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bioregulatory systems 🦠 > dermatology > Flashcards

dermatology Flashcards

1
Q

what does the skin arise from

A

1) epidermis

2) dermis

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2
Q

what is the epidermis

A

it originates from ectoderm (the outermost layer of the 3 primary germ layers)

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3
Q

what is the dermis

A

it arises from the mesoderm and is beneath the epidermis

comes into contact with inner surface if epidermis

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4
Q

what is the mesoderm essential for

A

inducing differentiation of epidermal structures (eg hair follicle)

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5
Q

what happens by week 4

A

the epidermis forms as a single basal layer of cuboidal cells

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6
Q

what happens in week 5

A

a secondary layer of squamous, non-keratinising cuboidal cells called the periderm forms
this generates a white, waxy protective substance called the vernix caseosa

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7
Q

what happens from week 11

A

basal layer of cuboidal cells (stratum germinativum) proliferates to form multilayered intermediate zone > 4 more superficial strata

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8
Q

name the layers that arise from the stratum germinativum

A 
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum germinativum
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9
Q

what happens to epidermal ridges

A

they protrude as troughs into the developing dermis underneath

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10
Q

what does the neurovascular supply develop into

A

dermal papillae

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11
Q

what happens from weeks 9-13

A

development of hair follicles in stratum germinativum

appearance of lanugo hair

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12
Q

give an overview of the structure of the skin (4 layers)

A

epidermis
basement membrane (dermal-epidermal junction)
dermis (connective tissue)
subcutaneous fat

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13
Q

what is the primary cell in the epidermis

A

keratinocytes

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14
Q

what does progressive differentiation and flattening of the cells in the basal layer give rise to and how long does it take

A 
stratum spinosum
stratum granulosum
stratum lucidum (palms and soles only)
stratum corneum (no nuclei or organelles)
30-42 days
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15
Q

what happens to the process of proliferation and flattening in psoriasis

A

it becomes accelerated and progressively flatter

red/scaly/itchy

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16
Q

what does the filamentous cytoskeleton of keratinocyte comprise of

A

in size order (smallest to biggest)
actin containing microfilaments (7nm)
intermediate filaments containing keratins (7-10nm)
tubulin containing microtubules (20-25nm)

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17
Q

what are the roles of keratin (SSWAC)

A 
stress response
structural properties
wound healing
apoptosis
cell signalling
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18
Q

what are 4 features within/between keratinocytes in the epidermis

A

desmosomes
gap junctions
adherens junctions
tight junctions

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19
Q

what are desmosomes

A

major adhesion complex in epidermis
they anchor keratin intermediate filaments to cell membrane
they also bridge adjacent keratinocytes
allows cells to withstand trauma

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20
Q

what are gap junctions

A

clusters of intracellular channels (connexons) - form pore for gap junction
directly form connections between cytoplasm of adjacent keratinocytes
essential for cell synchronisation, cell differentiation, cell growth and metabolic coordination

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21
Q

what are adherens junctions

A

transmembrane structures

engage with the actin skeleton

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22
Q

what are tight junctions

A

they have a role in barrier integrity and cell polarity

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23
Q

other cells in the epidermis (4)

A

melanocytes
langerhan cells
merkel cells
mast cells

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24
Q

what are melanocytes

A

they are dendritic
distribute melanin pigment (in melanosomes) to keratinocytes
the number of melanocytes are equal among skin types

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25
Q

what are langerhan cells

A

dendritic
antigen presenting cells
immune cells

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26
Q

what are merkel cells

A

mechanosensory receptors (sensory of mechanical stimuli)

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27
Q

what is the basement membrane

A

dermal epidermal junction

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28
Q

what does the basement membrane consist of

A

proteins and glycoproteins - collagen (most commonly 4,7), laminin and integrins

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29
Q

role of the basement membrane

A

cell adhesion and cell migration

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30
Q

what is the dermis

A

supporting the ECM - provides resilience
and is made of two layers
the papillary dermis and the reticular dermis

