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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
what are langerhan cells
dendritic antigen presenting cells immune cells
26
what are merkel cells
mechanosensory receptors (sensory of mechanical stimuli)
27
what is the basement membrane
dermal epidermal junction
28
what does the basement membrane consist of
proteins and glycoproteins - collagen (most commonly 4,7), laminin and integrins
29
role of the basement membrane
cell adhesion and cell migration
30
what is the dermis
supporting the ECM - provides resilience and is made of two layers the papillary dermis and the reticular dermis
31
what is the papillary dermis
- superficial - loose connective tissue - vascular
32
what is the reticular dermis
- deep - dense connective tissue - forms bulk of dermis
33
what is found in the dermis
proteins glycoproteins ground substance
34
what proteins are found in the dermis
``` collagen (80-85% of the dermis) - mainly types 1 and 3 elastic fibres (2-4%) - fibrillin and elastin ```
35
what glycoproteins are found in the dermis and what do they do
fibronectin, fibulin, integrins | facilitate cell adhesion and motility
36
what is ground substance in the dermis
it is between dermal collagen and elastic tissue | glycosaminoglycan and proteoglycan
37
what are the primary cells found in the dermis
fibroblasts
38
what are 5 other cells found in the dermis
``` histiocytes mast cells neutrophils lymphocytes dermal dendritic cells ```
39
vascular supply of the skin
blood supply - deep and vascular plexus and does not cross into the epidermis mostly in the papillary dermis
40
innervation of the skin
``` 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 ```
41
define cholinergic
inhibits or mimics actions of NT acetylcholine
42
define adrenergic
working on adrenaline/noradrenaline receptors
43
what are eccrine glands
open directly onto the surface of the skin | involved in thermoregulation
44
what are apocrine glands
scent | mostly in armpits and groin
45
what is the pilosebaceous unit
``` hair shaft hair follicle sebaceous gland errector pili muscle arterioles shunts ```
46
vascular supply of the skin pt2 hehehehe
afferent nerve fibres form branching network often accompanying blood vessels to form a mesh of interlacing nerves in the superficial dermis (papillary dermis)
47
innervation of nerves
varies by body site | face and genitalia have most innervation
48
explain afferent nerves
afferent nerves > corpuscular and free corpuscular > encapsulated receptors (dermis eg pacinian and meissners) free > non-encapsulated receptors (epidermis eg merkel cells)
49
what is the ruffini corpuscle (aka bulbous corpuscle)
``` slow acting mechanoreceptor deeper in dermis spindle shaped sensitive to skin stretch highest density around fingernails monitors slippage of objects ```
50
what is the pacinian corpuscle (aka lamellar corpuscles)
encapsulated rapidly adapting (phasic) mechanoreceptor deep pressure and vibration (deep touch) vibrational role - detects surface texture ovoid dermal papillae of hands and feet
51
what are merkel cells
non encapsulated mechanoreceptors light/sustained touch, pressure oval shaped
52
what are modified epidermal cells
in stratum basale - directly above basement membrane most populous in fingertips also in palms, soles, oral and genital mucosa
53
nerve endings and fibre for light touch
meissner merkel free fibre = A beta
54
nerve endings and fibre for touch and pressure
``` merkel ruffini pacinian free fibre = A beta and A delta ```
55
nerve ending and fibre for vibration
meissner pacinian fibre = A beta
56
nerve ending and fibre for temperature
thermoreceptors | fibre = A delta, C
57
nerve endings and fibres for pain
nociceptor (free nerve endings) | fibre = A delta, C
58
what is the microbiome
microbiota = bacteria, fungi and viruses | 1 million bacteria/cm2 of skin
59
what are the predominant bacteria on skin
``` actinobacteria firmicutes bacteroidetes proteobacteria the composition of each niche depends on the environment ```
60
what is the role of the microbiome
immune modulation and epithelial health | disease
61
functions of the skin (IPTSMA)
``` immunological barrier physical barrier thermoregulation sensation metabolism aesthetic appearance ```
62
langerhan cells in the epidermis
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
how do langerhan cells work
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
how does the skin function as an immune barrier (dermis)
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
how are keratinocytes involved in immune defence
keratinocyte derived endogenous antibiotics (defensins and cathelicidins) provide innate defence against bacteria, viruses and fungi
66
what can cathelicidin do
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
describe the skin as a physical barrier
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
how does the skin deal with thermoregulation
vasoconstriction and vasodilation in deep or superficial vascular plexuses > regulate heat loss eccrine sweat glands > cooling evaporating effect role in fluid balance
69
metabolic functions of the skin
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
the skin and its aesthetic appearance
psychosexual function | increased risk of suicide
71
what are the functions of the hair
``` 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
what are the 3 components of the hair cycle
1) anagen 2) catagen 3) telogen 4) loss of old hair
73
describe anagen
where new hair forms and grows | 85% of hair lasts 2-6 years
74
describe catagen
regressing phase | 1% of hair - lasts 3 weeks
