ch. 5 the integumentary system
DESCRIPTION
Ch. 5 The Integumentary System. Introduction. Integument consists of: Skin – largest organ Accessory structures (hair/sweat glands) Subcutaneous tissue Skin Barrier to many harmful substances. The Skin. 2 major layers (Fig. 5-1) Epidermis – outer layer Dermis – inner layer. - PowerPoint PPT PresentationTRANSCRIPT
Ch. 5 The Integumentary System
IntroductionIntegument consists of:
Skin – largest organAccessory structures (hair/sweat glands)Subcutaneous tissue
SkinBarrier to many harmful substances
The Skin2 major layers (Fig. 5-1)
Epidermis – outer layerDermis – inner layer
EpidermisStratified squamous keratinizing epitheliumThickest on palms, solesAbundant keratinocytesNo capillaries2 sublayers
inner stratum germinativumouter stratum corneum
Stratum Germinativum“stratum basale”Base of the epidermis where mitosis occurs
older cells pushed toward skin surface produce keratin and die
Merkel cells (Merkel discs)touch receptors (Fig. 5-2)
Stratum GerminativumKeratinocytes
living cells that synthesize antimicrobial “defensins” rupture pathogen membranes as part of
inflammatory processLiving portion produces vitamin D when
exposed to sunlight
Stratum CorneumOutermost epidermal layerKeratin prevents evaporation and water entryBarrier to pathogens & chemicals
Langerhans Cells“dendritic cells” (Fig. 5-2)Originate in red bone marrowPhagocytize foreign material
migrate to lymph nodes; take pathogen to lymphocytes triggers immune response
MelanocytesSee Fig. 5-2Produce melanin
those with darker skin produce large amountsproduction increased in when exposed to UV
raysMelanin gives color to hair, iris, choroid layer
of eyeSee Table 5-1
DermisMade of irregular fibrous connective tissue
fibroblasts produce collagen & elastic fibers allow strength & elasticity
Papillary layer – junction of dermis with epidermis (Fig. 5-1)abundant capillaries
Accessory structureshair & nail follicles, sensory receptors, glands
Hair FolliclesMade of epidermal tissueBase of follicle (Fig. 5-3)
Hair root; mitosis occurs in matrix1. Produce keratin 2. Get color from melanin3. Die & become incorporated into hair shaft4. Hair shaft pushed toward skin surface
Hair FolliclesEyelashes & eyebrows keep dust & sweat out
of eyesNostril hairs keep dust from entering nasal
cavitiesHair on head provides insulation
body hair doesn’t serve this purposePilomotor (arrector pili muscle) attached to
each folliclepull hair follicles upright (fear, cold)
Nail FolliclesOn ends of fingers & toesProduce nails; mitosis in nail root at the nail’s
base (Fig. 5-4)New cells produce keratin & dieNail is dead keratin cells, but nail bed is alive
NailsProtect fingers & toes from mechanical injuryAllow dexterityGood for scratching
ReceptorsCutaneous senses
touch, pressure, heat, cold, painSpecific receptor for each sensationReceptors & sensation provide CNS with
information about external environment
GlandsMade of epithelial tissue (Fig. 5-1)Sebaceous glands
Secrete sebum (oil) inhibits bacterial growth on skin’s surface prevents drying of skin, hair
Ceruminous glandsin the dermis of ear canalssecrete cerumen (ear wax)
keeps outer surface of eardrum pliable; prevents drying
GlandsSweat glands
2 types Apocrine – numerous in axillae (underarm), genital
areas Eccrine – numerous on forehead, upper lip, palms,
soles
Blood VesselsCapillaries in dermisArterioles
Smooth muscle in walls permits constriction or dilation maintains body temp.
Subcutaneous Tissue“superficial fascia”Made of areolar and adipose tissueConnects dermis to underlying musclesSecondary line of defense
Aging & The Integumentary SystemSkin layers become thinner, more fragileFibroblasts die & are not replacedRepair of breaks or cuts slowsSkin wrinkles Glands become less activeSkin becomes dryTemp. regulation becomes harderHair thins, turns white