Skin Structure + Function Flashcards
What is the histology of the epidermis
Stratified squamous epithelium
Name the layers of the epidermis from superficial to deep
- Keratin layer - stratum coreum
- Clear layer - stratum lucidum
- Granular layer - stratum granulosum
- Pricle layer - stratum spinosum
- Basal layer - stratum basale
Merkel cells are found in what layer of the epidermis
basal cell layer
Function of merkel cells
touch receptors
- contain mechanoreceptors
after how many weeks gestation is the skin considered to be fully formed
26 weeks
- basal layer + dermis formed by 4 weeks
- basic skin anatomy formed by 16 weeks
what are blaschko’s lines
lines which show development growth patterns of skin
what is the dermis mainly comprised of
connective tissue
what is the most prominent cell type in the epidermis
keratinocytes
why do cells in basal layer need to be protected by melanin
stem cells reside here
- DNA capped by melanin as this cannot be replaced
in which cell can you find a birbeck granule
langerhans cells
- they look like tennis rackets
name of melanin that is black/brown in colour
eumelanin
- most common type
name of melanin that is red/yellow in colour
pheomelanin
name the 3 stages of hair growth
- anagen - growing
- catagen - involuting
- telogen - resting
where do melanocytes originate from
neural crest
- in ectoderm during embyrogenesis
epidermis arises from which embryological tissue
ectoderm
dermis arises from which embyroglical tissue
mesoderm
which layer of epidermis contains filaggrin and involucrin? what is their function?
Granular layer
- maintain water barrier of the skin
which type of granules will release filaggrin and involucrin
Lamellar granulues in the granular layer
what are corneocytes
cells of the granular layer that are flattened, have lost their nucleus and released contents of lamellar granules (filaggrin and involucrin)
- create 2-3 layers to become the keratin layer
how many days does it take for cells to migrate from the basement membrane to the keratin layer?
28 days
which amino acid is converted to melanin within melanosomes
tyrosine
why do children with PKU often have pale skin
- Process of converting phenylalanine to tyrosine is disrupted
- tyrosine is required to be converted to melanin
- less melanin is produced – pale skin
name 3 different types of glands found in skin
- eccrine
- sebaceous
- apocrine
where are apocrine glands found
axillae and perineum
- androgen dependent
- produce oily fluid responsible for body odour as bacteria decompose it
where are sebaceous glands found
face and chest
most common skin gland
eccrine
name the three layers of the dermo-epidermal junction from superficial to deep
- Lamina lucida
- Lamina densa
- Sub-lamina zone
function of dermo-epidermal junction
- semi-permeable membrane acting as a filter + barrier
- support + anchorage of basal cells
receptor in the skin that is specialised for light pressure
meissners corpuscles
receptor in the skin that is specialised for deep pressure + vibration
pacinian corpuscles
what causes skin to sag with age
- less collagen produced
- disordered collagen
what layer of skin is papilla of hair follicle found
dermis
autoimmune condition that attacks papilla of hair follicles
alopecia areata
in which layer of the skin are immune cells most abundant ?
what cells can be found?
Dermis
- Macrophages
- Mast cells
- Lymphocytes
- Langerhans cells
what is a pilosebaceous unit
structure consisting of hair, hair follicle, erector pili muscle and sebaceous gland
what is the most abundant protein in dermis
collagen
what wavelength of light is required for Vit D synthesis ?
what does it do to produce Vit D ?
290 - 320 nm
converts 7 dehydrocholesterol to vitamin D3
MHC 1 binds to what in T cell activation
CD8
MHC 2 binds to what in T cell activaiton
CD4
which immune cells are most associated with atopic dermatitis
TH2
TH17
Which immune cells are most associated with psoriasis
TH1
TH17
What is the main immune cell in the epidermis
langerhans cell
How do the roles of plasmacytoid dendritic cells and dermal dendritic cells differ?
Plasmacytoid - associated with diseased skin and secrete INF alpha
Dermal- associated with antigen presentation in the dermis
Which T cell activates macrophages and how do they achive this
TH1
- by releasing IL2 and IFN gamma
