The Integumentary

System

Integumentary System• The Body Covering (Fun Fact! Largest organ of the body)

• Includes: Skin, Nails & Hairs• Skin A.K.A. Cutaneous Membrane• Functions:– Body Temperature Regulation: Sweating at surface and

adjusting blood flow in dermis.– Protection: Keratin protects from microbes, abrasions, heat

and chemicals, lipids slow evaporation of water, melanin protects from UV rays.

– Cutaneous Sensations: Sensory input/output– Excretion and Absorption: Eliminates substances, passage of

materials into body cells (drugs)– Synthesis of Vitamin D: UV light activates creation of Vit D

Structure• Skin is divided into two main parts:– Epidermis

(epi = above) Surface epithelial layer

– Dermis: Deeper connective tissue layer

• Subcutaneous Layer Deep dermis not part of the skin.– Fibers from dermis

anchor skin to this layer which then allows for attachment to other tissue and/or organs.

Epidermis• Made of keratinized stratified squamous epithelium• Capable of regeneration (new cells ~ q4 weeks)• 4 cell types:– Keratinocytes: 90% of epidermal cells, 4 – 5 layers,

produces keratin (rough fibrous protein that protects skin), waterproofs skin.

– Melanocytes: 8% of epidermal cells, produce the pigment melanin, transfer melanin to kertinocytes, susceptible to UV light damage.

– Langerhans cells: Produce immune response against pathogens entering skin.

– Merkel cells: Detect touch/sensory sensations.

Dermis• Consists of two distinct regions: – The superficial part is composed of

areolar connective tissue.

– The deeper part is composed of dense irregular connective tissue.• Attaches to the subcutaneous layer.

• The outer layer contains nerve endings for touch, thermal sensations, pain, tickling, and itching.

Skin Color• Skin color is due to the melanin in the epidermis,

carotene in the dermis, and hemoglobin in the capillaries of the dermis.– Melanin (Brown-Black pigment)• Darkness depends on amount of melanin produced. • Gives some protection against UV

– MALIGNANT MELANOMA, (cancer of the melanocytes), is a particularly serious skin cancer. Liver or age spots, are non-cancerous clusters of melanin.

– Carotene (Yellow-Orange pigment)• In deeper skin and adipose layers

– Hemoglobin (Pink-Red pigment)• Found in blood• Depends on blood flow

Review Part I1. What are the 5 functions of skin?2. What are the two main parts of skin called?3. What 4 cells make up the superficial/thinner part

of the skin?4. What is the function of the subcutaneous layer?5. Which skin layer contains nerve endings?6. Which pigments contribute to which skin color?7. The shade of your skin depends on which factors?8. What are the characteristics and functions of

keratinocytes?

Hair• Function: Protection• Found: On most skin surfaces

– Not on palmar surfaces of hand and fingers or plantar surfaces of feet

• Composition: – Keratinized cells– Shaft: Mostly above ground– Root: Below surface

• Surrounded by hair follicle

– Bulb: Base of hair follicle includes matrix producing cells and blood vessels.

– Nerves: Hair root plexuses• Sensitive to touch

– Muscle (Smooth): Arrector pili• Contraction causes goose

bumps

Hair Shaft

Hair Root

Arrector pili

muscle

Sebaceous Gland

Hair Root Plexus

Bulb

Apocrine sweat gland

Glands

• Sebaceous Glands: Secrete oily sebum– Protects skin from drying out and bacteria– Connected to hair follicles

• Sudoriferous (soo-dor-IF-er-us) Glands: Secrete sweat– Eccrine are widely distributed, & aid in thermoregulation– Apocrine are found in the axilla, groin, areolae, beard

• Ceruminous (se-ROO-mi-nus) Glands: Secrete wax– External auditory canal– Combine with sebum to produce earwax– Provide barrier against foreign bodies

Nails• Function: Help us grasp,

manipulate objects, protect ends of digits, scratching

• Composition: Plates of packed keratinized cells of the epidermis.– Nail body: Visible portion– Free edge: Part extending past

digit– Root: Part not visible

• Growth: 1 mm per WEEK! Slows within 2nd / 3rd decade Becomes brittle with age

Nail Body

Free Edge

Root

Review Part II1. What are the 5 functions of hair?2. What protein is hair composed of?3. What 5 structures make up hair within skin?4. What causes goose bumps?5. What is sebum? Which gland secretes sebum?6. Which gland aids in thermoregulation? How?7. Which glad’s secretions combine with sebum to

produce earwax? Why is this important?8. What are the functions of nails? 9. What specifically are nails made of?10.Of the 5 nail parts, name 3?