LESSON 7 THE INTEGUMENTARY SYSTEM The Integument Is the largest system of the body o 16 of body weight 1 5 to 2m 2 in area o The integument is made up of two parts Cutaneous membrane skin Accessory structures Cutaneous Membrane consists of two components Superficial epithelium epithelial tissues o Outer epidermis o Inner dermis Connective tissues Accessory Structure o Originate in the dermis o Extend through the epidermis to skin surface Includes Hair Nails Multicellular exocrine glands The 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 not part of integument o Below the dermis o Loose connective tissue separates integument from deep fascia around other organs o Location of hypodermic injections Five main functions of the skin Protection of underlying tissues and organs Excretion of salts water and organic wastes glands Maintenance of body temperature insulation and evaporation Production of melanin keratin vitamin D3 and storage of lipids 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 cells 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 of keratinocytes five strata of keratinocytes in thick skin The From basal lamina to free surface inferior to superior o Stratum basale o Stratum spinosum o Stratum granulosum o Stratum lucidum o Stratum corneum 1 Stratum Basale lowest layer Is attached to basement membrane by Hemidesmosomes Forms a strong bond between epidermis and dermis Forms epidermal ridges basis of fingerprints Dermal papillae tiny mounds o Increase the area of basement membrane o Strengthen attachment between epidermis and dermis Has many basal cells or germinative cells Ridge patterns on skin increase surface area and friction ensuring a secure grip 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 2 Stratum Spinosum the spiny layer Produced by division of stratum basale Eight to ten 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 3 Stratum Granulosum the grainy layer Stops dividing starts producing Keratin Keratohyalin o A tough fibrous protein o Makes up hair and nails o Dense granules o Cross link keratin fibers Cells here o Produce protein fibers o Dehydrate and die o Create tightly interlocked layer of keratin surrounded by keratohyalin 4 Stratum Lucidum the clear layer Found only in thick skin Covers stratum granulosum Cells here are flattened densely packed with keratin devoid of organelles 5 Stratum Corneum the horn layer Exposed surface of skin 15 30 layers of keratinized cells All exposed skin surfaces except anterior of eyes undergo cornification keratinization formations of protective superficial layers of cells filled with keratin o Cells are dead and linked together by desmosomes o Water resistant not waterproof o Shed and replaced every 2 weeks It takes 7 10 days for a cell to move from stratum basale to stratum corneum cells may stay an additional 2 weeks before shedding off Perspiration can occur by o Insensible perspiration Interstitial fluid lost by evaporation through the stratum corneum lose about 500ml or 1 pint of H2O per day o Sensible perspiration Water excreted by sweat glands Dehydration can result o From damage to stratum corneum e g burns and blisters insensible perspiration o From immersion in hypertonic solution e g seaweater osmosis dangerous for shipwreck survivors Hydration can also occur through osmosis o Results from immersion in hypotonic solution e g freshwater osmosis o Causes swelling of epithelial cells evident on the palms and soles o You pick up water through osmosis Skin Color is influenced by two pigments Carotene o Orange yellow pigment o Found in orange vegetables Ex Carrots squashes if consume too much 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 epithelial and photoreceptor function lack causes night blindness nyctalopia o Yellow brown or black pigment o Produced by melanocytes in stratum basale from the amino acid Melanin tyrosine o Stored in transport vesicles melanosomes o Transferred to keratinocytes o Note Albino individuals do not have melanocytes just do not have ability to produce melanin Also blood circulation red blood cells can affect skin color Melanin protects skin from sun damage o Ultraviolet UV radiation Causes DNA mutations and burns that lead to cancer and Melanosomes of keratinocytes concentrate around nucleus to o Note Skin color depends on melanin production not number of wrinkles protect DNA melanocytes Skin Color Caused by Blood Flow 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 Jaundice o Buildup of bile produced by liver o Yellow color Pituitary Tumor o Excess MSH melanocyte stimulating hormone o Extremely bronze tan o A disease of the pituitary gland release more ACTH similar effect on o Loss of melanocytes evidence points to autoimmune reaction by Addisons disease skin color as MSH o Skin darkening Vitiligo antibodies o Loss of color Vitamin D3 Production Epidermal cells produce vitamin D3 in the presence of UV radiation Liver and kidneys convert vitamin D3 into calcitriol o Aids absorption of calcium and phosphorus Insufficient vitamin D3 o Can cause rickets bending of weak bones under body weight The Dermis Located between epidermis and subcutaneous layer Hypodermis but is not part of integumentary system Anchors epidermal accessory structures hair follicles sweat glands Two components o Outer Papillary layer Superficial Consists of areolar tissue Contains smaller
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