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Membranes and the Integumentary System Chapter 3 Body membranes Cover surfaces Line body cavities Form protective sheets around organs Two major groups (classified by tissue makeup) Epithelial membranes Connective tissue membranes Epithelial membranes Include: Cutaneous membrane (skin) Mucous membranes Serous membranes All include a layer of epithelium but it is connected to a layer of connective tissue These are actually organs! Cutaneous membrane Skin Superficial epidermis Made of keratinizing stratified squamous epithelium Exposed to air A dry membrane (more info to come later) Mucous Membranes Called mucosa Epithelium resting on loose connective tissue membrane (lamina propria) Lines all body cavities that open to the exterior (respiratory, digestive, urinary, reproductive) Most contain stratified squamous or simple columnar epithelial cells These are “wet” membranes continuously bathed in secretions Serous membranes Called serosa Simple squamous epithelium resting on areolar connective tissue Line body cavities closed to the exterior (except the dorsal body cavity and joint cavities) Occur in pairs Parietal layer lines a part of the ventral body cavity Visceral layer covers the outside of the organs in the cavity Layers are separated by serous fluid (that prevents friction) Named for their locations Peritoneum – lines the abdominal cavity Pleura – surrounds the lungs Pericardium – surrounds the heart Connective tissue membranes Called synovial membranes Soft areolar connective tissue and have NO epithelial cells Line fibrous capsules around joints Provide a smooth surface and secrete lubricating fluid Line the bursae and tendon sheaths Cushion organs moving against each other during muscle activity Integumentary system Made of sweat and oil glands, hairs, nails, skin Mostly a protective organ Skin functions Controls homeostasis (in part) because it keeps things inside the body but also keeps things outside the body Insulation and cushioning for deeper organs Protects body from mechanical, chemical, and thermal damage, UV radiation, and bacteria Upper layer is full of keratin to prevent water loss Rich capillary network and sweat glands control temperature Excretes urea, salts, and water in perspiration Manufactures vitamins (Vitamin D) Cutaneous sensory receptors help detect touch, pressure, pain, and temperature Structure of skin Two kinds of tissue Epidermis – stratified squamous epithelium can keratinize or become tough Dermis – dense connective tissue Subcutaneous tissue (hypodermis) Adipose tissue (not part of the skin) anchors the skin to underlying organs Shock absorber Insulates Epidermis Five layers or strata Stratum basale (deepest) Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum corneum (outermost layer) Avascular – no blood supply Most cells are keratinocytes (produce keratin) that make the skin tough and protective Stratum basale Deepest layer of the epidermis Lies closest to the dermis Cells receive nutrition by diffusion from dermal cells Cells constantly undergo mitosis Daughter cells pushed upward away from the dermis and eventually become part of the stratum spinosum, then the stratum granulosum They become flatter and full of keratin, and die to become part of the stratum lucidum (only in areas with no hair: palms and feet) Stratum corneum Outermost layer of epidermis 20-30 cells thick Makes up about 75% of epidermal thickness These are dead, shingle-like cell remnants that are cornified (full of keratin and very tough) Most protective layer, but shed cells constantly Produce a new stratum corneum every 25-45 days Melanin Skin pigment Ranges from yellow to brown to black Produced by melanocytes (stratum basale cells) Exposure to sun stimulates cells to produce more melanin Stratum basale cells phagocytize the pigment Melanin makes a “umbrella” on the sunny side of the nucleus to protect DNA from UV radiation Freckles and moles appear where melanin is concentrated Sun exposure Excessive exposure to the sun damages skin Elastic fibers clump (making skin leathery) Depresses the immune system Can alter DNA in skin cells leading to skin cancer Black people rarely have skin cancer due to the protective effects of melanin Dermis Strong, stretchy Holds the body together Dense fibrous connective tissue has 2 regions Papillary reticular Varies in thickness Very thick on palms and soles of feet Very thin on eyelids Papillary layer Upper dermal region Uneven with fingerlike projections (dermal papillae) May contain capillary loops to provide nutrients to the epidermis May have pain receptors and touch receptors (Meissner’s corpuscles) On palms and soles, form loops and whorled ridges to provide grip On fingertips, ridges have sweat pores (provide the fingerprints) Dermal papillae are genetically determined Reticular layer Deepest skin layer Contains blood vessels, sweat and oil glands, and pressure receptors (Pacinian corpuscles) Have lots of phagocytes to get rid of bacteria Collagen and elastin fibers give toughness Collagen