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Integumentary System Integumentary System collagen
Integumentary System •Largest organ •Average adult skin is 2 square meters •From birth to adulthood will increase in size 7-fold •Weights approx. 6 lbs. •Receives 1/3 of circulating blood •Varies in thickness from 0.5 mm (tympanic membrane) to 6 mm (soles of feet and palms of hands) •One centimeter of skin contains: 15 sebaceous glands; 3 yards of blood vessels; 100 sweat glands; 3000 sensory cells; 4 yards of nerves; 300,000 epidermal cells; and 10 hair follicles Functions of the Skin: •Protection – physical barrier against trauma, bacterial invasion, excessive loss of fluids and proteins, skin cells provide immunity protection, skin pigmentation protects against UVR •Sensation – feel pain, pressure and temp (nerve endings) •Thermoregulation – regulates body temperature , involving the nerves, blood vessels and glands. Cold body leads to decrease in temperature leads to vasoconstriction leads to decrease blood flow to conserve body heat; if too hot leads to increase body temperature arteries in the skin dilate, blood flow and sweat production increases allowing body to cool. •Metabolism – when exposed to sunlight – synthesizes Vitamin D – mineralization of bones and teeth •Communication/Social interaction – body image, physical attraction; damage can lead to functional/physiologic consequences – impact on self-esteem. Layers of The Skin Epidermis: o Cells in Epidermis: Squamous cells Melanocytes- synthesize and excrete melanin with exposure to sunlight- Vit D- melanin stimulating hormone (MSH); shields against ultraviolet radiation Langerhans- from bone marrow; initiate immune response with exposure to environmental antigens Merkel Cells- associated with touch receptors; slowly adapt when stimulated o Barrier to water loss, protection, washing sheds the outer most layer o Formed from 5 layers (Memory Neumonic: C-ozy L-ayers G-enerating S-kin B- arriers) ; each layer is at a progressive stage of cell differentiation as it is growing (30 day average turnover) •Stratum Corneum – outer tough/cornified layer composed of squamous cells without nuclei or organelles and keratinocytes which produce keratin (scleroprotein); prevents dehydration to the lower layers •Stratum Luciderm – found on thicker parts of skin only (I.E. Soles of feet and palms of hands), clear eleidin which becomes keratin when it moves up to the corneum layer •Stratum Granulosum – Langerhans cells and squamous cells with obvious keratohylin granules •Stratum Spinosum –spinelike structures forming the thickest layer of new keratinocytes composed of tightly bound squamous cells by intercellular junctions (dermasomes) •Stratum Basalis, or stratum germinativum – reproductive layer of the epidermis where keratinocytes divide and move up to replace the surface cells Epidermal-Dermal Junction/Basement membrane zone Separates epidermis from the dermis Layer affected in blister formation Rete ridges (basal epidermis) linked to dermal papillae of papillary dermis – prevents shearing Dermis (Mesenchymal layer) o Cells in Dermis Fibroblasts- secrete connective tissue matrix Collagen gives tensile strength Elastin provides recoil and prevents permanent reshaping Mast cells- release histamine Machrophages- phagocytic; part of immune response Endothelial cells- lining of blood vessels o Thickest layer, supplies and support and nutrition to the epidermis, regulates heat , immune responses, receptors for heat and cold sensation. o Consists of hair follicles, sebaceous glands, sweat glands, blood vessels, lymph vessels, and nerves 2 layers •Papillary dermis – thinner collagen fibers •Reticular dermis – thicker collagen fibers Hypodermis (Superficial fascia- Adipose layer) o Cells in the Hypodermis o Macrophages o Fibroblast o Adipose o Attaches dermis to underlying structures o Provides insulation for the body, ready reserve of energy, additional cushioning, adds to the mobility of the skin over underlying structures. Skin Immune System (SIS) Cells that provide immune protection: •Langerhan’s cells – found in the stratum granulosom layer of the epidermis •Tissue macrophages – found in the dermis, most important cell of the SIS •Mast cells – found in the papillary dermis, epidermal appendages, blood vessels, nerves, fat tissue Dermal Appendages: •Nails – tightly packed keratin (“hard keratin”) plates at the end of fingers and toes * Continuously grow throughout life. FYI- I have actually witnessed a nail continuing to grow on a dry gangrenous finger! •Hair follicles and sebaceous glands are integrated units. * Growth is cyclic with periods of growth and rest over different body structures •Glands - originate in the dermis but are actually appendages of the epidermis. Sebaceous – sac-like gland that opens onto the surface through a canal. Secrete sebum – lipid-rich oily substance, lubricates the skin, contributes to ph of skin. Growth of sebaceous glands is dependent on testosterone; enlargement is one sign of puberty • Sweat – tightly coiled tubular gland –2 types • Apocrine – Located in axilla, scalp, abdomen and genital area: puberty, contains proteins/fatty acids (B.O) • Eccrine – greatest in number in palms of hands, soles of feet, and forehead. At birth, most important – regulates body temperature lacks protein/fatty acids – through evaporation. Blood Supply And Innervation: Blood to skin is limited to papillary capillaries/ plexus at the dermis. There are only alpha adrenergic receptors in the skin. Age Alters Skin Characteristics: Barrier functions of the stratum corneum is reduced: thinner, drier, wrinkled, and changes in pigmentation. Flattening of dermo-epidermal borders Shortening and decrease in capillary loops Decrease in number of melanocytes (grey hair) Decrease in Langerhan cells Loss of rete pegs leads to smooth, shiny appearance Decrease in vasculature leads to atrophy of glands and in turn the skin is drier. Loss of elastin fibers leads to wrinkles Integumentary Dysfunctions •Don’t Forget to Review Content Material for this Unit in Web CT! There is a great list of dermatology definitions. •In our text, there are pictures of different skin lesions. Clinical Manifestations: Leisons- observable and easily assessed for distribution and structure: Pressure Ulcers- ischemic ulcers r/t shearing force and pressure (Use the Braden Score!) I- Nonblanchable erythema of intact skin II- Partial thickness- Shallow wounds involving epidermis and possibly partial loss of the dermal layer= Epidermal and Dermal Repair III- Full thickness- Loss of the epidermal and dermal layers, extending at least to the SQ layer and possibly into the fascia-muscle layer and the bone= Inflammatory/Proliferative/Remodeling IV- Full thickness w/ extensive destruction (May be unstagable) Dysfunctions of the Skin Impentigo Contagiosa- bacterial infection characterized by reddish macules that become vesicles and easily rupture. Often seen around nose and mouth. Dry and form honey-brown crusts and pruitis is common. (Contact Precautions) Folliculitis- Staphylococcal infection of hair follicle. Papules and pustuals found around hair shaft. A furnuncle (boil) is a deeper form of folliculitis. Starts as a pimple and forms a boil w/ yellow or black center. A curbuncle is a more invasive form often found on the neck and buttocks area. Accompanied by fever, pain, increased WBC count and possible sepsis.- (Do Not Squeeze boils!) Cellulitis- Skin infection extending into the dermis and subcutaneous layers often r/t strep infection. Characterized as intense redness, swelling and streaking. Lymph node involvement often common. Monitor for sepsis. Psoriasis- Noninfectious inflammatory disease of skin where epidermal cells grow at faster rate than normal (often 9 times faster). Aggrevated by stress, trauma, infection and seasonal change. Characterized by red patches of skin covered with scales and is normally bilateral. Often seen on scalp, knees, shin and elbows. May benefit from UV light because the inhibits epidermal growth. Tinea Capitis- Fungal infection transmitted from person to person. Characterized by pruitic circular lesions at the scalp leaving bald patches. Tinea Corporis- Fungal infection usually contacted from pets. Characterized by pruitic, unilateral, circular lesions. Tinea Cruris (jock itch)- Don’t share towels! Tinea Pedis (Athletes foot)- Wear clean dry socks! Candidiasis (Candida albicans)- Fungal infection resulting