Chapter 5 A&P: Skin Repair, Aging, Perspiration, Pigmentation PDF

Chapter 5 A&P (Skin repair and aging, types of perspiration, pigmentation, apocrine vs merocrine, thermoregulation) Skin repair 5.2 The Dermis Skin damage –Loss of skin turgor is caused by ▪Dehydration (reversible) ▪Aging ▪Hormones ▪UV radiation –Excessive distortion of skin from pregna...

Chapter 5 A&P (Skin repair and aging, types of perspiration, pigmentation, apocrine vs merocrine, thermoregulation) Skin repair 5.2 The Dermis Skin damage –Loss of skin turgor is caused by ▪Dehydration (reversible) ▪Aging ▪Hormones ▪UV radiation –Excessive distortion of skin from pregnancy or weight gain may cause stretch marks Aging 5.10 Aging and the Integumentary System Learning Outcomes: Summarize the effects of aging on the skin. Effects of aging on skin –Epidermis thins –Number of dendritic cells decreases –Vitamin D3 production declines –Melanocyte and glandular activities decline –Blood supply to dermis is reduced –Function of hair follicles declines –Dermis thins and elastic fiber network shrinks –Sex-specific hair and body fat distribution fades –Repair rate slows Perspiration 5.1 Epidermis (11 of 12) Water is lost from skin in two ways –Insensible perspiration ▪Water diffuses across stratum corneum and evaporates from skin ▪500 mL per day ▪Rate increases if stratum corneum is damaged (ex: from burns) –Sensible perspiration ▪Water excreted by sweat glands  Apocrine sweat glands –Found in armpits, around nipples, and in pubic region –Secrete products into hair follicles via merocrine secretion –Produce sticky, cloudy secretions ▪Nutrient source for bacteria, which cause odors –Surrounded by myoepithelial cells ▪Squeeze secretions out of glands in response to hormonal or nervous signals  Eccrine(merocrine) sweat glands –Coiled, tubular glands that discharge directly onto skin surface (sensible perspiration) –Widely distributed on body surface ▪Especially on palms and soles –Secretions are 99 percent water plus salt, etc. –Functions include ▪Cooling surface of skin to reduce body temperature ▪Excreting water and electrolytes ▪Providing protection from environmental hazards –Eccrine sweat glands ▪Controlled precisely; sweating may occur locally Pigmentation 5.4 Skin Color (2 of 5) Melanin –Red-yellow or brown-black pigment –Produced by melanocytes –Stored in intracellular vesicles (melanosomes) ▪Transferred to keratinocytes ▪Dark-skinned people have large, numerous melanosomes –Protects skin from ultraviolet (UV) radiation ▪Small amounts of UV radiation are beneficial ▪Too much can damage DNA and cause cancer  Carotene –Orange-yellow pigment –Found in orange vegetables –Accumulates in epidermal cells, deep dermis, and subcutaneous layer –Can be converted to vitamin A, required for ▪Maintenance of epithelia ▪Synthesis of photoreceptor pigments in eye  Blood flow and oxygenation influence skin color –Hemoglobin is bright red when bound to oxygen ▪When blood vessels dilate from heat, skin reddens ▪When blood flow to skin decreases, skin pales –Hemoglobin turns dark red when oxygen is released ▪Can result in cyanosis (bluish skin) ▪May be caused by extreme cold, heart failure, severe asthma, etc.  Illness and skin color –Jaundice ▪Buildup of bile produced by liver ▪Skin and whites of eyes may turn yellow –Pituitary tumor ▪Excess MSH increases production of melanin –Addison’s disease ▪Causes pituitary gland to release excess ACTH, which has an effect similar to MSH –Vitiligo ▪Loss of melanocytes causing loss of color