principles

Question 1

what are the layers of the epidermis from outer to inner layer ?

Answer 1

keratin layer
granular layer
prickle cell
basal 
dermis

Question 2

what are B cells role in type 1 hypersensitivity reaction?

Answer 2

recognise antigen

produce antigen specific IgE antibody#

> T cells provide help for B cells

Question 3

what are mast cells role in type 1 hypersensitivity reaction?

Answer 3

inflammatory cells that release vasoactive substances

->histamine, tryptase, prostaglandins, cytokines

Question 4

what local effects (not cellular) do the release of vasoactive mediators have?

Answer 4

increased blood flow
contraction of smooth muscle
increased vascular permeability

Question 5

if previously sensitised to allergen, what serious consequence is there a risk of?

Answer 5

anaphylaxis

urticaria (nettle-like rash)

Question 6

anaphylaxis effects

Answer 6

A - throat swelling
B - bronchospasm, increased RR
C - tachycardia, hypotension

urticaria, angioedema, rhinitis

Question 7

cellulitis

Answer 7

inflammation of subcutaneous connective tissue

> a spreading infection in the dermis that is not associated with necrosis

Question 8

cells of innate immune system

Answer 8

macrophages, neutrophils, dendritic cells, mast cells, eosinophils, NK cells

Question 9

3 soluble mediators of innate immune system

Answer 9

CRP
cytokines
complement

Question 10

virulence factors of staph aureus + their mode of action

Answer 10

capsule - antiphygocytic
fibrinogen binding protein - adhesin
coagulase - clots plasma
fibrinolysin - digests fibrin
protein A - antiohagocytic
enterotoxin - vom+diarh
TSST-1 - shock, rash, desquam

Question 11

what 2 hypersensitivity reactions are most commonly seen in the skin and what is the difference between them?

Answer 11

type I = immediate reaction, mediated by IgE + mast cells

type IV = delayed, cell mediated involving lymphocytes + lymphokines

Question 12

cutaneous examples of type 1 hypersensitivity

Answer 12

urticaria - nettle rash
angioedema
anaphylaxis

Question 13

cutaneous examples of type 4 hypersensitivity

Answer 13

allergic contact dermatitis
photoallergy

-> require initial sensitisation with allergen, then any area will react

Question 14

what are the fphases of hair growth?

Answer 14

anagen = growing (3-7yrs, 90%)

catagen = involuting (3-4weeks, 10%, detaches from dermal papilla)

telogen = resting, club hair (50-100 days)

Question 15

3 types of glands

Answer 15

eccrine - everywhere except mucosal, thermoregulation

apocrine - axilla + anogenital, inactive till pubrty, androgen dependent

sebaceous - inactive till puberty, excrete sebum (antimicrobial actions)

Question 16

functions of sebaceous glands

Answer 16

control moisture loss
protect against fungal infection
sebum has antimicrobial actions

highest density in face, scalp + chest

Question 17

langerhans cells

Answer 17

• dendritic cells derived from bone marrow
• -> antigen presenting cell (APC) to T cells to activate them
• form network across prickle layer
• role in antigen presentation - picks up antigen in skin + circulate to lymph nodes

Question 18

melanocytes

Answer 18

• pigment producing dendritic cells
• originate from neural crest
• in basal layer
• contain melanosomes (melanin granules)

Question 19

role of melanin

Answer 19

absorbs UV + forms protective cap over nucleus of basal cells

melanin is transferred to adjacent keratinocytes via dendrites

-> racial differences due to variation in melanin NOT melanocyte numbers

Question 20

histology +origin of epidermis

Answer 20

statified squamous epithelium

from ectoderm

Question 21

histology + origin of dermis

Answer 21

connective tissue - matrix of collagen + elastin fibres

mesodermal origin

Question 22

layers from epidermis -> dermis

Answer 22

keratin
granular
prickle
basal
dermis

Question 23

what does the dermis contain?

Answer 23

• fibroblasts (mostly), mast cells, lymphocytes, dermal dendritic cells
• blood + lymphatics, nerves
• muscle, appendages (sweat glands, hair follicles)

Question 24

what endocrine functions does the skin have?

Answer 24

metabolism + detoxification

vit D - dietary, UV

thyroid metabolism - 20% in thyroid gland, 80% in peripheral (SKIN)

Question 25

keratinocytes involvement in immune response

Answer 25

produce antimicrobial peptides (AMPs) that directly kill pathogens --> high levels of AMPs in psoriasis patients produce cytokines + chemokines - recruit + regulate immune cells

Question 26

what type + where are T cells are found in the skin?

Answer 26

mainly CD8 in epidermis CD4 + CD8 in dermis

Question 27

different types of dendritic cells in dermis

Answer 27

dermal DC - antigen presenting + secreting chemo/cytokines plasmacytoid DC - produce IFNalpha, found in diseased skin

Question 28

immunopathology of atopic eczema

Answer 28

defective skin barrier allows access to allergen + promotes colonisation of microorganisms mutations in fillagrin gene associated with severe/early onset

Question 29

key cell types in epidermis involved in skin immunity

Answer 29

keratinocytes (non-immune cell) lagerhans T cells

Question 30

key cell types in dermis involved in skin immunity

Answer 30

dendritic cells macrophages T cells NK cells

Question 31

define virulence + virulence factors

Answer 31

virulence = severity / harmfulness of a disease virulent factors = factors responsible for variation in virulence between species

Question 32

staph epidermis

Answer 32

- coagulase negative - 100% colonisation - skin + mucous membranes - nosocomial infection/immunocompromised - -> associated with foreign devices - catheters

Question 33

what is the role of aggressin, impedin and modulin as virulence factors?

Answer 33

aggressin = causes damage to the host DIRECTLY impedin = enables organism to avoid host defence mechanisms modulin = causes damage to the host INDIRECTLY

Question 34

where are hemmi-desmososmes found?

Answer 34

epidermal junction

Question 35

what layer of the epidermis is most metabolically active?

Answer 35

basal layer

Question 36

how long does it take for a cell to migrate from the basal layer to keratin layer?

Answer 36

28days

Question 37

what cell in epidermis is responsible for vit D metabolism?

Answer 37

keratinocytes ?in basal layer

Question 38

what cells are responsible for epidermal proliferation?

Answer 38

basal cells cells in epidermis proliferate from the basal layer

Question 39

the developmental growth pattern of skin follows ...

Answer 39

Blaschko's lines

Question 40

function of pacinian corpuscles

Answer 40

pressure sensation

Question 41

function of meissner's corpuscles

Answer 41

vibration sensation

Question 42

highly metabolically active small cuboidal cells

Answer 42

basal layer

Question 43

where are odland bodies found?

Answer 43

granular layer

Question 44

where are corneocytes found?

Answer 44

keratin layer

Question 45

polyhedral cells with lots of desmosomes

Answer 45

prickle cell layer

Question 46

what do fibroblasts produce?

Answer 46

collagen