in an inflamed area with white material that peels easily and bleeds. Grows in moist areas. (Swish and swallow!) Scabies- Skin disruption caused by pregnant itch mite which burrows under the skin to lay eggs. The burrow leaves a trail that is grayish-brown and commonly found between the fingers and on the wrist. It itches more at night. * Highly contagious. Treat the whole family. Pediculosis capitis (head lice)- The female lies her eggs close to the scalp. This appears as tiny white specks that firmly attach. Nits hatch in 10 days. – NIX or RID. Contact dermatitis- Not contagious. Associated with allergens or familial history. Characterized by itching, redness, oozing vesicles and crusting. Acne- predominantly in adolescence. Has some hereditary components and is aggrevated by stress, hot, humid weather, and premenstrual periods in women. Closed comedones (white head) and open comedones (black heads) and pustules vary in severity. Benzoyl peroxide and Vit A depress sebum production. Physiology of Skin Repair Two mechanisms of repair – determined by the tissue layer or layers involved and their capacity to regenerate. Regeneration – replacement with more of the same (epidermal and superficial dermal layers) Connective tissue repair – scar formation (full thickness that extends through dermis) Types of Healing: •Primary intention- Healing ridge •Secondary- Heal by scar formation •Tertiary (delayed primary)- Example= Complicated abdominal wounds Normal Integument Healing Response •Inflammatory phase- last usually 1 - 4 days Hemostasis – initiates the entire wound healing cascade Inflammation •Proliferative phase- 4 – 20 days Neoangiogenesis Matrix deposition/collagen synthesis Contraction Epithelialization •Remodeling phase- 21 days to 2 years •Strengthening and reorganizing of collagen fibers Regulation of Wound Healing •Growth factors- Attract needed cells to the wound bed, stimulate cell division, and stimulate specific cellular activities •Cytokines- Regulate cellular function and wound repair – “fine tune” repair process •MMP’s and TIMP’s- MMP’s degrade the matrix, TIMP’s inhibit MMP’s •Hormones – insulin deficiency, excess levels of cortisol •Interplay of Regulatory Factors- Concentration/Combination of substances, Specificity of receptors, Cell Activation Factors Affecting Skin Characteristics Age – newborn skin is almost as thick as adults, difference is transcutaneous water loss, adolescence – increased activity of sebaceous glands due to hormonal stimulation, mature adult – dermis decreases in thickness by 20% , epidermal turnover is increased leads to slower healing times – young adult 21 days, 35+ 42 days, decrease in barrier function leads to friction, decrease in UVR protection due to decrease in melanocytes, dryness leads to wrinkles, decrease in sensory receptors leads to burns/trauma, decrease in Vit. D production, decrease in mast cells, decrease in inflammatory responses. UGH!! skin elasticity decreases related to age and solar damage – collagen unwinds and elastin lysis – starts at age 30. Sun – excessive exposure to UVR; dermotokelosis – dryness, tough leathery texture, wrinkling, irregular pigmentation; Ca; if more than 6 serious sunburns have increase risk of melanoma Hydration – provided by sebum and intact s. corneum, factors affecting – humidity, sebum prod. decrease and age Soaps – excessive use of alkaline soap, detergents decrease thickness # of cell layers, interferes with water-holding capacity of skin and impair bacterial resistance. Ordinary handwashing – takes 45 mins. to restore ph. Avoid alcohol and acetone. Nutrition – if with damaged skin – increase Vit. C – collagen formation; increase protein – supply amino acids for protein synthesis; CHO – for cell metabolism Nutritional status- Increased caloric needs: Protein 0.8 g/kg/day for avg. adult, with wound increases to 1.25 to 2.0 g/kg/day Vitamin A needs increase, Vitamin C 100 to 1000mg, 15 –30 mg of zinc and 200% of RDA of Vit. B, 20 –30 mg of iron Medications - corticosteroids – interfere with collagen formation; skin flora changed by antx, oral steroids, and hormones; NSAIDS, analgesics, antihistamines alter inflammatory reactions.
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