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Dermatology > Dermatology Intro > Flashcards

Dermatology Intro Flashcards

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Dermatology Board Prep flashcards
1
Q

Where does the Epidermis originate?

A

Ectoderm

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2
Q

What does the Dermis originate?

A

Mesoderm

  • mesoderm is essential for inducing differentiation of epidermal structures
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3
Q

How does skin come to be??

A

Juxtaposition between epidermis and dermis

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4
Q

How does the skin develop in utero?

A

Epidermis is as single basal layer of cuboidal cells ( week 4)

2ndry layer of squamous, non-keratinising cuboidal cells = periderm (week 5)

Generates white, waxy protective substance - vernix caseosa ( protects baby from fluid and after birth from bacteria )

From week 11, basal layer of cuboidal cells ( stratum germinativum) proliferates to form multilayered intermediate zone → four more superficial strata

Epidermal ridges protrude as troughs into developing dermis

beneath neurovascular supply develops into dermal papillae

Weeks 9-13 development of hair follicles in stratum germinativum and appearance of lanugo hair

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5
Q

What are melanocytes?

A

They are derived from neural crest which forms melanoblasts which migrate dorsally in week 6-8 to develop epidermis and hair follicles

By week 12-13, most melanoblasts have reached destination and differentiate into melanocytes

  • Subset of melanoblasts form melanocyte stem cells in hair follicle bulge that replenish differentiated melanocytes
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6
Q

How are melanocytes regulated?

A

Melanocortin 1 receptor ( MC1R ) and G protein coupled receptor = regulate quality and quantity

Controlled by:

  • agonists α-melanocyte-stimulating hormone (αMSH)
  • adrenocorticotropic hormone (ACTH) and antagonist
  • Agouti signaling protein (ASP).

Activation of MC1R by agonist → melanogenic cascade → synthesis of eumelanin

ACTH can also up-regulate expression of the MC1R gene

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7
Q

What reduces the effects of the melanogenic cascade?

A

ASP reverses those effects & elicit production of pheomelanin

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8
Q

How does exposure to UV increase melanin content?

A

Increased expression of MITF & downstream melanogenic proteins, including Pmel17, MART-1, TYR, TRP1, and DCT → increases in melanin content

and

Increased PAR2 in keratinocytes → increases uptake & distribution of melanosomes by keratinocytes

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9
Q

What is the structure of the skin ( top to bottom )

A

Epidermis : keratinocytes

Basement membrane

Dermis :
Connective tissue

Subcutaneous fat

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10
Q

How are the cells in the basal layer divided? (4)

A

Progressive differentiation:

( bottom )
dermis
-Stratum spinosum
-Stratum granulosum
-Stratum lucidum (palms and soles only)
-Stratum corneum (no nuclei or organelles)

( top )

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11
Q

What is psoriasis an example of?

A

Cellular progression from basal layer to the surface accelerated to less than 30 days.

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12
Q

What three filamentous cytoskeleton are in keratinocytes?

A
  • Actin‐containing microfilaments (7nm)
  • Tubulin‐containing microtubules (20-25nm)
  • Intermediate filaments (keratins) (7-10nm)
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13
Q

What are the roles of keratins? 5 ( intermediate filaments )

A 
Structural properties
Cell signalling
Stress response
Apoptosis
Wound healing
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14
Q

What are Desmosomes?

A

Major adhesion complex in epidermis to help cells withstand trauma.

Do this by connecting keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes,

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15
Q

Examples of proteins desmosomes connect?

A 
Desmogelin
Desmocollin
Plakoglobin
Plakophilin
Desmoplakin
Keratin
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16
Q

What are gap junctions?

A

Clusters of intercellular channels (connexons)

Directly form connections between cytoplasm of adjacent keratinocytes

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17
Q

What are gap junctions used for?

A

Essential for cell synchronization, cell differentiation, cell growth and metabolic coordination

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18
Q

What are adherens junctions?

A

Transmembrane structures

Engage with the actin skeleton

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19
Q

What are tight junctions?

A

Role in barrier integrity and cell polarity

20
Q

What are the characteristics of Melanocytes?

epidermis

A
  • Dendritic
  • Distribute melanin pigment (in melanosomes) to keratinocytes
  • Number of melanocytes = among skin types.
21
Q

What are the characteristics of Langerhans cells?

epidermis

A

-Dendritic

-Antigen‐presenting cells
Merkel cells

22
Q

What are Merkel cells?

epidermis

A

Mechanosensory receptors
Light / sustained touch, pressure
Oval-shaped

  • Mast cells are also found in the epidermis
23
Q

Characteristics of basement membrane?

