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Integumentary System Components Cutaneous membrane (skin) ▪ Epidermis ▪ Dermis ▪ Accessory structures Subcutaneous layer (hypodermis) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Main Functions of the Integument Protection Temperature maintenance Synthesis and storage of nutrients Sensory reception Excretion and secretion Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-1 The Epidermis Stratified squamous epithelium Several distinct cell layers ▪ Thick skin—five layers ▪ On palms and soles ▪ Thin skin—four layers ▪ On rest of body Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Epidermis Keratinocytes ▪ 90% of epithelial cells Melanocytes ▪ 8% of epithelial cells ▪ Produce pigment melanin ▪ Pigments skin (brown) ▪ Absorbs UV The Epidermis Langerhans cells ▪ Participate in immune responses Merkel cells ▪ Located in the deepest layer of epidermis ▪ Contact tactile (Merkel disk) of sensory neurons ▪ Help to detect touch sensations Cell Layers of The Epidermis Stratum germinativum (basale) Stratum spinosum Stratum granulosum Stratum lucidum (in thick skin) Stratum corneum ▪ Dying superficial layer ▪ Keratin accumulation Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Structure of the Epidermis Figure 5-2 Melanocytes Figure 5-3 Effects of UV Radiation Beneficial effect ▪ Activates synthesis of vitamin D3 Harmful effects ▪ Sun burn ▪ Wrinkles, premature aging ▪ Malignant melanoma ▪ Basal cell carcinoma Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-4 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Types of Skin Thin skin ▪Covers all of body except for palms, soles, and fingertips ▪Lacks stratum lucidum ▪Thin stratum spinosum and stratum corneum ▪Lacks epidermal ridges ▪Fewer sweat glands than thick skin ▪Sparser distribution of sensory receptors Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Types of Skin Thick Skin ▪ Covers palms, soles, fingertips ▪ Has stratum lucidum ▪ Thicker stratum spinosum and stratum corneum ▪ Lacks hair follicles, arrector pili muscles, and sebaceous glands ▪ Has a greater number of sweat glands ▪ Sensory receptors more densely clustered Epidermal Ridges Palms, fingers, soles, toes Ridges and grooves Develop during 3rd and 4th months of fetal development Skin Color Melanin ▪ Causes colors from pale yellow to tan to black ▪ Melanocytes ▪ More in areas of darker color (ex. Penis, nipples, areolae, face, limbs) ▪ Color determined by amount of pigment produced ▪ Accumulation of pigment = freckles or liver spots (age spots) Skin Color Carotene ▪ Yellow-orange pigment ▪ Precursor of vitamin A ▪ Used to synthesize pigments needed for vision ▪ Found in stratum corneum and fatty areas of dermis and subcutaneous layer Hemoglobin ▪ Oxygen carrying pigment ▪ Red ▪ Causes pink skin when little carotene or melanin are present Albinism Inherited Inability to produce melanin Vitiligo Partial or incomplete loss of melanocytes Produces white patches Skin Color Cyanotic ▪ Bluish ▪ Appears in mucous membranes, nail beds, skin ▪ Sign of lack of oxygen Jaundice ▪ Yellowish coloration ▪ Caused by buildup of bilirubin in the blood ▪ Can indicate liver disease Skin color Erythema ▪ Redness of the skin ▪ engorgement of capillaries in the dermis with blood ▪ Caused by injury, exposure to heat, infection, inflammation, or allergic reactions Hair Function = protection ▪ Scalp – from sun’s rays & injury ▪ Also decreases heat loss ▪ Eyebrows & eyelashes – protect eyes from foreign objects ▪ Nostrils – protect from foreign objects ▪ Ear canal – protect from foreign objects Function = touch ▪ Touch receptors associated with hair follicles (root hair plexus) ▪ Activated when hair is moved Hair Follicles Figure 5-5(b) Hair Follicles Figure 5-5(c) Hair growth cycle Each follicle goes through a growth cycle ▪ Growth stage ▪ Scalp: 2-6 years growth ▪ 0.3 mm/day growth rate ▪ Resting stage ▪ Growth of hair stops ▪ Scalp: 3 months ▪ After resting stage ▪ Hair replaced ▪ New growth stage Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Rate of growth & replacement altered by: Illness Radiation therapy Chemotherapy