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Integument 1 (Roles (Keratin, Skin glands/secretions, Vit D. synth,…
Integument 1
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Keratin
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Tough, insoluble & produces strong un-mineralised tissues
Soft-keratin - Elastic, desquamates (e.g. skin)
Hard-keratin - More sulfur than soft, less elastic, more permanent, resistant to degradation, does not desquamate (e.g. nails, horns, hoof)
Synthesis: Begins in stratum basale, final formation of K filmament matrix complex in stratum corneum
Skin glans & secretions
Sebaceous glands
Dead epithelial cells, lipids (tri-glys, cholesterol esters, waxes). Odourless until broken down by bacteria
Sebum - Oils hairs, forms oily film on skin. Reduces water loss, lubricates skin, inhibit certain bacterial growth. Increased production in response to androgens, decreased to oestrogens
Skin not V. permeable to water but NOT water proof - Insensible water loss, sebaceous gland secretion contributes to water resistance, keratinocytes (insol keratin). Skin can be route for drug administration/toxins
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Sweat glands
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Apocrine
Common in domestic species, sparce in primates
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Oily opaque secretion, smelly with bacterial breakdown
Ecrine
Common in primates, sparce in domestic animals (on footpads)
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Watery NaCl solution, modified by aldosterone
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Both contain myoepithelial cells, ceruminous glands of ear & mammary glands are modified sweat glands
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Melanin
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Control of synth - Genetic, local factors, hormones. Receptor binding, more binding to enzyme more darker pigment (eumelanin) produced
Regulation of pigment synth - Melanocytes stimulating hormones (MSH),
MSH produced by pars intermedia of pituitary glands, and by melanocytes
MSH stimulated by UV light and other external signals (e.g. camouflage). MSH increased in some disease states (e.g. hyperadrenocorticism therefore hyperpigmentation clinical sign)
Production of melanin
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- Camouflage
- Mimicry
- Social comm.
- Protection against solar radiation
Melanocytes:
- Cell bodies interspersed with other cells in basal layer epidermis
- Cell extensions squeezed between stratum spinosum
- Melanin synth/packed in vesicles
- Intact vesicles transferred to adjactent keratinocytes (pigmentation of skin and hair).
- Melanin shed when keratinocytes reach skin surface so much be constantly produced