chapter 007

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 skinepidermis

and dermis.• List the two major functions of the

subcutaneous layer.

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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


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Structure of the Skin

• Layers– Epidermis– Dermis– Subcutaneous – Accessory

structures


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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.



Dermis

• Lies under and supports the epidermis• Sits on the subcutaneous layer or hypodermis• Embedded with accessory structures– Includes blood vessels that nourish epidermis



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.



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



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



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– Bronzing: Melanin overproduction– Ecchymosis: Black and blue bruising



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



Accessory Structures: Nails

• Protect tips of fingers and toes from injury• Condition affected by oxygenation of blood

supply, trauma, and nutritional deficiencies



Accessory Structures: Glands

• Sebaceous glands:– Oil glands– Secrete sebum and in

fetus vernix caseosa

• Sudoriferous– Sweat glands



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)



Lesson 7-2 Objectives

• Explain four processes by which thebody loses heat.

• Describe how the skin helps regulate temperature.



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



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 Loss

• Sites: Skin (80%), lungs, and excretory products (20%)

• Types:– Radiation– Conduction– Convection– Evaporation



Temperature Regulation

• Hypothalamus– Heat lost by: • Dilation of blood

vessels• Sweating

– Heat conserved by• Shivering• Blood vessel

constriction• Less sweat



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



Issues in Temperature Regulation

• Hyperthermia: Syncope, cramps, heat exhaustion, heat stroke• Hypothermia: Slowed metabolism, fibrillation



Burns: Classified by Depth

• Partial thickness burns– First-degree– Second-degree

• Full-thickness burn– Third-degree



Burns: Classified by Extent

• “Rule of nines”

• Eschar– Acts like a

tourniquet– Breeds

bacteria– Secretes

toxins



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.



chapter 007

Health & Medicine

imprint of elsevier

body temperature copyright

skin cells

skin color

glands sebaceous glands

body shell temperature

chemicals skin

mammary glands