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S1 BIO 100 A&P 1 > Skin > Flashcards

Skin Flashcards

Chapter 10

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1
Q

Skin intro

A
  • largest organ of body
  • cutaneous membrane
  • 2 layers: epidermis (superficial epithelial layer) and dermis (deep vascular connective tissue layer)
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2
Q

Thin skin

A

Covers most of body surface, except palms of hands and soles of feet

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3
Q

Thick skin

A

Does not contain hair

  • soles of feet and palms of hands
  • friction ridges form fingerprints
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4
Q

Epidermis intro

A
  • most superficial layer

- composed of keratinocytes, melanocytes, dendrite cells, and tactile epithelial cells (merkel cells)

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5
Q

Keratinocytes

A
  • 90%+ of cell
  • eventually become filled with keratin (tough fibrous tissue)
  • keratin protects epidermis from mechanical and shearing forces
  • once the keratinocytes have migrated to the outer most layer and flattened out, they are called corneocytes
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6
Q

Melanocytes

A
  • in stratum basale
  • make granules of pigment (melanin)
  • melanocytes do not migrate
  • melanin granules are transported to adjacent keratinocytes
  • melanin migrates around nucleus to “shield” DNA from UV radiation by reducing the amount of UV that can penetrate into deeper layers of skin
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7
Q

Dendrite cells

A

Langerhans cells

- branched cells that play a role in the immune response

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8
Q

Tactile or Merkel cells

A
  • located in deepest layer of the epidermis near sensory nerve endings
  • serve as light touch receptors
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9
Q

Epidermis cell layers

A
  • 5 layers

- stratum corneum - stratum lucidum - stratum granulosum - stratum spinosum - stratum basale

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10
Q

Stratum basale

A
  • base layer
  • stratum germinativum: attached to basement membrane via rete pegs (downward projections into the papilary dermis)
  • 1 layer of columnar cells
  • some of these cells are stem cells that divide to produce new keratinocytes
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11
Q

Stratum spinosum

A
  • spiny layer (when dead on a slide)
  • cells arranged in 8-10 layers of irregularly shaped cells
  • cells are rich in RNA making them well equipped to initiate the protein synthesis required for production of keratin
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12
Q

Stratum granulosum

A
  • granular layer 3-5 layers thick
  • keratinocytes begin keratin formation
  • cell start degeneration getting further away from blood supply
  • cells are filled with keratohyalin granules - required for keratin synthesis
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13
Q

Stratum lucidum

A
  • clear layer
  • layer only present in thick skin
  • few layers thic of flattened, dead keratinocytes
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14
Q

Stratum corneum

A
  • horny layer
  • most superficial layer
  • 15-30 cell layers thick
  • composed of very thin squamos cells, which at the skin surface are dead and continually being shed and replaced
  • dead cells filled with keratin (barrier area)
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15
Q

Epidermal growth and repair

A

Regeneration time refers to time required for keratinocytes to form in the stratum basale and migrate to the skin surface -35 days (4-6 weeks)
- shortened turnover time will increase the thickness of the stratum corneum and may result in callus formation

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16
Q

Dermoepidermal junction

A

Basement membrane

  • contains polysaccharide gel that glues the two layers together (between rete pegs and papillary dermis)
  • resists shear forces
  • creates partial barrier to some large molecules
17
Q

Dermis

A
  • true skin: much thicker than epidermis and lies beneath it
  • gives strength to skin
  • provides protection against mechanical injury and compression
  • serves as a reservoir area for storage of water and electrolytes
  • contains many nerves and nerve endings
  • highly vascularized
18
Q

Papillary layer

A
  • composed of dermal papillae that project into the epidermis and transfer nutrients and molecules to avascular epidermis
  • composed of fine collagenous and elastic fibers - dense irregular connective tissue
  • forms a unique pattern that gives an individual fingerprints
  • makes up <20% of the dermis
19
Q

Reticular layer

A
  • contains dense, interlacing white collagenous fibers and elastic fibers to make the skin tough yet stretchable; dense irregular CT
  • contains many different sensory receptors and nerve endings
  • provides attachment site for skeletal muscle of the face and scalp
20
Q

