BSMP 2135 Anatomy and Physiology Chapter 6
BSMP 2135 Anatomy and Physiology Chapter 6 2135 BMSP
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This 18 page Class Notes was uploaded by Marlena Trone on Sunday September 25, 2016. The Class Notes belongs to 2135 BMSP at Virginia Polytechnic Institute and State University taught by in Fall 2016. Since its upload, it has received 7 views.
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Date Created: 09/25/16
CHAPTER 6: The Integumentary System INTEGUMENT: The skin The skin is the largest and heaviest organ 15% of body weight ACCESSORY ORGANS: the hair, nails and cutaneous glands DERMATOLOGY: The scientific study and medical treatment of the integumentary system. FUNCTIONS OF THE SKIN Resistance to trauma and infection ‾ Suffers the most physical injures to the body but resists and recovers from trauma better than other organs do ‾ Keratin: tough protein ‾ Acid mantle: protective acid film pH 46 Other barrier functions ‾ Waterproofing Keeps from losing water Keeps from absorbing excess water (like when you swim or take a bath) ‾ UV radiation Protects against cancer ‾ Harmful chemicals However permeable to drugs and poisons Vitamin D synthesis ‾ First step occurs in skin ‾ Liver and kidneys complete process Sensation ‾ Skin is our most extensive sense organ Variety of nerve endings ‾ Especially abundant on the face, palms, fingers, soles, nipples and genitals Thermoregulation ‾ Thermoreceptors: monitor body surface temperature ‾ Vasoconstriction (shrinking)/ vasodilation (opening) of dermal blood vessels Aids in maintaining body temperature. Nonverbal communication ‾ Facial expressions ‾ Social acceptance Transdermal absorption ‾ Administration of certain drugs through thin skin Adhesive patches OVERVIEW Integumentary System: consists of the skin and its accessory organs Most visible system and more attention paid to this organ system ‾ receives more medical treatment than any other organ system dermatology: scientific study and medical treatment of the integumentary system ‾ skin is the most vulnerable organ exposed to radiation, trauma, infection, and injurious chemicals SKIN AND SUBCUTANEOUS TISSUE The body’s largest and heaviest organ ‾ covers area of 1.5 2.0 m (square meters) ‾ 15 % of body weight ‾ most skin is 12 mm thick 0.5 mm on eyelids to 6 mm between the shoulder blades The skin consists of two layers: ‾ epidermis ‾ dermis ‾ hypodermis or subcutaneous tissue: connective tissue layer below the skin not part of the skin but often studied with skin STRUCTURE OF THE SKIN THICK SKIN AND THIN SKIN thick skin: on palms and sole, and corresponding surfaces on fingers and toes ‾ has sweat glands, but NO hair follicles or sebaceous (oil) glands ‾ epidermis 0.5 mm thick ‾ very thick surface layer of dead cells called the stratum corneum thin skin: covers rest of the body ‾ possesses hair follicles, sebaceous glands and sweat glands ‾ epidermis about 0.1 mm thick ‾ thin stratum corneum EPIDERMIS epidermis: keratinized stratified squamous epithelium ‾ dead cells at the surface packed with a tough protein called keratin ‾ avascular (lacks blood vessels) depends on the diffusion of nutrients from underlying connective tissue ‾ sparse nerve endings for touch and pain CELLS OF THE EPIDERMIS stem cells ‾ undifferentiated cells that give rise to keratinocytes ‾ in deepest layer of epidermis (stratum basale) keratinocytes ‾ great majority of epidermal cells ‾ synthesize keratin melanocytes ‾ occur only in stratum basale ‾ synthesize pigment melanin that shields DNA from ultraviolet radiation ‾ branched processes that spread among keratinocytes tactile (merkel) cells ‾ in basal layer of epidermis ‾ touch receptor cells associated with dermal nerve fibers dendritic (langerhans) cells ‾ macrophages originating in bone marrow that guard against pathogens ‾ found in stratum spinosum and granulosum ‾ stand guard against toxins, microbes, and other pathogens that penetrate skin LAYERS OF THE EPIDERMIS Stratum Basale ‾ deepest layer of the epidermis ‾ a single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane melanocytes and tactile cells are scattered among