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31
Q

what is the papillary dermis

A
  • superficial
  • loose connective tissue
  • vascular
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32
Q

what is the reticular dermis

A
  • deep
  • dense connective tissue
  • forms bulk of dermis
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33
Q

what is found in the dermis

A

proteins
glycoproteins
ground substance

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34
Q

what proteins are found in the dermis

A 
collagen (80-85% of the dermis) - mainly types 1 and 3
elastic fibres (2-4%) - fibrillin and elastin
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35
Q

what glycoproteins are found in the dermis and what do they do

A

fibronectin, fibulin, integrins

facilitate cell adhesion and motility

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36
Q

what is ground substance in the dermis

A

it is between dermal collagen and elastic tissue

glycosaminoglycan and proteoglycan

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37
Q

what are the primary cells found in the dermis

A

fibroblasts

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38
Q

what are 5 other cells found in the dermis

A 
histiocytes
mast cells
neutrophils
lymphocytes
dermal dendritic cells
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39
Q

vascular supply of the skin

A

blood supply - deep and vascular plexus
and does not cross into the epidermis
mostly in the papillary dermis

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40
Q

innervation of the skin

A 
sensory (free nerve endings, hair follicles, expanded tips)
and autonomic (cholinergic - eccrine and adrenergic - eccrine and apocrine)
Merkel cells
Pacinian corpuscle
Ruffini 
Meissner cell
Noiciceptors
Free nerve endings
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41
Q

define cholinergic

A

inhibits or mimics actions of NT acetylcholine

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42
Q

define adrenergic

A

working on adrenaline/noradrenaline receptors

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43
Q

what are eccrine glands

A

open directly onto the surface of the skin

involved in thermoregulation

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44
Q

what are apocrine glands

A

scent

mostly in armpits and groin

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45
Q

what is the pilosebaceous unit

A 
hair shaft
hair follicle
sebaceous gland
errector pili muscle
arterioles
shunts
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46
Q

vascular supply of the skin pt2 hehehehe

A

afferent nerve fibres form branching network often accompanying blood vessels to form a mesh of interlacing nerves in the superficial dermis (papillary dermis)

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47
Q

innervation of nerves

A

varies by body site

face and genitalia have most innervation

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48
Q

explain afferent nerves

A

afferent nerves > corpuscular and free
corpuscular > encapsulated receptors (dermis eg pacinian and meissners)
free > non-encapsulated receptors (epidermis eg merkel cells)

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49
Q

what is the ruffini corpuscle (aka bulbous corpuscle)

A 
slow acting mechanoreceptor
deeper in dermis
spindle shaped
sensitive to skin stretch
highest density around fingernails
monitors slippage of objects
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50
Q

what is the pacinian corpuscle (aka lamellar corpuscles)

A

encapsulated
rapidly adapting (phasic) mechanoreceptor
deep pressure and vibration (deep touch)
vibrational role - detects surface texture
ovoid
dermal papillae of hands and feet

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51
Q

what are merkel cells

A

non encapsulated mechanoreceptors
light/sustained touch, pressure
oval shaped

52
Q

what are modified epidermal cells

A

in stratum basale - directly above basement membrane
most populous in fingertips
also in palms, soles, oral and genital mucosa

53
Q

nerve endings and fibre for light touch

A

meissner
merkel
free
fibre = A beta

54
Q

nerve endings and fibre for touch and pressure

A 
merkel
ruffini
pacinian 
free
fibre = A beta and A delta
55
Q

nerve ending and fibre for vibration

A

meissner
pacinian
fibre = A beta

56
Q

nerve ending and fibre for temperature

A

thermoreceptors

fibre = A delta, C

57
Q

nerve endings and fibres for pain

A

nociceptor (free nerve endings)

fibre = A delta, C

58
Q

what is the microbiome

A

microbiota = bacteria, fungi and viruses

1 million bacteria/cm2 of skin

59
Q

what are the predominant bacteria on skin

A 
actinobacteria
firmicutes
bacteroidetes
proteobacteria
the composition of each niche depends on the environment
60
Q

what is the role of the microbiome

A

immune modulation and epithelial health

disease

61
Q

functions of the skin (IPTSMA)

