skin, even when immersed in water.

Skin works with the urinary system to sweat off some excess water.

3. Produces Vitamin D3. Produces Vitamin DMelanocytes produce melanin to

protect against harmful UV radiation from the sun and also to produce Vitamin D

Vitamin D helps regulate the uptake of calcium by the digestive system.Calcium is needed for strong bones.

4. Gathers Sensory 4. Gathers Sensory InformationInformation

Sensory receptors are linked to the nervous system

Receptors specialize in sensing◦Touch◦Pressure◦Pain◦Temperature (hot & cold)

Many receptors in hands

5. Regulates Body 5. Regulates Body TemperatureTemperatureWhen the body is too hot, the skin will help to release heat to cool the body temperature back to 98.6°:◦Sweat◦Dilation of dermal blood vessels

When the body is too cold, the skin will help to raise body temperature back to 98.6° by generating heat:◦Shivering (muscle contraction)◦Goosebumps (contraction of arector pili muscles attached to hair follicles) cause hair to trap heat

◦Constriction of dermal blood vessels

Bad things happen when body temp. is not constant:◦1. Hypothermia -Lower body temp. than normal interferes with the body’s normal functions and eventually ends in death

2. Hyperthermia—Higher body temp. than normal results in dehydration (from excess sweating) and heat stroke.