INTEGUMENTARY SYSTEM CLASSIFICATION OF BODY MEMBRANES • Epithelial membranes • Cutaneous membranes • Mucous membranes • Serous membranes • Connective tissue membranes • Synovial membranes SEROUS MEMBRANES • Functions • Secretes serous (watery) fluids • Lubricates surfaces of membranes • Locations • Lines body cavities with no outside openings • Parietal pleura, parietal peritoneum • Covers organs • Visceral pleura, peritoneum SEROUS MEMBRANES • Examples of specific serous membranes • Peritoneum • Abdominal cavity • Pleura • Around the lungs • Pericardium • Around the heart MUCOUS MEMBRANES • Function • Secretes mucus • Locations • Lines cavities, tubes with outside openings • Examples: oral and nasal cavities • Digestive, urinary, respiratory, reproductive systems CONNECTIVE TISSUE MEMBRANE • Synovial membrane • Functions • Secretes synovial fluid • Lubricates ends of bones • Locations • Inner linings of joint cavities of bones of freely movable joints CUTANEOUS MEMBRANE • Functions • Example: Skin • Protection • Dry membrane • Temperature regulation • Outermost protective • Excretion of water and boundary salts • Sense organs • Locations • Epidermis • Dermis • Subcutaneous layers INTEGUMENTARY SYSTEM • Skin (cutaneous membrane) • Skin appendages (derivatives) • Sweat glands • Oil glands • Hair • Nails SKIN FUNCTIONS • Reduces water loss • Regulates body temperature • Excretes waste • Prevents harmful substances and microorganisms from entering the body • Synthesizes vitamin D • Protection form UV radiation • Sensory receptors in skin monitor external environment SKIN STRUCTURE • Epidermis—outer layer • Stratified squamous epithelium • Dermis • Dense connective tissue • Subcutaneous tissue (hypodermis) is deep to dermis • Not part of the skin • Anchors skin to underlying organs • Composed mostly of adipose tissue EPIDERMIS • Epidermis—outer layer • Stratified squamous epithelium • Often keratinized (hardened by keratin) • Thin skin: 1-3 mm • Thick skin: 4-5 mm • Soles of feet • Palms of hands • Functions • Shields underlying tissues from excess water loss • Protects from mechanical injury • Prevents entrance of pathogens • Protects deeper cells from sunlight damage CELLS OF THE EPIDERMIS • Keratinocytes • Filled with tough fibrous keratin • 90% of epidermis • Principal structural element of outer skin • Melanocytes • Contribute color to skin • Filter UV light • Defense mechanism LAYERS OF THE EPIDERMIS • Stratum corneum • Horny layer • Outermost layer of epidermis • Shingle-like dead cells are filled with keratin • Cell membranes are thick and chemically resistant • Desmosomes hold adjacent keratinocytes together • Barrier to water loss, microorganisms, harmful chemicals, physical trauma LAYERS OF THE EPIDERMIS • Stratum lucidum • Clear layer • Keratinocytes are clear and closely packed together • Occurs only in thick, hairless skin of the palms of hands and soles of feet LAYERS OF THE EPIDERMIS • Stratum granulosum • Granular layer • Keratinization begins • Cells degenerating • May be missing in some thin skin LAYERS OF THE EPIDERMIS • Stratum germinativum • growth layer • Made of s. spinosum and s. basale LAYERS OF THE EPIDERMIS • Stratum spinosum • Spiny layer • Prominent desmosomes • Gives cells “prickly” look. • Rich in RNA to initiate protein synthesis LAYERS OF THE EPIDERMIS • Stratum basale • Base layer • Deepest layer of epidermis • Lies next to dermis • Cells undergoing mitosis LAYERS OF THE EPIDERMIS • Summary of layers from deepest to most superficial • Stratum basale • Stratum spinosum • Stratum granulosum • Stratum lucidum (thick, hairless skin only) • Stratum corneum LAYERS OF THE EPIDERMIS EPIDERMIS • Regeneration time • Approximately 35 days • Accelerated abrasion triggers increased mitotic activity, shortened turnover, and a callus develops EPIDERMIS: BLISTERS • Basic reaction of skin injury • Desmosomes are weakened or destroyed by physical or chemical stress • Skin falls away from body and fills with fluid • Results from burns, friction injuries, exposure to primary irritants, accumulation of toxic products following cell death in skin DERMIS • Thick layer with collagen and elastin fibers that give skin strength and flexibility • 0.5 mm in eyelids to 4 mm thick in the soles and palms • Function • Protection against mechanical injury • Provides padding • Storage area for water and electrolytes • Network of nerves and nerve endings provide sensory information • Muscle fibers, hair follicles, sweat, sebaceous glands, and blood vessels located here • Two layers: • Papillary • Reticular DERMIS: PAPILLARY LAYER • Upper dermal region • Thinner layer • Projections called dermal papillae • Project into epidermis • Epidermis clings tightly , forming ridges • important to survival • Allows us to grip