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BRS Term 2 > Introduction to dermatology (24) > Flashcards

Introduction to dermatology (24) Flashcards

1
Q

From where does the epidermis originate?

A

ectoderm

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2
Q

From where does the dermis originate?

A

mesoderm that comes into contact w/ inner surface of epidermis

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3
Q

What are the stages of development of the skin?

A
  • epidermis forms by week 4- single basal layer of cuboidal cells
  • 2y layer of squamous, non-keratinising cuboidal cells (periderm) develops in week 5–> generates vernix caseosa
  • from week 11, basal layer proliferates to form multilayered intermediate zone–> 4 more superficial strata: spinosum (deepest), granulosum, lucidum (only on palms and soles of feet), corneum
  • epidermal ridges protrude as troughs into the developing dermis–> dermal papillae
  • weeks 9-13 hair follicles develop in stratum germinativum
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4
Q

Which of gliae and melanocytes originate from cells migrating dorsally?

A

melanocytes: arise from neural crest, differentiate into melanoblasts and migrate dorsally to developing epidermis and hair follicles (wk6-8)–> become melanocytes
N.B. most melanoblasts have reached destination and differentiated into melanocytes by wk 12-13

(those that migrate ventrally become gliae)

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5
Q

How are melanocytes regulated?

A

MC1R, a G-protein coupled receptor
–> regulates quantity and quality of melanins produced under control of agonists and antagonists

  • agonists- aMSH and ACTH–> stimulate melanogenic cascade–> synthesises eumelanin (dark)
  • antagonists- ASP- reverses effects–> synthesises pheomelanin (pale)
  • ACTH also unregulated MC1R
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6
Q

What is the effect of UV exposure on the regulation of melanocytes?

A
  • inc. expression of MITF transcription factor + downstream melanogenic proteins e.g. Pmel17, MART-1, TYR, TRP1 and DCT–> inc. melanin
  • inc. expression of PAR2 in keratinocytes–> inc. uptake and distribution of melanosomes
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7
Q

What is the function of vernix caseosa?

A

protects developing foetus from amniotic fluid and microbes

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8
Q

What are melanocyte stem cells?

A
  • subset of melanoblasts
  • in hair follicle bulge
  • replenish melanocytes
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9
Q

What agonists/antagonists regulate melanocyte function?

A
  • agonists: alpha-melanocyte-stimulating hormone (aMSH) AND adrenocorticotropic hormone (ATCH)–> stimulate melanogenic cascade and inc. synthesis of eumelanin (dark pigment)
  • antagonists: Agouti signalling protein (ASIP) has opposite effect–> causes production of the phaeomelanin (found in pale skin and red hair)

N.B. ACTH can also upregulate MC1R gene

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10
Q

What is the overall structure of the skin?

A
  • superficial layer= epidermis
  • dermis= connective tissue
  • subcutaneous fat
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11
Q

What is the structure of the epidermis?

A
  • made of mainly keratinocytes (called corneocytes in stratum corneum)
  • keratinocytes divide in basal layer and progressively differentiate
  • cellular progression from basal layer to surface takes 30 days: stratum spinosum, stratum granulosum, stratum lucidum*, stratum corneum (no nuclei or organelles)
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12
Q

What does the filamentous cytoskeleton of keratinocytes comprise?

A
  • actin-containing microfilaments
  • tubulin-containing microtubules
  • intermediate filaments called keratins
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13
Q

What are the roles of keratins?

A
  • structure
  • cell signalling
  • wound healing
  • apoptosis
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14
Q

What are desmosomes?

A
  • cell adhesion complexes
  • anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes
  • allow cells to withstand trauma
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15
Q

What are gap junctions in the epidermis?

A
  • clusters of intercellular channels (connexons)
  • form connections between cytoplasm of adjacent keratinocytes
  • essential for cell synchronisation, cell differentiation, cell growth and metabolic coordination
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16
Q

What is the role of tight junctions in the epidermis?

A

to maintain barrier integrity of skin and cell polarity

17
Q

What are adherens junctions in the epidermis?

A

transmembrane structures that hold together actin filaments

18
Q

What cells are present in the epidermis and what are their roles?

A
  • keratinocytes
  • melanocytes: dendritic, distribute melanin pigment in melanosomes to keratinocytes
  • Langerhans cells: dendritic, antigen-presenting
  • Merkel cells: mechanosensory receptors
  • mast cells: role in inflammation
19
Q

What is the basement membrane of the skin?

A
  • dermal-epidermal junction
  • contains proteins and glycoproteins e.g. collagens IV and VII, laminin, integrins
  • roles: cell adhesion and migration
20
Q

What is the structure of the dermis?

A
  • provides resilience, supports skin
  • 2 layers: papillary dermis and reticular dermis
  • papillary: loose connective tissue, vascular, superficial
  • reticular: deep, dense connective tissue, forms bulk of dermis, less vascular supply
21
Q

What substances are found in the dermis?

A
  • contains mostly collagen I and II, and elastic fibres
  • glycoproteins that facilitate cell adhesion and motility: fibronectin, fibulin, integrins
  • ground substance between dermal collagen and elastic tissue, composed of glycosaminoglycans and proteoglycans
  • hyaluronic acid keeps water in dermis
22
Q

What cells are present within the dermis?

A
  • primarily fibroblasts (synthesise connective tissue)
  • histiocytes
  • mast cells
  • neutrophils
  • lymphocytes
  • dermal dendritic cells
23
Q

What is the innervation and vascular supply to the skin?

A
  • blood supply: deep and superficial vascular plexuses that don’t cross into epidermis
  • innervation: sensory and autonomic supply to hair follicles, blood supply, and eccrine and apocrine glands)
  • pilosebaceous unit: hair follicles
  • arrector pilli muscles
24
Q

What kind of nerve ending receptors are there in the layers of the skin?

A
  • corpuscular/encapsulated receptors in dermis

- free-ending/non-encapsulated receptors in epidermis

25
Q

What are the Meissner’s corpuscles?

A
  • tactile corpuscles
  • encapsulated, unmyelinated mechanoreceptors
  • detect light touch and slow vibration
  • at level of dermal papillae
  • most conc. in thick, hairless skin (finger pads and lips)
26
Q

What are the Ruffini corpuscles (also Bulbous)?

A
  • found deeper in dermis
  • sensitive to skin stretch
  • slow acting mechanoreceptor
  • highest density around fingernails
27
Q

What are the Pacinian corpuscles (also lamellar)?

A
  • rapidly adapting mechanoreceptor
  • detects deep pressure and vibration
  • ovoid shape
  • most conc. in hands and feet
28
Q

What are the Merkel cells?

A
  • non-encapsulated mechanoreceptors
  • detect light/sustained touch and pressure
  • modified epidermal cells, found in basal layer, directly above basement membrane
  • most populous in fingertips
  • also in palms, soles, oral and genital mucosa

BRS Term 2 (36 decks)

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