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BRS > Intro to Dermatology- Skin > Flashcards

Intro to Dermatology- Skin Flashcards

1
Q

What are the different layers of the skin?

A

Epidermis- arises from ectoderm
Basement membrane - dermal-epidermal junction
Dermis- arises from mesoderm
Subcutaneous fat

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2
Q

How is skin formed?

A

Week 4: epidermis is formed as a single layer of cuboidal cells
Week 5: secondary layer of squamous, non-keratinising cuboidal cells develops. Develops white waxy substance called vernix caseosa
Week 11: Basal layer of cuboidal cells (stratum germinativum) proliferates to form multi-layered intermediate zone- four more specific strata form (stratum spinosum, corneum, granulosum and lucidum)
Week 9-12: development of hair follicles in stratum germinativum and appearance of lanugo hair

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3
Q

What are melanocytes developed from and where do they migrate to?

A

Developed from the neural crest- melanoblasts
They migrate dorsally between week 6-8 to develop in epidermis and hair follicles
By week 12-13 most melanoblasts have reached destination and become melanocytes
A subset of melanoblasts form melanocyte stem cells in hair follicle bulge that replenish differentiated melanocytes

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4
Q

How are melanocytes regulated?

A

Melanocortin 1 receptor (MC1R), a G protein coupled receptor regulates quantity and quality of melanins produced:

  • Its controlled by agonist alpha-melanocyte-stimulating hormone (aMSH) and adrenocorticotrophin hormone (ACTH) and antagonist agouti signalling protein (ASP)
  • Activation of MC1R by agonist leads to melanogenic cascade and the synthesis of eumelanin
  • ASP reverses these effects and elicits production of pheomelanin
  • ACTH can also up regulate expression of MC1R gene
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5
Q

What is the effect of UV exposure to melanin?

A

It causes:

  • increased expression of MITF and downstream melanogenic proteins inc. Pmel17, MART-1, TYR, TRP1 and DCT- increases melanin content
  • Increases PAR2 in keratinocytes which leads to increased uptake and distribution of melanosomes by keratinocytes
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6
Q

What are the different layers of the epidermis?

A 
Composed of keratinocytes
Stratum Lucidum (palms and soles only)
Stratum Corneum (no nuclei or organelles)
Stratum Granulosum
Stratum spinousum
Basal layer
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7
Q

How are cells replaced in skin?

A

Cell division occurs in the basal layer

Cells move from the basal layer upwards towards the surface. This takes about 30 days (Accelerated in skin diseases)

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8
Q

How are keratinocytes structured?

A

Filamentous cytoskeleton includes:

  • Actin- containing microfilaments
  • Tubulin containing microtubules
  • Intermediate filaments (keratins)
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9
Q

What is the role of keratins?

A 
Structural properties
Cell signalling
Stress response
Apoptosis
Wound healing
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10
Q

How are keratinocytes renewed?

A

Keratinocytes in stratum corneum are dead and regularly removed and replaced by cells from deeper layers

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11
Q

What are desmosomes?

A

Major adhesion complex in epidermis
Anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes
Allow cells to withstand trauma

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12
Q

What are gap junctions?

A

Clusters of intracellular channels (connexons)
Directly form connections between cytoplasm of adjacent keratinocytes
Essential for cell synchronisation, cell differentiation, cell growth and metabolic coordination

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13
Q

What are adherent junctions?

A

Transmembrane structure

Engage with actin skeleton

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14
Q

What are tight junctions?

A

Role in barrier integrity and cell polarity

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15
Q

What other cells can be found in the epidermis?

A

Melanocytes: Dendritic. Distribute melanin pigment to keratinocytes. No. of melanocytes is the same in all skin types
Langerhans cells: Dendritic. Antigen presenting cell
Merkel cells: mechanosensory receptors
Mast cells

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16
Q

What makes up the basement membrane?

A

Aka. dermal-epidermal junction

Has proteins and glycoproteins: collagen (V, VII), laminin, integrins

17
Q

What is the role of the basement membrane?

A

Cell adhesion

Cell migration

18
Q

What are the 2 different layers of the dermis?

A

Papillary dermis: superficial and has loose connective tissue and is vascular
Reticula dermis: deep and has deep connective tissue and forms bulk of dermis

19
Q

What makes up the dermis?

