Biomedical core

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  1. At the distal end of the dorsal surface of fingers and toes, there is a fold of dermis that gives rise to a hard, dense covering made of keratin that is tightly packed to form a clear, tough
    nail body
  2. At the proximal end, a ____ ______ pushes out the nail.
    nail matrix
  3. An __________ fills the space where the epidermis ends.
    eponychium (cuticle)
  4. A ______ is sometimes seen near the cuticle as a slightly lighter area.
    lunula (little moon)
  5. At the ____ _____, another fold of epidermis with blood vessels dives under the surface of the nail.  Past the interface, the free edge of the nail loses contact with ______ _______ and can be trimed without blood or pain.
    free edge; living tissues
  6. Hair
    • Hair shaft has three layers
    • - this is what we see externally
    • - cuticle (purple layer) is outermost for external hairs

    Pigment cells (melanocytes) and blood vessels at base
  7. The external portion of hair is made up of three concentric layers:
    The medulla in the center, a cortex further out, and finally a covering, or cuticle, on the outside.
  8. Beneath the surface of the skin, the ____ _______ and ______ ____ ______ surround the medulla, cortex and cuticle.  At the base, ther are _____ ______ and melanocytes.
    hair follicle; dermal root sheath; blood vessels
  9. Color comes from pigment _______ trapped along with the ______ ______ in the hair shafts.
    granules (brown or black eumelanin; blonde or red pheomelanin); keratin protein
  10. White or gray hair occurs when pigment production is _______ or halted and ___ ______ replace pigment.
    reduced; air bubbles
  11. Hair follicle includes:
    Internal root sheath; External root sheath; Dermal root sheath
  12. In the hair root, additional layers of epidermis form a root sheath.  The ______ ____ ______ surrounds the whole root of the hair.  At the base, a small plexus of _____ _______ supplies _______ to the growing hair and the melanocytes.
    dermal root sheath; blood vessels; nutrition
  13. A single bundle of ______ muscle cells, the _______ ____ muscle, can contract to make the hair stand on end, or relax to let it lay flat.  A ________ gland is associated with the hair root.
    smooth; arrector pili; sebaceous
  14. Describe the first stage of growth cycle.
    Growth (anagen) stage. The hair matrix cells at the base of the follicle divide.  This pushes the hair a little further out of the root and makes the external hair just a little longer.  As these cells are pushed upward, they turn to bags of keratin and die (just as in the epidermis).  This stage lasts about 2-6 years
  15. Describe the second stage of the growth cycle.
    Regression (catagen) stage. The cells of the hair matrix stop dividing.  This stage lasts 2-3 weeks.
  16. Describe the final (3rd) stage of the growth cycle.
    Resting (telogen) stage. The hair falls out at the end of the resting stage and is replaced by a new hair in its growth stage. Lasts about 3 months.
  17. The anterior surface of hands (palms and fingers) do not have hair, and are classified as _____ ____.  Remember that thick skin has a _______ ______ while thin skin does not.
    Thick skin; stratum lucidum
  18. Along with differences in hair, there are differences in _____ ______.  If you get nervous, your palms sweat; there are more sweat glands in _____ skin than in ____ skin.
    sweat glands; thick; thin
  19. Because sebaceous glands are associated with hair follicles, they are present in _____ skin and absent in ___-_____ skin.
    hairy (thin); non-hairy (thick)
  20. The fingertips and lips are among the most sensitive parts of the body.  This is because they have the highest density of _____ _______.
    nerve endings
  21. Thick skin also has ridges because of the ______ _______ which underlie the epidermis.  These specializations help increase ____ and __________ on thick skin surfaces.
    dermal papillae; grip; sensitivity
  22. Skin develops from the outermost of the three embryonic layers, called the _______.  The dermis and epidermis are evident by __ _____. 
    Ectoderm; 11 weeks (40 weeks is full term)
  23. At the beginning of the second trimester (14 weeks), the precursors of _____ _____ and ____ _____ are evident.
    sweat glands; hair bulbs
  24. Hairs pop out on the surface by __ _____.  Melanocytes migrate into the skin from a location near the spinal cord called the ______ _____; they are among the last skin cells to arrive.
    18 weeks; neural crest
  25. On the other end of life, skin undergoes several changes with aging.  Toxins in cigarette smoke interfere with _______ _.  _______ _, in turn, is necessary for collagen synthesis.  The damage to the underlying dermis produces a characteristic _________ of the skin in cigarett smokers.
    Vitamin C; Vitamin C; slacking
  26. _______ is a common disease of aging skin.  It is characterized by ______ ____ ______ and pimples, especially around the nose and cheeks. The cause is unknown.
    Rosacea; dilated blood vessels
  27. Aging Skin: (long one I apologize)
    • decreased # of Langerhans cells (about 40%)
    • - increased risk of skin cancer & infections

    • decreased # of mast cells, melanocytes
    • decreased inflammatory response
    • decreased thermoregulation
    • -sweat glands, vascularity, subQ fat

    • flattening of dermal papillae and epidermal ridges (rete ridges)
    • -increased tendencey to tear

    • changes in collagen, elastin
    • -more wrinkles, sagging

    • decreased capillary loops in skin
    • -atrophy of hair bulbs, sweat, sebaceous glands

    • decreased mechanoreceptors
    • decreased speed of wound healing

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Biomedical core
2012-12-11 21:01:18

Objective 12-16
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