Integumentary System4

Integumentary System4 - Integumentary System 2 Divisions of...

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Integumentary System
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2 Divisions of the Integumentary system 1. Skin = integument = Cutaneous membrane Skin is the largest organ of the body – surface area of 1.2 to 2.2 square meters; weighs 9 to 11 pounds (4-5kg) = 7% of the total body weight Composed of the superficial EPIDERMIS and the deeper DERMIS 2 . Accessory skin structures = skin appendages : i) Sweat (sudoriferous) glands ii) Sebaceous ( oil) glands iii) Hair/hair follicles iv) Nails
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Figure 5.1: Skin structure, p. 153. Epidermis Dermis Hypodermis (superficial fascia) Hair root Hair shaft Pore Dermal papillae (papillary layer of dermis) Meissner's corpuscle Free nerve ending Reticular layer of dermis Sebaceous (oil) gland Arrector pili muscle Sensory nerve fiber Eccrine sweat gland Pacinian corpuscle Artery Vein Adipose tissue Hair follicle receptor (root hair plexus) Hair follicle Eccrine sweat gland
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Strata of the Epidermis Stratum Basale – deepest stratum Stratum Spinosum – contains tonofilaments Stratum Granulosum – contains granules Stratum Lucidum – present only in thick skin Stratum Corneum - superficial stratum
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Figure 5.2: The main structural features in skin epidermis, p. 154. Sensory nerve ending Melanocytes Melanin granules Merkel cell Langerhans’ cell Stratum corneum Stratum granulosum Stratum spinosum Stratum basale Dermis Dermis Cells are dead; represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Cells are flattened; organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. Cells contain thick bundles of intermediate filaments made of pre-keratin. Cells are actively mitotic stem cells; some newly formed cells become part of the more superficial layers. Keratinocytes Desmosomes (b) (a)
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Stratum Basale The deepest stratum. A single layer of cells including Keratinocytes, Melanocytes, Merkel cells: Keratinocytes are mitotically active producing cells for the superficial layers hence, the stratum basale is also known as the stratum Germinativum Melanocvtes produce the pigment MELANIN contained in melanosomes – melanosomes accumulate on the superficial surface of the keratinocvtes in the stratum basale. Melanin acts as a chemical shield to protect the nuclei of the keratinocytes from the harmful effects of UV radiation in sunlight. Melanin gives skin its color. Albinism- genetic condition in which melanin is not synthesized When you go out into the sun , these cells make extra melanin to protect you from getting burned by the sun's ultraviolet, or UV, rays = tanning Merkel cells at the epidermal-dermal junction associate with free nerve endings to form Merkel Discs which act as Touch receptors
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Several layers of cells Cells are connected by desmosomes – hold cells together which cause the cells to appear “spiny” during histological preparation Cells contain intermediate filaments called Tonofilaments
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This note was uploaded on 02/02/2012 for the course BSCI 201 taught by Professor Opoku during the Fall '07 term at Maryland.

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Integumentary System4 - Integumentary System 2 Divisions of...

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