Chapter 5 The Integumentary System 21 09 00 Introduction to the Integumentary System Is the largest organ system of the body o 16 of body 1 5 to 2 m 2 in area o The integument is made up of two parts 12 10 2011 Cutaneous membrane skin which consists of two parts Outer Epidermis superficial epithelium epithelial Inner dermis connective tissues Accessory Structures Originates in the dermis Extended through the epidermis to skin surface 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 o Below the Dermis o Loose connective tissue o Location of hypodermic injections Five Main Functions of the skin o Protection of underlying tissues and organs o Excretion of salts water and organic wastes glands o Maintenance of body temperature insulation and o Production of melanin keratin vitamin D3 and storage of evaporation lipids o Detection of touch pressure pain and temperature Epidermis Composed of stratified Squamous epithelium o Avascular nutrients and oxygen diffuse from capillaries in the o Dominated by keratinocytes most abundant type of epithelial dermis cells 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 The five strata of keratinocytes in thick skin o From basal lamina to free surface Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum Stratum Basale Lowest layer Forms a strong bond between epidermis and dermis Forms epidermal ridges Dermal papillae tiny mounds Is attached to basement membrane by hemidesmosomes o Increase the area of basement membrane o Strengthen attachment between epidermis and dermis Has many basal cells or germinative cells Specialized Cells of the 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 the spiny layer Produced by division of stratum basale Eight to ten layers of keratinocytes bound by desmosomes Calls shrink until cytoskeletons stick out spiny Continues to divide increasing thickness of epithelium Contain dendritic Langerhans cells active in immune response Stratum Granulosm the grainy layer Stops dividing starts producing o Keratin o Keratohyalin A tough fibrous protein Makes up hair and nails Dense granules Cross link keratin fibers Cells here o Provide protein fibers o Dehydrate and die o Create tightly interlocked layer of keratin surrounded by keratohyalin Stratum Lucidum the clear layer Found only in the thick skin Covers stratum granulosum Stratum Corneum the horn layer Exposed surface of the skin 15 30 layers of keratinized cells All exposed skin surfaces except anterior of eyes undergo cornification keratinization formation of protective superficial layers of cells filled with keratin o Cells are dead and linked together by desmosomes o Water resistant o Shed and replaced every two weeks It takes 15 30 Days for a cell to move from stratum basale to stratum corneum Stratum Corneum is Water Resistant Perspiration can occur by o Insensible perspiration Interstitial fluid lost by evaporation through the stratum corneum lose about 500 mL or 1 pint of water a day o Sensible Perspiration Water excreted by sweat glands Dehydration results from damage to stratum corneum e g burns and blisters insensible perspiration Hydration can also occur through osmosis o Results from immersion in hypotonic solution e g freshwater o Causes swelling of epithelial cells evident on the palms and osmosis soles o Carotene Skin Colors Skin color is influenced by two pigments Orange yellow pigment Found in orange vegetables Accumulates in epidermal cells and fatty tissues of the dermis o Melanin Can be converted to vitamin A for maintenance of epithelia and photoreceptor function Yellow Brown or black pigment Produced by melanocytes in stratum basale Stored in transport vesicles melanosomes Transferred to keratinocytes Note albino individuals do have melanocytes just do not have the ability to produce melanin Functions of Melanocytes Melanin protects skin from sun damage o Ultraviolet UV radiation causes DNA mutations and burns that lead to cancer and wrinkles o Note Skin color depends on melanin production not number of melanocytes Skin Color Caused by Blood Flow Capillaries carrying blood can alter skin color o Oxygenated red blood contribute to skin color Blood vessels dilate from heat skin reddens Blood flow decreases skin pales o Cyanosis bluish skin tint Cause by severe reduction in blood flow or oxygenation Illnesses that Affect Skin Color Jaundice o Buildup of bile produced by liver o Yellow color in skin Pituitary Tumor o Excess MSH Addison s Disease o A disease of the pituitary gland o Skin darkening Vitiligo o Loss of melanocytes o Loss of color Vitamin D3 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 bow legged picture in slides The Dermis The Dermis is located between the epidermis and the subcutaneous layer Anchors epidermal accessory structures hair follicles sweat glands Two Components o Papillary Layer Consists of areolar tissue Contains smaller capillaries lymphatics and sensory Has dermal papillae projecting between epidermal neurons ridges o Reticular Layer Consists of dense irregular connective tissue Contains larger blood vessels lymphatic vessles and nerve fibers Contains collagen and elastic fibers Contains connective tissue proper Inflammation of the Dermis Dermatitis o An inflammation of the papillary layer caused by infection radiation mechanical irritation or chemicals e g poison ivy o Characterized by itch or pain Fibers found in the Dermis Dermal strength and elasticity by o Presence of two types of fibers Collagen fibers Very strong resist stretching but bend easily Limit the flexibility of elastic fibers to prevent damage to tissue Elastic Fibers Permit stretching and them recoil to original length Provide flexibility Cleavage Lines Cleavage lines are formed from o Collagen and elastic fibers in the dermis Arranged in parallel bundles Resist force in a specific direction Cleavage tension lines
View Full Document
Unlocking...