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The Integumentary System Brainstorm: Write and share with someone near you everything you know about the skin Integumentary System SKIN Quick Brainstorm SKIN FACTS In 1 square inch of skin there are 4 yards of nerve fibers, 1300 nerve cells, 100 sweat glands, 3 million cells, and 3 yards of blood vessels. The Integumentary System Integument is skin Skin and its appendages make up the integumentary system A fatty layer (hypodermis) lies deep to it Two distinct regions Epidermis Dermis Functions of skin Protection Cushions and insulates and is waterproof Protects from chemicals, heat, cold, bacteria Screens UV Synthesizes vitamin D with UV Regulates body heat Prevents unnecessary water loss Sensory reception (nerve endings) Remember… Four basic types of tissue – epidermis just discussed Connective tissue - dermis Muscle tissue Nervous tissue Epithelium • SKIN • has 2 layers: DERMIS & EPIDERMIS Epithelium: layers (on left) and cell types (on right) • EPIDERMIS • made out of layers called STRATA (plural stratum) • Bottom Layer • Stratum Basale (aka: germinativum) • cell division here – new cells push up & out toward skin surface • Next 2 Layers • Stratum Spinosum • Stratum granulosum (cells begin to flatten in this layer) • Top Layer • Stratum Corneum • dead, KERATINIZED cells • Keratinization: cells die and change chemically to form a protective barrier • can be 25 or more layers • this layer is associated with dandruff, calluses, corns • Dandruff Example: • Callus & Corns Examples: • calluses are generally on the soles of the feet • corns are between the toes or on the outside of the toes Dermis Strong, flexible connective tissue: your “hide” Cells: fibroblasts, macrophages, mast cells, WBCs Fiber types: collagen, elastic, reticular Rich supply of nerves and vessels Critical role in temperature regulation (the vessels) Two layers (see next slides) Papillary – areolar connective tissue; includes dermal papillae Reticular – “reticulum” (network) of collagen and reticular fibers *Dermis layers *Dermal papillae * * • DERMIS (2 layers) • division of layers is not distinct 1. RETICULAR LAYER • dense connective tissue What type of tissue is this? Stratified squamous epithelium • collagen & elastin makes the skin strong and elastic 2. PAPILLARY LAYER • contains blood vessels – supplies epidermis with blood • this layer forms finger prints and foot prints Epidermis and dermis of (a) thick skin and (b) thin skin (which one makes the difference?) Fingerprints, palmprints, footprints Dermal papillae lie atop dermal ridges Elevate the overlying epidermis into epidermal ridges Are “sweat films” because of sweat pores Genetically determined Flexion creases Deep dermis, from continual folding Fibers Collagen: strength and resilience Elastic fibers: stretch-recoil Striae: stretch marks The dermis is the receptive site for the pigment of tattoos Flexure lines – where dermis is closely attached to the underlying tissue. Cleavage (tension) lines Separations between collagen fibers under the skin. Important to surgeons – incisions are made parallel to these lines. Stretch marks Caused by extreme stretching of the skin Actually small tears in the dermis Blisters Acute trauma to the skin Fluid-filled pocket that separates the epidermal and dermal layers Notes – Integumentary System • HYPODERMIS • Location: • beneath the skin • consists mostly of loose connective and adipose tissue • half of the body’s stored fat is here Skin color Three skin pigments Melanin: the most important Carotene: from carrots and yellow vegies Hemoglobin: the pink of light skin Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basale Digested by lysosomes Variations in color Protection from UV light vs vitamin D? POLYGENIC traits are recognizable by their expression as a gradation of small differences (a continuous variation). The results form a bell shaped curve. Image from Biology; Campbell and Reece; Pearson Prentice Hall publishing as Benjamin Cummings © 2005 Damage from excessive sun exposure Elastic fibers clump (leathery skin) Temporarily depresses immune system Alters DNA can cause cancer Destroys folic acid stores Hemoglobin gives skin its pinkish hue Seen better in Caucasian’s due to less melanin in their skin. Cyanosis – blue skin Low oxygen Palor, blanching – pale skin. Anemia or low blood pressure Jaundice – yellow skin. Liver disorders Bruises – blood escapes from vessels Skin appendages Derived from epidermis but extend into dermis Include Hair and hair follicles Sebaceous (oil) glands Sweat (sudoiferous) glands Nails Nails Of hard keratin Corresponds to hooves and claws Grows from nail matrix Hair and hair follicles: complex Derived from epidermis and dermis Everywhere but palms, soles, nipples, parts of genitalia *“arrector pili” is smooth muscle * Hair bulb: epithelial cells surrounding papilla Hair papilla is connective tissue________________ Functions of hair – less in man than other mammals Sense light touch of the skin Protection - scalp Warmth Parts Root imbedded in skin Shaft projecting above skin surface Make up of hair – hard keratin Three concentric layers Medulla (core) Cortex (surrounds medulla) Cuticle (single layers, overlapping) Types of hair Vellus: fine, short hairs Intermediate hairs Terminal: longer, courser hair Hair growth: averages 2 mm/week Active: growing Resting phase then shed Hair loss – age related Male pattern baldness Thinning Hair color Amount of melanin for black or brown; distinct form of melanin for red White: decreased melanin and air bubbles in the medulla Genetically determined though influenced by hormones and environment Sebaceous (oil) glands Entire body except palms and soles Produce sebum by holocrine secretion Oils and lubricates Sweat glands Entire skin surface except nipples and part of external genitalia Prevent overheating 500 cc to 12 l/day! (is mostly water) Humans most efficient (only mammals have) Produced in response to stress as well as heat Types of sweat glands Eccrine or merocrine Most numerous True sweat: 99% water, some salts, traces of waste Open through pores Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with time - odor Modified apocrine glands – secrete earwax Mammary – secrete milk Ceruminous Disorders of the integumentary system Burns Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection Types First degree – epidermis: redness (e.g. sunburn) Second degree – epidermis and upper dermis: blister Third degree - full thickness Infections Skin cancer Burns First-degree (epidermis only; redness) Second-degree (epidermis and dermis, with blistering) Third-degree (full thickness, destroying epidermis, dermis, often part of hypodermis) Critical burns Over 10% of the body has thirddegree burns 25 % of the body has seconddegree burns Third-degree burns on face, hands, or feet Estimate by “rule of 9’s” Tumors of the skin Benign, e.g. warts Cancer – associated with UV exposure (also skin aging) Aktinic keratosis - premalignant Basal cell - cells of stratum basale Squamous cell - keratinocytes Melanoma – melanocytes: most dangerous; recognition: A - Asymmetry B - Border irregularity C - Colors D - Diameter larger than 6 mm Skin Cancer Sqaumous cell carcinoma Basal cell carcinoma Melanoma