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MSK/Derm > Skin Structure and Function > Flashcards

Skin Structure and Function Flashcards

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Dermatology Board Prep flashcards
1
Q

What are the major skin functions?

A

barrier - resist mechanical stress, limit water loss, block entry from outside, UV shield

repair - wound healing

immunologic - tempter and alert the immune system

sensation - pain, itc, pressure, and pleasure

thermoregulation, insulation, and absorption

appearance - quality of life

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2
Q

What is the makeup of the epidermis?

A

keratinizing, stratified squamous epithelium

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3
Q

What is the makeup of the dermis?

A

connective tissue/stroma

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4
Q

What are the four layers of the epidermis starting from the bottom? What happens in each layer?

A

basal layer (stratum basale) - proliferation

spinous layer (stratum spinosum) - adhesion

granular layer (stratum granulosum) - differentiation

stratum corneum (cornified layer) - death

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5
Q

What cell types make up 90% of the epidermis?

A

keratinocytes and corneocytes

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6
Q

melanocytes

A

pigment producing cells

mostly found in basal layer

directly injects melanin and pigment

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7
Q

Langerhans cells

A

dendritic antigen presenting cells

important for recognizing antigen and alerting the immune system

also important in immunosuppression

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8
Q

Merkel Cells

A

mechanoreceptor cells

associated with the sense of light touch discrimination of shapes and textures

often give rise to tumors

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9
Q

What is the primary function of the epidermis?

A

building a semi-permeable barrier

  • resist physical trauma and repair wounds
  • prevent entry of noxious agents
  • limit excess water loss
  • protect against UV radiation from the sun
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10
Q

What are the strategies for building a barrier?

A

replenish - maintain a constant supply of keratinocytes to repopulate the upper layers

resist - adopt specialized structures to yield a strong, sticky cell

release - extrude lipids and cornified envelopt to form an impermeable seal

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11
Q

What are the characteristics of the epidermal self-renewal

A

normally, the epidermis turns-over every 30 days

stem cells in the basal layer give rise to proliferating compartments

basal layer cells exit the cell cycle and replenhishes the upper layer

outermost cells constantly sloughed off

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12
Q

How is stratification achieved in keratinocytes?

A

asymmetrical division

different polarity of cells dividing

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13
Q

What is psoriasis?

A

an inflammatory skin disease with increased keratinocyte proliferation and turnover

leads to abnormal differentiation and formation of thick, scaly plaques

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14
Q

How do keratinocytes maintain their shape?

A

they build cytoskeleton networks

  • microtubules
  • actin-based microfilaments
  • keratin-based intermediate filaments
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15
Q

keratin

A

keratins are major (~25%) protein in keratinocytes

keratin composition changes as keratinocytes differentiate

54 different human keratins pair up to form intermediate filaments

subtypes are expressed in distinct epidermal cell layers

1/10 in granular/spinous and 5/14 in basal

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16
Q

What are hemidesmosomes?

A

integrin-based junctions that connect basal keratinocytes to the basement membrane

mutations show generalized blistering - ex. junctional epidermolysis bullosa

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17
Q

What happens in bullous pemphigoid?

A

auto-antibodies target proteins found in hemidesmosomes

these break the connection between basal keratinocytes and basement membrane -> subepidermal blisters

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18
Q

What are desmosomes?

A

specialized junctions that anchor keratin to sites of cell-cell contact

genes - papkin, armadillo, and cadherins

Holds two cells together to form molecular rivets

Also allows cell-cell communications

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19
Q

Lethal Acantholytic Epidermolysis Bullosa

A

disease where desmosomes are compromised (Pakin mutation)

heart and skin defomiries result

20
Q

Pemphigus Vulgaris

A

auto-antibodies target proteins found in desmosomes (cadherin)

breaks the connection between adjacent keratinocytes -> suprabasal epidermal blisters

Pemphigus Foliaceus has more superficial phenotypes

21
Q

What is the role of lamellar bodies in the skin?

A

excrete lipid for waterproof seal

22
Q

What are the “bricks and mortar” of the Stratum Corneum?

