intro to derm 1 Flashcards by Anshu Banerjee

Describe how the skin acts as an immunological barrier

Langerhans cells:

‘sentinel’ cells

dendritic processes extend through intercellular tight junctions to reach the stratum corneum

without any danger it upregulates Treg

when it recognises PAMPs it upregulates innate and adaptive immune response

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Describe what happens to melanin synthesis in the presence of UV light (

1) increased PAR2 in keratinocytes so increased uptake and distribution of melanosomes 2)increased production of MITF and downstream melanogenic proteins (eg pmel 17, MART 1…) to increase melanin content

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Describe the blood supply to the skin

does NOT cross the epidermis
in vascular plexuses

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name the 2 parts of the dermis and compare and contrast

papillary dermis - superfical, vascularised and less dense connective tissue (contains meissener and pacinin corpuscle)

reticular dermis - deep, and more dense connective tissue

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What are the functions of the top middle layer and innermost of the stratum corneun

upper layer - absorbs solutes middle layer - absorbs water innermost - mechanical defence barrier (fatty acids and sterols )

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Describe the structure and function of desmosomes

FUNCTION: to anchor keratin to the cell membrane AND to form bridges between adjacent cells

DESCRIPTION: keratin is attached to desmoplakin, which is attached on the RHS to plakophalin. To the LHS of desmoplakin is plakogoblin and on top of that is desmogoblin

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think cytoskeleton

To what do adherens junctions engage with

actin cytoskeleton

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What is a protein involved in regulating the flatenning of keratinocytes

filagrin

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Why are the keratinocytes of the stratum corneum ‘brick like’

no organelles nor nuclei cytoskeleton of intermediate keratin filiaments

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Describe Meisseners corpuscles

non myelinated
encapsulated
fine touch
mechanoreceptors
in superficial dermis

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

●Light Touch (+slow vibration)

●Senses low-frequency stimulation at level of dermal papilla

lamellated capsule

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Whats the function of Merkel Cells and where are they

mechanoreceptors
in epidermis
non encapsulated

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What are the dermal papillae and why is it significant

where the epidermis produces into the dermis where the neurovascular supply is

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What is the predominant cell in the dermis

fibroblast

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Embryologically, from where does the dermis originate. Draw a diagram to show this

from mesoderm

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what is the purpose of tight junctions

barrier integrity and cell polarity

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Describe Merkel cells and their location in detail

●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

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What is the dermis mostly composed of

connective tissue

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What happens in weeks 9 to 13

hair follicles (pilosebacious units) develop and appearance of lanugo hair

How long does it take for a cell to go from the basal layer to the stratum corneun and when is it accelerated

30 days and in some diseases (eg psoriasis)

what parts of the skin are the most richly innervated

face, extremities and genitalia

Name the 5 roles of keratin

1) structural properties

Embryologically, from where does the epidermis originate. Draw a diagram to show this

from the ectoderm

Are melanocytes dendritic cells? Explain

Yes to allow them to distribute melanosymes via their dendritic processes to keratinocytes

What are the main components of the demis by percentage

proteins: collagen 1 and 3 (80-85% )

fibrilin and elastin

glycoproteins: fibronectin, fibulin, interins

ground substances: glycoaminoglycasides, proteoglycans (hylauronic acid can absorb a lot of water to keep the dermis hydrated)

What is the dermal epidermal membrane called

basement membrane

Describe the development of melanocytes

1)neural crest cells turn into bipotent melanoblast glia progenitor which turns into a melanoblast 2) a melanoblast can differentiate directly into a melanocyte OR 3) develops into a melanocyte stem cell which may later differentiate into a differentiated melanocyte

By which week have most melanocytes been differentiated into

weeks 12 to 13

By week 11 what happens to the basal layer of skin

proliferates to form 5 layers (from deepest to most superficial) stratum germinativum (basal layer of cuboidal cells) stratum spinosum stratum granulosum stratum lucidum (only in palms of hand and soles of feet) stratum corneum

From what week does the epidermis begin developing and what does it begin developing as

from WEEK 4 as a SINGLE BASAL LAYER of CUBOIDAL cells

What are gap junctions and what are they important for

Form connexions between cells (intercellular channels) Directly forms connections between cytoplasms of adjacent keratinocytes essential for cell synchronisation, cell differentiation, cell growth and metabolic co orination

What cells develop in week 5 and what does this layer develop

squamous non keratinising cells called periderm WHITE waxy protective substance called

Describe the pacinian corpuscle

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

describe the autonomic innervation to the skin

cholinergic - eccrine sweat glands adrenergic - eccrine and apocrine

What is the mesoderm essential for

inducing differentiation of epidermal structures (eg hair follicle)

Describe Ruffini's capsule

deeper in dermis than Meissners encapsulated spindle shaped detects skin stretching high density around fingernails monitors slipping

give 3 facts about melanocytes

- dendritic - makes melanosomes that they deliver to keratinocytes - people of all skin colours have the same number of melanin, those of darker tones just have more eumelanin whereas lighter tones have pheomelanin

In what layer of the epidermis do you find the flattened keratinocytes

stratum corneum

describe the structure of the basement membrane and its role

collagens 4 and 7, laminins and integrins roles: cell migration and cell adhesion

Name the 3 things that make up the filiamentous cytoskeleton of keratinocytes and their lengths

Actin containing filiaments (7nm) Tubilin containing filiaments ( 20-25nm) intermediate keratin filiaments (7-10nm)

What collagens are present in the dermis and by what percentage

collagens 1 and 3 and they are 80 to 85%

Describe how how the quantity and quality of melanin is produced (in the absence of UV light)

1) Melanocortin 1 Receptor ( MC1R) is a G coupled protein receptor that regulates the quality and quantity of granules produced 2) Agonists are alpha melanocyte stimulating hormone ( alpha MSH) and adrenocorticotrophic hormone (ACTH) which increases synthesis of eumelanin 3) ACTHS also upregulates transcription of the gene coding for the MC1R 4) Antagonist is Agouti signalling protein (ASP) which reverses synthesis of eumelanin and increases synthesis of pheomelanin

describe the sensory innervation of the skin

on expanded tips, hair follicles and free

what is below the dermis

subcutaneous fat

name the 6 functions of the skin

physical barrier immunological barrier metabolism sensation thermoregulation aesthetic