Notes on Chapter 6 Integumentary System (Lecture notes-shortened)

Transcription

1 Notes on Chapter 6 Integumentary System (Lecture notes-shortened) I. Integumentary system- the skin and all of its accessory organs such hair, nails & gland II. Skin & its Tissues A. Skin is largest organ of body B. Functions 1. maintenance of homeostasis 2. regulates body temperature 3. prevents water loss from deeper tissues 4. houses sensory receptors 5. synthesizes various biochemicals a. When exposed to sunlight, produces precursor to Vitamin D b. Vitamin D is important for proper bone & tooth development 6. excrete small quantities of wastes 7. as a diagnostic tool C. Two layers 1. epidermis outer layer composed of stratified squamous epithelium 2. dermis thicker inner layer which contains connective tissue with collagen & elastin, epithelial tissue, smooth muscle tissue, nervous tissue, & blood 3. basement membrane separates two layers (anchored to dermis) D. Epidermis made of stratified squamous epithelium 1. avascular 2. two layers a. stratum basale lower layers very close to dermis 1) nourished by dermal blood vessels 2) living cells that grow & divide 3) cell division causes older cells to be pushed upward toward skin surface b. stratum corneum outer layer of epidermis 1) made of many layers of tough, dead cells 2) as cells move farther away from blood supply, they lose nourishment & eventually die 3) Keratinization process of older cells filling with keratin as they move upward a) cytoplasm fills with strands of tough, fibrous, waterproof protein (keratin) 4) layers are thick and waterproof 5) eventually, cells break apart & are sloughed off 3. Functions of epidermis a. protects against water loss b. prevents mechanical injuries c. protects against effects of harmful chemicals d. keeps out disease-causing microorganisms 4. Skin color a. melanin dark pigment that provides skin color 1

2 1) absorbs ultraviolet radiation & protects deeper cells from damage b. melanocytes specialized cells in epidermis that produce pigments 1) lie in deepest part of epidermis (stratum basale) & underlying connective tissue of dermis 2) some pigment lies in nearby epidermal cells 3) have long, pigment-containing cellular extensions that pass between epidermal cells 4) transfers melanin granules into epidermal cells by cytocrine secretion 5) all people have about the same number of melanocytes in skin; 60,000 melanocytes per square inch of skin c. differences in skin color is because of amount of melanin produced & distribution and size of pigment granules (heredity) d. environmental & physiology factors influencing skin color 1) Environmental factors a) sunlight & ultraviolet light b) X rays 2) Physiological factors a) Blood in dermal vessels b) Blood oxygen concentration c) Thickness of epidermis d) Hormones and preganancy e. cyanosis when blood oxygen concentration is low & gives skin a bluish appearance; indicates respiratory problems f. jaundice when carotene pigments accumulate in cells giving skin a yellowish color; indicates liver problems E. Dermis- made of dense connective issue with tough collagenous fibers & elastic fibers within gel-like ground substance 1. vascular a. blood supply helps regulate body temperature 2. has nerve fibers to receive & respond to stimuli 3. includes hair follicles, sebaceous glands, & sweat glands 4. cleavage or tension lines where collagen or elastic fibers are oriented in one direction more than others a. where skin is most resistant to stretch b. cuts against cleavage lines lead to gaps or scarring 5. stretch marks lines visible though the epidermis if the dermis is overstretched F. Subcutaneous layer (hypodermis) layer beneath the dermis made of loose connective & adipose tissues 1. collagen & elastic fibers within are continuous with those in dermis 2. most fibers run parallel to surface of skin extending in all directions 3. no distinct boundary between hypodermis & dermis 4. contains about half the body s fat (varies with sex, age, & diet) 5. Functions a. adipose tissue insulates and cushions 2

3 b. contains major blood vessels III. Accessory organs of skin A. Hair present on all skin surfaces except palms, soles, lips, nipples, & parts of external genitalia 1. hair follicles tubelike depression with epidermal cells a. extends from surface of skin into the dermis b. contains hair root which is growth area of hair that lies below the skin; made of stratified squamous epithelium c. dermal papillae projection of connective tissue at deep end of follicle that nourishes epidermal cells at base of follicle 1) form fingerprints & footprints where dermal papillae is in parallel, curving ridges that shape the overlying epidermis d. epidermal cells in follicle are nourished, grow, & divide e. as cells divide, push older cells toward surface f. older cells become keratinized and die 2. hair shaft part of hair extending away from the skin surface a. made of keratinized, dead epidermal cells 3. arrector pili bundle of smooth muscle cells attached to each hair follicle a. positioned so that hair in follicle stands on end when muscle contracts b. creates goose bumps or gooseflesh 4. hair color like skin created by type & amount of pigment in melanocytes a. no pigments creates white hair b. trichosiderin another pigment found only in red hair 5. hair growth occurs in a cycle of growth and rest a. during resting stage, hair is held in follicle b. when new hair is formed during the next growth stage, old hair falls out c. scalp hair grows for 3 years & rests for 1 to 2 years d. eyelashes grow for 30 days and rest for 105 days e. Male patterned baldness - sex-linked trait from mother B. Sebaceous glands oil glands in dermis 1. contain groups of specialized epithelial cells 2. attached to hair follicles 3. holocrine glands 4. produce sebum - secretion of oily mixture of fatty material & cellular debris a. helps keep hair & skin soft, pliable, & waterproof b. Blackheads caused when ducts are plugged c. Pimples caused when ducts are plugged and inflamed C. Nails protective coverings on ends of fingers & toes 1. consists of keratinized stratified squamous epithelial cells with very hard keratin 2. Nail body visible part of nail 3. Nail root located in nails proximal ends and is the region where cells divide to produce nails; covered by skin 3