A 
immunological barrier
physical barrier
thermoregulation
sensation
metabolism
aesthetic appearance
62
Q

langerhan cells in the epidermis

A

dendritic cells
macrophage family
sentinel cells in epidermis
initiate immune response against microbial threats
contribute to immune tolerance
form dense network with which potential invaders must interact

63
Q

how do langerhan cells work

A

specialised at sensing environment
extend dendritic processes through intercellular tight junctions to sample outermost layers of skin - stratum corneum
interpret microenvironmental context > determine appropriate quality of immune response
in absence of danger - promote expansion and activation of skin resident regulatory cells (T-regs)
when they sense danger (PAMP) rapid initiation of innate antimicrobial responses
induction of adaptive response - power and specificity of T cell

64
Q

how does the skin function as an immune barrier (dermis)

A

immune surveillance is also carried out in the dermis by
tissue resident T cells
macrophages
dendritic cells

rapid effective immunological backup if epidermis is breached

65
Q

how are keratinocytes involved in immune defence

A

keratinocyte derived endogenous antibiotics (defensins and cathelicidins) provide innate defence against bacteria, viruses and fungi

66
Q

what can cathelicidin do

A

modulate cell differentiation
it is a microbicidal
modulates PRR (pattern recognition receptor) signalling
induce chemokines
chemotactic (movement due to chemical stimulus)
modulate cell function
modulate cell death
angiogenic (formation of new blood vessels)
cell proliferation

67
Q

describe the skin as a physical barrier

A

against external environment
cornified cell envelope and stratum corneum restrict water and protein loss from skin
- high output cardiac failure and renal failure in extensive skin disease
subcutaneous fat has important in cushioning trauma
UV barrier
melanin in basal keratinocytes - protection against UV - induced DNA damage-

68
Q

how does the skin deal with thermoregulation

A

vasoconstriction and vasodilation in deep or superficial vascular plexuses > regulate heat loss
eccrine sweat glands > cooling evaporating effect
role in fluid balance

69
Q

metabolic functions of the skin

A

vitamin D synthesis (regulates Ca2+ and PO43-)
subcutaneous fat > under skin
- calorie reserve
- 80% of total body fat in non obese individuals
- hormone leptin release - acts on hypothalamus > regulates hunger and energy metabolism

70
Q

the skin and its aesthetic appearance

A

psychosexual function

increased risk of suicide

71
Q

what are the functions of the hair

A 
protection against external factors
sebum
apocrine sweat
thermoregulation
social and sexual interaction
epithelial and melanocyte stem cells
terminal hairs (thicker, longer and darker) - scalp, eyebrows and eyelashes
the rest of the body has vellus hairs (except palms. soles, mucosal regions of lips and external genitalia)
72
Q

what are the 3 components of the hair cycle

A

1) anagen
2) catagen
3) telogen
4) loss of old hair

73
Q

describe anagen

A

where new hair forms and grows

85% of hair lasts 2-6 years

74
Q

describe catagen

A

regressing phase

1% of hair - lasts 3 weeks

75
Q

describe telogen

A

resting phase

10-15% of hair - lasts 3 months

76
Q

what does the pilosebaceous unit contain

A

hair shaft
hair follicle
sebaceous gland
arrector pili muscle

77
Q

STEPS for formation of pilosebaceous unit

A

pockets of epithelium are continuous with superficial epithelium
they envelop a small papilla of dermis at their base
arrector pili (smooth muscle) extends at angle between surface of dermis and point in follicle wall
holocrine (secretion is own disintegrated secretory cells and products) sebaceous glands open into the pillory canal
(in axillae - follicles are associated with apocrine glands)

78
Q

what is the infundibulum

A

uppermost portion of the hair follicle extending from the opening of sebaceous gland to surface of the skin

