Structure of the Skin Notes EQ Describe three

Structure of the Skin Notes EQ: Describe 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