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Bio 125: Integumentary System

  1. Is the skin considered an organ?
    Yes
  2. Remember an organ consists of tissues working together to perform certain functions
  3. Therefore...skin (integument) and its appendages (sweat glands, oil glands, hair and nails) are considered
    organs.
  4. Together these organs make up
    the integumentary system (“covering”).
  5. -The ____ is the largest of all the organs...accounts for __ of total body weight.
    • skin
    • 7%
  6. Varies in thickness from
    1.5 - 4 mm
  7. The skin has two distinct regions:
    • 1) epidermis (thick epithelium)
    • 2) dermis (fibrous connective tissue)
  8. These layers are firmly cemented together along an
    undulating border.
  9. Separation of these two layers results in a
    blister
  10. The hypodermis (lies deep to the dermis) is not part of
    the integumentary system...although it shares some of the skin’s functions.
  11. 8 Functions of skin:
    • -Protects the body from bumps, scrapes, and cuts
    • -Screens out harmful UV rays from the sun
    • -Metabolic duties...Synthesis of vitamin D
    • -Insulates/cushions underlying body tissues
    • -Protects the body from water loss
    • -Helps regulate body temperature
    • -Excretes wastes (urea, salt)
    • -Contains sense organs
  12. Epidermis consists of 4 distinct cell types:
    • 1) Keratinocytes
    • 2) Melanocytes
    • 3) Merkel cells
    • 4) Langerhans' cells
  13. Keratinocytes:
    • - The most abundant epidermal cell (connected to one another by desmosomes) whose role is to produce keratin
    • -Produce antibiotics and enzymes that detoxify harmful chemicals.
  14. Keratin
    a tough fibrous protein that gives the epidermis its protective properties
  15. Melanocytes (stratum basale):
    Spider-shaped cells which make the dark skin pigment melanin.
  16. The melanin is transferred to nearby _________ where it clusters on the superficial side of the cell.
    keratinocytes
  17. Why is it important for melanin to cluster on the superficial side of the cell?
    To block out the harmful UV light from hitting the DNA that is present inside the nucleus of the cells
  18. -Light-skinned people:
    the melanin is digested by lysosomes a short distance above the basal layer.
  19. -Dark-skinned people:
    no digestion occurs and melanin occupies keratinocytes throughout the epidermis.
  20. Merkel cells (stratum basale):
    Hemisphere-shaped cells that are associated with a disc-like sensory nerve ending and serves as a receptor for touch
  21. Langerhans’ cells (stratum spinosum):
    • These cells belong to a class of macrophages-like cells.
    • As part of the immune system, Langerhans cells police the outer body surface, using receptor-mediated endocytosis to take up foreign proteins (antigens) that have invaded the epidermis.
  22. -Langerhans cells then leave the skin and travel to a nearby lymph node, where they present the antigens to _____ _ _______, which proceed to attack all foreign cells that carry the antigen
    killer T lymphocytes
  23. The epidermis is composed of
    • avascular epithelium
    • stratified squamous
  24. Epidermis consists of 4 or 5 distinct layers:
    • 1) Stratum basale (basal layer)
    • 2) Stratum spinosum (spiny layer)
    • 3) Stratum granulosum (granular layer)
    • 4) Stratum lucidum (clear layer)
    • 5) Stratum corneum (horny layer)
  25. Stratum lucidum is only found on
    thick skin
  26. Stratum Basale (Basal layer):
    • -The deepest epidermal layer
    • -Attached to the underlying dermis along an undulating borderline.
    • -Consists of a single row of cells, mostly stem cells representing the youngest keratinocytes.
    • -Cells in this layer rapidly divide via mitosis
  27. Stratum Spinosum (Spiny layer):
    • -Several cell layers thick
    • -Mitosis occurs here, but less often than in the basal layer.
    • -Cells contain thick bundles of intermediate filaments, called tonofilaments (“tension filaments”)
  28. Stratum Granulosum (Granular layer):
    • -1 to 5 layers of flattened keratinocytes,
    • which contain:
    • a) keratohyaline granules: form keratin in the higher strata
    • b) lamellated granules: contain a waterproofing glycolipid that is secrete into the extracellular space and plays a major role in slowing water loss.