75
describe telogen
resting phase | 10-15% of hair - lasts 3 months
76
what does the pilosebaceous unit contain
hair shaft hair follicle sebaceous gland arrector pili muscle
77
STEPS for formation of pilosebaceous unit
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
what is the infundibulum
uppermost portion of the hair follicle extending from the opening of sebaceous gland to surface of the skin
79
what is the isthmus (not thyroid gland)
lower portion of the upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle
80
how does epithelium keratinisation begin
begins with lack of granular layer named trichilemmal keratinisation
81
what is the bulge
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
what happens when hair follicle stem cells migrate upwards (distally)
form sebaceous glands and to proliferate in response to wounding
83
what happens when hair follicle stem cells migrate downwards
generate new lower anagen hair follicle > enters hair bulb matrix > proliferate and undergoes terminal differentiation to form hair shaft and inner root sheath
84
what is the bulb
lowermost portion of the hair follicle | includes follicular dermal papilla and hair matrix
85
what is the outer root sheath
extends along from the hair bulb to the infundibulum and epidermis and serves as a reservoir of stem cells
86
what is the inner root sheath
undergoes proliferation and differentiation guides and shapes hair encloses dermal papilla, mucopolysaccharide rich strome, nerve fibre and capillary loop
87
what is the function of the nails
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
what is the nail plate
final product of proliferation and differentiation of nail matrix keratinocytes
89
where does the nail plate emerge from
proximal nail fold
90
how much does the nail plate grow each month
1-3 mm
91
what is the nail plate firmly attached to
nail bed
92
what does the nail plate detach at
hyponychium
93
what is the nail plate lined laterally by
lateral nail folds
94
what is the nail matrix
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
where does the nail matrix lie
under proximal nail fold, above the bone of distal phalanx (to which it is connected by a tendon)
96
what is the only visible portion of the nail matrix
lunula
97
what is psioriasis
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
what are the causes of psoriasis
polygenic predisposition combined with environmental triggers eg trauma, infections or medications
99
what is the most common form of psoriasis and common sites
sharply dermarcated, scaly, erythematous plaques | scalp, elbow, knees, nails, hands, feet and trunk (including intergluteal fold)
100
what is the most common systemic manifestation of psoriasis
psoriatic arthritis
101
what is the pathophysiology of psoriasis
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
what are flectures
skin to skin areas due to friction is not scaly
103
what is nail pitting (feature of psoriasis)
indents in nail
104
what is erythrodermic psoriasis
90%+ of your body = red
105
what is guttate psoriasis
spores
106
how to manage psoriasis (lifestyle)
alcohol smoking cormorbidities therapeutic ladder
107
topical therapies for psoriasis
vitamin D analogues topical corticosteroids (reduce inflammation) retinoids (vitamin A - immunity and skin health) topical tacrolimus/pimecrolimus
108
phototherapy as a treatment for psoriasis
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
what is atopic eczema
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
features of atopic eczema
acute inflammation of cheeks, scalp and extensors in infants | flexural inflammation and lichenification in children and adults
111
what is eczema dermatitis
umbrella term for atopic eczema, seborrheic dermatitis (dandruff), venous stasis eczema, allergic contact dermatitis, irritant contact dermatitis
112
pathophysiology for atopic eczema (not full version bc it's too long and im tired)
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
clincal features of atopic eczema
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
allergic contact dermatitis
allergic contact dermatitis posion ivy - bubbly nickel - small red bumps shoes - potassium chromate - weird butterfly shape
115
impetiginisation
- gold crust, staphylococcus aureus
116
venous stasis eczema
purple shade
117
eczema herpeticum
- on face - emergency, HSV, dark spots/scars
118
lifestyle management for atopic eczema
emollient | omission of soap
119
management - clinical nurse specialist involvement
topical application technique day treatment habit reversal
120
other managements for atopic eczema
``` comordities patch testing biopsy therapeutic ladder topical therapies ```
121
when should you always take a biopsy
nipple eczema because it could be Pagets or cutaneous lymphoma
122
what are topical therapies
``` topical corticosteroids - correct potency for correct site topical tacrolimus/pimecrolimus underuse = poor adherence overuse = tachyphylaxis/adverse effects FTU - fingertip unit ```
123
what is phototherapy
narrowband UVB | PUVA - hand dermatitis
124
what is the steroid ladder and list in potency
``` 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
adverse effects of topical corticosteroids
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
what are adverse effects of topical calcinuerin inhibitors
burning sensation
127
eczema management
``` retinoids (hand dermatitis) systemic immunosuppression: - methotrexate - ciclosporin - azathioprine - myocophenolate mofetil advanced therapies - biologics (anti IL4 alpha, anti IL-13) - JAK inhibitors ```

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