BIOL&251Ch5NotesSpr11

BIOL&251Ch5NotesSpr11 - Ch. 5 The Integumentary System Is...

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1 Ch. 5 – The Integumentary System Is a.k.a. “the integument” – from the Latin word meaning “to cover” Has 2 main parts : The cutaneous membrane (skin) = the epidermis +the dermis Accessory structures – e.g. hair, glands, nails, etc. Also, there is a subcutaneous layer (hypodermis) , which is not technically part of the skin (it’s actually superficial fascia) Fig. 5-1, p. 158 Functions of the integumentary system Protection of underlying tissues from: – Abrasion, chemicals, dehydration, UV radiation, infection, etc. Excretion of salts, wastes, and water Body temperature regulation via insulation, evaporation, and vasodilation/vasoconstriction Vitamin D 3 synthesis –for±ca lc ium± metabolism Lipid energy storage General sensation
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2 Epidermal layers (strata) Fig. 5-3, p. 160 Note: the stratum lucidum is found in thick skin only • The tissue = keratinized stratified squamous epithelium Fig. 5-2, p. 159 The epidermis Thin skin –has±4 strata; it covers most of the body Thick skin – has 5 strata (the stratum lucidum is the 5 th ); it’s found on the palms and the soles of the feet only; it has a much thicker stratum corneum; it has no hair or sebaceous glands, but more sudoriferous (sweat) glands • The cells = mostly keratinocytes , but there are also dendritic (Langerhans) cells , Merkel cells , and melanocytes present
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3 Keratinocytes • Make up ~ 90% of epidermal cells (by far, most of the cells you see in the figure to the right) • Produce the tough, fibrous protein keratin (a.k.a intermediate filaments) – Functions : abrasion resistance; water loss • Produce the dense granular protein keratohyalin – Functions : dehydrate cells as they get pushed toward the surface; cross-link keratin fibers • Have desmosomes to hold cells together • The basal cells have hemidesmosomes to anchor cells to the basement membrane • Can also produce and release a lipid-rich secretion to help make skin even more water resistant Dendritic (Langerhans) cells • Make up ~ 1% of epidermal cells • Are found in the stratum spinosum • Are mobile • Have an immune function : – They stimulate a defense against invading microorganisms and superficial skin cancers
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4 Merkel cells • ~ 1% of epidermal cells • Are found in the stratum germinativum (basale) of hairless skin • Are specialized to produce receptor membrane potentials and release neurotransmitter chemicals that… – Activate Merkel discs (which are sensory neuron cell processes) • Function in light touch and pressure reception Melanocytes • Make up ~ 8% of epidermal cells • Their cell bodies are found in the stratum basale • Their cell processes extend into the stratum spinosum • With the help of the enzyme tyrosinase, they can convert tyrosine (an amino acid) into melanin (a dark pigment) – The pigment is packaged in melanosomes – Nearby keratinocytes engulf melanosomes
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This note was uploaded on 12/29/2011 for the course BIOLOGY 24011 taught by Professor Pan during the Fall '11 term at HCCS.

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BIOL&251Ch5NotesSpr11 - Ch. 5 The Integumentary System Is...

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