    • -Cells above this layer are dead
  29. Stratum Lucidum (Clear layer):
    • -Occurs only in thick skin
    • -Consists of a few rows of flat dead keratinocytes
  30. Stratum Corneum (Horny layer):
    • -The most external part of the epidermis
    • -Composed of many layers of dead keratinocytes...which resemble flat sacs filled with keratin because their nuclei and organelles disintegrated upon death.
    • -The keratin and thickened plasma membrane of cells protect the skin against abrasion and penetration
  31. How much skin does a person shed in a lifetime?
    40lbs
  32. Dermis: The “hide”
    • The dermis binds the entire body together like a body stocking
    • it is your “hide” and corresponds to animal hides that are used to make leather products
  33. Dermis is a strong flexible _______ tissue
    • connective
    • areolar connective tissue- richly supplied with blood vessels and nerves
  34. Cells found in dermis: (4)
    • fibroblasts
    • macrophages
    • mast cells
    • white blood cells
  35. Fibers found in dermis: (3)
    • collagen
    • elastic
    • reticular
  36. What is a vascular plexus?
    a network of converging and diverging vessels
  37. The dermal blood vessels consist of two vascular plexuses:
    • a) Cutaneous plexus (deep)
    • b) Subpapillary plexus (superficial)
  38. Cutaneous plexus (deep)
    • -Located between the hypodermis and the dermis.
    • -Nourishes the hypodermis and the structures located within the deeper portions of the dermis.
  39. Subpapillary plexus (superficial):
    • -Located just below the dermal papillae
    • -Supplies the more superficial dermal structures (the dermal papillae and the epidermis)
  40. The vascular plexuses play a role in
    thermal regulation
  41. The dermis has two layers:
    • 1) Papillary layer
    • 2) Reticular layer
  42. Papillary layer:
    • - Superficial 20% of the dermis
    • -Composed of areolar connective tissue (thin collagen/reticular fiber)
  43. Dermal papillae
    fingerlike projections that extend into the overlying epidermis
  44. What function(s) do these dermal papillae perform?
    There is a greater surface area allowing for more exchange and for a tighter connection between layers
  45. On the palm and soles, the dermal papillae lie atop larger mounds
    • called
    • dermal ridges
  46. Dermal ridges elevate the
    overlying epidermis into epidermal ridges (fingerprints, palmprints, and footprints)
  47. What function(s) do these epidermal ridges provide?
    They allow you to grip things
  48. Sweat pores open along the crests of the epidermal ridges, which leave distinct
    fingerprints (“sweat films”)
  49. Reticular layer (“network”):
    • -80% of thickness of dermis
    • -The deepest skin layer composed of dense irregular connective tissue
    • -The ECM contains thick bundles of interlacing collagen and elastic fibers where most fibers run parallel to the skin surface
  50. Network of what?
    Network of collagen fibers
  51. The collagen fibers of the dermis gives skin its
    strength and resilience
  52. The elastic fibers in the dermis provide the skin with
    stretch-recoil properties.
  53. “Extreme stretching” of the skin (obesity and pregnancy) can tear the collagen in the dermis, which cause slivery white scars called
    striae
  54. The hypodermis is not part of the
    skin
  55. Hypodermis is deep to the skin – also called (2 names)
    superficial fascia and subcutaneous layer
  56. Hypodermis contains (2 types of CT)
    areolar and adipose connective tissues
  57. Hypodermis anchors skin to
    underlying structures (mostly to muscles)
  58. Hypodermis helps insulate the body (stores fat) because fat is a
    poor conductor of heat, it prevents heat loss from the body
  59. The hypodermis thickens with
    weight gain
  60. -In females: subcutaneous fat accumulates first in the
    thighs and breasts
  61. -In males: it first accumulates in the
    anterior abdomen (“beer belly”)
  62. Three pigments contribute to skin color:
    • 1) melanin
    • 2) carotene
    • 3) hemoglobin
  63. Melanin is made from an amino acid called
    tyrosine
  64. Melanin is present in several varieties
    yellow - reddish - brown -black
  65. Melanin is made in
    melanocytes, which contain an enzyme called tyrosinase
  66. ______ passes from melanocytes to keratinocytes in the stratum basale of the epidermis
    Melanin
  67. -Freckles and pigmented moles are localized accumulation of
    melanin
  68. - Freckles:
    melanin is restricted to the basal layer of the epidermis and form as the result of exposure to the sun.
