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MSS: post-midterm > Epidermis/Dermis > Flashcards

Epidermis/Dermis Flashcards

1
Q

The epidermis is derived from what embryonic layer?

A

Ectoderm

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2
Q

Describe the epidermis location and function

A

Outermost layer of skin, barrier function

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3
Q

What are the layers of the epidermis?

A
  • stratum corneum (outermost)
  • stratum granulosum
  • stratum spinosum
  • stratum basale (innermost)
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4
Q

Describe the stratum basale

A

Deepest layer of the epidermis; attached to the basement membrane

**Contains kertainocyte stem cells

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5
Q

Where are stem cells located in the skin? How do they mature?

A

**The stratum basale of the epidermis

  • each stem cell divides into a daughter stem cell and a transient amplifying cell (TA cell)
  • TA cell undergoes a few more cell division cycles before separating from the basement membrane
  • keratinocyte moves suprabasally to join the stratum spinosum (SP cells)
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6
Q

Describe the stratum spinosum

A
  • Composed of differentiating keratinocytes
  • Makes up most of the epidermis in most parts of the body
  • Synthesizes keratin
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7
Q

What are the junctions of the epidermis?

A

Cell-cell:

  • tight junctions
  • adherens junctions
  • desmosomes (main junction between keratinocytes in the stratum spinosum)

Cell-basement membrane:

  • focal adhesions
  • hemidesmosomes
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8
Q

Describe the assembly of intermediate filaments

A

Filaments combine and build upon each other:

  • keratin
  • heterodimer
  • tetramer
  • protofilament
  • intermediate filament
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9
Q

Describe the two types of granules in the stratum granulosum

A
  • Keratohyalin granules made of proteins:
    • filaggrin
    • involucrin
    • loricrin
  • Lamellar granules (odland bodies) made of fats and enzymes:
    • ceramides
    • cholesterol
    • fatty acids
    • hydrolytic enzymes
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10
Q

What makes up the stratum corneum?

A

Composed of corneocytes (dead; lack nucleus and organelles) held together by corneodesmosomes

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11
Q

Describe the stratum corneum

A
  • primary barrier of the epidermis
  • variable thickness
    • No stratum corneum: oral, genital, ocular mucosa
    • Thinnest: face, genitalia
    • Thickest: palms, soles
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12
Q

Describe the keratinization process

A

**also called cornification

  1. differentiation of the stem cell into a keratinocyte and separation from the basement membrane.
  2. cell migrates (also flattens out and loses its water content)
  3. lamellar granules and keratohyaline granules form
  4. keratinocyte progressively loses its cellular organelles and nucleus, and releases its intracellular granules
  5. keratinocyte becomes an anucleate corneocyte within the cornified envelope
  6. eventually shed in the process of desquamation
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13
Q

How long does keratinization take?

A

The full process of keratinocyte migration and maturation averages 28 days

(14 basale to corneum, 14 corneum to shedding)

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14
Q

Describe how a cell changes from the stratum granulosum to stratum corneum (cornification)

A
  • Keratohyalin granules become the “bricks” of the cornified envelope
  • Lamellar granules become the “mortar” of the lipid envelope
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15
Q

Describe pemphigus vulgaris

A

**Epidermal disease

  • acquired
  • autoimmune bullous disease (auto-antibodies to desmosomal proteins desmoglein 1 and 3)
  • intraepidermal blistering (thin layer between damage and outside, bursting/ulceration common)
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16
Q

What are the clinical features of pemphigus vulgaris?

A
  • flaccid, easily ruptured bullae
  • oral and mucosal lesions
  • Nikolsky’s sign positive (slight rubbing of the skin results in exfoliation of the outermost layer)
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17
Q

How can you treat pemphigus vulgaris?

A
  • prednisone
  • azathioprine
  • mycophenolate mofetil
  • rituximab
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18
Q

Describe ichthyosis vulgaris

A

**Epidermal disease

  • autosomal dominant genetic condition
  • mutation in profilaggrin gene (defective filaggrin protein)
  • affects 1 in 250
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19
Q

What are the clinical features of ichthyosis vulgaris?

A
  1. “fish scales” especially on shins
  2. dry skin
  3. hyperlinear palms

Associated with:

  • atopic dermatitis
  • allergic rhinitis
  • food allergies
  • asthma
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20
Q

What are the types of UV light?

A
  • UVC: 200-280 nm (doesn’t reach earth, absorbed by ozone)
  • UVB: 280-320 nm (penetrates skin epidermis)
  • UVA: 320-400 nm (penetrates skin deep into dermis)
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21
Q

When/where are the highest levels of UV observable?

A

10am-4pm at high altitudes

22
Q

What are the two components of sunscreen?

A
  1. Physical ingredients (reflect/scatter UV light) **better
    - titanium dioxide
    - zinc oxide
  2. Chemical ingredients (absorb UV light)
    - PABA
    - oxybenzone
    - avobenzone
23
Q

What is SPF? How is it calculated?

A

Sun Protection Factor

SPF= MEDprotected/MEDunprotected

MED= minimal erythema dose= minimum amount of UVB that causes skin redness at 24 hours

**NOTE: only measures UVB protection!

24
Q

Describe the ideal sunscreen

A
  • Broad spectrum
  • water resistant
  • SPF 30

Bonus, describe your ideal date.

A: April 25th. Because it’s not too hot, not too cold, all you need is a light jacket. (and some SPF 30!)

25
Q

What is the perfect way to apply sunscreen?

