Structure and Function Flashcards
what are the two layers of the skin
epidermis and dermis
what cells make up the epidermis
stratified squamous cells
where is the epidermis derived from
the ectoderm
what cells make up 95% of the epidermis
keratinocytes
what are the four defined layers of the epidermis
keratin
granular
prickle cell
basal
what is the dermis derived from
the mesoderm
What are the 4 types of epidermal cell
keratinocytes
melanocytes
Langerhans cells
Merkel’s cells
what are melanocytes and where do they originate from
pigment producing cells originating from the neural crest
what 3 layers are formed at 4 weeks of foetal skin development
Periderm
Basal layer
Dermis
by 16 weeks what are the 5 layers of skin formed
keratin layer granular layer prickle cell layer basal layer dermis
at how many weeks do hair, melanocytes and appendages form
26 weeks
what pattern does the development of skin follow
Blashko’s lines
what factors regulate epidermal turn over
growth factors
cell death
hormones
(loss of this control is seen in skin cancer and psoriasis)
How many days does it take for the epidermis to regenerate (from bottom to top)
28 days
which layer is one cell thick, has small cuboidal shaped cells, contains intermediate filaments and is highly metabolically active
basal layer
the prickle cell layer is thinner in psoriasis true/false
false
its thicker
what layer contains island bodies (secretory cells)
granular
what does the keratin layer consist of
corneocytes (overlapping, non-nucleated cell remnants, differentiated keratinocytes)
what other than corneocytes does the keratin layer contain
cornfield envelope
keratin and filaggrin
lamellar granules (release lipids)
where do melanocytes originate
neural crest (migrate to the epidermis in the first 3 month of development)
where are melanocytes found
the basal layer
what do melanocytes do
pigment producing dendritic cells, convert tyrosine to melanin pigment
melanin granules are transferred to adjacent keratinocytes via dendrites
form a protective cap over DNA in the basal cells to protect from UV light and hormones
what colour is Eumelanin
brown or black
what colour is Phaemelanin
red or yellow
where do langerhans cells originate
bone marrow
what do langerhans cells do
antigen presenting cells
where are Merkel cells found
basal layer, on the ends of nerve fibres, direct extension of the brain
what do merkels cells do
mechanoreceptors (respond to mechanical stimuli)
what is vitiligo
a skin condition involving hypo pigmentation of the skin due to the melanocytes being attacked by T cells
what is Nelson’s syndrome
where melanin stimulating hormone is produced in excess by the pituitary gland causing bronzing of the skin
what are the three stages of hair growth
Anagen -growing
Catagen -involuting
Telogen -resting
at what rate do nails grow
0.1mm per day
what is the demo-epidermal junction and what are its functions
the interface between the dermis and the epidermis
provides anchorage, support, and adhesion as well as being a semi permeable membrane acting as a barrier and a filter
What are the three layers of the demo-epidermal junction
Lamina Lucida (top) Lamina Densa (middle) Sub-lamina Densa (bottom)
failure of function of the demo-epidermal junction leads to
fragile skin
fluid filled blisters
what is the dermis made up of
ground substance (gives structure) collagen elastin immune cells blood vessels lymphatics nerves hair follicles
the blood supply to the skin is greater than metabolic need true/false
true
what is an angioma
a benign overgrowth of blood vessels
what do pancain nerves do
sense pressure
what do meissners nerves do
sense vibration
what causes pigmentation of hair
melanocytes above the papilla
what do sebaceous skin glands produce and whats their function
produce oily, waxy sebum, hormone sensitive glands which control moisture and protect from fungal infections
what do apocrine glands produce and whats their function
sweat glands which produce odour due to bacterial decomposition, linked to hair follicles
what do eccrine produce whats there function
sweat glands occurring everywhere
not attached to hair follicle
