Structure and function of skin Flashcards
what embryological layer forms epidermis
ectoderm - to make periderm
what embryological layer forms dermis
mesoderm
what forms melanocytes
neural crest
what are Blaschko’s lines
pattern of developmental growth of skin cells. it does not follow vessels, nerves or lymphatics
true/false - epidermis is stratified columnar epithelia
false - it is stratified squamous epithelia
what is the primary cell type of the epidermis
keratinocyte
name 2 examples of where control of cell turnover is lost in the epidermis
skin cancer
psoriasis
the basal layer is how many layers thick and is made up of what type of stem cells
1 layer thick
cuboidal stem cells
what intercellular junctions do cells in the prickle cell layer contain
desmosomes
what is the keratin layer made up of
non-nucleated remnants of keratinocytes
keratin
filaggrin
how is the keratin layer waterproof
filaggrin binds water
tight intercellular junctions limit diffusion
intercellular lipid bilayer and lipid content repels water
what do keratohyalin granules contain and where are they found
keratin and filaggrin
granular layer
what do lamellar bodies contain/secrete
lipids and filaggrin
how do melanocytes create colour in the skin?
contain melanosomes that travel up dentrites to release melanin to keratinocytes
what is the compound converted to melanin by melanocytes?
tyrosine
how does melanin protect basal cells
blocks passage of UV radiation from light to basal cells to prevent DNA damage
where are langerhans cells found and what is their function
prickle cell layer, dermis and lymph nodes
act as APC, and circulates to lymph node
where are merkel cells found and what do they do
found between keratinocytes and nerve fibres
mechanoreceptors for touch sensation
a hair follicle contains a d___ p___ and what gland?
dermal papilla
sebaceous gland
what determines hair colour in the follicle
melanocyte above dermal papilla
describe anagen
growth phase that majority of hairs are in
describe catagen
involuting phase where growth stops and hair clubs ready to fall out
describe telogen
resting phase where hair falls out
what is the function of the cuticle
protective barrier for nail to prevent infection
describe nail growth
nail matrix is made up of stem cells. these replicate and push out keratinocytes that flatten, lose nucleus and become elongated to form shape of nail
what is the dermo-epidermal junction and what is its function
semi permeable barrier between dermis and epidermis
barrier and support/adhesion for basal cells
two types of dermis
papillary dermis
reticular dermis
what is the dermis made up of
ground substance
collagen and elastin
fibroblasts (main cell), langerhans, mast cells, macrophages, lymphocytes
muscles, blood vessels, lymphatics, nerves
deep plexuses run horizontally in the reticular/papillary dermis and superficial plexuses run horizontally in the reticular/papillary epidermis
reticular
papillary
describe the function of lymphatic vessels of the dermis
drains debris, excess interstitial fluid and plasma
allows travel of langerhan cells and lymphocytes for immune surveillance
pacinian corpuscles sense?
pressure
meissners corpuscles sense?
vibration
function of sebaceous gland?
lubricates hair haft, skin and antimicrobial
what is the arrector pili muscle controlled by?
ANS
what hormones alter hair growth?
androgens and thyroxine
where are sebaceous glands largest and when are they most active
head, face, shoulders and upper chest
during puberty as they are hormone sensitive
where are apocrine glands found
axialla and perineum
where are eccrine glands found, what is their function and control?
everywhere but mostly hands, feet, hair
thermoregulation - cools by evaporation
control by sympathetic part of ANS
functions of the skin?
barrier metabolism and synthesis communication immunity sensory thermoregulation
how does the skin synthesise vitamin D
converts 7-dehydrocholesterol to vitamin D3 by UVB
What hormone is synthesised from thyroxine by the skin
T3
