skin structure and function Flashcards
what does the embrylogical development of skin follow
Blaschkos lines
what is the dermis derived from
mesoderm
what is the epidermis derived from
ectoderm
what is are melanocytes derived from
neural crest
define the epidermis
stratified squampus epithelium mainly made of keratinocytes and forms the outer protective layer of skin
what are the main functions of keratinocytes
production of keratin, synthesis of vitD and immune functions
what are the 4 layers of the epidermis created by
the travelling of keratinocytes
how long does it take for keratynocytes to travel from the deepest to the most superficial layer of the epidermis
28 days
what are the 4 layers of the epidermis from deepest to most superficial
basal layer, prickle cell layer, granular layer, keratin layer
what layer of the epidermis conatins merkel cells, melanocytes, abundance of keratin and a single layer of cuboidal keratinocytes
basal layer
what does the prickle cell layer of the epidermis consist of
polyhedral keratinocytes
what does the granular layer of the epidermis consist of
2-3 layers of flattened keratinocytes and langerhans cells
what is the functions of the granular layer of the epidermis
to produce a cornified envelop by producing keratin and other proteins such are filaggrin and involucrin
what are distinguishing features of keratinocytes in the granular layer of the epidermis
lack of nuclei, high lipid content, odland bodies
what is the keratin layer of the epidermis also known as
stratum corneum
what is the keratin layer of the epidermis made of
corneocytes and insoluble cornified envelope
what are corneocytes
non nucleated remanants of keratinocytes
what does the insoluble cornified envelop consist of
keratin, lipids and filaggrin
what epidermis layer varies in thickness the most throughout the body
keratin layer
what are melanocytes
dendritic cells that migrate from the neural crest
what are melanocytes responsible for
producing melanin from tyrosine
what happens to melanin
it is transferred to keratinocytes
why is the melanin transferred to keratinocytes
to protect DNA from damage from UV rays by absorbing them
what are langerhans cells and where are they found
dendritic cells found in the prickle cell layer of the epidermis and the dermis
what is the primary function of langerhans cells
antigen presentation to T cells
what is the distinguishing feature of langerhans cells
birckbeck granules
where are merkel cells found
in the basal layer
what is the function of merkel cells
mechanoreception
what is the dermoepidermal junction
an avascular zone which acts as the interface between the dermis and epidermis
what results from alterations of the dermo-epidermal junction
bullae
what are the functions of the dermoepidermal junction
semi permuable membrane that acts as a barrier to filtration, support, adhesion and anchorage of epidermal cells
components of the dermoepidermal junction from superficial to deep
hemi desmosomes, lamina lucida, lamina densa, sub lamina densa
what is the primary function of the dermis
to support and cushion the epidermis
what is the majority of the dermis compoased of
connective tissue
components of connective tissue
collagen, elastin, ground substance which is gel like composed of glycoaminoglycans
what cells are found in the dermis
mast cells, fibroblasts, langerhans cells, lymphocytes and macrophages
how many types of skin glands are there
3
where are all 3 of the skin glands found
in the dermis
what are the 3 skin glands
sabeceous, apocrine, eccrine
what are sabaceous glands
glands that wrap around the hair follicles
where are sabaceous glands found on the body
face, chest and upper back
what do sabaceous glands produce
sebum
what does sebum do
prevent moisture loss and protects against infection
where are apocrine glands found
deep in the dermis and project up towards and open out into the hair follicle
where are apocrine glands glands found on the body
axilla and perineum
what do apocrine glands do
produce scented oily fluid
what are eccrine glands
sweat glands that open directly onto the skin
where are eccrine glands found on the body
every where especially the axilla, palms and soles
what allows the skin to undertake its role in thermoregulation
extensive blood supply that far outweighs the metabolic demand
what do the blood vessels in the dermis form
a horizontal plexus
what do the blood vessels in the dermis also supply
the epidermis
what does the dermis have
abundant amount of autonomic, sensory and motor nerves
where are meissners corpuscles
groups of sensory nerves that are found HIGH in the dermis
what do meissners corpuscles respond to
light touch and vibration
what are pacinian corpuscles found
groups of sensory nerves found DEEP in the dermis
what do pacinian corpuscles respond to
heavy, deep pressure
describe the lymphatics of the skin
it is extensive and the vessels form a meshed network within the dermis
what are the 3 types of hair
terminal, vellus, lanago
what is terminal hair
course hair
where is terminal hair found
scalp, beard and pubic region
what is vellus hair
fine hair
where is vellus hair found
on the face of women and pre pubescent children
what is lanago
soft hair
where is lanago found
in new borns
what are the 3 stages of hair growth
anagen, catagen, telogen
what is anagen
period of active growth
what is catagen
period of no active growth but with involution of the hair
what is telogen
hair falls out
what are the functions of the skin
barrier, sensation, thermoregulation, immune defence, metabolism - vit D3 and activation of T4-T3
what arethe cells responsible for vitamin D production
Keratinocytes
