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Chapter 7: Skin and Appendages 1 Lesson 7-1 Objectives • List six functions of the skin. • Define stratum germinativum and stratum corneum. • Describe the two layers of the skinepidermis and dermis. • List the two major functions of the subcutaneous layer. 2 Introduction Skin (integument) is body’s largest organ Integumentary system describes the skin and its appendages—the hair, nails, and skin glands You shed about 1.5 lbs per year 3 Skin Perspective • On average, 1 cm2 of skin contains: – 3,000,000 cells – 10 hairs – 15 sebaceous glands – 3 feet of blood vessels – 700 sweat glands – 3000 sensory cells at nerve endings – 12 feet of nerves • 200 pain receptors • 2 cold receptors • 12 sensors for heat 4 Functions of the Skin • • • • • • • Serves as mechanical barrier Protects internal structures Participates in the immune response Acts as a gland for vitamin D synthesis Performs excretory function Performs sensory role Helps regulate body temperature 5 Structure of the Skin • Layers – Epidermis • (lays upon dermis) – Dermis (skin) • Subcutaneous • a.k.a: Hypodermis • Accessory structures • Hair, nails, glands..etc. 6 7 Overview Structure of the Skin Skin classified as cutaneous membrane Two primary layers—epidermis and dermis; joined by dermoepidermal junction Hypodermis lies beneath dermis Thin and thick skin (Figure 7-3) “Thin skin” —covers most of body surface (1 to 3 mm thick); has hair and smooth surface “Thick skin”—soles and palms (4 to 5 mm thick); ridged surface with no hair 8 9 10 Layers of Epidermis From deep to Superfical: • Stratum Basale • A.k.a Stratum Germinativum • • • • • • Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum 2. ** 3. 4. 11 Layers uncovered 12 Epidermis: Outer Layer continued… • Layers of the epidermis – Stratum corneum (surface layer); composed of dead, flattened cells that slough off , our horns – Stratum germinativum (deepest), a.k.a. stratum basale: cells continuously dividing and moving toward surface • Keratinization: The protein keratin makes skin cells hard, flat, and water resistant. • (Keratinocytes…cells that actually produce protein) 13 Epidermal growth and repair • Shortened turnover time increase thickness of the stratum corneum; results in callus formation • Normally 10% to 12% of all cells in stratum basale enter mitosis daily 14 Structure of the Skin Dermopidermal junction (DEJ) A basement membrane Polysaccharide gel serve to “glue” the epidermis to the dermis below Partial barrier to the passage of some cells and large molecules 15 Dermis • Our “hide”, strong and stretchy – “true skin” • Lies under and supports the epidermis – Gives strength • Sits on the subcutaneous layer or hypodermis • Embedded with accessory structures – Includes blood vessels that nourish epidermis – Reservoir storage for water and electrolytes 16 Dermis continued… • 2 major regions: – Papillary: upper/superficial dermal layer • • • • • Pain receptors (free nerve endings) Touch receptors: Meissner’s corpuscles Allow for grip Genetically unique= fingerprints Arrector pili (goose bumps) – Reticular: Deepest of skin layer • • • • Blood vessel, sweat glands, oil glands Pacinian corpuscles: Deep pressure receptors Last line of defense Leather 17 18 Dermis (cont) During wound healing fibroblasts begin forming an unusually dense mass of new connective fibers if not replaced by normal tissue, this mass remains a scar Cleavage lines (Figure 7-7)—patterns formed by the collagenous fibers of the reticular layer of the dermis also called Langer’s lines 19 Langer’s lines 20 Scar formation • Cleavage lines - patterns formed by the collagenous fibers of the reticular layer also 21 Subcutaneous Layer: Hypodermis • A.k.a = subcutaneous layer • Connection point to tissue that lies beneath skin • Highly vascularized • Two main roles: – Its fat insulates body from extreme temperature changes. – Its connective tissue anchors the skin to underlying structures. • NOT PART OF THE SKIN 22 Problems… • Decubitus ulcers; Bed sores – Blood supply is cut off – Bedridden patients who are not regularly moved – Pressure of bone on skin eventually cuts off supply line 23 Real life… 24 Accessory Structures: Hair • Functions: Detect insects, protect eyes, keep dust out of lungs • Hormones affect growth. • Melanin influences color. • Hair arises in epidermis. • Cosmetic role 25 Accessory Structures: Nails • Protect tips of fingers and toes from injury • Condition affected by oxygenation of blood supply, trauma, and nutritional deficiencies 26 Fingernails • Scale-like modifications of the epidermis • Heavily keratinized • Stratum basale extends beneath the nail bed • Responsible for growth • Lack of pigment makes them colorless Accessory Structures: Glands • Sebaceous glands: – Oil glands – Secrete sebum and in fetus vernix caseosa • Sudoriferous – Sweat glands 28 Sudoriferous Glands • Apocrine glands: Found with hair follicles; more active at puberty – Axillary and Genital Regions • Eccrine glands: Everywhere; Critical for temperature regulation 29 Sweat and Its Function Composition Mostly water Some metabolic waste Fatty acids and proteins (apocrine only) Function Helps dissipate excess heat Excretes waste products Acidic nature inhibits bacteria growth Odor is from associated bacteria Sweet Sweat Types of modified sweat glands: • Mammary glands: Secrete milk • Ceruminous glands: Secrete ear wax (cerumen) • Pheromones: Sex attractants – Copuline (copulation) 31 Skin Color Determined by: genes, physiology, and sometimes pathology Dark pigment: Melanin • Melanocyte= Make melanin in epidermis(St.Basale) • Yellow to brown to black • Melanocyte malfunctions: – Albinism (defect in melanin) – Vitiligo (loss of brown pigment) 32 Skin color continued Yellow pigment: Carotene • Orange-yellow (some veggies) • Presence of melanin overshadows carotene’s tint in most people Hemoglobin • Red coloring from blood cells in dermis capillaries • Oxygen content determines the extent of red coloring 33 Skin Color (cont’d.) • Physiological changes: – Blushing: Blood vessel dilation – Pallor: Blood vessel constriction • Pathological changes: – Cyanosis or bluish tint: Poor oxygenation – Jaundice or yellowing: Bilirubin deposition (Bile and Liver products) – Bronzing: Melanin overproduction – Ecchymosis: Black and blue bruising 34 Lesson 7-2 Objectives • Explain four processes by which the body loses heat. • Describe how the skin helps regulate temperature. 35 Body Temperature: Key Terms • Core temperature: The inner parts of the body • Shell temperature: The surface areas of the body • Thermoregulation: Balance of heat production and heat loss 36 Heat Production • Metabolism: basis of body temperature • Blood disperses heat throughout the body. • Most heat is produced by muscles, the liver, and endocrine glands. • Affected by food consumption, hormones, disease, and physical activity 37 Heat Loss • Sites: Skin (80%), lungs, and excretory products (20%) • Types: – Radiation= heat transfer from object to another without touching – Conduction= heat transfer through contact – Convection= transfer of heat AWAY from surface by movement – Evaporation= heat expended from fluid(liquid) 38 Temperature Regulation • Hypothalamus – Heat lost by: • Dilation of blood vessels • Sweating – Heat conserved by • Shivering • Blood vessel constriction • Less sweat Issues in Temperature Regulation • Hyperthermia: Syncope (fainting), cramps, heat exhaustion, heat stroke • Hypothermia: Slowed metabolism, fibrillation (random heart beat) 40 Temperature Regulation: Neonates • Lose more heat than they produce – Large surface area – Large bald head – Less insulation – Must rely on nonshivering thermogenesis: metabolism of brown adipose tissue (BAT) • Have limited capacity to dissipate heat 41 Skin Homeostatic Imbalances Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Dehydration Electrolyte imbalance Circulatory shock Burns: Classified by Depth • Partial thickness burns – First-degree – Second-degree • Full-thickness burn – Third-degree Severity of Burns First-degree burns Only epidermis is damaged Skin is red and swollen Second degree burns Epidermis and upper dermis are damaged Skin is red with blisters Third-degree burns Destroys entire skin layer Burn is gray-white or black Types of Burns 1st Degree Burn 2nd Degree Burn 2nd vs. 3rd Severe 2nd Degree Burn 3rd Degree Burn RD 3 Degree Burns Critical Burns Burns are considered critical if: Over 25% of body has second degree burns Over 10% of the body has third degree burns There are third degree burns of the face, hands, or feet Rules of Nines Way to determine the extent of burns Body is divided into 11 areas for quick estimation Each area represents about 9% Rule of Nines 50 Burns: Classified by Extent • “Rule of nines” • Eschar (scab) – Acts like a tourniquet – Breeds bacteria – Secretes toxins 51 Skin Care • All ages: – Reduce exposure to UV radiation. • Especially in older adults: – Skin dries out more easily; retain moisture by limiting excessive bathing and use of soap. – Thinner skin bruises more easily and does not insulate as well. 52 Skin, Drugs, and Chemicals • Skin can absorb many chemicals. • Drug delivery systems: • Hypodermic injections • Transdermal patches • Intradermal injections (allergy testing) • Topical applications • Danger of absorption of toxins 53