Physiology Flashcards
what is the largest organ in the body?
the skin
what are the core layers of the skin?
epidermis appendages derma-epidermal junction dermis sub-cutis layer
what are the layers of the epidermis
keratin layer
granular layer
prickle cell layer
basal layer
what epithelium is the epidermis composed of?
stratified squamous epithelium
another name for the keratin layer
stratum corneum
what is the keratin layer made up of?
corneocytes (overlapping, non-nucleated remnants) and lamellar granules containing lipids and keratinocytes
function of the keratin layer
waterproof barrier
what does the granular layer consist of?
2-3 layers of flatten cells with keratohyalin granules that contain filaggrin and involucres protein
role of the granular layer
envelope that protects corneocytes
what does the prickle layer consist of?
larger polyhedral cells with lots of desmosomes connected to intermediate filaments
what does the basal layer consist of?
cuboidal cells with intermediate filaments
high metabolic rate
melanocytes are found here and transfer melanin via dendritic processes
describe epidermal turnover
keratinocytes migrate from the basement membrane to the stratum corneum over 28 days
what is epidermal turnover regulated by?
growth factors
cell death
hormones
when is epidermal control lost?
cancer
psoriasis (immature epidermis)
other cells present in the epidermis
melanocytes
Langerhans cells
Merkel cells
describe melanocytes
pigment-producing dendritic cells that contain melanosomes that transfer to keratinocytes via dendrites
role of melanocytes
convert tyrosine to melanin (eumelanin- brown and phaeomelanin- yellow/red)
what does melanin in melanocytes do?
absorbs sunlight forming a protective cap over the nucleus
which layer are langerhans cells found in?
prickle cell layer, dermis and lymph nodes
what are Langerhans cells associated with?
birbeck granules
where are Meckel cells located?
between keratinocytes and nerve fibres
role of Meckel cells
mechnoreceptors
risk in Meckel cells
viral cancer
what are the three appendages present in the skin?
nails
hair
glands
describe nails
specialised keratins
what is hair made of
keratin
what is hair attached to?
sebaceous gland
how is hair colour formed
melanocytes above the dermal papilla
phases of hair growth
anlagen
catagen
telogen
hormonal influences on hair
thyroxine
androgens
three types of glands
sebaceous
apocrine
eccrine
describe sebaceous glands
attached to hairs
hormone sensitive and produce sebum
control moisture loss and protect from fungal infection
describe apocrine glands
present in axilla and perineum
androgen dependent producing oil
describe eccrine glands
whole skin surface under sympathetic cholinergic nerves
functions with ultrafiltration and thermoregulation
describe the derma-epidermal junction
epithelial-mesenchymal interaction
basement membrane is laminin and collagen
what does the dermis consist of?
connective tissue, fibroblasts, macrophages, mast cells, fibres and ground substances
what fibres are in the dermis
collagen and elastin
what ground substances in the dermis
hyaluronic acid
chondroitin sulphate
what appendages are present in the dermis?
blood vessels
muscles
lymphatics
nerves
how are the blood vessels arranged in the dermis?
horizontal plexuses
what muscles are present in the dermis?
arrestor pili attached to hair follicles
what lymphatics are present in the dermis
lymphocytes and langerhans for immune surveillance and removal of toxins
what two types of nerves are present in the dermis
somatic sensory (dermatomes) autonomic
role of somatic sensory
free nerve endings with pacinian (deep pressure and vibrations) and Meissner’s (light pressure) corpuscles
role of autonomic NS
supplying blood vessels, nerves and glands
what is the sub-cutis layer made up of
fat
role of the skin
barrier thermoregulation immune defence metabolism (vitamin D and thyroxine) communications (visual, odour, stigma) sensation
