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Animal Science
ANSC 2340
Ira Mandell

Integument Integument:  One of the largest & most extensive organ systems in the body (covers the entire animal)  Components: skin or hide, sweat and oil glands, hair (wool, fur, feathers), nails (hooves, claws, foot pads), and horns **these are all considered modifications of the surface epithelium  Functions: *protective against microbes, insects, external parasites, environmental, chemical, UV radiation, and physical abrasion (skin surfaces deal with all this daily + constant rubbing, scratching & direct contact with the physical environment) (grazing animals are completely exposed to the sun, dark hair=warmer due to light absorption) – animals must have access to shade for animal welfare *animals housed outside during winter must have suited hide coat, hide thickness, and backfat thickness which can vary between breeds. *prevents dehydration *body temp regulation – heat is transferred through blood to the skin to dissipate heat (cutaneous blood flow = blood flow to the skin), hair coat, and perspiration (sweating, but does not occur in all animals) *Detects sensory info (touch & pressure) and relays info to CNS *Excretes organic waste, excess salts & water (sweat) *Synthesizes Vitamin D (animals outside most of the year can synthesize enough vitamin D to not need any supplementation *Protection (ie, nails, horns, and claws) *Food Gathering (claws needed for birds b/c they have wings instead of forlimbs) SKIN (HIDE)  Characteristics *covers external surface of animal *ability to regenerate & heal -human epidermis replaced every 4-7 weeks -25-50 days is the range across species *Species differences in: -skin thickness[evolved to save nutrients & energy + heat control] …thickest where most environment exposure (back, pads of paws, btwn shoulder blades) …thinnes where animal is best covered (groin, around eye) - how loosely (firmly) skin is attached to underlying body structures .....................(loose attachment enables movement without tearing, tight causes movement issues)  3 layers  Epidermis (outer layer) -layer of fat cells: stratified squamous epithelium -Avascular & usually free of nerve endings (no blood vessels going in) gets nutrients from simple diffusion from the underlying skin layer (the dermis) -made of 3-5 histological layers w species differences (don’t memorize) -Basal layer of epidermis(basement membrane) is adjacent to the dermis -made up of keratinocytes which divide via mitosis to form daughter cells that push older cells toward skin surface (cells dividing by mitosis produce daughter cells that migrate to outside surface) -in this “cell conversion” process, superficial cells harden & dry out by the processes of keratinization and cornification -as cells migrate towards the surface they lose access to nutrients since they are too far away from the dermal capillaries; cells flatten, die, and undergo changes including loss of nuclei, cytosol and organelles which are replaced by the fibrous protein, keratin and waterproofing granules made up of glycolipid (provides skin w ability to protect against water loss & makes room for keratin, the cells must dump their vital nuclei and organelles live cell, dumps parts = dead cell= provided skin with the ability to prevent water loss and protection -function of keratin: keratinization *cornification make skin tough & resistant to drying, keeps water in & bacteria, foreign bodies, chemicals, parasites, insects, etc. out -Shedding of epidermal cells (turnover; exfoliation) – millions/day -Keratin is a fibrous protein w poor essential amino acid balance ( 10 essentials required for diet, keratin has very few b/c skin cells will be lost through exfoliation process) -Other cell types: -Desmosomes: anchors and connects keratinocytes to form a more protective barrier -Melanocytes: produces pigment, melani
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