BSCI 201: Anatomy & Physiology Chapter 5 Part 1 Notes
BSCI 201: Anatomy & Physiology Chapter 5 Part 1 Notes BSCI201
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This 6 page Class Notes was uploaded by mehrnazighani Notetaker on Sunday October 9, 2016. The Class Notes belongs to BSCI201 at University of Maryland - College Park taught by Justicia Opoku-Edusei in Fall 2016. Since its upload, it has received 28 views.
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Date Created: 10/09/16
BSCI 201: Anatomy & Physiology Chapter 5 (Integumentary System) Notes- Part 1 by Mehrnaz Ighani . Integumentary system consists of: Skin Hair Nails Sweat glands Sebaceous (oil) glands . Skin consists of 2 distinct regions: (Fig. 5.1) 1. Epidermis: superficial region that’s avascular 2. Dermis: underlies epidermis that consists of mostly fibrous connective tissue and is vascularized Hypodermis (superficial fascia): . subcutaneous layer deep to skin . mostly adipose tissue that absorbs shock and insulates . anchors skin to underlying structures: mostly muscle . Cells of the epidermis: Epidermis consists mostly of keratinized stratified squamous epithelium 4 types of cells found in epidermis: 1. Keratinocytes: . produce fibrous keratin which gives skin its protective properties . major cells of epidermis . tightly connected by desmosomes . millions slough off everyday 2. Melanocytes: . spider shaped cells located in deepest epidermis . produce pigment melanin, which is packaged into melanosomes . melanosomes are transferred to keratinocytes where they protect nucleus from UV damage 3. Dendritic (Langerhans) cells: . star shaped macrophages that patrol deep epidermis (key activators of the immune system) 4. Tactile (Merkel) cells: . sensory receptors that sense touch . Epidermis is made up of 4 to 5 layers (strata): Thick skin consists of 5 layers and is found in high abrasion areas (hands, feet) Thin skin consists of 4 layers . 5 layers of skin: (from deepest to the most superficial) 1. Stratum basale 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum (only in thick skin) 5. Stratum corneum . Stratum basale: Deepest of all epidermal layers Firmly attached to dermis Consists of a single row of stem cells that actively divide (mitotic), producing 2 daughter cells each time . one daughter cell journeys from basal layer to surface taking 25-45 days to reach surface . other daughter cell remains in stratum basale as a stem cell Layer that is also known as stratum germinativum b/c of active mitosis 10-25 % of layer also composed to melanocytes . Stratum spinosum (prickly layer): Several layers Cells contain web-like system of intermediate pre-keratin filaments attached to desmosomes . allows them to resist tension and pulling Keratinocytes in this layer appear spikey so they are called prickle cells Scattered among keratinocytes are abundant melanosomes and dendritic cells . Stratum granulosum (granular layer): 4-6 layers thick, but cells are flattened so layer is thin Cell appearance changes; transitional stratum . cells flatten, nuclei and organelles disintegrate . keratinization begins Cells accumulate keratohyaline granules that help form keratin fibers in upper layers cells also accumulate lamellar granules, a water resistant glycolipid that slows water loss cells above this layer die b/c they’re too far from dermal capillaries . Stratum lucidum (clear layer): found only in thick skin consists of thin, translucent band of 2-3 rows of clear, flat, dead keratinocytes lies superficial to the stratum granulosum . Stratum corneum: 20-30 rows of flat, anucleated, keratinized dead cells Accounts for ¾ of epidermal thickness Tough dead cells function to: . protect deeper cells from the environment . prevent water loss . protect from abrasion and penetration . acts as a barrier against biological, chemical, and physical assaults . Cells change by going through apoptosis (controlled cell death) Dead cells slough off and dander Humans can shed 50,000 cells every minute . Dermis: (Fig. 5.3) Strong, flexible connective tissue Cells include fibroblasts, macrophages, and occasionally white blood cells and mast cells Fibers in matrix bind body together Contains nerves, blood vessels, and lymphatic vessels Contains hair follicles, oil glands, and sweat glands 2 layers: 1. Papillary layer 2. Reticular layer . Papillary layer: o Superficial layer of areolar connective tissue consisting of loose, interlacing collagen and elastic fiber ad blood vessels o Loose fibers allow phagocytes to patrol microorganisms o Dermal papillae: superficial region of dermis that sends fingerlike projections up into epidermis o Projections contain capillary loops, free nerve endings, and touch receptors (tactile corpuscles, also called Meissner’s corpuscles) o In thick skin, dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges (Fig. 5.4a) . collectively ridges are called friction ridges which: Enhance gripping ability Contribute to sense of touch Sweat pores in ridges leave unique fingerprint pattern . Reticular layer: o Makes up to 80% of dermal thickness o Consists of coarse, dense fibrous (irregular) connective tissue o Many elastic fibers provide stretch- recoil properties o Collagen fibers provide strength and resiliency . bind water, keeping skin hydrated o Extracellular matrix contains pockets of adipose cells o Cleavage (tension) lines in reticular layer are caused by many collagen fibers running parallel to skin surface (Fig. 5.4b) . important to surgeons b/c incisions parallel to cleavage lines heal more readily o Flexure lines of reticular layer are dermal folds at or near joints (Fig. 5.4c) . dermis is tightly secured to deeper structures . skin’s inability to slide easily for joint movement causes deep creases . visible on hands, wrists, fingers, soles, toes . Extreme stretching of skin can cause dermal tears, leaving silvery white scars called striae, aka stretch marks . Acute, short term traumas to skin can cause blisters, fluid filled pockets that separate epidermal and dermal layers . 3 pigments contribute to skin color: 1. Melanin: . only pigment made in skin; made by melanocytes Packages into melanosomes that are sent to keratinocytes to shield DNA from sunlight Sun exposure stimulates melanin production . 2 forms: reddish yellow to brownish black . all humans have the same # of keratinocytes, so color differences are due to amount and form of melanin . freckles and pigmented moles are local accumulations of melanin 2. Carotene: . yellow to orange pigment . most obvious in palm and soles . accumulates in stratum corneum and hypodermis . can be connected to vitamin A for vision and epidermal health 3. Hemoglobin: . pinkish hue of fair skin is due to lower levels of melanin . in Caucasians the color of hemoglobin shows through . Excessive sun exposure damages skin Elastic fibers clump, causing skin to become leathery Can depress immune system and cause alterations in DNA that may lead to skin cancer UV light destroys folic acid . necessary for DNA synthesis so insufficient amount is especially dangerous for developing embryos Photosensitivity is increased reaction to sun . some drugs and perfumes cause photosensitivity leading to photosensitivity . Alterations in skin color can indicate diseases: 1. Cyanosis: blue skin color, low oxygenation of hemoglobin 2. Erythema (redness): fever, hypertension, inflammation, allergy 3. Pall or (blanching or pale color): anemia, low blood pressure, fear, anger 4. Jaundice (yellow cast): liver disorders 5. Bronzing: inadequate steroid hormones or very high levels of iron (such Addison’s disease) 6. Bruises: clotted blood beneath skin Works Cited Lindsey, Jerri K., Katja Hoehn, and Elaine Nicpon Marieb. Human Anatomy & Physiology, 9th Edition Elaine N. Marieb, Katja Hoehn. Boston, MA: Pearson, 2013. Print.
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