Skin Structure and Function 2 Flashcards
are skin appendages preserved in scarring?
no
what cells make up the epidermis?
95% are keratinocytes
melanocytes
Langerhans cells
merkel cells
what are melanocytes and where do they come from?
pigment producing dendritic cells (can form freckles)
they migrate from the neural crest to the epidermis in first 3 months of development and sit at the basal layer and above
what do melanocytes do?
contain organelles called melanosomes which convert tyrosine to melanin pigment
what does melanin do?
absorbs light and acts as a neutral density filter
forms a protective cap over nucleus of basal cells to protect DNA
what stimulates melanocytes to produce melanin?
UV light
hormones
what happens to melanin granules after being produced?
transferred from melanocyte to a keratinocyte
what is vitiligo?
autoimmune disease where melanocytes are attacked by T cells
what is albinism?
genetic partial loss of pigment production
what is nelson’s syndrome?
Pituitary tumour produces too much ACTH which results in over-stimulation of melanocytes and dark skin
what is a melanoma?
tumour of the melanocyte cell line
where do Langerhans cells originate and where do they end up?
mesenchymal origin in bone marrow and end up in the prickle layer as well as dermis and lymph nodes
what do Langerhans cells do?
pick up antigens in skin and circulate to lymph nodes to present the antigen
(hence are dendritic in shape)
what are birbeck granules?
tennis racket shaped organelles found in Langerhans cells that
what are merkel cells?
mechanoreceptors in the basal layer between the keratinocytes and nerve fibres that detect the feeling of something crawling over you
can merkel cells become cancerous?
yes
rare but very high mortality
caused by viral infection
what is another name for hair follicles?
pilosebaceous unit
describe the hair follicle
epidermal component + dermal papilla with adjacent sebaceous gland
specialised keratins and melanocytes above dermal papilla which give hair matrix pigmentation
what are the 3 phases of hair growth?
anagen = growing catagen = regressing telogen = resting (will fall out)
can growth patterns of hair vary?
yes
variations depending on area of body
hormones also have an influence
which phase is most hair usually in?
anagen (90%)
10% in catagen
<1% in telogen
is the telogen phase synchronous or asynchronous in humans? what does this mean?
asynchronous
not all hair falls out at same time (drugs can cause it to become synchronous)
what can affect the % of hairs in the anagen phase?
hormones (ie - pregnancy/childbirth)
e.g - low % of anagen hairs after childbirth
what can cause virilisation (development of male characteristics) in females?
excess androgen from a tumour or polycystic ovary syndrome (androgen is precursor for testosterone)