the stem cells and keratinocytes ‾ stem cells of stratum basale divide give rise to keratinocytes that migrate toward skin surface replace lost epidermal cells Stratum Spinosum ‾ consists of several layers of keratinocytes ‾ thickest stratum in most skin in thick skin exceeded by stratum corneum ‾ produce keratin filaments which causes cell to flatten ‾ dendritic cells found throughout this stratum ‾ named for artificial appearance created in histological section numerous desmosomes and cell shrinkage produces spiny appearance Stratum Granulosum ‾ consists of 3 to 5 layers flat keratinocytes ‾ contain coarse darkstaining granules Stratum Lucidum ‾ only in thick skin ‾ thin translucent zone ‾ cells have no nucleus or other organelles ‾ zone has a pale, featureless appearance with indistinct boundaries Stratum Corneum ‾ up to 30 layers of dead, scaly, keratinized cells ‾ form durable surface layer surface cells flake off (exfoliate) ‾ resistant to abrasion, penetration, and water loss LIFE HISTORY OF KERATINOCYTES keratinocytes are produced deep in the epidermis by stem cells in stratum basale ‾ some deepest keratinocytes in stratum spinosum also multiply and increase their numbers mitosis requires an abundant supply of oxygen and nutrients ‾ deep cells acquire from blood vessels in nearby dermis ‾ once epidermal cells migrate more than two or three cells away from the dermis, their mitosis ceases newly formed keratinocytes push the older ones toward the surface in 30 40 days a keratinocyte makes its way to the skin surface and flakes off ‾ slower in old age ‾ faster injured or stressed skin calluses or corns – thick accumulations of dead keratinocytes on the hands or feet cells grow flatter in stratum granulosum three important developments occur ‾ keratinocyte nucleus and other organelles degenerate, cells die ‾ granules release a protein binds the keratin filaments together into coarse, tough bundles ‾ membranecoating vesicles release lipid mixture that spreads out over cell surface and waterproofs it EPIDERMAL WATER BARRIER epidermal water barrier: forms between stratum granulosum and stratum spinosum consists of: ‾ lipids secreted by keratinocytes ‾ tight junctions between keratinocytes ‾ thick layer of insoluble protein on the inner surfaces of the keratinocyte plasma membranes critical to retaining water in the body and preventing dehydration cells above the water barrier quickly die ‾ barrier cuts them off from nutrients below ‾ dead cells exfoliate (dander) ‾ dandruff – clumps of dander stuck together by sebum (oil) DERMIS dermis: connective tissue layer beneath the epidermis ‾ ranges from 0.2 mm (eyelids) – 4 mm (palms & soles) well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings hair follicles and nail roots are embedded in dermis smooth muscle: piloerector muscles associated with hair follicles ‾ contract in response to stimuli, such as cold, fear, and touch – goose bumps dermal papillae – upward fingerlike extensions of the dermis ‾ friction ridges on fingertips that leave fingerprints papillary layer – superficial zone of dermis ‾ thin zone of areolar tissue in and near the dermal papilla ‾ allows for mobility of leukocytes and other defense cells ‾ rich in small blood vessels reticular layer – deeper and much thicker layer of dermis ‾ consists of dense irregular connective tissue ‾ stretch marks (striae) – tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity HYPODERMIS subcutaneous tissue more areolar and adipose than dermis pads body binds skin to underlying tissues drugs introduced by injection ‾ highly vascular & absorbs them quickly subcutaneous fat ‾ energy reservoir ‾ thermal insulation ‾ thicker in women LAYERS OF THE SKIN From superficial to deep: ‾ Epidermis stratum corneum stratum lucidum stratum granulosum stratum spinosum stratum basale ‾ Dermis papillary layer reticular layer ‾ Hypodermis or Subcutaneous tissue underlies the dermis, but is not considered part of the skin SKIN COLOR melanin – most significant factor in skin color ‾ produced by melanocytes ‾ accumulate in the keratinocytes of stratum basale and stratum spinosum people of different skin colors have