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Western University
Anatomy and Cell Biology
Anatomy and Cell Biology 3309
Martin Sandig

Integumentary System Epidermis stratified squamous epithelium Dermis connective tissue loose and dense irregular Hypodermis loose CTmainly adipose tissue called superficial fascia in gross anatomyDerivatives of skin include sweat glands hair sebaceous glands and nailsFunction1 protection 2 prevent water loss 3 PNS receptors 4 Vitamin D production 5 Heat regulation 6 Waste product secretion 7 Immunologic functionsLangerhans cellsantigen processingThick skin is glabrous without hair Thin skin has hair thick and thin refer to epidermis onlyThick skin has a thinner dermis than thin skinThick skin found on palms and soles of feetThick skin 5 layers 1 stratum basalestratum germinativum a progenitor cells constantly renew epithelium 2 stratum spinosum a Nodes of Bizzozzarodesmosomes 3 stratum granulosum a keratohyalin granules 4 stratum lucidum a eosinophilic refractile cells containing large amounts of keratinnuclei not visible Only in thick skin 5 stratum corneum a no cytoplasmic organelles b cell membranes coated with glycolipid acylglucosylceramide c gets thicker when exposed to more wear and tear callus formationDermis dermal papillaeepidermal ridgesinterpapillary pegs down growth ofepidermis into dermis where sweat duct passes from dermis to epidermisdermal ridges form basis for fingerprintsbasal cells attach to dermis via hemidesmosomes attach to basement membrane via anchoring filamentsanchoring fibrils run from basal lamina to the dermis belowPapillary layer loose CT carrying blood vessels and nervesform dermal papillaeReticular layer deep CT dense irregular CTCells of the epidermiskeratinocytes i main cell type in epidermis with standard synthetic machinery in the stratum basale Basophilic due to large numbers of ribosomes ii Become eosinophilic as the tonofilaments intermediate filaments are formed iii In stratum spinosum cells make keratohyalin granules and lamellar bodieslarge numbers accumulate in stratum granulosum 1 keratohyalin granulestonofilamentskeratin soft 2 lamellar bodies contain acylglucosylcermide waterproofingmelanocytes skin pigment producing cellsmake melanin i usually in stratum basale ii enzymes tyrosinase convert tyrosine to 34 dihydroxyphenylalanine DOPA iii DOPA converted to melanin in melanosomes membrane bound structures in melanocytes iv Melanosomes transferred to keratinocytesMelanosomes degraded in light skin more stable in darker skinLangerhans cells i Macrophage like cell that presents antigens to recirculating Tcells ii Nucleus very basophilic cytoplasm clearSkin Appendages1 hair follicles and hairnails 2 sebaceous glands and sebum 3 eccrine sweat glands and sweat 4 apocrine sweat glandsserous secretions Haircomposed of keratinized cells develop from hair folliclesall thin skin with minor exceptions has hairinfluenced by hormones facial and pubic hair male pattern baldnesstwo kinds of hair terminal hair thick and vellus hair difficult to seecolour comes from melanin Structurei Bulb at base ii Dermal papillavascularized iii Outside of hair down growth of epithelium called external root sheathsurrounded by basement membrane called glassy membrane iv Rest of bulb called matrix which consists of1 basal layer of stem cells keratinocytes 2 melanocytes which impart colour to the hair v Bulb gives rise to the 1internal root sheath which is discontinued after the hair leaves the epidermisContains keratinocytes which form soft keratin 2the hair itself which is divided into three layersHair is composed of hard keratin a the outer cuticle b the middle cortex c the central medulla may not be present in fine hairsarrector pili muscle associated with hair follicleSmooth muscle under autonomic nervous system control Sebaceous glandsdevelop as a growth off the side of the hair follicleSecrete sebum holocrine secretion Basal cells renew and cells fill up with lipid secretion until the cell dies and all is secreted into the hair follicleProcess takes approximately 8 daysWell developed SER for production of lipids
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