Dermal growth and repair

A
  • dermis does not continually shed and regenerate itself like the epidermis
  • during wound healing, the fibroblasts begin forming an unusually dense mass of new connective fibers
  • if the epidermis is damaged, it will simply re-epithialize. If dermal damage is present a scar may form
  • tension/cleavage lines - patterns formed by the collagenous fibers of the reticular layer of the dermis; also called langer’s lines
21
Q

Hypodermis

A

Subcuatneous loayer or superficial fascia

  • not part of the skin - accessory structure
  • lies deep to the dermis
  • functions to anchor skin to underlying tissues (muscles), energy source, thermoregulation
  • mostly loose fibrous and adipose tissue
22
Q

Skin color

A
  • determined by pigment concentration and genetics
  • melanin granules produced by tyrosine and tyrosinase
  • UV exposure increases activity of tyrosinase
  • albinism: lack/decreased function of tyrosinase
23
Q

Functions of skin (7)

A
  1. Protection
  2. Sensation
  3. Flexibility
  4. Excretion
  5. Hormone (vitamin D) production
  6. Immunity
  7. Homeostasis of body temp
24
Q
  1. Protection
A
  • protects underlying tissues against invasion by microorganisms, chemical hazards, and mechanical trauma
  • provides protection against dehydration caused by loss of fluid
  • protects us from the harmful effect of overexposure to UV light
25
Q
  1. Protection (acid)
A
  • epidermis is slightly acidic pH5
  • acid mantle of skin
  • acidic pH prevents bacteria present on skin form becoming pathogenic
  • important to maintain acid mantle of skin
26
Q
  1. Sensation
A
  • skin acts as a sophisticated sense organ covering the entire body surface
  • receptors permit us to detect pressure, touch, temperature, pain and other general sensations
  • allows the body to respond to changes occurring in both the external and internal environments
27
Q
  1. Flexibility
A
  • skin is supple and elastic (elastin fibers)

- permits change in body contour without injury

28
Q
  1. Excretion
A
  • regulates the volume and chemical content of sweat

- influences the total fluid volume of the body as well as amounts of certain waste products

29
Q
  1. Hormone production
A

Vitamin D

  • exposure of skin to UV light converts a cholesterol molecule in the dermal blood supply to a vitamin D precursor
  • blood transports (hormone) precursor to liver and kidneys, where vitamin D is produced
  • excessive sunscreen use may decrease/prevent the synthesis of vitamin D
30
Q
  1. Immunity
A
  • important defensive cells that destroy pathogenic microorganisms are found in the skin and play an important role in immunity
  • langerhans cells - macrophages
  • langerhans/dendritic cells trigger helpful immune reaction by working with helper T cells
31
Q
  1. Homeostasis of body temperature
A
  • to maintain homeostasis of body temp, heat production must equal heat loss
  • skin plays a critical role in this process through various processes: heat production, heat loss, evaporation, radiation, conduction, and convection
32
Q

Evaporation

A
  • constitutes one method by which heat is lost from the body

- heat energy must be expended to evaporate any fluid

33
Q

Heat production and loss

A
  • by metabolism of foods in skeletal muscles and liver
  • chief determinant of heat production is the amount of muscular work being performed
  • approx 80% of heat loss occurs through the skin; remaining 20% occurs through the mucosa of the respiratory, digestive, and urinary tracts
  • heat loss occurs through vasodilation
34
Q

Homeostatic regulation of heat loss

A
  • heat loss by the skin is controlled by a negative feedback loop
  • receptors in the hypothalamus monitor the body’s internal temperature
  • if body temperature is increased, the hypothalamus sends a nervous signal to the sweat glands and blood vessels fo the skin
  • the hypothalamus continues to send signals until the body’s temperature returns to normal
35
Q

Rule of nines

A 
Head: 9%
UE x2: 9%
Trunk: 18%
Back: 18%
LE x2: 18%
1%

S1 BIO 100 A&P 1 (24 decks)

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