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Dermatology 1 > Skin function, epidermis > Flashcards

Skin function, epidermis Flashcards

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Dermatology Board Prep flashcards
1
Q

skin as physical barrier (3)

A
  • prevention of water, electrolyte, macromolecule loss
  • prevention of invasion by external agents (chemical, physical, microbial)
  • anatomic (atratum corneum, hair)
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2
Q

skin as physiologic barrier (2)

A
  • turnover rate (30-45 days for keratinocyte to go from basal layer to surface)
  • sebum (bacteriostatic, fungistatic)
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3
Q

skin as immunologic barrier

A

-keratinocytes, langerhans cells (macrophages), and lymphocytes provide the skin with an immunosurveillance capability that effectively protects against the development of cutaneous neoplasms and persistent infections

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4
Q

skin microbial flora

A
  • normal bacteria inhibit the growth of pathogens and compete with pathogens for nutrients/space
  • fungal, viral phyla protect skin against pathogens
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5
Q

skin and communication

A
  • sensory: primary sense organ for touch, pressure, pain, itch, heat, cold
  • immunologic: langerhans cells present antigen to lymphocytes in regional lymph nodes
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6
Q

skin and temperature regulation (4)

A
  • hair coat
  • cutaneous blood supply
  • subcutaneous fat
  • sweat glands (horses - apocrine, dogs/cats - eccrine in footpads)
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7
Q

skin and secretion

A

secretory organ by virtue of apocrine, eccrine, and sebaceous glands

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8
Q

skin and storage

A

reservoir of electrolytes, water, vitamins, fat, carbs, proteins, and other materials

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9
Q

skin and pigmentation

A
  • melanin formation, vascularization, and keratinization help determine the color of the skin/coat
  • pigmentation protects from solar radiation damage (UV light)
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10
Q

skin and vitamin D production

A

vitamin D produced in skin through stimulation by solar radiation

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11
Q

akin and adnexa production

A

skin produces keratinized structures such as hairs, nails, claws, hooves, and the horny layer of the epidermis

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12
Q

skin as an indicator

A

may be an indicator of general health and internal diseases

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13
Q

skin and motion/shape

A
  • flexibility, elasticity, and toughness allow motion, provide shape and form
  • many species differences as to structure and function of skin
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14
Q

4 main skin regions

A
  • epidermis
  • dermal-epithelial junction
  • dermis
  • hypodermis/subcutaneous tissue
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15
Q

what are epidermally derived appendages

A
  • hair follicles
  • sebaceous glands
  • apocrine sweat glands
  • eccrine sweat glands
  • nails/claws/hooves
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16
Q

layers of the epidermis (inner to outer)

A
  • stratum basale (basal layer)
  • stratum spinosum (spinous layer)
  • stratum granulosum (granular layer)
  • stratum lucidum (clear layer)
  • stratum corneum (horny layer)
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17
Q

cells in basal layer

A

cuboidal cells called keratinocytes (90%), melanocytes (10%), and merkel cells (1%)

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18
Q

what is important about basal layer

A

site of cell division (mitosis)

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19
Q

how are basal cells attached to basement membrane zone

A

hemidesmosomes

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20
Q

cell to cell attachments in basal layer - what are they?

A

desmosomes (in between keratinocytes): junctions which can breakdown and reform to allow other cells to pass between keratinocytes and allow keratinocytes to move upward in epidermis to become keratinized and form stratum corneum

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21
Q

why are desmosomes important to us

A

they are the target antigen for the most common autoimmune skin diseases of domestic species called pemphigus foliaceus (also the target antigen for other forms of pemphigus)

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22
Q

what is stratum spinosum composed of

A

the daughter cells of the stratum basale

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23
Q

layers in stratum spinosum

A
  • number of layers varies between species and within the animal
  • tends to be 1-3 layers thick in hairy skin
  • thickest layer of the skin
  • thicker in footpads, nasal planum, and mucocutaneous junctions (20 layers)
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24
Q

cells in stratum spinosum (structure)

A
  • polyhedral in shape

- “prickle cells” have desmosomes

25
Q

what do cells of the stratum spinosum do

A
  • start the process of differentiation to become completely keratinized
  • synthesize proteins that will be part of the cornified cell envelope and the membrant coating granule, which produce the lipids that will form the intercellular lipid lamellae
26
Q

what is acanthosis and what can cause it abnormally

A
  • an increase in thickness of the stratum spinosum

- chronic inflammatory processes can result in it

27
Q

granular layer layers

A
  • variably present in haired skin (1-2 layers)

