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Integumentary System. Integument(Skin). Integument is nothing but the skin. Integument(=to cover in latin Skin and its appendages are the largest organ of the body Functions: Protection Heat regulation Sensation Synthesis and storage of Vit D. Integumentary system.
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Integument(Skin) • Integument is nothing but the skin. • Integument(=to cover in latin • Skin and its appendages are the largest organ of the body • Functions: • Protection • Heat regulation • Sensation • Synthesis and storage of Vit D
Integumentary system Skin along with the • exocrine gland(sebaceous gland • Hair • Nails • Associated blood vessels and • Associated nerves Comprise integumentary system
Skin • Superficial epidermis • middle dermis • Deep hypodermis(superficial fascia)
Epidermis • Superficial layer composed of keratinized stratified squamous epithelium • Avascular with no blood vessels or lymphatics • Has basal cells which has regenerative capacity • Thick skin has 5 layers of cells • Thin skin has 4 layers of skin
Dermis • Middle layer composed of Dense irregular connective tissue • Contains nerve endings,hair follicles, and glands • They nourish the avascular epidermis • Contains dermal papillae(projections of dermis into epidermis)
Langer(incision or tension) lines in skin • They are the direction in which the most collagen fibres run in any particular location in the skin. • Incision should be made parallel to the direction to avoid minimal scarring.
Hypodermis • Deepest layer • Stores fat and anchors upper layers to other tissues • Composed of areolar and adipose connectieve tissue
Epidermal layers From base to top • Stratum basale • Stratum spinosum • Stratum granulosum • Stratum lucidum • Stratum corneum
Stratum basale • Single layer of columnar or cuboidal cells resting on basement membrane • The epidermis is renewed every 15-30 days; proliferative activity takes place in this layer; cells are very mitotic
Stratum spinosum • several layers of polygonal shaped cells with spines. • Spines are nothing but keratin filaments. • It resists the effects of abrasion and the layer is thicker in thick skin which is subjected to continuous friction and pressure(eg: soles and palms)
Stratum granulosum • 3-5 layers of flattened polygonal cells with visible granules • Cells undergo keratinization which is a process in which nucleus shivels up, cells dies, and cell fills up with protein keratin • This layer acts as a barrier to penetration by foreign materials and provides sealing effect
Stratum lucidum • 2-3 layers of dead, anucleated, clear cells. Only found in thick skin Stratum Corneum • 20-30 layers of dead, anucleated cells. • They are cornified( brittle, hardened). These outer cells are constantly shed
Epidermal cells Keratinocytes: most numerous(90%);found in all layers; produces keratin which provides the protective barrier mechanically as well as immunologically Melanocytes: 2nd most numerous(8%);found in stratum basale;produces melanin which is a photoprotector
Epidermal cells • Merkel cells: 3rd numerous(1%) found in stratum basale;provides tactile(light touch) sensation • Langerhans cells: <1% found in stratum spinosum; phagocytic action
Dermal layers Pappillary Layer: uppermost; composed of dermal papillae; contatains blood vessels, sensory receptors, ducts of glands; and hair shafts Reticular Layer: deepest;contains blood vessels; sensory recptors(neurons); secretorypoertions of glands and hair follicles
Epidermal derivatives(skin appendages) Hair : contains bulb, root and shaft ; associated with arrectorpili muscle; functions to protect UV light, trauma, and heat loss Nails : formed from stratum corneum ; functions in protection and grasping Exocrine Glands: Sebaceous glands Sweat(sudoriferous) glands Ceruminous
Exocrine glands in skin • Sebaceous glands(sebum=oil):associated with hair follicles and functions in lubrication and bactericidal • Sweat(sudoriferous) glands: • appocrine: in axiallary and pubic regions, secreates onto hair shafts and release an odiferous secretion • Eccrine : found everywhere, funtioning to release perspiration • Ceruminous: modified sweat glands ; found in external auditory canal; cerumen is an insect repellent and a water proofing agent