  69. - Moles:
    • clusters of melanocytes transform into melanin-containing cells and accumulate in the basal layer of the epidermis and the top layers of the dermis.
    • Not formed by exposure to the sun.
  70. Carotene
    • -A yellow-orange pigment that the body obtains from vegetable sources such as carrots and tomatoes.
    • -Accumulates in the stratum corneum of the epidermis and in the fat of the hypodermis
  71. Hemoglobin
    -The crimson-color of oxygenated hemoglobin
  72. Another factor influencing skin color is _______ _, a vital hormone required for the uptake of calcium from the diet and essential for healthy bones
    vitamin D
  73. -UV rays stimulate the deep epidermis to produce
    vitamin D
  74. The trade-off between protection from the harmful effects of UV radiation and production of vitamin D may have been the selective pressure behind the evolution of ___ ______ as early humans moved away from the tropics
    skin coloration
  75. 2 categories of cutaneous glands
    • 1) sebaceous glands
    • 2) sweat glands
  76. Sebaceous (“greasy”) glands occurs over entire body, except ____ ___ ____
    palms and soles
  77. Most sebaceous glands are associated with a
    hair follicle
  78. Simple alveolar glands with several _____ opening into a single duct
    alveoli
  79. -The alveoli are filled with cells (no lumen) that make
    oily lipids
  80. Sebaceous glands secrete
    sebum
  81. What is sebum?
    • an oily substance that acts as a lubricant to keep skin soft and moist and to keep the hair from becoming brittle.
    • Also, collects dirt, prevents water loss, and kills bacteria.
  82. The sebaceous glands are particularly active during _____ (hormones/androgen) making the skin very oily
    puberty
  83. -Blackheads are accumulations of
    dried sebum and bacteria in the oil duct
  84. Acne is an ____ ______ of the sebaceous glands
    active infection
  85. Sebum is made via a process called
    • holocrine secretion
    • whole cells break up to from the product
  86. What is sweat?
    Sweat is a filtrate of blood that passes through the secretory cells of the sweat glands and is released by exocytosis
  87. How much sweat do we normally produce in one day?
    500 ml
  88. On hot days or vigorous exercise
    12 L
  89. Only mammals have sweat glands used for
    thermoregulation
  90. ______ have the most sweat glands of all mammals
    Humans
  91. Hair usually interferes with the evaporation of sweat and the ability to cool the body...therefore the need for temperature regulation through sweating led to a reduction of
    hairiness
  92. What is true sweat?
    • -99% water
    • -1% salts (NaCl) and metabolic wastes (urea, ammonia, uric acid)
  93. Sweat is _____ so it retards the growth of bacteria on the skin
    acidic
  94. Two types of sweat glands:
    • Eccrine
    • Apocrine
  95. Both eccrine and apocrine respond to ___ and ____
    stress and heat
  96. Eccrine glands are the more numerous type and produce
    true sweat
  97. Eccrine is abundant on which body parts (3)
    palms, soles, and forehead
  98. Eccrine gland has coiled simple tubular gland. The coiled secretory base lies in the
    deep dermis and hypodermis
  99. Apocrine glands
    Confined to axillary, anal, and genital areas--- produces a special kind of sweat
  100. Apocrine glands are _____ in size
    larger
  101. Milky or yellow color sweat consisting of fatty substances and proteins (odorless), however organic molecules are decomposed by bacteria on skin resulting in
    body odor
  102. Apocrine glands start to function at puberty under the influence of
    androgens.
