The Human Body in Health and Illness, 4th edition Barbara Herlihy Chapter 7: Integumentary System and Body Temperature

Lesson 7-1 Objectives List six functions of the skin. Define stratum germinativum and stratum corneum. Describe the two layers of the skinepidermis and dermis. List the two major functions of the subcutaneous layer. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 The skin, the accessory structures, and the subcutaneous tissue form the integumentary system . Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Structure of the Skin Layers Epidermis Dermis Subcutaneous Accessory structures Oxygen and nutrients diffuse into the lower epidermis from the richly nourished dermis. In which layers are the blood vessels found? The blood vessels are found in the dermis and subcutaneous. Where are the statum germinativum and stratum corneum found? Both are layers of epidermis; the statrum germinativum is the deeper of the two. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Epidermis: Outer Layer Layers of the epidermis Stratum germinativum (deeper); cells continuously dividing and moving toward surface Stratum corneum (surface layer); composed of dead, flattened cells that slough off Keratinization: The protein keratin makes skin cells hard, flat, and water resistant. As the cells of the stratum germinativum divide, they push the older cells toward the surface of the epithelium. To what do the terms exfoliation and desquamation refer? These terms describe the sloughing off of the stratum corneum. What are dander and dandruff? Individual dead cells are called dander; when clumped together by oil, they are dandruff. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Dermis Lies under and supports the epidermis Sits on the subcutaneous layer or hypodermis Embedded with accessory structures Includes blood vessels that nourish epidermis What role do the collagen and elastin fibers of the dermis play? These fibers make the dermis stretchable and strong. What accessory structures are embedded in the dermis? The hair, nails, and certain glands are embedded in the dermis. The sensory receptors that detect pain, temperature, pressure, and touch are also located in the dermis. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Subcutaneous Layer: Hypodermis 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. Is the subcutaneous layer considered to be part of the skin? No, it is not. Why are many drugs injected subcutaneously (SC)? The hypodermis has a rich supply of blood vessels. The blood vessels absorb the drug and distribute it throughout the body. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 What are some drugs that can be given transdermally? Examples are nitroglycerin and contraceptive patches. What are some toxins that can be absorbed through the skin? Examples are pesticides, dry cleaning fluid, acetone, and mercury. Distinguish between transdermal and topical applications of drugs. Transdermal applications enter the bloodstream; topical applications remain on the skin’s surface. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Skin Color Determined by genes, physiology, and sometimes pathology Dark pigment: Melanin Secreted by melanocytes in the epidermis Melanocyte malfunctions: Albinism, vitiligo, moles Yellow pigment: Carotene Presence of melanin overshadows carotene’s tint in most people What is the physiological basis of the summer tan? UV radiation boosts melanin production, beginning with a tan, and potentially leading to permanent damage. Moles are abnormal but harmless concentrations of melanin. What are signs that a mole may be becoming a melanoma? Signs of possible melanoma are asymmetrical shape, irregular borders, change in color, and diameter larger than a pencil eraser. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Skin Color (cont’d.) Physiological changes: Pathological changes: Blushing: Blood vessel dilation Pallor: Blood vessel constriction Pathological changes: Cyanosis or bluish tint: Poor oxygenation Jaundice or yellowing: Bilirubin deposition Bronzing: Melanin overproduction Ecchymosis: Black and blue bruising Jaundice can be a sign of liver disease; the liver is unable to excrete bilirubin, so it is deposited in the skin. In light-skinned people, bronze skin can signal poor adrenal function. A bruise, or ecchymosis, is clotted blood under the skin. Fear can make a person look white as a sheet. Physiologically, what is going on? Vasoconstriction is part of the fear response. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 What role do the arrector pili muscles play? When the arrector pili muscles contract, they cause the hair to stand up on end. The hair follicle is surrounded by epidermal tissue. Distinguish between hirsuitism and alopecia. The former can be caused by steroid therapy and the latter can be caused by cancer or chemotherapy. