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Lily BRS Dermatology > Intro 1 > Flashcards

Intro 1 Flashcards

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Dermatology Board Prep flashcards
1
Q

The skin develops from two major embryological elements, what are these?

A

Epidermis - originates from the ectoderm

Dermis - originates from the mesoderm that comes into contact with the epidermis

The mesoderm is essential for inducing differentiation of epidermal structures (eg. Hair follicle)

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2
Q

When does the epidermis develop?

A

Week 4 - single layer of cuboidal cells (basal layer)

Week 5 - secondary layer of squamous non keratinising cuboidal cells. This generates a waxy protective substance (vernix caseosa)

Week 11 - basal layer of cuboidal cells proliferates to form multi layered intermediate zone (spinous, granolosum, lucidum, corneum)

Epidermal ridges protrude as troughs into developing dermis beneath, neurovascular supply develops into dermal papillae

Weeks 9-13 - development of hair follicles in basal layer (stratum germinativum) and appearance of lanugo hair

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3
Q

What are the layers of the epidermis (bottom to top)?

A

Basal layer

Stratum spinosum

Stratum granulosum

Stratum lucidum

Stratum corneum

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4
Q

Where do the melanocytes in the skin develop from?

A

Derived from the neural crest ->

Melanoblasts ->

Migrate for sally between 6-8 weeks to developing dermis ->

By weeks 12-13 most melanoblasts have reached their destination and differentiate into melanocytes

There is a subset of melanoblasts that form melanocyte stem cells in hair follicle bulge that replenish differentiated melanocytes

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5
Q

How are melanocytes regulated?

A

Melanocortin 1 receptor (MC1R) is a G protein coupled receptor that regulates the quantity and the quality of melanoma produced

It is controlled by agonists aplha melanocyte stimulating hormone (aMSH) and adrenocorticotrophic hormone (ACTH). And antagonist agouti signalling protein (ASP)

Activation of MC1R by agonist -> melanobenic cascade -> synthesis of eumelanin (dark)

ASP reserves these effects and elicits production of pheomelanin (light)

ACTH can also up regulate expression of the MC1R gene

Exposure to UV light leads to increased expression of MITF and downstream melanogenic proteins, this increases melanin content

Increased PAR2 in keratinocytes -> increased uptake and distribution of melanosomes (pigment) by keratinocytes

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6
Q

What is the structure of the skin? (Top to bottom)

A

Epidermis

Basement membrane (dermal epidermal junction)

Dermis - connective tissue

Subcutaneous fat

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7
Q

What is the structure of the epidermis (cells and progressive differentiation)?

A

Epidermis - composed of keratinocytes

Division of cells in basal layer ->

Progressive differentiation/flattening: stratum spinosum, stratum granulosum, stratum lucidum (only present in palms and soles), stratum corneum (no nuclei or organelles)

Pruu I version from basal layer to surface takes around 30 days but is accelerated in skin disease (eg psoriasis)

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8
Q

What is the composition of keratinocytes?

A

Filamentous cytoskeleton of keratinocytes comprises:

Actin containing micro fillaments

Tubules containing microtubules

Intermediate fillaments (keratins)

Role of keratins:

Structural properties

Cell signalling

Stress response

Apoptosis

Wound healing

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9
Q

What are desmasomes ?

A

Major adhesion complex in epidermis

Anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes

Allows cells to withstand trauma

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10
Q

What are the junctions between adjacent cells?

A

Gap:

Clusters of intercellular channels

Directly form connections between cytoplasm of adjacent keratinocytes

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

Desmasomes

Adherens junctions:

Transmembrane structures

Engage with the actin skeleton

Tight junctions:

Role in barrier integrity and cell polarity

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11
Q

What are the cells other than keratinocytes that are present in the epidermis?

A

Melanocytes: dendritic, distribute melanin pigment to keratinocytes

Langerhans cells: dendritic, antigen presenting cells

Merkel cells: mechanisensory receptors

Mast cells

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12
Q

What is the basement membrane comprised of? And what is it’s role?

A

Aka dermal epidermal junction

Proteins and glycoproteins: collagens (IV and VII), laminin, integrins

Role: cell adhesion and cell migration

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13
Q

What are the layers of the dermis?

A

Papillary dermis: superficial, loose connective tissue, vascular

Reticular dermis: deep, dense connective tissue, forms bulk of dermis

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14
Q

What are the components of the dermis?