Age Genetics Gender Severe emotional stress Rapid weight loss (reduction of calories and/or protein) Hair loss Normal = 100 per day (from scalp) Rate of hair shedding increases 3-4 months after childbirth Alopecia ▪ Partial or complete loss of hair ▪ May result from genetic factors, aging, endocrine disorders, chemotherapy, or skin disease Types of hair Lanugo ▪ Very fine, nonpigmented hairs ▪ Produced by the 5th month of fetal development ▪ Cover body of fetus ▪ Usually shed before birth (except scalp, eyebrows, eyelashes) Vellus hairs ▪ “peach fuzz” ▪ Replace lanugo ▪ Short, fine hairs ▪ Slightly thicker than lanugo Terminal hairs Head Eyebrows Eyelashes Coarse pigmented hairs ▪ Develop in presence of androgens ▪ During puberty ▪ In axillae (armpits) and pubic regions Male = 95% terminal hair:5% vellus hair Female =65% terminal hair:35% vellus hair Hair color amount and type of melanin in keritinized cells ▪ melanocytes found in the matrix of bulb Dark hair = pure melanin Blond or red hair = variants of melanin ▪ More sulfur or iron Graying = decline of tyrosinase ▪ Enzyme that catalyzes production of melanin White = accumulation of air in medullary shaft Sebaceous Glands - Oil glands In dermis Usually open into the neck of hair follicle ▪ Except in lips, glans penis, labia minora, and tarsal glands Absent in palms and soles Small on trunk and limbs Large on breasts, face, neck and upper chest Secrete sebum ▪ Oily substance - triglycerides, cholesterol, proteins, and inorganic salts ▪ Coats surface of hairs - Prevents drying and becoming brittle ▪ Prevents excessive evaporation from skin ▪ Keeps skin soft & Inhibits growth of certain bacteria Acne Inflammation of sebaceous glands Usually begins during puberty ▪ Infected by bacteria Sudoriferous glands - Sweat glands 3 to 4 million Secrete through exocytosis into hair follicles or onto skin surface through pores Sudoriferous glands (continued) Eccrine sweat glands ▪ Simple, coiled tubular ▪ More common type ▪ Distributed throughout skin, except: ▪ Lips, nail beds, glans penis, glans clitoris, labia minora, eardrums ▪ Most numerous on forehead, palms, soles ▪ Sweat consists of water, ions, urea, uric acid, ammonia, amino acids, glucose, and lactic acid ▪ Function = regulate body temperature ▪ Insensible perspiration – sweat that evaporates before perceived as moisture ▪ Sensible perspiration – sweat seen as moisture ▪ Function = eliminate waste Sudoriferous glands (continued) Apocrine sweat glands ▪ Simple, coiled tubular ▪ Found in axilla (armpit), groin, areolae, and bearded regions of face ▪ Secretions through exocytosis ▪ These are actually merocrine glands They used to be thought to be apocrine Sudoriferous Glands (continued) Ceruminous glands ▪ Sweat glands of the external ear ▪ waxy secretion ▪ Combined secretion of ceruminous and sebaceous glands in the ear is called earwax ▪ In combinations with hairs – impedes entrance of foreign objects Figure 5-7 Accessory Structure Nails ▪ Plate of tightly packed, hard, keratinized epidermal cells Average growth = 1mm /week Function = grasp small objects, protection, scratching Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-8 Deep Wound Healing Occurs when injury extends into the dermis and hypodermis 4 phases: ▪ Inflammatory phase ▪ Blood clot forms; inflammation ▪ Migratory phase ▪ Clot becomes scab; granulation tissue forms ▪ Proliferative phase ▪ Extensive growth of epithelial cells in random patterns ▪ Maturation phase ▪ Scab sloughs off Deep Wound Healing Fibrosis ▪ Scar tissue formation ▪ Hypertrophic scar ▪ Scar remaining within boundaries of wound ▪ Keloid scar ▪ Scar extending beyond boundaries of wound Skin Grafts Covering a wound with healthy skin taken from a donor site ▪ Transplanted skin taken from: ▪ Self = autograft ▪ Identical twin = isograft ▪ Analogous skin transplantation Especially with burn patients Major Age-Related Changes Injury and infection increase Immune cells decrease Sun protection diminishes Skin becomes dry, scaly Hair thins, grays Sagging, wrinkles occur Heat loss decreases Repair slows Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings