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Integumentary AKA Skin. Introduction. Skin comprises the largest organ system in the body Weighs approximately 17 Kg Takes up 2.0 square meters. Functions. Regulates body temp. Acts as an excretory organ Stores chlorides
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Introduction • Skin comprises the largest organ system in the body • Weighs approximately 17 Kg • Takes up 2.0 square meters
Functions • Regulates body temp. • Acts as an excretory organ • Stores chlorides • Manufactures vitamin D which is essential for the mineralization of bones and teeth • Serves as the most extensive and varied of the sense organs – high concentration of sensory receptors, especially where this is critical – lips, finger tips
The Envelope • Prevents the loss of essential host constituents or the entry into the host of toxic physical, chemical and microbiotic agents • Properties go beyond a mere envelope • Is waterproof and prevents the evaporation and escape of tissue fluids • Becomes thick when subjected to rough treatment • Fastened down where most likely to be pulled off • Has friction ridges to lessen slippage – e.g., finger tips
Anatomy • Non-Homogeneous • Large differences in form, color, and consistency in various parts of the same body • Three distinct types of tissue – epidermis, dermis, and subcutaneous
Epidermis • Ectodermal embryonic origin – two basic layers – superficial and deep • Two main cell types are Melanocytes or pigment cells and Karatinocytes or epithelial cells • Superficial layer is called the StratumCorneum • Dead layer, less than 1 micrometer thick • Consists of several strata of dry, flattened, scaly cells without visible nuclei • The surface cells are perpetually being rubbed away and replaced by cells from the next layer – the Germative layer
Germative Layer • AKA Basal Layer • This layer is living • Cell division occurs here and the cells biochemically and functionally mature as they ascend through the more superficial layers • Elapsed time from the cell division to shedding is at least 4 weeks – in abnormal states such as psoriasis = may turn over in 4 days
Dermis • Has a mesodermal embryonic origin, similar to CT • Primarily made up of collagen, elastin, and reticulin fiber • Dermis accounts for 5% of body mass • The outer aspect of dermis nearest to the epidermis is called the papillary dermis – rich in nerves, vessels, and various sensory receptors
Dermis • The deeper dermis is called the ReticularDermis that contains the cutaneous vascular network • These vessels subserve the thermoregulatory functions • Also, there are more neuroreceptors and lymph glands
Subcutaneous Tissue • Deep to dermis • Fatty structure of various thickness • Functions as a thermal barrier and protective cushion • AKA superficial fascia or tela subcutanea
Skin Color • Due primarily to melanin, a pigment in the epidermis and to carotene, a pigment in dermis as well as the blood in the capillaries of the dermis • Melanin is synthesized in cells called melanocytes – found in basal layer • Number of melanocytes is essentially the same in all races. Therefore, differences in skin color due to the amount of pigment the melanocytes produce and disperse • When skin is exposed to ultraviolet radiation – enzymatic activity is increased and both the amount and darkness of melanin increase and the skin darkens as a protective measure
Sweat Glands • Two types – eccrine and sebaceous • Eccrine – produce watery sweat that reaches the surface of skin – found in very high concentration throughout the body and serve to regulate temperature • Sebaceous – are outgrowths of hair follicles into the dermis • Are filled with cells which secrete greasy substance called sebum and give skin a greasy feels and make the skin waterproof • Are found in high concentration in upper torso
Hairs • Are distributed throughout the whole body except selected areas • May be short or long • Have a shaft which projects beyond skin surface, a root that lies in a follicle of the skin and a bulb • Hairs last 2-4 years on head, 3-5 months on an eyelash • The erector pili muscles are bundles of smooth muscle that pass next to the hairs, are involuntary, cause hairs to stand up, typically an ANS reaction to fear
Brief Overview of Burns • 1st degree – damages only epidermis, a sunburn with reddening of the skin • 2nd degree – burn destroys much of the epidermis but leaves some epidermal remnants • Re-growth from remnants is possible • Blisters are common and pain is often severe since the skin nerves are irritated by the products of cellular destruction
Burns • 3rd Degree – reaches to and thru dermis – often exposing muscle and bone • No epidermal remnants are present • Little or no feeling because of destruction of nerves • Treatment requires skin grafts to provide epidermal cells • Healing is slow at best
Major Problems of Burns • Infection • Maintaining fluid • Maintaining electrolyte balance which requires food and fluid intake • Contractures of skin and underlying CT and muscle (all soft tissue) due to intense scarring
Other Common Problems with Skin • Decubitus Ulcers – AKA bed or pressure sores • Caused by constant deficiency of blood to tissues overlying a bony prominence subjected to prolonged pressure – especially if CNS or PNS not functioning fully • Tissue breakdown leads to infection, necrosis, etc.
Skin Problems • Skin Cancer • Prolonged overexposure to sunlight is primary cause with higher risk for fair skin • South and southwest have higher incidence • Main types • Basal Cell – most common • Appears as small, shiny, fleshy nodules on the head, neck and/or hands • Untreated, the nodular lesions will begin to bleed, crust over, and repeat the cycle • Does not metastasize – may cause localized destruction of tissue
Problems • Squamous Cell • Nodules or red, scaly, plate-like patches that are sharply outlined • Typically develops on ear, lips, mouth and can metastasize • Cure rate for basal and squamous is 95% if treated
Problems • Melanoma • Uncommon • Serious, can metastasize, can lead to death • Appears as a dark brown or black mole-like growth with irregular borders and irregular pigmentation • Lesions may turn shades of gray, blue and white • Most common sites are upper back in males and female, anterior body in males, lower legs in females