A
  1. Proteins

collagen ( 80% of dermis) mainly types I and III

Elastic fibres (2-4%). Fibrin and elastin

  1. Glycoproteins

Fibronectin, fibulin, integrins - facilitate cell adhesion and motility

  1. Ground substance

Between dermal collagen and elastic tissue - glycosaminoglycan/proteoglycan

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15
Q

What are the cells in the dermis?

A

Mainly fibroblasts

Also: histiocytes, mast cells, neutrophils, lymphocytes, dermal dendritic cells

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16
Q

What is the blood supply and innervation of the skin?

A

Blood: deep and superficial vascular plexus. Does not cross into epidermis

Innervation:

Sensory - free, hair follicles, expanded tips

Autonomic - cholinergic (eccrine), adrinergic (eccrine and apocrine)

17
Q

Which afferent nerves are present in the skin?

A

Corpuscular -> encapsulated receptors (dermis) (Pacinian, meissners)

Free -> non encapsulated receptors (epidermis) (merkel cell)

18
Q

What are meissners corpuscles?

A

Tactile corpuscles

Encapsulated, unmyelinated mechanireceptors

Lamellated capsule

Superficial dermis

Most concentrated in thick hairless skin (finger pads and lips)

Sense light touch and slow vibration

Senses low frequency stimulation at level of dermal papilla

19
Q

What are ruffini corpuscles?

A

Slow acting mechanoreceptor

Deeper in dermis

Spindle shaped

Sensitive to skin stretch

Highest density around nails

Monitors slippage of objects

20
Q

What are pacinian corpuscles?

A

Encapsulated

Rapidly acting (physic) mechanoreceptor

Deep in dermis

Deep pressure and vibration(detects surface texture)

Ovoid

Dermal papillae of hands and feet

21
Q

What are merkel cells?

A

Non encapsulated mechanoreceptors

Light/sustained touch and pressure

Oval shaped

Modified epidermal cells, stratum basale directly above basement membrane

Most populous in fingertips

Also in palms, soles, oral and genital mucosa

22
Q

What is the micro biome of the skin?

A

Microbiota: bacteria, fungi and viruses

~ 1 million bacteria per cm^2 of skin

Predominantly actinobacteria, formicutes and proteibacteria

Composition of each niche depends on environment

Role in immune modulation and epithelial health

Role in disease

23
Q

What are the functions of the skin?

A

Immunological barrier

Physical barrier

Thermoregulation

Sensation

Metabolism

Aesthetic appearance

24
Q

What are langerhans cells?

A

Dendritic cell/ macrophage family

Sentinel cells in epidermis

Initiate immune response against microbial threats

Also contribute to immune tolerance

Form a dense network with which potential invaders must interact

Extend dendritic processes through intercellular tight junctions to sample outermost layers of skin

Interpret microenvironmental context and determine appropriate quality of immune response

In absence of danger promote expansion and activation of T reg cells

When sense danger (PAMPs) -> rapid initiation of innante antimicrobial responses

Induction of adaptive response. Power and specifity of T cell

25
Q

Apart from langerhans cells what other cells have an immune roll in the skin?

A

Dermis:

Tissue resident T cells

Macrophages

Dendritic cells

(Rapid effective immunological backup of epidermis is breached)

26
Q

What are keratinocyte derived endogenous antibiotics?

A

Defendinsins and cathelicidins

Innate immune defence against bacteria viruses and fungi

27
Q

How does the skin act as a physical barrier against the external environment?

A

Cornified cell envelope and stratum corneum restrict water and protein loss from skin

High output cardiac failure and renal failure can result from excessive skin disease

Subcutaneous fat has an important role in cushioning trauma

UV barrier

Melanin in basal keratinocytes - protection against UV induced DNA damage

28
Q

What is the role of the skin in thermoregulation?

A

Vasodilation or vasoconstriction in deep or superficial vascular plexes regulates heat loss

Eccrine sweat glands have a cooling effect

This also has a role in fluid balance

29
Q

What is the role of the skin in metabolism?

A

Vitamin D synthesis

Subcutaneous fat acts as a calorie reserve, it is where 80% of total body fat is stored. It also releases leptin (hormone) - this acts on the hypothalamus and regulates hunger and energy metabolism

30
Q

What are the effects of skin with aesthetic appearance?

A

Some skin disorders may affect psychosexual function

They may also give a higher risk of suicide

Lily BRS Dermatology (2 decks)

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