A

bricks - corneocytes

mortar - lamellar membrane

23
Q

corneocytes

A

anucleate, keratin-filled, dead keratinocytes encased in a highly crosslinked, specialized membrane - the cornified envelope

24
Q

lamellar membrane

A

lipids (ceramides, cholesterol, and free fatty acids) extruded from the keratinocytes to form a hydrophobic seal

25
Q

What skin diseases does a “leaky” barrier predispose people for?

A

ichthyosis vulgaris - caused by filaggrin mutations, leading to dr, scaly skin

many (7%) Europeans have mutations in this gene

filaggrin mutations commonly found in atopic dermatitis/exzema

26
Q

filaggrin

A

a keratin aggregating protein that is important for cornified envelope formation, hydration and barrier function

27
Q

What is the atopic march?

A

the progression of chythyosis to atopic dermatitis and then asthma/hayfever

28
Q

What is the role of tight junctions?

A

serve as a permeability barrier in simple epithelia

work in concert with the Stratum Corneum to make a barrier in skin

29
Q

What happens to the stratum corneum in atopic dermatitis (eczema)?

A

decreased FLG, LOR, INV

lipid defects

increased proeases, decreased protease inhibitors

trauma from itch-scrath cycle

30
Q

What happens to tight junctions in atopic dermatitis (eczema)?

A

decreased CLDKN1

cleavage of TJ proteins by proteases (endogenous, allergn-associated, microbe-associated)

31
Q

What is the purpose of the dermis?

A

makes up the bulk of the skin

designed for maintaining pliability and tenssile strength

32
Q

What is the composition of the matrix of the skin?

A

fibroblasts secrete different kinds of connective tissue:

  • collagen fibers for tensile strength (interstitial-type I/III)
  • elastic fibers - stretch and recoil, surrounded by fibrillin
  • ground substance - glycosaminoclycans and fibronectin
33
Q

What happens in scleroderma?

A

an autoimmune disease where excess collagen is produced along with fibrosis

ightly packed parallel collagen bundles, which leads to destruction of lood vessels

skin appendages are absent

34
Q

What causes dystrophic epidermolysiis bulbosa?

A

mutations in Collagen VII, which anchors to the basement membrane

pliable and malleable

35
Q

What is the result of mutations int he gene producing amorphous elastin?

A

caues Cutis Laxa

skin folds and sags because of lass of recoil

36
Q

What happens fom mutations int he fibrillin 1 gene?

A

protein encases elastin

mutation leads to Marfan’s Syndrome

37
Q

What is the role of mesenchymally-derived fibroblasts?

A

the main matrix secreting cell type in the dermis

38
Q

Aside form fibroblasts, what are other cell types in the dermis?

A

dermal papilla cells - specialized fibroblasts (hair growth cycle)

mast cells - heparin and histamine release (immediate hypersensitivity, hives-urticaria)

monocyte and macrophages - phagocytic (wound healing-debris clearance)

lymphocytes (T, NKT, B cells) - immunoregulatory (inflammatory skin disease)

39
Q

What is the organization of the hair follicles?

A

epithelial origin and associated with arrector pilorum muscles and sebaceous glands

epithelial layer of the hair flollicle is is important for communication

40
Q

What are the components of the pilosebaceous unit?

A

hair follicle

sebaceous gland

arrector pili muscle

apocrine sweat glands

41
Q

What is the life cycle of a hair follicle, and what are the signals that allow it to develop?

A

dermal papilla communicates with hair follicle and stems cells to promote growth

anagen - growth

catagen - involution

telogen - rest

42
Q

What is the makeup of nails?

A

appendage of the skin that is contiguous with the surrounding epidermis and made up of keratinocytes that produce a specialized set of keratins

43
Q

What is the role of the sebaceous gland?

A

contains sebocytes that secrete their entire cell contents (holocrine secretion) into the duct

hyperactivity, hormones, bacterial colonization, and HF pligging contribute to acne

44
Q

What is the structure and function of eccrine sweat glands?

A

cool the body

stratified cuboidal epithelium

in thick and thin skin

have ducts that are directly connected to the interfollicular epidermis

45
Q

What is the structure and function of apocrine sweat glands?

A

odor-producing, found in the axilla and perineum

large lumen, secretes into hair follicle

simple cuboidal/columnar epithelium

surrounded by contractile myoepithelial cells

have ducts that directly connect to hair follicles - pilosebaceous unit

MSK/Derm (54 decks)

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