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dermatology > intro to derma > Flashcards

intro to derma Flashcards

1
Q

How does the skin arise?

A

joining of the epidermis (from ectoderm) and dermis(from mesoderm) touching thinner surface of epidermis *diagram

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2
Q

What is the mesoderm important for?

A

induces differentiation of structures in epidermis e.g. hair follicle

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3
Q

how does the skin develop by week 4?

A

epidermis is formed: single basal layer of cuboid cells

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4
Q

In week 5?

A

a secondary layer of squamous, non-keratinisng cuboidal cells (periderm) developed

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5
Q

What does the periderm generate?

A

White, waxy, protective substance == Vernix caseosa

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6
Q

What does vernix caseosa do?

A

protects doetus from aminotic fluid during gestation and protects from bacteria at birth

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7
Q

from week 11 of skin develop?

A

basal layer of cuboidal cells STRATUM germinativum proliferates and forms multilayered intermediate zone

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8
Q

By week 20 what happens?

A 
4 more superficial strata:
Spinosum (spinous)
Granulosum(granular)
Lucidium(clear; found on palms and soles)
Corneum (horny) - most super
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9
Q

between weeks 10-17?

A

epidermal ridges develop , protrude into dermis beneath. gaps = dermal papillae where neurovascular supply develops

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10
Q

weeks 9-13?

A

hair follicles aka pilosebaceous unit ( inc. hair foll, errector pili muscle, sebaceous gland) in stratum germinativum and appearance of lanugo hair (fine)

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11
Q

What are melanocytes?

A

pigment cells - give skin and hair colour

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12
Q

how are melanocytes developed?

A

melanoblasts (precursor cells) arise from neural crest. they migrate dorsally between week 6-8 to developing epidermis (& dermis) and hair follicles. by weeks 12-13 most at their destination and differentiate into melanocytes

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13
Q

how are differentiated melanocytes replenished?

A

subset of melanoblasts form melanocyte stem cells in hair follicle bulge

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14
Q

Regulation of melanocytes?

A

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

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15
Q

What is MC1R controlled by?

A

agonists: alpha melanocyte-stimulating hormone (alphaMSH) and adrenocorticotropic hormone (ACTH) and antagonist, Agouti signalling protein (ASP)

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16
Q

What does activation of MCR lead to?

A

agonist activates -> melanogenic cascade (pigment production) -> synthesis of eumelanin

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17
Q

what does ASP do?

A

reverses effects of agonists and elicits production of pheomelanin(pale pigment)

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18
Q

What upregulates the expression of the MC1R gene

A

ACTH

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19
Q

what happens to melanocytes when exposed to uv?

A

increased expression of MITF & downstream melanogenic proteins, inc Pmel 17, MART-1, TYR, TRP1 & DCT

also increases PAR2 in keratinocytes which increases uptake and distribution of melanosomes (pigment packages) by keratinocytes

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20
Q

what allows melanocytes to distribute melanosomes?

A

the fact that is a dendritic cell

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21
Q

Structure of the skin ( overview)

A 
epidermis
basement membrane (dermal-epidermal junction)
dermis: 
-connective tissue
subcutaneous fat
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22
Q

What is the epidermis made of?

A

looks like a brick wall:

keratinocytes

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23
Q

How are cells divided in the basal layer?

A

Progressive differentiation:

  • stratum spinosum
  • stratum granulosum
  • stratum lucidum (palms and soles only)
  • stratum corneum ( no nuclei or organelles)
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24
Q

How long to surface?

A

cells progress from basal layer to surface in approx 30 days

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25
Q

When is cell progression accelerated?

A

in skin diseases such as psoriasis

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26
Q

What is in the cytoskeleton of keratinocytes and sizes?

A

filamentous cytoskeleton:
actin containing microfilaments (7nm)
tubulin - containing microfilaments (20-25nm)
intermediate filaments (7-10nm)

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27
Q

What are the 5 roles of keratin?

A 
structural properties
cell signalling
stress response
apoptosis
wound healing
28
Q

What are desmosomes?

A

Major adhesion complexes in epidermis

29
Q

What are the functions of desmosomes?

A

anchors keratin intermediate filaments to cell membrane and bridges adjacent keratinocytes

allows cells to withstand trauma

30
Q

What are gap junctions?

A

Clusters of intercellular channels (connexons)

31
Q

What do gap junctions do and why are they important?

