The Integumentary System Skin, Hair, Glands, Nails

the skin is the largest organ it serves as a protective covering it helps regulate body temp it prevents water loss it houses sensory receptors it excretes wastes

Integumentary System Three layers Skin Epidermis 2. Dermis 3. Hypodermis (Subcutaneous layer) Adipose Accessory Structures Hair - Nails -sebaceous glands sweat glands (4 types)

The skin is composed of: the dermis (deep) and the epidermis (superficial) Beneath the dermis is a layer composed of adipose and loose connective tissue called the Hypodermis (subcutaneous layer)

Epidermis composed of stratified squamous lacks blood vessels – no vascularization prevents water loss by secreting protein, keratin keratinization of cells takes about 2 weeks

Epidermis (cont) Contains cells called melanocytes that produce melanin (absorbs light energy & protects deeper cells); melanin gives skin its color

Skin Color all people have similar #s of melanocytes diff. in skin color result from diffs in the amount of melanin that melanocytes produce and the distribution and size of the melanin granules Albinism-inability to produce melanin

Dermis Is made up of two layers Top layer (papillary layer) composed of areolar or loose connective tissue Bottom layer (reticular layer) composed of dense connective tissue Well vascularized & innervated Also contains accessory structures such as; hair follicles, sebaceous glands, and sweat glands

Hair Composed of epidermal cells that have keratinized and died Hair color is determined by the type and amount of pigment the melanocytes produce arrector pili muscle - surrounds hair follicle & contracts when a person is cold or frightened (causes goose bumps) WHY?

Sebaceous Glands a gland located around the hair follicle which secretes its contents when contracted by the arrector pili secrete an oily mixture of fat and cellular debris called sebum which keeps the hair and skin soft, pliable, and waterproof This is why hair get oily when not washed

Nails Composed of dead stratified squamous epithelial cells which are extremely keratinized Nail production occurs at the nail root which is underneath the skin and proximal to the visible nail. Nails are basically clear and appear pink over skin because of underlying blood vessels

Sweat Glands (Exocrine Glands) Eccrine Glands respond to elevated body temp. due to heat or exercise Cool by allowing water to be evaporated from skin lowering temp. Common on forehead, neck, and back

Sweat Glands (Exocrine Glands) release fluids thru pores Gland located in dermis but release fluid through tube onto the top of the epidermis sweat = water + salts and wastes. One salt is urea a key component in urine.

Sweat glands (cont.) 2. Apocrine glands active when a person is emotionally upset, frightened, or in pain found under the armpits and in the groin Sweat is food for bacteria which increases the bad smell.

Sweat Glands (cont) 3. Other - ceruminous glands - secrete ear wax - mammary glands - secrete milk

Regulation of Body Temperature Regulation is important b/c heat affects the rate of metabolic reactions when temp rises above the set point, dermal blood vessels dilate (get larger) and glands secrete sweat when temp drops below the set point, dermal blood vessels constrict (get smaller) and glands become inactive WHAT TYPE OF FEEDBACK?

Healing of Wounds Skin injuries trigger inflammation; blood vessels dilate and become more permeable, forcing fluids to leave the blood vessels and enter the damaged tissues WHAT TYPE OF FEEDBACK? Dilated blood vessels supply the damaged cells with more oxygen and nutrients; this speeds healing. More platelets are supplied to clot blood More white blood cells needed to fight infection

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