surfaces to walk and grasp tools DERMIS: RETICULAR LAYER • Deepest skin layer • Thicker layer • Tough, interlacing white collagenous fibers • Elastic fibers allow stretching • Contains skeletal muscle in face and scalp, allowing for facial movements • Arrector pili muscles (smooth muscle) attached hair follicles • Blood vessels • Sweat and oil glands • Deep pressure receptors DERMIS: RETICULAR LAYER • Regeneration • Does not regenerate much • To heal wounds, fibroblasts reproduce and form an unusually dense mass of new connective tissue • Results in scar if not replaced by normal tissue STRETCH MARKS • Elastic fibers stretched too much, weaken, and tear. • Forms pinkish or bluish depressed furrows • When healed, striae (furrows) appear as silver/ white scar lines TEMPORARY COLOR CHANGES OF SKIN • Vasoconstriction • When skin blood vessels constrict, blood volume is reduced and skin becomes paler. • Vasodilation • When blood vessels dilate, skin becomes pinker • Cyanosis • Excess amount of unoxygenated hemoglobin in blood of skin capillaries SUBCUTANEOUS LAYER • Layer of tissue below the dermis attaching the skin to the underlying muscle or bone • Rich in fat and areolar tissue • Density and arrangement of fat cells and collagen fibers determine the relative mobility of skin SKIN STRUCTURE NORMAL SKIN COLOR DETERMINANTS • Melanin • Yellow, brown, or black pigments • Carotene • Orange-yellow pigment from some vegetables • Hemoglobin • Red coloring from blood cells in dermal capillaries • Oxygen content determines the extent of red coloring MELANIN • Pigment (melanin) produced by melanocytes • Number of melanocytes produces is about the same among all races • Melanocytes are mostly in the stratum basale • Amount of melanin produced depends upon genetics and exposure to sunlight • Accounts for most color variations SKIN COLOR • Amount of melanin produced accounts for most skin color variations • Amino acid tyrosine is converted to melanin • Pigment granules are transferred to other epidermal cells • Process regulated by tyrosine (responsible for bruises in fruit) FACTORS AFFECTING SKIN COLOR • Heredity (4-6 genes) • Sunlight • Prolonged exposure causes increased production • Hormone secretion • Adrenocorticotropic hormone (ACTH) • Melanocyte stimulating hormone (MSH) • Increasing age • Decrease in tyrosine activity • Results in gray hair SKIN APPENDAGES • Hair • Hair follicles • Nails • Cutaneous glands are all exocrine glands • Sebaceous glands • Sweat glands APPENDAGES OF THE SKIN: HAIR • Location • Found everywhere except palms, soles, lips, nipples, areas of genitalia • Functions • Protection • Regulation of body temperature • Produced by hair follicle • Small tube formed by epidermal cells that spread down into dermis APPENDAGES OF THE SKIN: HAIR • Consists of hard keratinized epithelial cells • Germinal matrix: Responsible for forming hairs. Cells become keratinized as they push upward following mitosis. • Hair papilla • Small mound of dermis protruding into matrix containing capillaries to nourish matrix • Melanocytes provide pigment for hair color APPENDAGES OF THE SKIN: HAIR • Hair anatomy • Root: hidden in follicle • Shaft: visible part of hair • Central medulla: inner core. • Cortex surrounds medulla. Layers of keratinized cells. Amount of melanin deposited here determines color, adds strength. • Cuticle on outside of cortex • Most heavily keratinized APPENDAGES OF THE SKIN: HAIR • Associated hair structures • Hair follicle • Dermal and epidermal sheath surround hair root • Arrector pili muscle • Smooth muscle • Pulls hairs upright when cold or frightened • Sebaceous gland • Sweat gland APPENDAGES OF THE SKIN: HAIR APPENDAGES OF THE SKIN: NAILS • Scale-like modifications of the epidermis • Heavily keratinized • Stratum basale extends beneath the nail bed APPENDAGES OF THE SKIN: NAILS • Nail structures • Free edge • Nail body is the visible attached portion • Root of nail embedded in skin; hidden by cuticle • Lunula: crescent shaped white area • Nail bed: layer of epithelium under nail. APPENDAGES OF THE SKIN: SWEAT GLANDS • Fluid rich in salts, ammonia, uric acid, urea, other wastes • Widely distributed in skin • Two types • Eccrine glands • Apocrine glands APPENDAGES OF THE SKIN: SWEAT GLANDS • Eccrine sweat glands • Structure: simple, coiled, tubular gland • Location: most numerous • Distributed all over body surface except lips, ear canal, glans penis, and nail beds • Function • Help maintain constant core temperature by producing sweat APPENDAGES OF THE SKIN: SWEAT GLANDS Apocrine sweat glands Structure: simple, branched tubular glands connected with hair follicles Location: deep in subcutaneous layer of axilla, areola of breast, pigmented skin around anus Function Enlarge and begin to function at puberty.