Lesson 7 The Integumentary System The Integument Largest system of the body o 16 of body weight o 1 5 to 2 m2 in area Made up of two parts o Cutaneous membrane skin o Accessory structures Cutaneous Membrane o Two components Outer Epidermis Superficial epithelium epithelial tissues Inner Dermis Connective tissues Accessory Structures o Originate in the dermis o Extend through the epidermis to skin surface o Includes Hair Nails Multicellular exocrine glands Integumentary system is connected to o Cardiovascular system blood vessels in the dermis o Nervous system sensory receptors for pain touch and temperature Hypodermis Superficial Fascia or Subcutaneous Layer o Below the dermis o Loose connective tissue o Location of hypodermic injections Five functions of the skin o 1 Protection of underlying tissues and organs o 2 Excretion of salts water and organic wastes glands o 3 Maintenance of body temperature insulation and evaporation o 4 Production of melanin keratin vitamin D3 and storage lipids o 5 Detection of touch pressure pain and temperature Epidermis Composed of stratified squamous epithelium o Avascular nutrients and oxygen diffuse from capillaries in the dermis o Dominated by keratinocytes most abundant type of epithelial calls Contain large amounts of keratin protein Thin Skin Thick Skin o Covers most of the body o Has four layers of keratinocytes o Covers the palms of the hands and soles of the feet o Has five layers keratinocytes The five strata of keratinocytes in thick skin o From basal lamina free surface inferior to superior 1 Stratum basale 2 Stratum spinosum 3 Stratum granulosum 4 Stratum lucidum 5 Stratum corneum Stratum Basale Lowest layer Hemidesmosomes o Attaches the stratum basale to basement membrane Forms a strong bond between epidermis and dermis Forms epidermal ridges o Basis of fingerprints o Ridge patterns of skin increase surface area and friction ensuring a secure grip Dermal papillae tiny mounds o Increase the area of basement membrane o Strengthen attachment between epidermis dermis Has many basal cells or germinative cells Specialized cells of stratum basale o Merkel Cells Found in hairless skin Respond to touch trigger nervous system o Melanocytes Contain the pigment melanin Scattered throughout stratum basale Stratum Spinosum Spiny layer Produced by division of stratum basale 8 10 layers of keratinocytes bound by desmosomes Cells shrink until cytoskeletons stick out spiny Continue to divide increasing thickness of epithelium Contain dendritic Langerhans cells Active in immune response Stratum Granulosum Grainy layer Stops dividing starts producing Keratin Tough fibrous protein that makes up hair and nails Keratohyalin Dense granules cross link keratin fibers Cells of the stratum granulosum o Produce protein fibers o Dehydrate and die o Create tightly interlocked layer of keratin surrounded by keratohyalin Stratum Lucidum Clear layer Found only in thick skin Covers stratum granulosum Cells are flattened densely packed with keratin devoid of organelles Stratum Corneum Horn layer Top layer Exposed surface of skin 15 30 layers of keratinized cells All exposed skin surfaces except anterior of eyes undergo cornification keratinization o Formations of protective superficial layers of cells filled with keratin o Cells are dead linked together by desmosomes o Water resistant not waterproof o Shed replaced every 2 weeks It takes 15 30 days for a cell to move from stratum basale to stratum corneum o Cells may stay an additional 2 weeks before shedding off Perspiration occurs by stratum corneum o Insensible Perspiration Interstitial fluid lost by evaporation through the Lose about 500 mL 1 pint of H2O per day o Sensible Perspiration Water excreted by sweat glands Dehydration can result o From damage to stratum corneum Ex burns blisters insensible perspiration o From immersion in hypertonic solution Ex Seawater osmosis dangerous for shipwreck survivors Hydration can also occur through osmosis o Results from immersion in hypotonic solution Ex freshwater o Causes swelling of epithelial cells evident on palms soles Skin Color Influenced by two pigments o Carotene o Melanin Blood circulation red blood cells can affect skin color Carotene Orange yellow pigment o Found in orange vegetables Ex Carrots squashes if too much is consumed can turn skin orange carotenosis o Accumulates in epidermal cells and fatty tissues of the dermis o Can be converted to vitamin A for maintenance of epithelia photoreceptor function Lack causes night blindness nyctalopia Melanin Yellow brown or black pigment o Produced by melanocytes in stratum basale from the amino acid tyrosine o Stored in melanosomes transport vesicles o Transferred to keratinocytes o Albino individuals have melanocytes but lack the ability to produce melanin o Protects skin from sun damage Ultraviolet UV Radiation Causes DNA mutations and burns that lead to cancer and wrinkles Melanosomes of keratinocytes concentrate around nucleus to protect DNA o Skin color depends on melanin production not number of melanocytes Blood flow o Capillaries carrying blood can alter skin color o Oxygenated red blood contributes to skin color Blood vessels dilate from heat skin reddens Blood flow decreases skin pales o Cyanosis Bluish skin tint caused by severe reduction in blood flow or oxygenation Illnesses that affect skin color o Jaundice Buildup of bile produced by liver yellow color o Pituitary Tumor Excess MSH melanocyte stimulating hormone Extremely bronze tan o Addison s Disease Disease of the pituitary gland Releases more ACTH adrenocorticotropic hormone Similar effect on the skin color as MSH bronze tan o Vitiligo Loss of melanocytes loss of color Evidence points to autoimmune reaction by antibodies Vitamin D3 Production Vitamin D3 produced by epidermal cells in the presence of UV radiation Liver and kidneys convert vitamin D3 calcitrol o Aids absorption of calcium phosphorous Insufficient vitamin D3 o Can cause rickets bending of weak bones under body weight The Dermis Located between epidermis subcutaneous layer hypodermis Anchors epidermal accessory structures o Hair follicles o Sweat glands Two components o Outer papillary layer o Deep reticular layer Papillary Layer superficial o Consists of areolar tissue o Contains smaller capillaries lymphatics and sensory neurons o Has dermal papillae projecting between epidermal ridges Reticular Layer o Consists of dense irregular connective tissue o Contains larger blood vessels
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