Derm- physiology and pathophysiology Flashcards
largest vital organ in body
skin
What is the outermost layer of skin called?
epidermis
Blaschko’s lines
developmental growth pattern of skin
type of epithelium in epidermis
stratified cellular epithelium
dermis location
beneath epidermis
subcutis skin
fat layer beneath dermis
what are melanocytes
pigment producing cells from neural crest- migrate to epidermis in first three months of foetal development
Which germ layer forms epidermis
ectoderm
which germ layer forms dermis
formed from mesoderm below ectoderm
which makes up 95% of epidermis
keratinocytes
In foetal skin development, which layers are formed after 16 weeks
Keratin layer
granular layer
prickle cell layer
basal layer
melanocytes convert _____ to melanin pigment
tyrosine
eumelanin colour
brown or black
phaeomelanin colour
red, yellow
function of langerhans cells
involved in the skin immune system
keratin layer of epidermis
non-specific
physical barrier to pathogens
keratinocytes produce…
Produce antimicrobial peptides (AMPs) that can directly kill pathogens
what are langerhans cells
antigen presenting cells
which ig mediates type I hypersensitivity reactions (allergy)
IgE
which ig mediates type II and type III hypersensitivity reactions
IgM, IgG
which cell mediates type IV hypersensitivity reactions
TH1 cell mediated
dermo-epidermal junction
interface between epidermis and dermis
immune cells of the dermis
dendritic cells- dermal DC, plasmacytoid DC
fibroblasts
macrophages
neutrophils
mast cells
Major histocompatability complex (MHC)- chromosome _
chromosome 6
Major histocompatability complex (MHC) roles
Control the immune response through recognition of self and non-self
Responsible for immunological recognition and transplant rejection
MHC class I found-
Found on almost all cells
MHC class II found-
Found on antigen presenting cells (dendritic cells, B cells, macrophages)
antigen presenting cells
dendritic cells
B cells
macrophages
MHC class I present endogenous/exogenous antigens to _____
Present endogenous antigens to cytotoxic T cells
MHC class II present endogenous/exogenous antigens to _____
Present exogenous antigens to TH cells
three types of skin glands
sebaceous
apocrine
eccrine
sebaceous glands functions
control moisture loss- provide lubrication
protect from fungal infection
largest sebaceous glands found where?
face and chest
sebaceous glands produce sebums-
squalene
wax esters
triglycerol
free fatty acids
mechanism of secretion in sebaceous glands
holocrine secretion
hormonal control of sebaceous glands
increased in puberty
what are sebaceous glands
specialized exocrine glands in the skin that produce and secrete an oily substance called sebum
where are apocrine sweat glands found
axillae
groin
eyelids
ears
mammary and perineal regions
apocrine sweat glands activated by ___
hormones- androgen
most abundant type of sweat gland in body
eccrine sweat gland
control of eccrine sweat glands
sympathetic cholinergic nerve supply
pilosebaceous unit
half follicle
hair shaft
arrector pili muscle
sebaceous glands
Which layer of skin are langerhans cells found
prickle cell layer
where do langerhans cells derive from
bone marrow
which layer of skin are melanocytes found
basal layer
hair phases of growth
anagen
catagen
telogen
anagen hair phase of growth
growing
catagen hair phase of growth
involuting
telogen hair phase of growth
resting
is skin metabolically active?
yes
main role of vitamin D
increase the flow of calcium into the bloodstream
vitamin D2 present in
plants
vitamin D3 present/made in
small amounts of some foods eg oily fish, meat
skin from sunlight
thyroid hormone metabolism
thyroxine (T4)- triiodothyronine (T3)
where does T4-T3 conversion occur?
20% in thyroid gland
80% in peripheral tissues including skin
which cells are important in the skins immune defence
langerhans cells and T cells
functions of skin (7)
barrier function
metabolism and detoxification
thermoregulation
communication
sensory function
wound healing
immunisation
keratin layer aka
stratum corneum
granular layer aka
stratum granulosum
prickle cell layer aka
stratum spinosum
basal cell layer aka
stratum basale
what are langerhans cells characterised by
the birbeck granule (“tennis racquet”)
pruritoceptive
something (usually dryness/inflammation) in skin triggers itch
where do melanocytes derive from
neural crest
cytotoxic T cells aka
CD8 + T cells
TH cells aka
CD4 + T cells
what are merkel cells
mechanoreceptors that aid sensation
where are merkel cells found
between keritanocytes and nerve fibres
what do TH1 cells do
activate macrophages to destroy microorganisms
what do TH2 cells do
help B cells make antibodies
ratio of melanocytes:basal cells
1:10
what is an allergy
hypersensitivity disorder of the immune system
allergic reactions occur when-
a persons immune system reacts to normally harmless substances in the environment
how long does allergic reaction occur after exposure to allergen in type I allergy
immediate- occurs within minutes and up to two hours after exposure
how long does allergic reaction occur after exposure to allergen in type IV allergy
delayed- 12-24 hours
which cells produce collagen
fibroblasts