79
Q

what is the isthmus (not thyroid gland)

A

lower portion of the upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle

80
Q

how does epithelium keratinisation begin

A

begins with lack of granular layer named trichilemmal keratinisation

81
Q

what is the bulge

A

segment of the outer root sheath located at insertion of arrector pili muscle
hair follicle stem cells reside here
they can migrate upwards or downwards

82
Q

what happens when hair follicle stem cells migrate upwards (distally)

A

form sebaceous glands and to proliferate in response to wounding

83
Q

what happens when hair follicle stem cells migrate downwards

A

generate new lower anagen hair follicle > enters hair bulb matrix > proliferate and undergoes terminal differentiation to form hair shaft and inner root sheath

84
Q

what is the bulb

A

lowermost portion of the hair follicle

includes follicular dermal papilla and hair matrix

85
Q

what is the outer root sheath

A

extends along from the hair bulb to the infundibulum and epidermis and serves as a reservoir of stem cells

86
Q

what is the inner root sheath

A

undergoes proliferation and differentiation
guides and shapes hair
encloses dermal papilla, mucopolysaccharide rich strome, nerve fibre and capillary loop

87
Q

what is the function of the nails

A

protection of underlying distal phalanx
counter pressure effect to pulp important for walking and tactile sensation
increase dexterity/manipulation of small objects
enhance sensory discrimination
facilitate grooming or scratching

88
Q

what is the nail plate

A

final product of proliferation and differentiation of nail matrix keratinocytes

89
Q

where does the nail plate emerge from

A

proximal nail fold

90
Q

how much does the nail plate grow each month

A

1-3 mm

91
Q

what is the nail plate firmly attached to

A

nail bed

92
Q

what does the nail plate detach at

A

hyponychium

93
Q

what is the nail plate lined laterally by

A

lateral nail folds

94
Q

what is the nail matrix

A

produces nail plate
nail matrix keratinocytes grow outwards and differentiate > lose their nuclei and are strictly adherent - cytoplasm is completely filled by hard keratins
also contains melanocytes - when injured = pigment
hard nuclear without other organelles

95
Q

where does the nail matrix lie

A

under proximal nail fold, above the bone of distal phalanx (to which it is connected by a tendon)

96
Q

what is the only visible portion of the nail matrix

A

lunula

97
Q

what is psioriasis

A

chronic, immune mediated disorder (long term inflammatory)

a skin disease that causes red, itchy scaly patches, most commonly on the knees, elbows, trunk and scalp

98
Q

what are the causes of psoriasis

A

polygenic predisposition combined with environmental triggers eg trauma, infections or medications

99
Q

what is the most common form of psoriasis and common sites

A

sharply dermarcated, scaly, erythematous plaques

scalp, elbow, knees, nails, hands, feet and trunk (including intergluteal fold)

100
Q

what is the most common systemic manifestation of psoriasis

A

psoriatic arthritis

101
Q

what is the pathophysiology of psoriasis

A

keratinocytes undergo stress > release DNA/RNA > form complex with antimicrobial peptides (endogenous antibodies) > induce cytokines (TNF-alpha, IL-1 and IFN-alpha) production > activate dermal dendritic cells (dDCs)
dDCs migrate to lymph nodes > promote Th1, Th17, Th22 cells > chemokine release - migration of inflammatory cells into dermis > cytokine release > keratinocyte proliferation > psoriatic plaque

102
Q

what are flectures

A

skin to skin areas due to friction is not scaly

103
Q

what is nail pitting (feature of psoriasis)

A

indents in nail

104
Q

what is erythrodermic psoriasis

A

90%+ of your body = red

105
Q

what is guttate psoriasis

A

spores

106
Q

how to manage psoriasis (lifestyle)

A

alcohol
smoking
cormorbidities
therapeutic ladder

107
Q

topical therapies for psoriasis

A

vitamin D analogues
topical corticosteroids (reduce inflammation)
retinoids (vitamin A - immunity and skin health)
topical tacrolimus/pimecrolimus