A
  • apply 15 minutes before sun exposure
  • apply generously (1 oz)
  • reapply every 2 hours (40-80 min if wet)
26
Q

The dermis is derived from what embryonic layer?

A

Mesoderm

27
Q

Describe the function of the dermis

A
  • structure/flexibility
  • vascular support
  • immunologic protection
  • nerve sensation
28
Q

What are the layers of the dermis?

A
  • papillary dermis (outermost, increases surface area to connect with epidermis)
  • reticular dermis
29
Q

What is the function of the extracellular matrix? What are its components?

A

Supports cells of the dermis and regulates their functions

Made up of collagen, elastic fibers, and extrafibrillar matrix

30
Q

What are the important characteristics of collagen?

A
  • main component of the dermis (20% of overall skin volume, 75% of dry weight of skin)
  • produced by dermal fibroblasts
  • very strong and stretches very little
31
Q

What are the main types of collagen?

A
  • Collagen I
    • most abundant (80-90%)
  • Collagen III
    • second most abundant
    • increased levels in embryogenesis/infancy and during wound healing
  • Collagen IV, VII, and XVII are in the basement membrane
32
Q

What is the function of elastic fibers? What are their components?

A

Give skin elasticity

Made of microfibrils (mainly fibrillin) and elastin

33
Q

What makes up the extrafibrillar matrix?

A

Also called ground substance:

  • water
  • electrolytes
  • plasma proteins
  • proteoglycans
34
Q

What is the function of proteoglycans? What are their components?

A

Bind large amounts of water

Made up of a protein core and glycosaminoglycans (long chain polysaccharides e.g. dermatan sulfate)

35
Q

Fibroblasts are derived from what embryonic layer? What is their function?

A

Mesoderm

**Synthesize ECM components (collagen, elastic fibers, and ground substance)

36
Q

Describe the vascular network of the dermis

A
  • interconnected superficial plexus in the papillary dermis and deep plexus in the lower reticular dermis
    • composed of arterioles and venules
  • from these plexuses come capillaries that supply the structures of the dermis
  • Responsible for temperature regulation, leukocyte trafficking, and wound healing
37
Q

Describe a pacinian corpuscle

A
  • present in weight-bearing surfaces, as well as the lips, nipples, penis, and clitoris
  • located in the deep dermis and subcutaneous tissue and detect pressure.
38
Q

Describe a meissner’s corpuscle

A
  • located just below the epidermis in the dermal papillae
  • sensitive to light touch and are concentrated on palms and soles.
39
Q

Describe the structure of collagen

A
  • triple helix, composed of 3 α-chains
  • each α-chain contains 3 nucleotide repeats where very third amino acid is a glycine (Gly-X-Y)
  • proline and hydroxyproline residues are commonly in the X and Y positions
40
Q

Describe Marfan syndrome

A
  • mutations in fibrillin
  • autosomal dominant condition
  • high degree of variability in its clinical manifestations
    • Tall and thin body type, Long limbs and fingers, Scoliosis, Flexible joints, Striae, Nearsightedness (myopia), Ectopia lentis (dislocation of the lens of the eye), Aortic dilation or aneurysm, Mitral valve prolapse
41
Q

Describe Ehlers-Danlos syndrome

A
  • group of inherited connective tissue disorders
  • abnormalities of collagen strucutre, production, processing, or assembly
  • variable inheritance and clinical features based on mutation
    • fragile/elastic skin, flexible joints/joint dislocations and early arthritis, scoliosis, collagen within blood vessels and internal organs -> rupture of blood vessels, intestines, and the uterus
42
Q

Describe morphea

A
  • acquired autoimmune disease
  • causes sclerosis (thickening of collagen)
  • children and adults may be affected, more common in females
  • erythematous and indurated plaques that slowly expand (can leave behind fibrotic or atrophic scars)
  • Limb/joint complications and neurologic involvement possible
43
Q

Describe systemic sclerosis

A
  • autoimmune disease
  • common in middle aged women
  • clinical features:
    • widespread sclerosis of the skin (microstomia/can’t open mouth, sclerodactyly), raynaud’s, telangiectasia, arthritis, internal organ development (pulm fibrosis, renal crisis, esophageal dysmotility)
44
Q

What are the stages of wound healing?

A
  1. Hemostasis
  2. Inflammation
  3. Proliferation
  4. Maturation
45
Q

Describe the main parts of hemostasis in wound healing

A
  • reflexive vasoconstriction
  • coagulation through platelet activation
  • formation of fibrin plug
46
Q

Describe the main parts of inflammation in wound healing

A
  • hours to 3 days
  • vasodilation
  • increased vascular permeability
  • leukoctye rectruitment
47
Q

Describe the main parts of proliferation in wound healing

A
  • 4-12 days
  • angiogenesis by endothelial cells
  • collagen, elastin, and matrix synthesis by fibroblasts
  • re-epithelialization through keratinocyte migration from edges
48
Q

Describe the main parts of maturation in wound healing

A
  • 12 days to 2 years
  • inflammatory cells cleared
  • fibroblast apoptosis
  • blood vessel and collagen maturation

**scar forms

49
Q

Subcutaneous fat is derived from what embryonic layer?

A

Mesoderm

50
Q

What are the functions of subcutaneous fat?

A

Energy storage, insulation, and shock absorption

51
Q

Describe erythema nodosum

A
  • reactive panniculitis
    • streptococcal pharyngitis
    • oral contraceptives
    • IBD
    • malignancy
  • most common in young women
  • tender red nodules on the shins

MSS: post-midterm (26 decks)

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