the same number of melanocytes ‾ dark skinned people produce greater quantities of melanin & melanin breaks down more slowly melanin granules are spread out in the keratinocytes melanized cells seen throughout the epidermis ‾ light skinned people melanin clumped near keratinocyte nucleus little seen beyond stratum basale amount of melanin also varies with exposure to ultraviolet (UV) rays of sunlight hemoglobin: red pigment of red blood cells ‾ adds reddish to pinkish hue to skin carotene: yellow pigment acquired from egg yolks and yellow/orange vegetables ‾ concentrates in stratum corneum and subcutaneous fat Skin color results from combination of evolutionary selection pressures ‾ especially differences in exposure to ultraviolet radiation (UVR) UVR has two adverse effects: ‾ causes skin cancer ‾ breaks down folic acid needed for normal cell division, fertility, and fetal development UVR has a desirable effect: ‾ stimulates synthesis of vitamin D necessary for dietary calcium absorption ‾ women have skin averaging about 4% lighter than men need greater amounts of vitamin D and folic acid to support pregnancy and lactation ‾ ancestral skin color is a compromise between vitamin D and folic acid requirements populations native to the tropics and their descendants tend to have wellmelanized skin to screen out excessive UVR populations native to far northern or southern latitudes where the sunlight is weak, tend to have light skin to allow for adequate UVR penetration high altitude and dry air increases skin pigmentation ‾ Andes, Tibet, Ethiopia UVR accounts for up to 77% of variation in human skin color exceptions: ‾ migration, cultural differences in clothing and shelter ‾ intermarriage of people of different geographic ancestries ‾ darwinian sexual selection: a preference in mate choice for partners of light or dark complexion ABNORMAL SKIN COLORS cyanosis: blueness of the skin from deficiency of oxygen ‾ airway obstruction (drowning or choking) ‾ lung diseases (emphysema or respiratory arrest) ‾ cold weather or cardiac arrest erythema: abnormal redness of the skin due to dilated cutaneous vessels ‾ exercise, hot weather, sunburn, anger, or embarrassment pallor: pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen shows through ‾ emotional stress, low blood pressure, circulatory shock, cold, anemia albinism: genetic lack of melanin that results in white hair, pale skin, and pink eyes jaundice: yellowing of skin and sclera due to excess of bilirubin in blood ‾ cancer, hepatitis, cirrhosis, other compromised liver function hematoma: (bruise) mass of clotted blood showing through skin SKIN MARKINGS friction ridges: the markings on the fingertips that leave oily fingerprints on surfaces we touch ‾ everyone has a unique pattern formed during fetal development and remain unchanged throughout life ‾ allow manipulation of small objects flexion lines (flexion creases): lines on the flexor surfaces of the digits, palms, wrists, elbows ‾ marks sites where the skin folds during flexion of the joints freckles and moles: tan to black aggregations of melanocytes ‾ freckles are flat, melanized patches ‾ moles (nevus) are elevated melanized patches often with hair moles should be watched for changes in color, diameter, or contour may suggest malignancy (skin cancer) HAIR AND NAILS hair and nails are composed of mostly of dead, keratinized cells ‾ pliable soft keratin makes up stratum corneum of skin ‾ compact hard keratin makes up hair and nails tougher and more compact due to numerous crosslinkages between keratin molecules HAIR pilus: another name for hair pili: plural of pilus hair: a slender filament of keratinized cells that grows from an oblique tube in the skin called a hair follicle DISTRIBUTION OF HUMAN HAIR hair is found almost everywhere on the body except: ‾ palms and soles ‾ ventral and lateral surface of fingers and toes ‾ distal segment of the finger ‾ lips, nipples, and parts of genitals limbs and trunk have 55 – 70 hairs per cm2 ‾ face about 10 times as many ‾ 30,000 hairs in a man’s beard ‾ 100,000 hairs on an average person’s scalp ‾ number of hairs does not differ much from person to person or even