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Explore how the skin protects the body, regulates temperature, and senses stimuli. Learn about the structure of the skin, layers of the epidermis, and functions of keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Understand the different types of skin and common disorders like psoriasis. Discover the dermis, its regions, and the factors contributing to skin color. Unravel the role of hair, nails, and glands as accessory structures. Enhance your knowledge of the integumentary system for a deeper understanding of your body's largest organ.
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Honors Anatomy & Physiology Integumentary system
What are the ways skin protects the body? Essential question
functions: protecting the body helping to regulate body temperature allows you to sense stimuli in your environment stores blood synthesis of vit. D excretion & absorption of materials Integumentary system
skin = cutaneous membrane • largest organ of body • in adults: covers ~ 2 m² & weighs ~ 4.5 – 5 kg (10 – 11 lb) • 2 parts: • epidermis • dermis • sub Q below dermis & not technically part of skin: contains fat (insulation), & blood vessels, nerves that supply the skin Structure of the skin
keratinzed stratified squamous epithelium 4 main cell types: keratinocytes melanocytes Langerhans cells Merkel cells Epidermis
~ 90% of all epidermal cells • produce fibrous protein: keratin: • protects skin & underlying tissue from • heat • microbes • chemicals • also release a water-repellant sealant from lamellar granules • decreases water entry/loss • inhibits entry of foreign materials keratinocytes
~8% of epidermal cells • produce melanin keratinocytes • pigment (yellow-red to brown-black) that contributes to skin color • * absorbs UV radiation • “covers” nucleus in keratinocyte melanocytes
arise in red bone marrow then migrate to epidermis easily damaged by UV radiation function: immune response vs. microbes that invade Langerhans Cells
least numerous of epidermal cells (>1%) deep in epidermis in contact with Merkel disc (tactile disc) together detect different aspects of touch Merkel Cells
covers most of body 4 layers: stratum basale stratum spinosum stratum granulosum stratum corneum Thin Skin
found in areas where exposure to friction is the greatest • “thick” because has 1 extra layer: • stratum lucidum (between stratgumgranulosa & a thicker stratum corneum) Thick Skin
common & chronic skin disorder in which keratinocytes divide & move more quickly than normal from stratum basale stratum corneum • make abnl keratin flaky, silvery scales @ skin surface • most often over knees, elbows, or scalp psoriasis
2nd, deeper layer of skin composed mostly of CT 2 regions: papillary region reticular region Dermis
~ 1/5th of total dermis • surface area greatly increased by finger-like structures: dermal papillae that project into epidermis • contain: • capillary loops • tactile receptors: Meissner corpuscles • free nerve endings (temp, pain, tickle, itch) Papillary region of dermis
develop during 3rd month of fetal development • pattern is genetically determined & unique to individuals (x identical twins) • on finger tips ridges deeper finger prints • allow you to grasp things by increasing surface area Epidermal ridges
attached to subcutaneous layer beneath • contains: • dense irregular CT • hair follicles • sebaceous glands • sudoriferous (sweat) glands • collagen & elastic fibers (gives skin its elasticity, strength): extreme stretching striae (stretch marks) Reticular region of dermis
3 pigments contribute: Melanin Hemoglobin (hgb) Carotene Basis of skin color
made from a.a. tyrosine using enzyme tyrosinase then stored in organelle called a melanosome exposure to UV light increases enzymatic activity & more (& darker) melanin produced melanin absorbs UV radiation preventing it from damaging DNA which skin cancer melanin
in RBCs rosy color to lighter skinned individuals blushing: due to increased blood flow (autonomic nervous system at work) hemoglobin
yellow-orange pigment precursor of vit. A Carotene
inherited inability to produce melanin most due to cell’s inability to produce tyrosinase albinism
partial or complete lack of melanocytes from patches of skin produces irregular white spots ? Immune system malfunction? vitiligo
cyanotic: when blood not adequately oxygenated mucous membranes, nail beds & skin appears bluish Skin color as diagnostic clue
jaundice: due to build up of bilirubin (yellow pigment) in skin, sclera; usually indicates liver disease Skin color as diagnostic clue
erythema: redness of skin caused by engorgement of capillaries due to: injury, infection, inflammation, allergic reaction Skin color as diagnostic clue
pallor: paleness of the skin, seen in shock & anemia Skin color as diagnostic clue
all develop from embryonic epidermis • include: • Hair • Nails • Glands Accessory structures of the skin
present on most skin surfaces x palmar surfaces of hands, soles & plantar surfaces of feet genetic & hormonal influences determine the thickness & pattern of distribution of hair Hair (pili)
functions: • protection • scalp, eyebrows, eyelashes: from getting foreign objects in eyes • nose, ear canals: trap foreign objects • sensitive to light touch • touch receptors in hair root plexus hair
composed of columns of dead, keratinized cells bonded together by extracellular proteins hair
shaft: portion of hair that projects from scalp root: portion below scalp follicle: surrounds root of hair arectorpili: smooth muscle extends from side of hair follicle superficial dermis Anatomy of a hair
lanuga: grows on fetus @ ~ 5 months fetal age; sheds b/4 birth vellus hair: short, fine hair that grows over baby @~ 2-3 months after birth terminal hair: coarse hair that develops after puberty Types of hair
mostly due to amt & type of melanin in keratinzed cells dark hair has eumelanin blondes & redheads have pheomelanin gray: loss of melanin white: loss of melanin + air bubbles in shaft of hair Hair color