Dermal Structure and Disease Flashcards
Term used to describe the admixture of collagen fibers, elastic fibers, and ground substance of which are all synthesized by dermal fibroblasts
dermal matrix
interlocking of epidermis and dermis
dermoepidermal junction
downward projection of epidermis
epidermal rete
interlocking dermoepidermal junction (2 functions)
increased sa
increased strength adherence
provides the tensile strength of the skin
collagen
comprises 85% wt of adult dermis
collagen I
procollagen is synethesized
intracellulary within fibroblasts
procollagen consists of
three separate chains of proteins arranged in an alpha helical structure
characteristic pattern of procollagen
striations with 68nm intervals
collagen chain repeating unit
Gly X Y
X = proline
Y = hydroxyproline
once the collagen proteins are synthesized, what happens?
they are secreted and assembled into collagen fibrils extracellularly
cofactor required for collagen fibril assembly
VitC (Ascorbic acid)
Acquired abnormality in collagen production
scurvy (vit-c deficiency)
- poor wound healing
- poor hair growth
- fragile blood vessels
- teeth fall out
congenital abnormailties in collagen production?
ehlers danlos
4 clinical features of ehlers danlos
skin hyperextensibility
joint hypermobility
tissue fragility
poor wound healing
Genetic defect –> disordered collagen production
ehlers danlos
provide skin with tensile strenght
collagen
provide skin with resliency
elastic fibers
what do collagen fibers look like under microscope
large eosinophilic (pink) bundles
elastic fibers under microscope
agryophilic (silver loving)
acquired eslatic fiber disorder
solar elastosis
solar elastosis - cause
accumulation of significant sun damage over lifetime –> degeneration of elastic fibers –> clump / aggregate
sun-damage elastic fibers in solar elastosis under microscope?
basophilic - important when evaluating for sun induced neoplasms
inherited (Genetic) elastin disorders?
PXE
Pseudoxanthoma elasticum
Pseudoxanthoma elasticum =
genetic disorder effecting elastin
caused by mutation in gene encoding for part of the “multidrug resistance complex”
What happens in Pseudoxanthoma elasticum
elastic fibers of the dermis become enlarged, tangled, and calcified resulting in a characteristic purple blue color
clinical sign of PXE
Plucked chicken apperence of skin in flexural areas -
elastic fibers of the blood vessels are also damaged leading to hypertension adn bleeding disorders, particularly of the eye
ground substance is composed of?
glycosaminoglycans: hyaluronic acid / dermatan sulphate
fibronectins
function of ground substance
sponge - helps facilitate nourishment via diffusion - water based environment
ground substance life cycle
in contrast to collagen fibers which are renewed mostly when necessary, the ground substance is constantly being destroyed by enzymes and renew via production from friboblasts
enzyme that eats ground substance
hyaluronidase
why is hyaluronic acid (restylane) such a good filler
it is a natural substance that is already present in teh skin and it does not engender an immune response while absorbing a tremendous amount of water
two levels of vasculature of dermis
superficial
deep
important function of cutaneous vascular system
3
wound healing
control of homeostasis (Temp)
modulation of inflammation
wound healing of cutaneous vasculature - the _________, a single cell lining on the innermost surface of blood vessels elaborate important cytokines including ________________
endothelium
endothelial growth factor
the cutaneous vasculature
homeostasis - via a structure called_______________, a smooth muscle derived valve-like structure, blood may be directed twoard teh skin during overheating or away during hypothermia
Sucquet-Hoyer canal
cutaneous vasculature - modulation of inflammation - via the expression of _____________________ white blood cells begin the process of first adhering and rolling, and second diapedesis, so that they may exit the vasculature to fight infection in the skin and soft tissue
ICAMs
The actual capillary structures of the skin are contained in the
uppermost portion of the papillary dermis - a portion sometimes called the suprapapillary plate
Auspitz sign
when thickened scaled of psoriasis are forcefully removed, pinpoint bleeding is noted in the area of removal
The presence of central thrombosed capillar loops is reassuring that a neoplasm is in fact a
verruca - wart (viral neoplasm)
leukocytocalstic vasculitis
common disease involving post capillary venules
what happens in leukocytoclastic vasculitis
formation of immune complexes - (most commonly due to strep) - precipitation of complexes in the walls of vessels leads to disease
What type of immune reaction is leukocytoclastic vasculitis
TYPE III
Gel and Coombs
What happens as a result of immune complex precipitation in leukocytoclastic vasculitis
leads to inflammation - neutorphils attach to vessel wall and degranulate leading to damage and extravasation of RBCs into the dermis
in leukocytoclastic vasculitis what is it called when there is the fibrinoid deposition in the vessel walls with infiltrating neutrophils and neutrophil debris?
leukocytoclasia :)
Clinically vasculitis manifests as
palpable purpura
why is palpable purpura palpable
inflammation
what is purpura purpuric?
