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BRS DERMATOLOGY > Introduction to Dermatology I > Flashcards

Introduction to Dermatology I Flashcards

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Dermatology Board Prep flashcards
1
Q

How does skin arise?

A

By the juxtaposition of 2 major embryological elements:
epidermis
dermis

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2
Q

Where does the epidermis originate from?

A

ectoderm

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3
Q

Where does the dermis originate from?

A

mesoderm that comes into contact with the inner surface of epidermis

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4
Q

What is the mesoderm essential for?

A

for inducing differentiation of epidermal structures (e.g., hair follicles)

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5
Q

What are the layers of the skin?

A

starting top:

stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum germinativum
papillary and reticular layers of the dermis

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6
Q

What is the layer only found in palms and soles?

A

stratum lucidum

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7
Q

What is lanugo hair?

A

Lanugo is fine, soft, unpigmented hair that is often present in fetuses, newborns, and certain disease states.

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8
Q

What is the overview of the structure of the skin?

A

Epidermis
BAsement membrane (dermal-epidermal junction)
Dermis
Subcutaneous fat

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9
Q

What is the epidermis composed of?

A

keratinocytes

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10
Q

Where does start of cell division initiate?

A

cells in basal layer

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11
Q

What is the structure of the skin epidermis?

A

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

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12
Q

How long does it take for cells to reach the surface, and when can it accelerate?

A

roughly 30 days
can accelerate in skin disease (e.g., psoriasis)

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13
Q

What does the filamentous cytoskeleton of keratinocytes in the epidermis comprise of?

A

➢ Actin-containing microfilaments (7nm)
➢ Tubulin-containing microtubules (20-25nm)
➢ Intermediate filaments (keratins) (7-10nm)

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14
Q

What is the role of keratins? (5)

A

● Structural properties
● Cell signaling
● Stress response
● Apoptosis
● Wound healing

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15
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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16
Q

What are the different types of desmosomes? (6)

A

Desmoglein
Desmocollin
Plakoglobin
Plakophilin
Desmoplakin
Keratin

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17
Q

What are the different types of junctions between cells in the epidermis?

A

tight junction
adherens junction
desmosomes
gap junction

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18
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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19
Q

What are adherens junctions?

A

➢ Transmembrane structures
➢ Engage with the actin skeleton

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20
Q

What are tight junctions?

A

role in barrier integrity and cell polarity

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21
Q

What are cells present in the epidermis of the skin?

A

Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Mast cells

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22
Q

What are melanocytes?

A

➢ Dendritic
➢ Distribute melanin pigment (in melanosomes) to keratinocytes
➢ Number of melanocytes same among all skin types

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23
Q

What are melanosomes?

A

Melanosomes are intracellular organelles that are uniquely generated by pigment cells in the skin and eye, where they function to synthesize and store melanin pigments.

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24
Q

What are langerhans cells?

A

➢ Dendritic
➢ Antigen-presenting cells

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25
Q

What are merkel cells?

A

mechasensory receptors

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26
Q

What are mast cells for?

A

hypersensitivity and immunity

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27
Q

What is another word for basement membrane?

A

dermal-epidermal junction

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28
Q

What proteins and glycoproteins are in the basement membrane?

A

colagens (IV, VII), laminin, integrins

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29
Q

What are the roles of the basement membrane?

A

Cell adhesion

Gate-keeping functions
- Cell migration
- Diffusion of bioactive molecules

Rete ridges (downward projections)
- Strength
- Niche for epidermal stem cells

Roles in development, morphogenesis, wound healing, and skin remodeling

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30
Q

What are the 2 aspects of the dermis?

A

Papillary and reticular dermis

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31
Q

What is the dermis?

A

Supporting (extracellular) matrix- that provides resilience

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32
Q

What is the papillary dermis?

A

➢ Superficial
➢ Loose connective tissue
➢ Vascular

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33
Q

What is the reticular dermis?

A

➢ Deep
➢ Dense connective tissue
➢ Forms bulk of dermis

34
Q

What is the reticular dermis?

A

➢ Deep
➢ Dense connective tissue
➢ Forms bulk of dermis

35
Q

What is the structure of the dermis?

A
  1. proteins
  2. glycoproteins
  3. ground substances
36
Q

What are the proteins in the dermis?

A

a) Collagen (80-85% of dermis) – mainly types I and III
b) Elastic fibres (2-4%) – fibrillin, elastin

37
Q

What are the glycoproteins in the dermis and what do they do?

A

Glycoproteins – fibronectin, fibulin, integrins

– facilitate cell adhesion and cell motility

38
Q

What are the ground substances in the dermis?

A

between dermal collagen and elastic tissue
- glycosaminoglycan/ proteoglycan

39
Q

What are the cells in the dermis?

A

➢ Fibroblasts
➢ Histiocytes
➢Mast cells
➢ Neutrophils
➢ Lymphocytes
➢Dermal dendritic cells

40
Q

What is the primary cell within the dermis?

A

Fibroblasts

41
Q

Where are melanocytes derived from?

A

the neural crest

42
Q

How would you compare the papillary and reticular dermis?

A

The reticular dermis is composed of deep dense connective tissue while the papillary dermis is more superficial and composed of loose connective tissue

43
Q

How would you describe the blood supply of the skin?

A

Deep and superficial vascular plexus
➢ Does not cross into epidermis

44
Q

What are the types of innervation of the skin?

