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Dermatology > Introduction to Dermatology > Flashcards

Introduction to Dermatology Flashcards

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Dermatology Board Prep flashcards
1
Q

How is the skin formed?

A

Skin arises by juxtaposition of two major embryological elements:
Epidermis - originates from ectoderm
Dermis - arises from mesoderm that comes into contact with inner surface of epidermis

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2
Q

What is the importance of the mesoderm?

A

essential for inducing differentiation of epidermal structures (e.g. hair follicle)

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3
Q

By when is the epidermis formed?

A

Week 4

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4
Q

By when is the periderm formed?

A

Week 5

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5
Q

What is the periderm?

A

Secondary layer of squamous, non-keratinising cuboidal cells

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6
Q

What does the periderm develop?

A

Generates white, waxy protective substance - 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 → four more superficial strata

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8
Q

What are the 4 types of superficial strata?

A

Spinosum(spinous)
granulosum(granular)
lucidum(clear; found on palms of hands and soles of feet)
corneum(horny).

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9
Q

What happens during weeks 9-13?

A

development of hair follicles in stratum germinativum and appearance of lanugo hair

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10
Q

What are melanocytes?

A

derived from neural crest →melanoblasts → migrate dorsally between week 6-8 to developing epidermis (& dermis) and hair folliicles

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11
Q

What happens by week 12-13 to melanocytes?

A

most melanoblasts have reached destination and differentiated into melanocytes

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12
Q

How are melanocytes regulated?

A

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

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13
Q

What are the three mechanism of regulation?

A

Agonists α-melanocyte-stimulating hormone (αMSH) & adrenocorticotropic hormone (ACTH) → activation of MC1R by agonist → melanogenic cascade → synthesis of eumelanin
Agouti signaling protein (ASP) reverses those effects & elicit production of pheomelanin
ACTH can also up-regulate expression of MC1R gene

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14
Q

When expose to UV how are melanocytes regulated?

A

Increased expression of transcription factor MITF & downstream melanogenic proteins, including Pmel17, MART-1, TYR, TRP1, and DCT → increases in melanin content
Increased PAR2 in keratinocytes → increases uptake & distribution of melanosomes by keratinocytes

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15
Q

Outline the structure of the skin?

A 
Epidermis: 
Basement membrane (dermal-epidermal junction)
Dermis: 
Connective tissue
Subcutaneous fat
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16
Q

What is the epidermis composed of?

A

Keratinocytes

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17
Q

Describe te progressive differentiation of keratinocytes?

A

Progressive differentiation / flattening:
Stratum spinosum
Stratum granulosum
Stratum lucidum (palms and soles only)
Stratum corneum (no nuclei or organelles)

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18
Q

How long does cellular progression from basal layer to the surface take?

A

30 days

Accelerated in skin diseases e.g. psoriasis

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19
Q

What is the role of keratin?

A 
Structural properties
Cell signalling
Stress response
Apoptosis
Wound healing
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20
Q

What are the functions of 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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21
Q

What are gap junctions?

A

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

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22
Q

What are adheres junctions?

A

Transmembrane structures

Engage with actin skeleton

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23
Q

What are tight junctions?

A

Role in barrier integrity and cell polarity

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24
Q

What is the role of melanocytes?

A

Dendritic

Distribute melanin pigment (in melanosomes) to keratinocytes

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25
Q

What other cells are present in the epidermis?

A

Melanocytes
Langerhans cells
Merkel cells
Mast cells

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26
Q

What is the basement membrane also know as?

A

dermal-epidermal junction

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27
Q

What comprises the basement membrane?

A

Proteins and glycoproteins

Collagens (IV, VII), laminin, integrins

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28
Q

What are the roles of the basement membrane?

A

Cells adhesion

Cell migration

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29
Q

What comprises the dermis?

A

Papillary dermis

Reticular dermis

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30
Q

What is the papillary dermis?

A

Superficial
Loose connective tissue
Vascular

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31
Q

What is the reticular dermis?

A

Deep
Dense connective tissue
Forms bulk of dermis

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32
Q

What is the dermis made up of?

A

Proteins
Collagen (80-85% of dermis) – mainly types I and III
Elastic fibres (2-4%) – fibrillin, elastin
Glycoproteins – fibronectin, fibulin, intregrins – facilitate cell adhesion and cell motility
Ground substance – between dermal collagen and elastic tissue – glycosaminoglycan / proteoglycan

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33
Q

What cells are present in the dermis?

