Skin Structure and Function Flashcards
where are the epidermis and dermis derived from? when does this begin?
epidermis = ectoderm
dermis = mesoderm (below ectoderm)
gastrulation begins 7-10 days into development
what are melanocytes?
pigment producing cells from neural crest
how does skin progress from 4 weeks to 16 weeks to 26 weeks?
4 weeks = 3 layers - periderm, basal layer and dermis
16 weeks = 5 layers - keratin layer, granular layer, prickle cell layer, basal layer, dermis
26 weeks = same as 16 but with appendages (hair follicles, glands etc)
what are Blaschko’s lines?
developmental growth pattern of skin/lines of tension
skin drawn out to make room for limbs as they develop
how can blaschko’s lines be used clinically?
if a rash/malformation follows blaschko’s line this would show that it is a developmental problem
what are the components of skin?
epidermis appendages (hair, nails, glands, mucosae) dermo-epidermal junction dermis sub-cutis
what is the sub-cutis responsible for?
elasticity/malleability
predominantly fat
where in the skin are blood vessels found?
dermis
where do sweat glands descend into?
sub-cutis
where are sebaceous glands found?
dermis
where does hair follicle begin?
sub-cutis
what type of epithelium covers the epidermis?
stratified squamous epithelium
what cells are present in the epidermis?
keratinocytes (95%)
melanocytes
Langerhans cells
merkel cells
how does the epidermis grow and how long does this take from start to finish?
moves and grows up from the basement membrane
takes 28 days to get to the top
what is the basal layer?
embryological ectoderm that keeps dividing constantly
like stem cells of the skin
is the epidermis the same everywhere?
no
varies at different body sites - e.g more hair on scalp, more sweat glands on soles of feet etc
thickness can also vary
how is the constant production of epidermis controlled?
growth factors, cell death, hormones
rate can also be affected by genetics, temperature etc
what happens when the regulation of epidermis turnover fails?
skin cancer
psoriasis
what causes the red and white parts of psoriasis?
red = blood vessels shine through thin parts of prickle layer as it varies in thickness in psoriasis white = thickened keratin does not fall away
how does epidermis turnover vary in psoriasis?
takes 28 days in normal people
takes 5 days in psoriasis
describe the basal layer structure
usually one cell thick layer of cuboidal cells with lots of intermediate filaments (keratin)
why are prickle cells called such?
large polyhedral cells briefly connected by many desmosomes
what is the function of the prickle cell layer?
produce keratin
organise cells as they move upwards towards epidermis
what is the function of the granular layer?
thin layer of cells with large keratohyalin granules containing filaggrin and involucrin proteins
high lipid content
what do the granular cells become and how?
origin of the cornified envelope
cells shrink in size and loose nuclei and burst open as they use last resources to overproduce proteins and left overs combine to form envolope
what are the components of the keratin layer?
corneocytes cornified envelope 80% keratin and filaggrin lamellar granules which release lipids forms tight waterproof barrier
what is the function of filaggrin and keratin?
broken down into amino acids which allow skin to retain water
give an example of a disease which affects keratinocytes?
HPV (causes warts)
describe wart histology
very thick dermis
very few blood vessels hence why warts aren’t red
where are mucosal membranes found?
anywhere the skin stops (e.g - eyes, nose, genital tracts, mouth etc)
are all mucosal membranes the same?
no, specialised for function
how is oral mucosa specialised for function?
masticatory = keratinised
lining = non-keratinised
specialised (tongue papillae)
how is ocular mucosae specialised?
lacrimal glands
eye lashes
sebaceous glands