  103. They enlarge and recede with phases of a woman’s
    menstrual cycle
  104. The apocrine glands activity increases with
    sexual foreplay
  105. Apocrine glands are analogous to the sexual scent glands of other
    animals
  106. Hair
    long filaments
  107. Hair follicles
    tubular invaginations of the epidermis from which the hairs grow
  108. The main function of hair is to
    sense things that lightly touch the skin
  109. The hair on the scalp protects the head against _____ ______ in summer and _______ ____ _____ on cold days
    • direct sunlight
    • against heat loss
  110. Eyelashes shield
    the eyes
  111. nose hairs filter
    large particles such as insects and lint from inhaled air.
  112. Hair is composed of
    dead, keratinized cells
  113. The hard keratin in hairs has two advantages over the soft keratin found in typical epidermal cells:
    • 1) It is tougher and more durable
    • 2) The cells of hard keratin do not flake off
  114. Chief parts of hair: (2)
    • a) root
    • b) shaft
  115. root:
    the part of the hair embedded within the skin
  116. shaft:
    the part that projects above the skin surface
  117. The hair is composed of three concentric layers of keratinized cells:
    • a) Medulla
    • b) Cortex
    • c) Cuticle
  118. Medulla:
    central core that consists of large cells and air spaces
  119. Cortex:
    • surrounds medulla
    • consists of several layers of flattened cells.
  120. c) Cuticle:
    • outermost layer
    • a single layer of cells that overlap one another from below like shingles on a roof
  121. The cuticle provides strength and keeps the inner layers
    tightly compacted
  122. Hair pigment is made by melanocytes at _____ and is transferred to _____
    • the base of the hair follicle
    • the cells of the hair root
  123. Different proportions of two types of melanin (black-brown and yellow-rust) combine to produce
    all the common hair colors...black, brown, red and blond
  124. Graying or whitening of hair results from a decrease in the
    • production of _______ and from the replacement of melanin by ____ ___ ____ in the hair shaft
    • melanin
    • colorless air bubbles
  125. Hair bulb:
    deep, expanded end of the hair follicle
  126. Root plexus:
    knot of sensory nerves around hair bulb bending of the hair stimulates nerve endings.
  127. The wall of the hair follicle is composed of an
    outer connective tissue root sheath (derived from the dermis) an inner epithelial root sheath (derived from the epidermis)
  128. Arrector pili muscle:
    bundle of smooth muscle that runs from the most superficial part of the dermis to a deep-lying hair follicle
  129. Relaxed:
    hairs lie at an angle
  130. Contracted:
    hairs stand errect and skin forms dimples
  131. For animals...insulating layer of
    air
  132. A nail is a
    scalelike modification of the epidermis made up of hard keratin.
  133. Each nail has (3)
    • a) a distal free edge
    • b) a body
    • c) a proximal root
  134. The nail rests on a bed of epidermis called the
    nail bed
  135. Nail bed contains
    only the deeper layers of the epidermis (the nail itself corresponds to the superficial keratinized layers)
  136. Nails look pink because of the rich network of
    • _______ in the underlying dermis
    • capillaries
  137. At the root and the proximal end of the nail body, the bed thickens to form the
    nail matrix
  138. The nail matrix is the
    actively growing part of the nail
  139. The matrix is so thick in the proximal region that the pink dermis cannot
    show through it.
  140. Instead, we see a white crescent called the
    lunula (“little moon”)
  141. The lateral and proximal borders of the nail are overlapped by skin folds called
    nail folds
  142. The proximal nail fold is the called the
    eponychium (cuticle)
  143. A burn is
    tissue damage inflicted by heat, electricity, radiation, extreme friction, or certain harmful chemicals.
  144. The immediate threat to life from serious burns is the loss of
    • body fluids (water) and salts.
    • This dehydration leads to fatal circulatory shock (inadequate blood circulation).
  145. In addition ______ becomes the main threat
    infection
  146. Partial thickness burns: (2)
    • - First-degree burns
    • - Second-degree burns
  147. Full thickness burns: (1)
    - Third-degree burns
  148. First-degree burns:
    only the epidermis is damaged
  149. Second-degree burns:
    injury to the epidermis and the upper part of the dermis
  150. Third-degree burns:
    • consume the entire thickness of the skin
    • Skin is usually grafted onto the burned area.
Author
jocelyn8
ID
361071
Card Set
Bio 125: Integumentary System
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