physiology Flashcards
epidermis is derived from?
ectoderm
dermis is derived from?
mesoderm
melanocytes derived from?
neural crest
what is the epidermis structure?
stratified squamous epithelium
layers of the epidermis
keratin, granular, prickle cell, basal
what is characteristic of the prickle cell layer
lots of desmosomes
what is present in palms/soles
a fifth layer called stratum lucidium
where is the stratum lucindium
between corner-granulosum
what are basal cells
cuboidal shaped stem cells that are precursors of the keratinocytes
what are most epidermal cells
keratinocytes
where are keratinocytes dead
in the corneum
what are keratinocytes
cells that excrete and store keratin
how long for keratinocytes to migrate from the basement membrane
28days
what are melanocytes
pigment producing dendritic cells
what do melanocytes to
convert tyrosine to melanin
what do melanocytes contain
melanosomes
what does melanin do
absorb light
what happens with meloanosomes are full
they are transferred to adjacent keratinocytes by dendrites
what do full melanosomes do
form a protective cap over the nucleus protecting nuclear DNA in basal cells
where are langerhans cells found
in spinous level
what are langerhans cells
antigen presenting dendritic cells
where are Merkel cells found
basal level between keratinocytes and nerve fibres
what are Merkel cells
mechano- receptors
what causes pigmentation in hair
melanocytes above dermal papilla
what causes hair growth
hormones - thyroxine androgens
stages of hair
anagen, catagen, telogen
what happens in anagen
growth
what happens in catagen
involuting
what happens in telogen
resting (balding)
what can cause hair growth in cancer
cancers that release excess androgen
what is a nail body made of
densely packed dead keratinocytes
where is the derma-epidermal junction
between dermis and epidermis
what bonds layers together at the derma-epidermal junction
collagen fibres
what increases the strength of the layers at the dermal epidermal junction
dermal papilla
what is the dermis made of
two layers of connective tissue (collagen and elastin)
what does the dermis contain
blood and lymphatic vessels and nerves
somatic sensory nerves
dermatomes
pressure
pacinian
vibration
meissners
sabecous glands produce
sebum
apocrine glands produce
oily fluid - cause sweat smell
eccrine
true sweat gland
nerve supply of eccrine
sympathetic cholinergic nerve supply
functions of skin
barrier, metabolism and detoxification, thermoregulation, immune defence, communication, sensor function s
what does skin metabolise
vit D and Thyroid hormone
Thyroid hormone changed
T4- T3