A

( Dermal epidermal junction )

Made of proteins and glycoproteins:
- Collagens (IV, VII), laminin, integrins

Roles:

  • Cell adhesion
  • Cell migration
24
Q

describe the papillary dermis?

A

Superficial
Loose connective tissue
Vascular

25
Q

Describe the reticulr dermis?

A

Deep
Dense connective tissue
Forms bulk of dermis

26
Q

What proteins are found in the dermis?

A

Collagen (80-85% of dermis) – mainly types I and III

Elastic fibres (2-4%) – fibrillin, elastin

27
Q

What in the dermis facilitates cell adhesion and motility?

A

Glycoproteins – fibronectin, fibulin, intregrins

28
Q

What substance is found between dermal collagen and elastic tissue?

A

Ground substance:

glycosaminoglycan / proteoglycan

29
Q

Fibroblasts are the most common cells within the dermis, what other cells are there? ( 5 )

A
  • Histiocytes
  • Mast cells
  • Neutrophils
  • Lymphocytes
  • Dermal dendritic cells
30
Q

Describe the blood supply and innervation to the skin?

A

Blood supply – deep and superficial vascular plexus
(Does not cross into epidermis)

Innervation:
- Sensory – free, hair follicles, expanded tips

Autonomic:

  • Cholinergic – eccrine
  • Adrenergic – eccrine and apocrine
31
Q

What is the Pilosebaceous unit?

A

The pilosebaceous unit consists of the hair shaft, the hair follicle, the sebaceous gland, and the erector pili muscle

32
Q

What is the Meisserner’s corpuscle?

A
  • Encapsulated, unmyelinated mechanoreceptors
  • Lamellated capsule
    Superficial dermis

They are mostly found in thick hairless skin

Sensitive to slow vibration and light touch

33
Q

What is the Ruffini Corpuscle?

A 
Slow acting mechanoreceptor 
Deeper in dermis
Spindle-shaped 
Sensitive to skin stretch 
Highest density around fingernails 
Monitors slippage of objects
34
Q

What is the Pacinian corpuscle?

A

Encapsulated
Rapidly adapting (phasic) mechanoreceptor
Deep pressure and vibration (deep touch)
Vibrational role - detects surface texture
Ovoid
Dermal papillae of hands and feet

35
Q

What do merkel cells do?

A

Non-encapsulated mechanoreceptors
Light / sustained touch, pressure
Oval-shaped

Modified epidermal cells
Stratum basale, directly above basement membrane
Most populous in fingertips
Also in palms, soles, oral & genital mucosa

36
Q

Where do afferent corpuscular nerves innervate?

A

Encapsulated receptors in the dermis

e.g. pacinian Messners

37
Q

Where do afferent free nerves innervate?

A

Non Encapsulated receptors in Epidermis

Merkel cell

38
Q

What is the Microbiome required for?

A
  • Host defence
  • Immune modulation
  • Epithelial health
  • Metabolism
39
Q

What are the functions of the skin?

A 
Immunological barrier
Physical barrier 
Thermoregulation
Sensation 
Metabolism
Aesthetic appearance
40
Q

What characteristics of the skin allow it to become an immune barrier?

A

Langerhans cells: Initiate immune response in skin

  • DC/macrophage
  • Sentinel cells in epidermis
  • stops autoimmune
  • Dendritic processes through intercellular tight junctions to sample outermost layers of skin (stratum corneum)
  • In absence of danger, promote expansion and activation of skin-resident regulatory - cells (Tregs)
  • (PAMP) → rapid initiation of innate antimicrobial responses
  • Induction of adaptive response - T-cells
41
Q

What cells carry out immune surveillance

A
  • Tissue‐resident T-cells
  • Macrophages
  • Dendritic cells
  • Rapid, effective immunological backup if epidermis breached
42
Q

What are Defensins and cathelicidins?

A

Antibiotics made by keratinocytes acting as innate immune defence

43
Q

How can the skin act as a barrier?

A
  • Cornified cell envelope and stratum corneum restrict water and protein loss from skin – NB high-output cardiac failure and renal failure in extensive skin disease
  • Subcutaneous fat cushioning trauma
  • UV barrier
  • Melanin in basal keratinocytes - protection against UV-induced DNA damage
44
Q

How can the skin play a part in thermoregultion?

A

Vasodilatation or vasoconstriction in deep or superficial vascular plexuses → regulate heat loss.
Eccrine sweat glands → cooling effect
Role in fluid balance

45
Q

Describe the metabolic functions of skin?

A
  • Vitamin D synthesis
  • Subcutaneous fat
  • Calorie reserve
  • 80% of total body fat (in non-obese individuals)
  • Hormone (leptin) release : acts on hypothalamus → regulates hunger and energy metabolism

Dermatology (3 decks)

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