T H E I N T E G U M E N TA RY S Y S T E M

CHAPTER 5

THE INTEGUMENTARY SYSTEM

• Largest organ in the body• 10% of body weight• Skin and associated structures

STRUCTURE OF SKIN

• Skin consists of two layers• Epidermis• Strata

• Dermis• Blood vessels, nerve endings, and glands

EPIDERMIS

• Surface portion of the skin is made of Stratum corneum• Stratum basale or stratum germinativum forms

the base of the epidermis

DERMIS

Contains most of the accessory structures of the skin• Blood vessels• Nerves• Sweat glands• Oil glands• Hair• Dermal papillae- help create fingerprints

SUBCUTANEOUS LAYER

Connects the skin to the surface muscles• Loose connective tissue• Adipose (fat) tissue• Blood vessels• Nerves and nerve endings

• Site of injections

ACCESSORY STRUCTURES

• Some structures of the integumentary system protect the skin and have some more generalized functions as well

SEBACEOUS (OIL) GLANDS

Produce a variety of secretions• Sebum (oil)• Vernix caseosa (oily layer on developing fetus)• Eye lubrication

SUDORIFEROUS GLANDS (SWEAT)

Located in the dermis and subcutaneous tissue• Eccrine type sweat glands (on most skin)• Apocrine sweat glands (in pubic and armpit

areas)• Ceruminous glands (ear wax)• Ciliary glands• Mammary glands

HAIR

Composed mainly of keratin and is not living• Hair follicles• Melanocytes• Arrector pili (help make goosebumps)

NAILS

Made of keratin produced by cells that originate in the outer layer of the epidermis•Nail root•Nail plate•Nail bed•Lunula•Cuticle

FUNCTIONS OF SKIN

Four major functions• Protection against infection• Protection against dehydration (drying)• Regulation of body temperature• Collection of sensory information

PROTECTION AGAINST INFECTION

Intact skin forms a primary barrier against invasion• Interlocking pattern resists penetration• Shedding removes pathogens• Protects against bacterial toxins• Protects against some harmful environmental

chemicals

PROTECTION FROM DEHYDRATION

Skin prevents water loss by evaporation• Keratin in the epidermis• Hardens the skin cells closer to the surface

• Sebum release from the sebaceous glands• Forms oily layer to keep moisture in

REGULATION OF BODY TEMP

Loss of excess heat and protection from cold are important functions of the skin•Constriction of blood vessels- when its cold (cold feet/hands)•Dilation of blood vessels (swell when hot)•Evaporation of perspiration (evaporative cooling)

COLLECTION OF SENSORY INFORMATION

Skin has many nerve endings and other special receptors• Free nerve endings• Touch receptors (Meissner corpuscle)• Deep pressure receptors (Pacinian corpuscle)

OTHER FUNCTIONS OF SKIN

• Absorption of substances such as medications• Excretion• Water• Electrolytes• Wastes

• Manufacture of vitamin D

SKIN COLORFactors that influence skin color• Amount of pigment in the epidermis• Melanin• Carotene

• Blood in surface blood vessels• Composition of blood • Oxygen• Hemoglobin • Other chemicals

AGINGChanges in• Skin• Tissues• Pigment • Hair • Sweat glands • Circulation • Fingernails and toenails

CARE OF SKIN• Proper nutrition• Adequate circulation• Regular cleansing• Removes dirt and dead skin• Sustains slightly acid environment to inhibit bacteria

• Protection from sunlight• Exposure to UV light causes genetic mutations in skin

that can lead to cancer, and causes premature aging.