108
Q

phototherapy as a treatment for psoriasis

A

narrowband UVB
PUVA (psoralen + UVA)
acitretin (vit A analogue tablets > keratin differentiation process > does not proliferate wrong)
systemic immunosuppression methotrexate ciclosporin
advanced therapies PDE4 inhibitors (apremilast) biologics (anti-TNF alpha, anti IL-17, anti-IL23) JAK inhibitors

109
Q

what is atopic eczema

A

has to be itchy
intensely pruritic chronic inflmammatory condition
conplex genetic disease with environmental influences
typically begins during infancy/childhood
and is often associated with other atopic disorders eg. asthma, rhinoconjunctivitis

110
Q

features of atopic eczema

A

acute inflammation of cheeks, scalp and extensors in infants

flexural inflammation and lichenification in children and adults

111
Q

what is eczema dermatitis

A

umbrella term for
atopic eczema, seborrheic dermatitis (dandruff), venous stasis eczema, allergic contact dermatitis, irritant contact dermatitis

112
Q

pathophysiology for atopic eczema (not full version bc it’s too long and im tired)

A

barrier defect : filaggrin binds and aggregates keratin filaments and intermediate filaments to form cellular scaffold in corneocytes (in stratum corneum)
immune dysregulation Th2 lymphocytes stimulated and subversion of T-reg, T cell infiltrate

113
Q

clincal features of atopic eczema

A

exaggeration of skin
lichenification, crusting and excoriation and dyspigmentation, post inflammatory dyspigmentation, flexural dermatitis causing hypopigmentation
fissuring - vertical cracks in skin
infantile phase atopic dermatitis = erythematous, oedematous papule and plaques and or not vesiculation (tiny blisters or erosions)

114
Q

allergic contact dermatitis

A

allergic contact dermatitis
posion ivy - bubbly
nickel - small red bumps
shoes - potassium chromate - weird butterfly shape

115
Q

impetiginisation

A
  • gold crust, staphylococcus aureus
116
Q

venous stasis eczema

A

purple shade

117
Q

eczema herpeticum

A
  • on face - emergency, HSV, dark spots/scars
118
Q

lifestyle management for atopic eczema

A

emollient

omission of soap

119
Q

management - clinical nurse specialist involvement

A

topical application technique
day treatment
habit reversal

120
Q

other managements for atopic eczema

A 
comordities
patch testing
biopsy
therapeutic ladder
topical therapies
121
Q

when should you always take a biopsy

A

nipple eczema because it could be Pagets or cutaneous lymphoma

122
Q

what are topical therapies

A 
topical corticosteroids - correct potency for correct site
topical tacrolimus/pimecrolimus
underuse = poor adherence
overuse = tachyphylaxis/adverse effects
FTU - fingertip unit
123
Q

what is phototherapy

A

narrowband UVB

PUVA - hand dermatitis

124
Q

what is the steroid ladder and list in potency

A 
underuse - poor adherence
overuse - tachyphylaxis/adverse effects
correct steroid for correct site
FTU
least potent to most:
hydrocortisone
clobetasone (eumovate)
betamethasone (betnovate)
mometasone (elocon)
clobetasol (dermovate)
125
Q

adverse effects of topical corticosteroids

A

rare = skin atrophy, folliculitis, exacerbation of acne and rosacea, infection
very rare = perioral dermatitis (right), rebound syndrome (tachyphylaxis), allergy (to steroid itself or vehicle)
extremely rare = hormonal imbalance (suppression of hypothalamic pituitary adrenal axis), hirsutism

126
Q

what are adverse effects of topical calcinuerin inhibitors

A

burning sensation

127
Q

eczema management

A 
retinoids (hand dermatitis)
systemic immunosuppression:
- methotrexate
- ciclosporin
- azathioprine
- myocophenolate mofetil
advanced therapies
- biologics (anti IL4 alpha, anti IL-13)
- JAK inhibitors

bioregulatory systems 🦠 (54 decks)

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