dermatology

Question 1

epidermis vs dermis origin

Answer 1

ectoderm vs mesoderm (essential for inducing differentiation of epiderm)

Question 2

layers of epidermis (differentiate as they migrate up)

Answer 2

stratum spinosum => granulosum => lucidum => corneum => basalis

Question 3

changes to epidermal layers in thick skin vs thin

Answer 3

thick = presence of stratum lucidum + thicker stratum spinosum

Question 4

parts of filamentous cytoskeleton of keratinocytes

Answer 4

actin containing microfilaments
tubulin containing microtubules
intermediate filaments

Question 5

role of keratins

Answer 5

structure, signalling, stress response, apoptosis, wound healing

Question 6

desmosomes

Answer 6

major adhesion complex in epidermis

anchor keratin intermediate filaments to cell membrane + bridge adjacent keratinocytes

allow cells to withstand trauma

Question 7

gap junctions

Answer 7

form direct connections between cytoplasm of adjacent keratinocytes

clusters of intercellular channels: connexons

roles in: cell synchronization, differentiation, growth + metabolic coordination

Question 8

tight junctions functions

Answer 8

role in barrier integrity and cell polarity

Question 9

adherens junctions functions

Answer 9

transmembrane structures => engage with actin skeleton

Question 10

melaocyte function

Answer 10

distribute melanin pigment (in melanosomes) to keratinocytes

Question 11

langerhans cell function

Answer 11

antigen‐presenting cells

Question 12

papillary vs reticular dermis

Answer 12

papillary: loose connective tissue => vascular

reticular: dense connective tissue

hypodermis:

Question 13

proteins in basement membrane vs dermis

Answer 13

BM: collagens 4+7, laminin, integrins

D: collagen 1+3, fibrillin, elastin, fibronectin, fibulin, intregrins

Question 14

main cells in dermis

Answer 14

fibroblasts

(+ histiocytes, mast cells, neutrophils, lymphocytes, dermaldentritic cells)

Question 15

autonomous (sweat) cholinergic vs adrenergic innervation of dermis

Answer 15

ch: eccrine (open directly onto skin surface)

ad: eccrine + apocrine (open into hair follicle)

Question 16

meissners/tactile corpuscle (what, where, function)

Answer 16

unmyelinated mechanoreceptor

in thick/hairless skin
superficial dermic

detect light touch + slow vibration

Question 17

pacinian/lamellar corpuscle (what, where, function)

Answer 17

rapid acting mechanoreceptor

hands + feet
papillary dermis

detect deep pressure + vibrations

Question 18

ruffini/bulbous corpuscle (what, where, function)

Answer 18

slow acting mechanoreceptor

around nails (to monitor slippage) in deep dermis

detect stretch of skin

Question 19

merkel cell

Answer 19

non-encapsulated mechanoreceptor

oval

most populous in fingertips (and palms, soles, oral & genital mucosa)

detects light/sustained touch, pressure

Question 20

main bacteria on skin

Answer 20

actinobacteria
firmicutes
bacteriodetes
proteobacteria

Question 21

nerve fibres + what they transmit

Answer 21

A-beta => touch related information
A-delta => pain + temperature + pressure
C => pain, temp, itch

Question 22

skin as physical barrier

Answer 22

corneum restricts water + protein loss from skin
subcutaneous fat cushions trauma
UV barrier - melanin protects against dna damage

Question 23

skin as thermoregulator

Answer 23

vasodilation/vasoconstriction
eccrine sweat glands = cooling effect
role in fluid balance

Question 24

skin in metabolism

Answer 24

vit D synthesis

subcutaneous fat = calorie reserve

hormone release => leptin => hypo => hunger + energy metabolism regulator

Question 25

skin as immune barrier

Answer 25

dendritic, macrophage, sentinel cells

Question 26

immune surveilence in dermis

Answer 26

tissue‐resident T-cells
macrophages
dendritic cells
rapid, effective backup if epidermis breached

Question 27

terminal vs vellus hairs

Answer 27

terminal = scalp, brows, lashes, pubic hair

vellus = rest of the body (fine, lighter)

Question 28

phases of hair cycle (what happens, what % of hair at single time, duration)

Answer 28

anagen => new hair forms + grows - 85% + 2-6y

catagen => regression + shrinking - 1% + 3 weeks

telogen => resting phase (loss of old hair) - 10-15% + 3 months

Question 29

pilosebaceous unit

Answer 29

hair follicle, hair shaft and sebaceous gland

Question 30

process by which hair follicle starts forming

Answer 30

trichilemmal keratinization

Question 31

3 sections of hair follicle

Answer 31

infundibulum - sebaceous gland opening → skin surface

isthmus - sebaceous gland opening → insertion of arrector pili

bulb - follicular dermal papilla and the hair matrix

Question 32

formation of sebaceous gland in hair follicle

Answer 32

hair follicle stem cells in bulge migrate down + generate new lower anagen follicle

enter bulb matrix => proliferate => terminal differentiation

form hair shaft + inner root sheath

migrate up => form sebaceous glands + proliferate in response to wounding

Question 33

functions of nail

Answer 33

protection of distal phalanx
counter pressure effect to pulp => walking + tactile sensation
dexterity
sensory discrimination
scratching/grooming

Question 34

nail plate

Answer 34

final product of proliferation + differentiation of nail matrix keratinocytes

Question 35

matrix

Answer 35

produces nail plate

under proximal nail fold

Question 36

what happens to nail matrix keratinocytes as they differentiate

Answer 36

lose nuclei and are strictly adherent - cytoplasm completely filled by hard keratins