between sexes differences in appearance due to texture and pigmentation of the hair TYPES OF HUMAN HAIR Three kinds of hair grow over the course of our lives ‾ Lanugo: fine, downy, unpigmented hair that appears on the fetus in the last three months of development ‾ Vellus: fine, pale hair that replaces lanugo by time of birth twothirds of the hair of women onetenth of the hair of men all of hair of children except eyebrows, eyelashes, and hair of the scalp ‾ Terminal: longer, coarser, and usually more heavily pigmented forms eyebrows, eyelashes, and the hair of the scalp after puberty, forms the axillary and pubic hair male facial hair and some of the hair on the trunk and limbs STRUCTURE OF HAIR AND FOLLICLE hair is divisible into three zones along its length ‾ bulb: a swelling at the base where hair originates in dermis or hypodermis only living hair cells are in or near bulb ‾ root: the remainder of the hair in the follicle ‾ shaft: the portion above the skin surface dermal papilla: bud of vascular connective tissue encased by bulb ‾ provides the hair with its sole source of nutrition hair matrix: region of mitotically active cells immediately above papilla ‾ hair’s growth center follicle: diagonal tube that dips deeply into dermis and may extend into hypodermis hair receptors ‾ nerve fibers that entwine each follicle ‾ respond to hair movement piloerector muscle (arrector pili) ‾ bundles of smooth muscle cells ‾ extends from dermal collagen to connective tissue root sheath ‾ goose bumps HAIR IN CROSSSECTION medulla ‾ core of loosely arranged cells and air spaces cortex ‾ constitutes the bulk of the hair ‾ consists of several layers of elongated keratinized cells cuticle ‾ composed of multiple layers of very thin, scaly cells that overlap each other ‾ free edges directed upward FUNCTIONS OF HAIR most hair on trunk and limbs is vestigial ‾ little present function ‾ warmth in ancestors hair receptors alert us of parasites crawling on skin scalp helps retain heat and protects against sunburn gender identification pubic and axillary hair signify sexual maturity and aids in transmission of sexual scents guard hairs (vibrissae) guard nostrils and ear canals eyelashes and eyebrows nonverbal communication NAILS fingernails and toenails: clear, hard derivatives of the stratum corneum composed of very thin, dead cells packed with hard keratin flat nails allow for more fleshy and sensitive fingertips ‾ tools for digging, grooming, picking apart food, and other manipulations nail plate ‾ free edge: overhangs the finger tip ‾ nail body: visible attached part of nail ‾ nail root: extends proximally under overlying skin nail bed: underlying skin nail matrix: growth zone ‾ mitosis here accounts for nail growth ‾ 1 mm per week in fingernails, slightly slower on toenails Lunule: an opaque white crescent at proximal end of nail eponychium (cuticle): narrow zone of dead skin CATANEOUS GLANDS The skin has five types of glands ‾ Merocrine sweat glands ‾ Apocrine sweat glands ‾ Sebaceous glands ‾ Ceruminous glands ‾ Mammary glands SUDORIFEROUS (SWEAT) GLANDS two kinds of sudoriferous (sweat) glands ‾ merocrine (eccrine) sweat glands most numerous skin glands 3 to 4 million in adult skin are simple tubular glands watery perspiration that helps cool the body ‾ apocrine sweat glands occur in groin, anal region, axilla, areola, bearded area in mature males ducts lead to nearby hair follicles produce sweat that is thicker, milky, and contains fatty acids scent glands that respond to stress and sexual stimulation develop at puberty pheromones: chemicals that influence the physiology of behavior of other members of the species bromhidrosis: disagreeable body odor produced by bacterial action on fatty acids SWEAT sweat: begins as a proteinfree filtrate of blood plasma produced by deep secretory portion of gland ‾ potassium ions, urea, lactic acid, ammonia, and some sodium chloride remain in the sweat, most sodium chloride reabsorbed by duct ‾ some drugs are also excreted in sweat ‾ on average, 99% water, with pH range of 4 to 6 acid mantle: inhibits bacterial growth ‾ insensible perspiration – 500 ml per day does not produce