A

Protein: collagen (mainly I and III), elastic fibres (fibrillin, elastin)
Glycoproteins: fibronectin, fibrin, integrins- facilitate cell adhesion and cell motility
Ground substance: between dermal collagen and elastic tissue (glycosaminoglycan and proteoglycan)
Cells: mainly fibroblasts but also histocytes, mast cells, neutrophils, lymphocytes, dermal dendritic cells

20
Q

What gives blood supply to the skin?

A

Deep and superficial vascular plexus- doesn’t cross into epidermis

21
Q

What supplies innervation to the skin?

A

Sensory
Autonomic:
-Cholinergic- eccrine (swear found all over body)
-Adrenergic- eccrine and apocrine (body odour sweat)
Afferent nerve receptors:
-Corpuscular- encapsulated receptors (dermis)
-Free- non-encapsulated receptors (epidermis)

22
Q

What is the pilosebaceous unit?

A

Follicle, hair shaft, sebaceous gland, pili arrector muscle

23
Q

What are the different receptors found in the skin?

A

Meissner’s corpuscle
Ruffini corpuscle
Pacinian corpuscle
Merkel cell

24
Q

What is a meissner’s corpuscle?

A

Aka. Tactile corpuscle
Encapsulated, unmyelinated mechanoreceptors
Lamellated capsule
Found in superficial dermis
Most concentrated in thick, hairless skin (finger pads, lips)
Detect light touch and slow vibration
Senses low frequency stimulation at levels of dermal papilla

25
Q

What is a Ruffini corpuscle?

A 
Aka. Bulbous corpuscle
Encapuslated
Slow acting mechanoreceptor
Deep in dermis
Sensitive to skin stretch
Highest density in finger nails
Monitors slippage of objects
26
Q

What is a pacinian corpuscle?

A

Aka. Lamellar corpuscle
Encapuslated
Rapidly adapting mechanoreceptor
Detects deep pressure, vibrations and surface texture
Ovoid in shape
Found in dermal papilla of hands and feet

27
Q

What is a Merkel cell?

A

Non- encapsulated mechanoreceptor
Detects light/ sustained touch and pressure
Oval shaped
Found in stratum basal (directly above basement membrane) (in epidermis)
Found mostly in fingertips
Also in palms, soles, oral and genital mucosa

28
Q

What are functions of the skin?

A 
Immunological barrier
Physical barrier
Thermoregulator
Sensation
Metabolism
Aesthetic appearance
29
Q

How do langerhan cells aid skin function as an immune barrier?

A

They’re dendritic cells and the sentinel cell in epidermis (first line of defence)
Initiate immune response against microbial threats- when they sense danger there’s rapid initiation of innate antimicrobial responses
Also contribute to immune tolerence
They extend dendritic processes through intracellular tight junctions to sample outermost layers of skin
They interpret the environmental context and determine appropriate response

30
Q

What else is immune surveillance carried out in the dermis by?

A

Tissue resident T cells
Macrophages
Dendritic cells
Defensins and Cathelicidins

31
Q

What are defensins and cathelicidins?

A

Keratinocyte- derived endogenous antibiotics which innitatite immune defence against bacteria, viruses and fungi

32
Q

How does the skin function as a barrier?

A

Its a physical barrier against the environment
Cornified cell envelop and stratum corneum restrict water and protein loss from skin- can lead to high output cardiac failure and renal failure if extensive in skin disease
Subcutaneous fat cushions trauma
Skin is a UV barrier
Melanin in basal keratinocytes protect against UV-induced DNA damage

33
Q

How does the skin function as a thermoregulator?

A

Vasodialtion or vasoconstriction in deep or superficial vascular plexus regulates heat loss
Eccrine sweat glands cause cooling effect
Ha a role in fluid balance

34
Q

How does the skin have a role in metabolic function?

A

Vitamin D synthesis
Subcutaneous fat is a calorie reserve
Hormone (leptin) release- acts on hypothalamus and regulates hunger and energy metabolism

35
Q

What makes up the microbiome of skin?

A

Microbacteria: bacteria. fungi and viruses

Predominantly actinobacteria

36
Q

What is the role of the microbiome of the skin?

A

Role in immune-modulation and epithelial health

Role in disease

BRS (60 decks)

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