THE INTEGUMENTARY SYSTEM 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 COLOR Factors that influence skin color Amount of pigment in the epidermis Melanin Carotene Blood in surface blood vessels Composition of blood Oxygen Hemoglobin Other chemicals
AGING Changes 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.