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Accessory Structures: Nails Protect tips of fingers and toes from injury Condition affected by oxygenation of blood supply, trauma, and nutritional deficiencies Nails are thin plates of stratified squamous epithelial cells. They contain a very hard form of keratin and slide over a layer called the nail bed, which is part of the epidermis. Clubbing is an indication chronic lung or heart disease; it results from chronically poor oxygenation of the nail and fingertip. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Accessory Structures: Glands Sebaceous glands: Oil glands Secrete sebum and in fetus vernix caseosa Sudoriferous Sweat glands What is the role of the vernix caseosa? This cream cheese–like covering found on the fetus protects it from maceration. What happens when the sebaceous glands become blocked? When accumulated sebum blocks a sebaceous gland and is exposed to air and dries out, it turns black and forms a blackhead. If it becomes infected with staphylococci, it becomes a pustule, or pimple. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Sudoriferous Glands Apocrine glands: Usually associated with hair follicles; more active at puberty Eccrine glands: Critical for temperature regulation Types of modified sweat glands: Mammary glands: Secrete milk Ceruminous glands: Secrete ear wax (cerumen) There are two types of sweat glands, apocrine and eccrine. Apocrine sweat glands are found in the axillary and genital areas. These glands develop during puberty. When broken down by bacteria on the skin surface, sweat from these glands cause body odor. The eccrine glands are active at birth and located throughout the body. Crucial for temperature regulation, eccrine gland sweat cools the body as it evaporates from the skin surface. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lesson 7-2 Objectives Explain four processes by which the body loses heat. Describe how the skin helps regulate temperature. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 What is the “normal” body temperature? Normal body temperature can range from 97 to 100 F. What are excessive decrease and increase in body temperature? Excessive decrease is hypothermia; excessive increase is hyperthermia. How can core and shell temperature be measured? Core temperature is measured rectally and shell temperature is measured at the axillary site. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 Heat is produced by metabolizing cells. The amount of heat is affected by food consumption, physical activity, and hormonal secretion (as in thyroid gland disorders). Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Heat Loss Sites: Skin (80%), lungs, and excretory products (20%) Types: Radiation Conduction Convection Evaporation Why do most people feel so uncomfortable on a hot and humid day? Humidity prevents evaporation, so less heat is carried away from the skin. A cooling blanket to treat hyperthermia is an example of conduction. An example of convection is the use of a fan to cool the body. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Temperature Regulation Hypothalamus Heat lost by: Dilation of blood vessels Sweating Heat conserved by Shivering Blood vessel constriction Less sweat Pyrogens reset the hypothalamus at a higher temperature. Intense heat can cause heat syncope, heat cramps, heat exhaustion, or heat stroke. In heat stroke, thermoregulatory mechanisms fail. Core temperature exceeds 104° F, and hallucinations or altered mentation may occur. With slower metabolisms and thinner skin, older adults are more prone to hypothermia. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 Neonates wear hats in the nursery because so much heat loss happens through their large, bald skulls. Preterm infants have less capacity to thermoregulate, so they are often in incubators. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Issues in Temperature Regulation Hyperthermia: Syncope, cramps, heat exhaustion, heat stroke Hypothermia: Slowed metabolism, fibrillation Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Burns: Classified by Depth Partial thickness burns First-degree Second-degree Full-thickness burn Third-degree What type of burn is sunburn? It is a first-degree burn. Third-degree burns are pain-free, but the areas of first- and second-degree burns that often surround the more severe burn will still hurt. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Burns: Classified by Extent “Rule of nines” Eschar Acts like a tourniquet Breeds bacteria Secretes toxins What is the extent of a burn on the front and back of an adult’s limbs? According to the rule of nines, 36% of the body is burned. Why is eschar removed as part of postburn therapy? Eschar can act like a tourniquet, cutting off blood supply or preventing chest expansion. It becomes a breeding ground for bacteria and secretes toxins into the blood. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Skin Care All ages: Especially in older adults: 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. Both the sun and tanning beds expose people to UV radiation. In older adults, frequent bathing with soap dries the skin. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.