A

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

45
Q

What other structures are involved in the innervation and vascular supply of the skin?

A

● Pilosebaceous unit
● Arrector pili muscle / arterioles / shunts

46
Q

How many nerve fibres involved in skin innervation and how are they distributed?

A

● One million afferent nerve fibers.

● Form branching network, often accompanying blood vessels, to form a mesh of interlacing nerves in superficial dermis

● Distribution varies by body site

➢Face, extremities & genitalia > rest of skin

47
Q

What are the types of afferent nerves?

A

Corpuscular= pacinian, meissner’s
non-encapsulated= merkel cell

48
Q

What is meissner’s corpuscle?

A

aka tactile corpuscles

● Encapsulated, unmyelinated mechanoreceptors
● Lamellated capsule
● Superficial dermis
● Most concentrated in thick hairless skin, (fingertips and lips)
● Light Touch (+slow vibration)

49
Q

What is ruffini corpuscle?

A

aka bulbous corpuscle

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

50
Q

What are pacinian corpuscles?

A

aka lamellar corpuscles

● Encapsulated, ovoid
● Rapidly adapting (phasic) mechanoreceptor
● Deep pressure and vibration (deep touch)
➢ Vibrational role - detects surface texture
● Dermal papillae of hands and feet

51
Q

What are merkel cells?

A

● Non-encapsulated mechanoreceptors
● Light / sustained touch, pressure
● Oval-shaped

52
Q

What are modified epidermal cells?

A

➢ Stratum basale, directly above basement membrane
➢ Most populous in fingertips
➢ Also in palms, soles, oral & genital mucosa

53
Q

What are the nerve endings and fibres for light touch?

A

Meissner, merkel, free
Abeta

54
Q

What are the nerve endings and fibres for touch and pressure?

A

merkel, ruffini, pacinian, free
Abeta, Agamma

55
Q

What are the nerve endings and fibres for vibration?

A

meissner and pacinian
Abeta

56
Q

What are the nerve endings and fibres fro temperature?

A

thermoreceptor
Agamma, C

57
Q

What re the nerve endings and fibres for pain?

A

nociceptor (free nerve endings)
Agamma, C

58
Q

DO ruffini’s corpuscles detect skin stretch?

A

Yes, they are slow acting mechanoreceptors of touch and pressure, highly concentrated around fingernails, that detect skin stretch and slippage

59
Q

What is microbiota?

A

bacteria, fungi, viruses

60
Q

What is the microbiome?

A

genome of microbiota

61
Q

How many bacteria per cm^2 of skin?

A

roughly 1 million bacteria/ cm^2

62
Q

What is the microbiota predominantly made of?

A

Predominantly Actinobacteria (including Propionibacteria and Corynebacteria), Firmicutes (Clostridia and Bacilli [Staphylococcus] , Bacteroidetes & Proteobacteria

63
Q

What is the composition of each niche dependent on?

A

environment

64
Q

What is the role of the skin microbiota?

A

role in immune-modulation and epithelial health
role in chronic disease

65
Q

What are the descriptions of niches for the microbiota?

A

Sebaceous sites
Moist sites
Dry sites

66
Q

What are the functions of the skin?

A

● Immunological barrier
● Physical barrier
● Thermoregulation
● Sensation
● Metabolism
● Aesthetic appearance

67
Q

What the cells involved in the immune barrier of the skin?

A

langerhans cells

68
Q

What are langerhans cells?

A

● Dendritic cell (DC)/macrophage family
● Sentinel cells in epidermis
● Initiate immune response against microbial threats
● Also contribute to immune tolerance
● Form dense network with which potential invaders must interact.

69
Q

How do langerhans cells work?

A

● Specialized 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 (Tregs)

● When toll-like receptors (TLRs) sense danger (via pathogen associated molecular patterns [PAMP]) → rapid initiation of innate antimicrobial responses

● Induction of adaptive response - power and specificity of T-cell / B-cell and antibodies (immunoglobulins)

70
Q

How else is immune surveillance carried out in the dermis?

A

tissue resident T cells
Macrophages
Dendritic cells
- rapid, effective immunological backup if epidermis is breached

71
Q

What are antimicrobial peptides?

A

Keratinocyte-derived endogenous antibiotics (defensins and cathelicidins)–> innate immune defence against bacteria, viruses and fungi

72
Q

What are the differences between the innate and adaptive immune response?

A
73
Q

What is the function of the skin barrier?

A

Physical barrier against external environment

Cornified cell envelope and stratum corneum restrict water and protein loss from skin
- high cardiac output and renal failure in extensive skin disease

UV barrier

74
Q

What is the role of subcutaneous fat as a barrier?

A

cushioning trauma

75
Q

What is the role of melanin as a barrier?

A

melanin in basal keratinocytes- protection against UV induced DNA damage

76
Q

How is the skin involved in thermoregulation?

A

➢Vasodilation or vasoconstriction in deep or superficial vascular plexuses
→ regulate heat loss

➢Eccrine sweat glands
→ cooling effect

77
Q

Does the skin have a role in fluid balance?

A

Yes

78
Q

How does the thermoregulation work?

A
79
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)

➢ Hormone (leptin- supresses hunger) release - acts on hypothalamus
→ regulates hunger & energy metabolism

80
Q

Why does the skin have a aesthetic function?

A

Psychosexual function
Increased risk of suicide

BRS DERMATOLOGY (8 decks)

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