also binds water to keep the skin hydrated Blood vessels help maintain body temperature Dilate to release heat Constrict to retain heat Restriction of dermal blood supply Restriction of blood supply results in cell death Prolonged = decubitus ulcers Loss of blood supply results in cracks and permanent damage Degeneration and ulcers occur Skin color Three pigments contribute to skin color Amount and kind of melanin in epidermis Amount of carotene deposited in stratum corneum (carotene is a yellow-orange pigment found in orange, deep yellow, and leafy green vegetables) Amount of oxygen bound to hemoglobin (pigment in red blood cells) in the dermal blood vessels High melanin production produces brown-toned skin Caucasians have less melanin so the pink-rosy color from hemoglobin shows through transparent cells Skin color Low oxygen in hemoglobin makes caucasians appear bluish (cyanosis) Common during heart failure and breathing disorders Doesn’t show in dark-skinned people but will be obvious in fingernails and mucous membranes Skin color can be influenced by emotional stimuli Skin color Skin color changes can sometimes indicate disease states Redness (erythema) can be due to embarrassment, fever, hypertension, inflammation, or allergy Pallor (blanching): emotional stress (fear, anger), anemia, low blood pressure, impaired blood flow Jaundice (yellowing): liver disorder causing bile pigments to be absorbed in blood and deposited in tissues Bruises: blood has left circulation and clotted in tissues; unusual bruising can indicate vitamin C deficiency or hemophelia Skin appendages Cutaneous glands Exocrine glands that release secretions into the skin surface by ducts Found in the dermis Include sebaceous glands and sweat glands Hairs and hair follicles Nails Sebaceous (oil) glands Found all over skin (except palms and soles) Ducts empty into hair follicles, some open to the skin surface Produce sebum (oil and fragmented cells) Keeps skin soft and moist Kills bacteria Become very active when male sex hormones are produced (highly productive during puberty) Problems with sebaceous glands Blocked ducts result in “whiteheads” Blockage that oxidizes and dries results in “blackhead” Acne is an active infection of the sebaceous glands or “pimples”. Seborrhea (cradle cap) common in infants is the result of over-active sebaceous glands Pink, raised lesions that become brown and crusty Sloughs off as oily dandruff Careful washing helps remove it Sweat glands (sudoriferous) Widely distributed in skin Two types Eccrine More numerous Produce sweat (water, salts, and metabolic wastes) which is acidic Releases sweat to the skin via pores Aprocrine Found in axillary (under arms) and genital areas Ducts empty into hair follicles Secretion contains fatty acids, proteins, and sweat Eccrine glands Sweat produced is used for Killing bacteria and preventing them from entering the body (low pH inhibits bacterial growth) Controlling body temperature Evaporative cooling of the skin surface (sweat evaporates off the skin) helps keep body temperature within a normal range) Apocrine glands Secretions may appear milky or yellowish, are odorless Bacteria on the skin may use the proteins as a food producing an unpleasant musky odor Glands begin to function during puberty, influenced by androgens (hormone that controls male, secondary sex characterisitcs) Minimal role in thermoregulation Activated by nerve fibers during pain, stress, and sexual foreplay Hairs and hair follicles Hair has minimal functions for humans Guards the top of the head Prevents debris from getting in eyes Keeps foreign particles out of respiratory tract In early humans (and mammals) hair is insulation and a means of controlling body temperature. Hairs and hair follicles Hairs produced by hair follicles Root is enclosed by the follicle Shaft projects from the skin surface Hair produced by division of stratum basale epithelial cells in growth zone (hair bulb matrix) As hair grows, it becomes keratinized and dies (shaft is mostly dead material and protein) Hair Hair has 3 regions Medulla (central region) Cortex (bulky area around the medulla) Cuticle (surrounds the cortex) Keeps hairs separated and prevents matting Provides strength Wears away at the tip resulting in “split ends” Hair Pigment Produced by melanocytes in hair bulb Varying amounts and types of melanin Hair Sizes and shapes vary Depends on shape of the hair shaft Shaft is oval – hair is wavy Shaft is flat – hair is curly or kinky Shaft is round – hair is straight and coarse Born with all the follicles you will ever have Hair is everywhere EXCEPT palms, soles, nipples, lips Hormones produce hair as secondary sex characteristics Hair follicles Arrector pili (smooth muscles) connect follicle to the dermal tissue; if contracted make hair stand up (goose bumps) Has two areas Epidermal sheath Epithelial tissue and forms hair Dermal sheath Dermal connective tissue Supplies blood vessels and reinforcement Nails Scale-like modification of the epidermis Three parts Free edge Body (visible attached portion) Root (embedded in the skin). Nail fold – skin folds that border / overlap the nail Cuticle – thick proximal nail fold Nails Stratum basale Extends beneath the nail as the nail bed Thickened are is the nail matrix (makes nails grow) Nails become keratinized and die N ails - mostly nonliving materials - nearly transparent (appear pink due to blood supply) - thickened nail matrix looks white (crescent at end) is the lunula Injuries to the skin Minor injuries (cuts, abrasions, blisters) heal quickly Skin regenerates epidermal cells every 25-45 days Infection is always a concern Decubitus ulcers Pressure ulcers (bed sores) Caused by localized pressure that restricts blood flow causing cells to die Most common over bony areas (lower back, coccyx, hips, elbows, ankles) but can occur everywhere Most often seen in people undergoing prolonged bed rest or those that are bed ridden Treatment includes oral antibiotics and removal of dead tissue Tissue removal can be surgical or vacuum-assisted Burns Due to exposure to excessive heat, corrosive chemicals, electricity, or UV radiation Cause tissue damage and cell death First degree Only on epidermal layer Reddening of the skin and mild pain; heal within 1 week (sunburn) Second degree Damage to epidermis and upper dermis Blisters; intense pain, longer healing times Third degree Destroy entire thickness of skin Damages nerve endings (so initially no pain) Scarring and severe pain come later; must be treated with grafting Burns Rule of nines- used to estimate the extent of the burned tissue 9% -for both anterior and posterior head and neck 18% -for anterior and 18% for posterior of torso 9% -for both anterior and posterior of each arm 18% -for both anterior and posterior of each leg 1% -for genital region Infections Herpes infections causes small, painful, blister-like sores Herpes will stay with the person for a life time but is usually dormant Flare-ups accompany periods of stress or illness Herpes varicella (chickenpox)- childhood disease; highly infectious Herpes zoster (shingles)- caused by herpes varicella taking a different form; extremely painful blisters/rash with headache, fever, chronic nerve pain Infections Herpes simplex 1 – (cold sores or fever blisters) occur around the mouth Herpes simplex 2 – genital herpes Both forms are highly contagious and can be transmitted to the mouth or genital areas Infections Human papillomavirus (HPV)-(warts) On hands and fingers generally disappear without treatment Plantar warts grow inward on the feet and can be painful Genital warts are the most common STD in the U.S.; can be spread by direct contact during vaginal, anal, or oral sex Two categories Low risk – cause warts on skin around the genital area and anus but do not cause cancer High risk – cause cervical cancers, most anal cancers, and 50% of all vaginal, vulvar, and penile cancers o Cause cancers of soft palate, base of tongue, tonsils Fungal infections Occur in areas of the body that are moist More prevalent in warm weather More common in people that have frequent periods of sweating Fungal infections Athlete’s foot (Tinea pedis)-most common; cracked, flaky skin between toes on sides of foot, can be red and itchy; highly contagious Jock itch (Tinea cruris)-in males around the groin and scrotum; caused by sweating and friction from clothing; spread through direct contact with skin or unwashed clothes Ringworm (Tinea corporis)-red, ring-shaped rash with pale center; highly contagious, common in children Toenail fungus (Tinea unguium)-fungal infection under the nails of the fingers or toes; discoloration and thickening; needs a prescription Bacterial infections Impetigo – highly contagious staph infection; common in elementary children; pink, blister-like bumps on face around mouth that develop a yellow crust Cellulitis – staph infection, inflamed area of the skin; red, swollen, and painful Inflammation of the skin General response to tissue injury or disease Increases blood flow, and sends WBCs to attack infectious agents and destroy dead tissue Causes pain and swelling Inflammatory conditions Pleurisy – inflammation of the pleura (membrane) that lines the thoracic cavity and lungs; produce “friction rub” with each breath; painful, can lead to a bluish color, shortness of breath, coughing Psoriasis – redness and irritation; areas of thick, red skin with flaky white patches (scales) that itch, burn, crack, bleed; autoimmune disorder or inappropriate immune response to a substance in the skin; NOT contagious but may be hereditary; most common on elbows, knees, and trunk but may occur anywhere Skin cancers Most common cancers in U. S. Over exposre to the sun or UV radiation is a major risk Basal cell carcinoma – most common, least malignant; can be surgically removed before they spread Squamous cell carcinoma – seen mostly on scalp, ears, lower lip, backs of hands in fair-skinned people; grow rapidly and can spread to lymph nodes; surgically removed and treated with radiation to cure Malignant melanoma – most serious; typically dark colored and irregular in shape