A

directly forms connections between cytoplasm of adjacent keratinocytes

essential for cell synchronisation, cell differentiation, cell growth, and metabolic coordination

32
Q

what are adherens junctions?

A

transmembrane structures which engage with actin skeleton

33
Q

What are tight junctions?**

A

barrier integrity and cell polarity

34
Q

What are melanocytes?

A

dendritic cells that distribute melanin pigment in melanosomes to keratinocytes

35
Q

what are Langerhans cells?

A

dendritic cells that are antigen-presenting

36
Q

What are Merkel cells?

A

mechanosensory receptors

37
Q

What are the roles of the basement membrane?

A

Cell adhesion and cell migration

38
Q

What is the basement membrane also known as ?

A

dermal-epidermal junction

39
Q

What proteins are present in the basement membrane?

A

collagens (IV, VII), laminin and integrins

40
Q

What does the dermis do?

A

supports extracellular matrix - provides resistance

41
Q

What is the papillary dermis?

A

superficial, vascular, loose areolar tissue

42
Q

What is the reticular dermis?

A

deep, dense connective tissue -> forms bulk of dermis

43
Q

Describe the protein make up of the dermis

A

80-85% is collagen: mainly type I and III, 2-4% elastic fibres: fibrillin, elastin

44
Q

What is the function of glycoproteins

A

facilitate cell adhesion and cell motility :

e.g. fibulin, integrins and fibronectin

45
Q

Where/what is the ground substance?

A

glycosaminoglycan and proteoglycan ( maintain hydration) between dermal collagen and elastic tissue

46
Q

What cells are present in the ground substance?

A 
fibroblasts - main primary cells 
mast cells
neutrophils
histiocytes
lymphocytes
dermal dendritic cells
47
Q

Describe the blood supply of the skin

A

deep and superficial vascular plexus which doesn’t cross into epidermis

48
Q

sensory innervation of skin ?

A

//

49
Q

autonomic innervation

A

//

50
Q

describe the distribution of nerves

A

1 million afferent nerve fibres, branching network often accompanies blood vessels
forms mesh of interlacing nerves in the superficial dermis
distribution varies by body site (face, extremities and genitalia)

51
Q

What are corpuscular nerves?

A 
(afferent nerves)
encapsulated receptors (dermis e.g. Pacinian, Meissner)
52
Q

What are free nerves?

A

afferent nerves

non-encapsulated receptors (epidermis e.g. Merkel cells)

53
Q

What is Meissner’s corpuscle?

A
  • encapsulated, unmyelinated, mechanoreceptors
    for light touch and slow vibration
    senses low-frequency stimulation at level of dermal papilla
54
Q

Where is the Meissner’s corpuscle most concentrated?

A

thick hairless skin (finger pads and lips)

55
Q

What is the Ruffini corpuscle?

A

aka bulbous corpuscle
slow-acting mechanoreceptor
sensitive to skin stretch
deeper in dermis

56
Q

What shape is the ruffini corpuscle?

A

spindle

57
Q

Where is the ruffini corpuscle most dense?

A

highest density around finger nails - monitors slipage of of objects

58
Q

What is the Pacinian corpuscle?

A

encapsulated and ovoid
rapidly adapting - phasic mechanoreceptor
for deep pressure and vibration - detects surface texture
dermal papillae of hands and feet

59
Q

What are Merkel cells/ discs?

A

Oval shaped Non-encapsulated mechanoreceptors that sense light, sustained touch/pressure

they are a type of modified epidermal cells

60
Q

WHere are Merkel cells found?

A

They are in the startum basale, directly above basement membrane
most dense in fingertips but also found in palms, soles, oral and genital muscosa

61
Q

Describe the distribution of bacteria on the skin and what affects this?

A

~ 1 million bac per cm squared
predominantly actinobacteria
affected by environment

62
Q

What is the role of bacteria on skin?

A

immune modulation and epithelial health

63
Q

What are the functions of the skin?

A 
immunological barrier
physical barrier
thermoregulation
sensation
metabolic features
aesthetic appearance
64
Q

How does the skin act as an immune barrier?

A

through Langerhans cells
-responds against the microbial threat and contribute to immune tolerance.
a dense network is formed for potential invaders to interact.*

65
Q

Describe the function of Langerhans cells

A

specialised to sense the environment, they initiate an immune response.

66
Q

How do Langerhans cells prevent autoimmune response?

A

by causing the production of t regulatory cells

dermatology (3 decks)

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