Structure of the Skin NotesEQ: Describe the three layers of

the skin.

EQ: Identify and locate accessory structures of the skin.

Skin Facts• Largest organ in the body.

• Most of the dust in your home is really dead skin.

• Skin accounts for about 15% of your body weight.

• You grow a completely new layer of skin every 28 days.

• Over 1000 species of bacteria are naturally found on human skin.

Layers of the Skin

• Cutaneous membrane• Epidermis + dermis

Layers of the Skin

• Epidermis• mostly dead cells• Thick skin – 5 layers; hands and feet• Thin skin – 4 layers; everywhere else• Melanocyte – produce skin pigment (melanin)

Squamous epithelium

Layers of the Skin

• Dermis• Living cells• Nerves, blood vessels, glands, collagen

and elastin

Dermal Tissue

Layers of the Skin

• Hypodermis (subcutaneous layer)• Mostly adipose (fat) tissue• Hair follicles

Hypodermal Cells

Accessory Structures of the Skin

• A – hair shaft

• B – sebaceous gland– Produce sebum– Lubricate hairs– Antibacterial

• C – hair follicle

Acne Formation

Accessory Structures of the Skin

• D – arrector pili muscle– Make hair stand up

• E – sweat gland– Homeostasis - as

sweat evaporates, it cools the body

– Body odor

Accessory Structures of the Skin

• F – blood vessel– Bring nutrients to

skin cells– Homeostasis –

warms the skin

• G – nerve receptor– Touch– Pain– pressure

Functions of the Skin Notes

EQ: What are the functions of the skin in the human body?

Recurring Theme

• Homeostasis– Means “steady state”– The body has mechanisms to keep its internal

conditions the same when the environment changes

Function of Epidermis

• Protection– Bacteria– Dirt– Minor wounds

• Melanocytes– Protection from UV

Function of Dermis

• Makes skin elastic and tough– Collagen– Elastin– Fibrillin

• Homeostasis – “goose bumps” caused by arrector pili muscles create insulation

Function of Hypodermis

• Insulation

• Padding

• Energy storage

Functions of Accessory Structures

• Hair – Homeostasis - warmth– Touch sensitivity– Protection from injury

• Melanocyte– Produces melanin– Protects from UV rays