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The Integumentary System Skin, Hair, Glands, Nails Anatomy & Physiology Ch. 5 Learning Targets • Identify the anatomical structures of the integumentary system. • Explain the role of skin and all of its accessory organs. • Describe the diseases/disorders of the integumentary system. Human 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 1. Epidermis 2. Dermis 3. Hypodermis (Subcutaneous layer) • Adipose – Accessory Structures • Hair - Nails -sebaceous glands • sweat glands (4 types) • The skin is composed of 3 layers; the epidermis (superficial), the dermis (middle) and the hypodermis (deep). Epidermis • composed of stratified squamous. • lacks blood vessels – no vascularization. • prevents water loss by secreting protein, keratin. • keratinization of cells takes about 2 weeks. • No innervation – lacks nerves. Keratinized stratified squamous Epidermis (cont) • Contains cells called melanocytes that produce melanin (absorbs light energy & protects deeper cells); melanin gives skin its color. Melanocyte Skin Color • All people have similar numbers of melanocytes. • Skin colors result from differences in the amount of melanin that melanocytes produce and the distribution & 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. Hypodermis • Made of adipose tissue and some loose connective tissue. • Insulates body from losing too much heat. • Also known as the subcutaneous layer. • Men and women store subcutaneous fat differently. 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. What are “goose bumps’? 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 gets 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) 1. 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 releases fluid through tube onto the top of the epidermis. • sweat = water + salts (mainly sodium chloride) and other wastes. Where do you have the most eccrine glands? 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 just increases the bad smell. Other Integumentary Glands - Ceruminous glands - secrete ear wax to trap foreign particles before reaching the ear drum. Why does ear wax smell bad? - 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 IS THIS? 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 IS THIS? • 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. Page 170-1 Skin cancer • There are three main types of skin cancer; basal cell carcinoma, melanoma, and squamous cell carcinoma. • Both UVA and UVB contribute to skin cancer. • Basal cell carcinoma is the most prevalent affecting over 2 million Americans a year. • Basal cell carcinoma develops in the cells of the basement membrane typically due to sun exposure. Melanoma • Melanoma is the most deadly form of skin cancer while also being the most rare. • 120,000 new cases are diagnosed in the U.S. each year. • If caught early it is usually treatable, however if it spreads to other parts of the body treatment becomes much more difficult. • Melanoma develops in the melanocytes located in the epidermis. • Melanoma usually appears black or brown. Squamous cell carcinoma • Squamous cell carcinoma is the second most prevalent type of skin cancer. • It originates in squamous cells of the epidermis. • It is more prevalent in areas exposed to the sun and in people with lighter skin. • Twice as many men as women develop this type of skin cancer. • http://www.skincancer.org/skin-cancer-video.html