4 a. eponychium/cuticle stratum corneum that grows onto the nail body 4. lunula half-moon shaped area at base of nail; is most active growing region of nail 5. nail bed/nail matrix layer of epithelium to which the nail remains attached; area of growth for nail a. as nail develops, it slides forward over nail bed b. is continuous with epithelium of skin c. grows continuously; does not have a resting stage D. Sweat Glands (sudoriferous glands) exocrine glands widespread throughout skin 1. consists of a tiny tube that originates as a ball-shaped coil in deeper dermis or hypodermis a. coiled portion is closed at its deep end b. lined with sweat-secreting epithelial cells c. 650 sweat glands per square inch of skin 2. Types: a. eccrine glands glands common on forehead, neck & back 1) most numerous sweat glands 2) type of merocrine gland 3) respond throughout life to body temperature elevated by environmental heat or physical exercise 4) sweat produced is carried to surface & released on surface of skin through pore 5) Sweat is mostly water, but also contains small amounts of salt, urea, & uric acid a) this makes sweat an excretory function b. apocrine glands glands in the axillary regions and groin 1) connect to hair follicles 2) produces thick secretion rich in organic substances a. body odor - sweat is odorless, but when broken down by bacteria causes smell 3) become active during puberty 4) sweat production occurs during strong emotions or pain c. modified sweat glands changed structurally and functionally to secrete specific fluids 1) ceruminous glands glands of external ear canal that secrete earwax 2) mammary glands in female; secrete milk IV. Effect of aging on integumentary system A. blood flow to skin is reduced B. skin becomes thinner & more transparent C. collagen decreases which causes skin to be more easily damaged & repair itself slower D. less elastic fibers & loss of fat causes skin to sag & wrinkle E. Decreased production of melanin V. Disorders of skin 4

5 A. Skin cancer most common type of cancer 1. caused by exposure to chemicals, radiation, & exposure to ultraviolet light (main cause) 2. Three types: a. Cutaneous carcinomas most common type of skin cancer 1) occur in light skinned people over forty years 2) occur in people regularly exposed to sunlight 3) develop from hard, scaly lesions that have reddish bases a) can be flat or raised b) firmly adhere to skin c) typically slow growing d) can be removed by radiation or surgery e) Two types i) basal cell carcinoma begins in stratum basale & extends into dermis producing an open ulcer ii) squamous cell carcinoma develops from cells superficial to stratum basal; produces nodular, keratinized tumor b. Melanoma rare form of cancer 1) develops from melanocytes 2) may arise from mole (nevus) 3) varied colors from brown, black, gray, or blue 4) irregular outlines 5) appear in people of any age 6) caused by short, intermittent exposure to high-intensity sunlight 7) grows horizontally at first, but then thickens and grows downward a) if removed while growing horizontally, it can be arrested 8) metastasis spreading of cancerous cells to other parts of body; occurs if melanoma is growing downward B. Burns- classified according to depth of burn 1. Partial thickness burns leave some of stratum basale viable; regenerate from burn area & edges of wound a. First degree burns involve only epidermis 1) symptoms include redness, pain, & slight edema (swelling) 2) caused by sunburn or brief exposure to hot or cold objects 3) heal without scarring in approximately one week b. Second degree burns damages epidermis & dermis 1) minimal damage causes redness, pain, edema, & blisters 2) deeper damage appears tan, red, or white & take months to heal 3) epidermis regenerates from epithelial cells in hair follicles & sweat glands 4) heals in two weeks months; some scarring 2. Full thickness burns third degree burns epidermis & dermis completely destroyed 5

6 a. often surround by areas of 1 st & 2 nd degree burns b. painless because sensory receptors have been destroyed c. appear white, tan, brown, black, or deep cherry red d. can cause excessive fluid loss e. must be isolated because of exposure to microorganisms f. form scars & skin grafts are often necessary g. take a lot of time to heal C. Acne disease of sebaceous glands that produces blackheads & pimples D. Athlete s foot fungus infection (tinea pedis) usually in the skin of the toes & soles E. Birthmark congenital blemish or spot on the skin; visible at birth or soon after F. Dermatitis inflammation of the skin G. Eczema noncontagious skin rash that produces itching, blistering, & scaling H. Herpes infectious disease of the skin, usually caused by the Herpes simplex virus and characterized by recurring formations of small clusters of vesicles I. Keloid elevated, enlarging fibrous scar usually initiated by an injury J. Mole fleshy skin tumor (Nevus) that is usually pigmented; colors range from brown to black K. Pediculosis disease produced by infestation of lice L. Scabies disease resulting form an infestation of mites M. Ulcer open sore N. urticaria allergic reaction of the skin that produces reddish, elevated patches (hives) O. wart flesh-colored, raise area caused by a viral infection P. hyperhidrosis a condition of unknown origin in which the person sweats for no apparent reason profusely, uncontrollably, and unpredictably Q. Liver spots caused by aging where melanocytes quite producing melanin except in accumulated areas causing dark splotches 6