- thicker in hairless skin

28
Q

keratinocytes in stratum granulosum

A
  • flattened in this layer

- contain keratohyalin granules –> keratinization process, barrier function

29
Q

other products of granular layer keratinocytes

A

membrane coating granules –> produce the lipid in the intracellular spaces of stratum corneum

30
Q

what cells does stratum lucidum contain

A

fully cornified flat cells (non-staining)

31
Q

where is stratum lucidum present

A

only in areas of friction and areas where the epidermis is thick

32
Q

what is stratum corneum composed of

A

several layers of flattened, anuclear fully cornified cells arranged in vertical columns

33
Q

another name for keratinocytes in stratum corneum

A

corneocytes

34
Q

what are intracellular spaces of stratum corneum filled with

A

lamellar lipids

35
Q

function of stratum corneum

A
  • skin barrier/protective functions

- cornified cells envelope composed of cross-linked proteins and provide structural support, resist invasion

36
Q

what does stratum corneum constitute

A

the major barrier of the epidermis –> “brick wall”

37
Q

define: hyperkeratosis

A

increase in thickness of stratum corneum

38
Q

what is most abundant cell in epidermis

A

keratinocyte (called corneocytes in stratum corneum)

39
Q

origin and location of keratinocytes

A
  • origin: ectoderm

- location: throughout epidermis

40
Q

functions of keratinocytes (3)

A
  • production of keratin
  • production of intracellular lamellar lipid (stratum corneum)
  • epidermal immunity (cytokines, defensins)
41
Q

what are defensins

A
  • produced by keratinocytes in dermis

- make holes in wall of bacteria, viruses, protozoa (epidermal immunity)

42
Q

what are melanocytes

A
  • dendritic cells (no immune function) in epidermis

- appear clear on H&E, long dendritic processes

43
Q

origin and location of melanocytes

A
  • origin: neural crest

- location: basal layer of epidermis, hair follicles, ducts of sebaceous/apocrine glands

44
Q

functions of melanocytes (2)

A
  • production of melanin (coloration, UV protection)

- communication with keratinocytes

45
Q

what are langerhans cells

A
  • epidermal dendritic cells

- clear cells on H&E –> “tennis racket” granules (birbeck granules)

46
Q

origin and location of langerhans cells-

A
  • origin: bone marrow

- location: suprabasal layers of epidermis

47
Q

functions of langerhans cells (3)

A
  • immune surveillance
  • antigen processing and presentation
  • development of allergic dermatitis and graft rejection
48
Q

what epidermal cells are positive for Thy 1 antigen

A

NK cells

49
Q

what are merkel cells

A

-pidermal clear cells confined to stratum basale of tylotrich pads

50
Q

origin and function of merkel cells

A
  • origin: neural crest or ectoderm

- function: slow adapting mechanoreceptors

51
Q

what other cells are present in epidermis transiently in diseased states - how are they present

A
  • neutrophils, eosinophils, lymphocytes, erythrocytes

- process: exocytosis (inflammatory process)

52
Q

what other epidermal cells are present in most mammals and participate in skin immunologic barrier

A

gamma-delta T cells

53
Q

3 stages of epidermis life cycle

A

mitosis, differentiation, exfoliation

54
Q

is normal desquamation usually visible or not

A

rarely visible

55
Q

what does the shedding of visible scale indicate and why

A
  • indicates a disorder of keratinization (inflammation)
  • more basal keratinocytes are undergoing mitosis, therefore more differentiate, keratinize, and turnover faster (basal cells become keratinized faster)
56
Q

haired skin info

A
  • thin epidermis and thin stratum corneum
  • slightly undulating but without rete pegs
  • thickness varies within species according to the area of the body
57
Q

glabrous/unhaired skin info

A
  • epidermis and stratum corneum are thicker

- prominent rete pegs protrude into dermis

58
Q

in general, where is the skin thickest and thinnest

A
  • thickest over dorsum and neck

- thinnest over ventrum, axillae, inguinal regions

Dermatology 1 (4 decks)

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