A 
Fibroblasts
Histiocytes
Mast cells
Neutrophils
Lymphocytes
Dermal dendritic cells
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34
Q

How is the skin supplied with blood?

A

– deep and superficial vascular plexus

- does not cross into epidermis

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35
Q

How is the skin innervated?

A

Sensory – free, hair follicles, expanded tips
Autonomic
Cholinergic – eccrine
Adrenergic – eccrine and apocrine

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36
Q

What are the two types of afferent nerves in the skin?

A

Corpuscular

Free

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37
Q

What are corpuscular nerves?

A

Encapsulated receptors

dermis e.g. Pacinian, Meissners

38
Q

What are free nerves?

A

Non-encapsulated receptors

epidermis e.g. Merkel cell

39
Q

What is the meissner’s corpuscle?

A

Encapsulated, unmyelinated mechanoreceptors
Light Touch (+slow vibration)
Senses low-frequency stimulation at level of dermal papilla
Most concentrated in thick hairless skin, (finger pads and lips)

40
Q

What is the ruffini corpuscle?

A 
Slow acting mechanoreceptor 
Sensitive to skin stretch
Deeper in dermis
Spindle-shaped 
Highest density around fingernails 
Monitors slippage of objects
41
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

42
Q

What is a Merkel cell?

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

43
Q

What is microbiota?

A

bacteria, fungi and viruses
~ 1 million bacteria /cm2 skin
Predominantly Actinobacteria

44
Q

What is the function of the skin?

A 
Immunological barrier
Physical barrier 
Thermoregulation
Sensation 
Metabolic functions 
Aesthetic appearance
45
Q

How does the skin act as a physical barrier?

A

Physical barrier against external environment
Subcutaneous fat has important roles in cushioning trauma
UV barrier

46
Q

How does the skin act as an immune barrier?

A

Immune surveillance is also carried out in dermis by:
Tissue‐resident T-cells
Macrophages
Dendritic cells
Rapid, effective immunological backup if epidermis breached

47
Q

How does the skin play a role in thermoregulation?

A

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

48
Q

What are the metabolic functions of the 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

49
Q

Why is aesthetic appearance of the skin important?

A

Psychosexual

Increased risk of suicide

50
Q

What is the function of the hair?

A 
Protection against external factors
Sebum
Apocrine sweat
Thermoregulation
Social and sexual interaction
Epithelial and melanocyte stem cells
51
Q

Where are terminal hairs found?

A

Scalp, eyebrows and eyelashes

52
Q

Where are vellus hairs found?

A

Rest of body

hairs (except palms, soles, mucosal regions of lips, and external genitalia)

53
Q

What are the three components of hair cycle?

A

Anagen
Catagen
Telogen

54
Q

What happens during anagen?

A

where new hair forms and grows

85% of hair; lasts 2-6 years

55
Q

What happens during catagen?

A

regressing phase

1% of hair; lasts 3 weeks

56
Q

What happens during telogen?

A

resting phase
10-15% of hair; lasts 3 months
Then loss of old hair

57
Q

Describe the structure of hair?

A

Hair follicles (pilosebaceous unit)
Pockets of epithelium continuous with superficial epidermis
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 sebaceous glands which open into pilary canal → in axillae

58
Q

What is the infundibulum?

A

Uppermost portion of hair follicle - from opening of sebaceous gland to surface of skin

59
Q

What is the isthmus?

A

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

60
Q

What does epithelium keratinisation begin with?

A

with lack of granular layer named “trichilemmal keratinisation”

61
Q

What is the bulge?

A

Segment of outer root sheath located at insertion of arrector pili muscle
Hair follicle stem cells reside here

62
Q

How can the bulge migrate?

A

Downward

Upward

63
Q

Describe downward migration?

A

generate lower anagen hair follicle → enter hair bulb matrix, proliferate and undergo terminal differentiation to form hair shaft and inner root sheath

64
Q

Describe upward migration?

A

form sebaceous glands and to proliferate in response to wounding

65
Q

What is the bulb?

A

Lower most portion of hair follicle, includes follicular dermal papilla and hair matrix

66
Q

What is the outer roots sheath?

