<p> Human Anatomy & Physiology 03B.2 Epi-N-Dermis</p><p>Layers of the Epidermis Leave space for the following diagram to be glued.</p><p>The following are to be labeled on the above diagram:  Stratum germinativum  Stratum basale  Stratum spinosum  Stratum granulosum  Stratum lucidum  Stratum corneum</p><p>Stratum germinativum  “growth layer”  Includes stratum basale & stratum spinosum</p><p>Stratum basale  “base layer”  Closest to blood supplyhealthiest  Only layer that can reproduce  Keratinocytes o Keratin (tough, water-resistant protein)</p><p>03B.2 Epi-N-Dermis 1 of 6 6/6/2018 Human Anatomy & Physiology  Melanocytes o Melanin (brown protein pigment) . Absorbed by surrounding keratinocytes</p><p> Two categories of melanin: o Eumelanins (dark brown) o Pheomelanins (light brown/red/orange)</p><p> Freckle o clusters of concentrated melanin which are most often visible on people with a fair complexion http://www.medterms.com/script/main/art.asp?articlekey=10102 http://en.wikipedia.org/wiki/Freckle</p><p> Mole o Clusters of concentrated melanin o Often raised http://www.webmd.com/skin-problems-and-treatments/guide/moles </p><p>Stratum spinosum  “spiny layer”  as pushed from below become “squished” & look “spiny” on cross section  spot desmosomes can pull out “spines” as cells shrink away from each other, when pulled apart  less healthy  don’t reproduce</p><p>Stratum granulosum  “grainy layer”  as cells from stratum germinativum die, they enter stratum granulosum  all cells are dead  look grainy when stained / no nuclei</p><p> basophilic keratohyalin granules (seen on the close-up view). These granules contain lipids, which along with the desmosomal connections, help to form a waterproof barrier that functions to 03B.2 Epi-N-Dermis 2 of 6 6/6/2018 Human Anatomy & Physiology prevent fluid loss from the body. </p><p>Stratum lucidum  “light layer” or “clear layer”  Layer looks almost clear  Gets more full of keratin</p><p>Stratum corneum  “horny layer” meaning “like an animal’s horm”  Keratin is fully formed, making keratinzed stratified squamous epithelium.</p><p>A complete new epidermis forms every 25-45 days.</p><p>DERMIS  Your “hide”  Irregular dense fibrous connective tissue</p><p>Papillary region  superficial region has bumps called dermal papillae  bumps in the human body are often called papillae (sing. papilla = “nipple”  increase surface area for glue to “hold” more tightly  Arranged in rows to form "prints" of hands/fingers and feet/toes to improve grip  Fingerprints http://www.reachoutmichigan.org/funexperiments/agesubject/lesson s /prints.html</p><p>Reticular region  Deeper, irregular swirls of collagen fibers  Nerves, nerve endings, blood vessels, sweat glands, etc.  Reticular = “netlike”</p><p>Leave space for the following diagrams to be glued.</p><p>03B.2 Epi-N-Dermis 3 of 6 6/6/2018 Human Anatomy & Physiology</p><p>The following are to be labeled on the above diagram. Those not italicized need to be placed into your notes.: Epidermis Dermis Subcutaneous tissue (hypodermis) Stratum basale 03B.2 Epi-N-Dermis 4 of 6 6/6/2018 Human Anatomy & Physiology Stratum corneum Hair shaft</p><p>Hair follicle  lined by cells derived from the epidermal (outside) layer of the skin  Each follicle normally goes through a five-year cycle of growth and rest, with about 90% of the follicles growing hair at any one time</p><p>Papilla of hair bulb  Provides nutrients for growth and development of the hair</p><p>Sweat gland</p><p>Sebaceous (oil) gland  Lubricates the hair  Keeps hair & skin from drying out</p><p>Pore</p><p>Arrector pili  when contracted, causes hair to “stand up” or goose bumps</p><p>Nerve fibers (will need to draw in)</p><p>Pacinian corpuscle  receptive to deep pressure</p><p>Meissner’s corpuscle  sensitive to light touch</p><p>Adipose (fat) tissue</p><p>Blood vessels  draw this in red = from heart (arteries);  blue = back to heart (veins)</p><p>Other Items: Blisters  epidermis & dermis are tightly connected. 03B.2 Epi-N-Dermis 5 of 6 6/6/2018 Human Anatomy & Physiology  Sometimes when too much friction or burns occur that connection is lost & area fills with interstitial fluid http://en.wikipedia.org/wiki/Blister</p><p>Scars  form when a denser-than-usual mass of fibers are produced to replace those damaged in an injury  Keloid Scars o Abnormally large scars</p><p>Stretch marks  occur when the skin is overstretched and the dermis tears beneath the epidermis</p><p>Remember to: Reduce, Recite, Reflect, & Review! Make your Flashcards & Study 3 x 5!</p><p>03B.2 Epi-N-Dermis 6 of 6 6/6/2018</p>