visible wetness of skin ‾ diaphoresis: sweating with wetness of the skin exercise – may lose one liter of sweat per hour SEBACEOUS GLANDS sebum: oily secretion produced by sebaceous glands flaskshaped glands with short ducts opening into hair follicle classified as a holocrine gland – secretion consists of brokendown cells ‾ replaced by mitosis at base of gland keeps skin and hair from becoming dry, brittle, and cracked CERUMINOUS GLANDS found only in external ear canal their secretion combines with sebum and dead epithelial cells to form earwax (cerumen) ‾ keep eardrum pliable ‾ waterproofs the canal ‾ kills bacteria ‾ makes guard hairs of ear sticky to help block foreign particles from entering auditory canal MAMMARY GLANDS Breasts of both sexes contain very little glandular material mammary glands: milkproducing glands that develop only during pregnancy and lactation ‾ modified apocrine sweat gland ‾ richer secretion released by ducts opening into the nipple additional nipples (polythelia) ‾ may develop along milk line SKIN CANCER skin cancer: induced by the ultraviolet rays of the sun ‾ one of the most common & easiest to treat has one of the highest survival rates if detected and treated early ‾ most often on the head and neck ‾ most common in fairskinned people and the elderly ‾ three types of skin cancer named for the epidermal cells in which they originate basal cell carcinoma, squamous cell carcinoma, and malignant melanoma Basal Cell Carcinoma ‾ Most common type ‾ Least dangerous because it seldom metastasizes ‾ Forms from cells in stratum basale ‾ Lesion is small shiny bump with central depression and beaded edges Squamous Cell Carcinoma ‾ Arise from keratinocytes from stratum spinosum ‾ Lesions usually appear on scalp, ears, lower lip, or back of the hand ‾ Have raised, reddened, scaly appearance later forming a concave ulcer ‾ Chance of recovery good with early detection and surgical removal ‾ Tends to metastasize to lymph nodes and may become lethal Malignant Melanoma ‾ Skin cancer that arises from melanocytes ‾ Often in a preexisting mole ‾ Less than 5% of skin cancers, but most deadly form ‾ Treated surgically if caught early ‾ Metastasizes rapidly unresponsive to chemotherapy usually fatal many live only 6 months from diagnosis 5% to 14% survive 5 years ‾ Greatest risk factor: Familial history of malignant melanoma ‾ High incidence in: Men Redheads People who experience severe sunburn in childhood ABCD Rule ‾ For recognizing malignant melanoma A: Asymmetry B: Border (irregular border; not smooth) C: Color (two or more colors) D: Diameter (larger than a pencil eraser; 6mm) UVA, UVB and SUNSCREENS UVA and UVB are improperly called “tanning rays” and “burning rays” both thought to initiate skin cancer sunscreens protect you from sunburn but unsure if provide protection against cancer ‾ chemical in sunscreen damage DNA and generate harmful free radicals BURNS burns: leading cause of accidental death ‾ fires, kitchen spills, sunlight, ionizing radiation, strong acids or bases, or electrical shock ‾ deaths result primarily from fluid loss, infection and toxic effects of eschar – burned, dead tissue ‾ debridement – removal of eschar ‾ classified by layer of tissue involved firstdegree burns – partial thickness burn – epidermis only ‾ marked by redness, slight edema, and pain ‾ heal in a few days ‾ most sunburns are first degree burns seconddegree burns – partial thickness burn involve the epidermis and part of the dermis ‾ leaves part of the dermis intact ‾ red, tan, or white ‾ two weeks to several months to heal and may leave scars ‾ blistered and very painful thirddegree burn – full thickness burn – to the hypodermis and often some deeper tissues (muscles or bones) are destroyed ‾ often require skin grafts ‾ needs fluid replacement and infection control Burn First Aid Treatment 1. First remove any constricting jewelry, such as rings. 2. Do NOT use butter or oils on a burn. 3. The affected area should be dowsed with cool water as soon as possible. Do NOT apply ice or cool to nearfreezing temperatures (this can cause additional tissue injury).
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