A

Extends along from hair bulb to infundibulum and epidermis

Serves as a reservoir of stem cells

67
Q

What is the inner root sheath?

A

Guides / shapes hair

Encloses follicular dermal papilla, mucopolysaccharide-rich strome, nerve fibre & capillary loop.

68
Q

What is the function of the nails?

A

Protection of underlying distal phalanx
Counterpressure effect to pulp important for walking and tactile sensation
Increase dexterity / manipulation of small objects
Enhance sensory discrimination
Facilitate scratching or grooming

69
Q

Describe the main features of the nail plate?

A 
Final product of proliferation and differentiation of nail matrix keratinocytes
Emerges from proximal nail fold
Grows at 1-3mm/month
Firmly attached to nail-bed 
Detaches at hyponychium
Lined laterally by lateral nail folds
70
Q

Describe the main features of the nail matrix?

A

Produces nail plate
Lies under proximal nail fold, above bone of distal phalanx (to which it is connected by a tendon
Lunula only visible proportion
Nail matrix keratinocytes differentiate → lose their nuclei and are strictly adherent - cytoplasm completely filled by hard keratins
Also contains melanocytes

71
Q

What is psoriasis?

A

Chronic, immune-mediated disorder

72
Q

What are risk factors for psoriasis?

A

Polygenic predisposition combined with environmental triggers, e.g. trauma, infections, or medications

73
Q

Describe the pathophysiology of psoriasis?

A

involves T-cells and their interactions with dendritic cells and cells involvement in innate immunity, including keratinocytes

74
Q

What characterises the most common form of psoriasis?

A

Sharply demarcated, scaly, erythematous plaques

75
Q

What are common sites of involvement ?

A

are scalp, elbows and knees, followed by nails, hands, feet and trunk (including intergluteal fold)

76
Q

What is the most common systemic manifestation of psoriasis?

A

Psoriatic arthritis

77
Q

How can psoriasis be managed?

A

Lifestyle: alcohol and smoking
By a dermatologist
By a rheumatologist
By a psychologist

78
Q

What topical therapies can be used for psoriasis?

A

Vitamin D analogues
Topical corticosteroids
Retinoids
Topical tacrolimus / pimecrolimus

79
Q

What phototherapy can be used for psoriasis?

A

Narrowband UVB

PUVA (Psoralen + UVA)

80
Q

What immunosuppressive drugs can be used for psoriasis?

A

Methotrexate
Ciclosporin
Fumaric acid esters
Apremilast

81
Q

What advanced therapies can be used for psoriasis?

A

Biologics (anti-TNF, anti-IL17, anti-IL23)

JAK inhibitors

82
Q

What is atopic eczema?

A

Intensely pruritic chronic inflammatory condition

Complex genetic disease with environmental influences

83
Q

When does eczema typically begin?

A

During infancy or early childhood

84
Q

What other atopic disorders is it often associated with?

A

asthma

rhinoconjunctivitis

85
Q

How does eczema present?

A

Acute inflammation of cheeks, scalp and extensors in infants
Flexural inflammation and lichenification in children and adults
Fissuring
Impetiginisation (Gold crust)

86
Q

How is eczema managed?

A

Daily emollients and anti-inflammatory therapy
Omission of soap
Clinical nurse specialist involvement

87
Q

What are the two parts to the pathophysiology of eczema?

A

Barrier defect

Immune dysregulation

88
Q

Describe the barrier effect

A

Filaggrin - bind and aggregate keratin bundles and intermediate filaments to form cellular scaffold in corneocytes
Reduced extracellular lipids and impaired ceramide production
Increased transepidermal water loss (TEWL)
Impaired protection against microbes and environmental allergens

89
Q

Describe immune dysregulation

A

Staphylococcal superantigens stimulate Th2 lymphocyte responses and subvert T‐reg
T-cell infiltrate - bias towards Th2 responses
Role of microbiome?
Eosinophils

90
Q

What topical therapies are used for eczema?

A

Topical corticosteroids - correct potency for correct site
Retinoids (hand dermatitis)
Topical tacrolimus / pimecrolimus

91
Q

What phototherapies are used for eczema?

A

Narrowband UVB

PUVA (hand dermatitis)

Dermatology (4 decks)

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