extravasation of RBCs
Is palpable purpura blanchable
no because the RBCs have extravasated
example of Type I skin reaction
IgE - immediate
urticaria (Hives)
example of Type II skin reaction
anitbody mediated - bullous pemphigoid
example of Type III skin reaction
immune complex mediated leukocytoclastic vasculitis (palpable purpura)
example of Type IV skin reaction
delayed type hypersensitive
- allergic contact dermatitis - nickel allergy
where do free nerve endings traverse?
pass through the upper dermis to terminate at the dermoepidermal junction
free nerve endings sense
pain and itch
itch originates where
free nerve endings at dermoepidermal junction
where is itch conducted
centripetally by affarent nerves
affarent nerves in pruritus
unmyelinated C fibers with slow conduction rate
after entering the spinal cord, the primary affarent nerves of the skin synapse with
secondary neurons whose axons cross to the opposite side of the body and travel cephalide
are itch and pain the same sensory modality
no - regardless of the fact that local anesthesia can abolish both - receptors and transmission apparti are thought to differ
Pine cone receptors
Meissners - fine touch and tactile discrimination
meissner’s corpuscles are in highest concentration
digital aspects of the digits
onion receptors :)
pacinian corpuscles
pressure and virbatory
terminal hairs begin
deep in the dermal / sub-cu junction
vellus hairs -
fine apigmented hairs that begin higher in the dermis
small smooth msucle which when activated by teh ANS brings hair into a more erect psoition
arrector pilli
secretes sebum onto hair and idirectly onto skin
sebaceous gland
local of sebaceous glands
face neck chest upper back
divide the hair follicle into thirds
top - infundibulum
middle - isthmus (sebaceous duct to arrector pilli insertion)
bottom - matrical (bottom)
follicular unit is derived from
primitive ectodermal germ PEG
development of the PEG is an example of _____________ via the _____________
induction via
underlying mesenchyme, which will become the dermal papillae of the hair inducing formation of the PEG in the overlying fetal skin
BULGES OF THE PEG
Upper
Middle
Loower
Lower - attachment for arrector pilli
Middle - sebaceous gland
Upper - apocrine gland (axillae, groin)
adult scalp # hairs
100,000
anagen
85% adult hairs (growth phase)
telogen
10-15% adult hairs (resting)
catagen
1-5% transition phase between anagen and telogen
scalp hairs are what kind
terminal hairs
andronergic alopecia
hairs become miniaturized, finer and lie higher in the dermis - resemble vellus hairs
frequency of alopecia
50% both sexes
important in promoting change from terminal to vellus hair in alopecia?
converstion of T to 5-DHT
Medicne for male alopecia?
finasteride - a 5-alpha reductase inhibitor
what does minoxidil do?
drug for alopecia that promotes the anagen phase of hair growth - both sexes
oil secreting glands?
sebaceous
Sebaceous glands secrete via?
holocrine
holocrine secretion
involves entire sebocyte
requsite to sebum secretion?
sex hormones
are sebaceous glands innervated by ANS?
No!
Medicine that decreases sebum production
isotretinoin (Accutane)
Acne =
ubiquitous disorder of the pilosebaceous unit - multifactorial
brief cause of acne
plugging of the ostia of the pilosebaceous unit by hyperkeratotic debris leads to accumulation of oil within
once the ostia of the pilosebaceous unit is plugged by hyperkeratotic debris –> the accumulation of oil causes?
propionbacteriam acnes to multiply and convert sebum to pro-inflammatory fatty acids
what causes characteristic inflammatory zit?
rupturing of the pilosebaceous unit
what are blocked pores called?
comedones
open comedones?
blackheads
closed comedones?
whiteheads
general sweat glands =
eccrine
eccrine sweat gland fx
thermoregulation
eccrine sweat glands most numerous where?
forehead, upper cutaneous lip, palms/soles
eccrine secretion type?
merocrine -
merocrine secretion?
The gland releases its product and no part of the gland is lost or damaged (compare holocrine and apocrine). The term eccrine is specifically used to designate merocrine secretions from sweat glands (eccrine sweat glands).
eccrine glands develop from?
eccrine germ
three main components of eccrine gland?
coiled secretory portion deep in the dermis
intradermal ducts (coiled and straight duct)
intraepidermal portion (acrosyringium)
what portion of the ANS mediates sweating?
sympathetic
sweating is triggered via?
acetylcholine secretion
why do drugs that increase acetylcholine levels (neostigmine, physostigmine, organophosphate based peticides) result in increased sweating despite a parasympathetic response systemically?
they increase acetylcholine levels - which stimulates sweating
what does atropine poisoning (a drug which has anticholinergic activity) result in?
warm / flushed / but anhidrotic patient
apocrine glands are outgrowths of the?
upper bulge of the pirmitive ectoderm
apocrine glands are located primarily?
axillary and anogenital area
speiclized variants of apocrine glands?
Moll’s –> eyelids
Cerumen –> external auditory
Lactation –> boobs
apocrine glands respond mainly to _____________ stimuli
sympathetic adrenergic
apocrine gland anatomy
coiled portion deep in dermis
straight duct traverse dermis and empties into hair follicle
contractile myoepithelial cells surround the coiled gland - the straight duct runs from the coiled gland to the hair follicle
predominant form of apocrine secretion?
decapitation -
decapitation secretion?
portion of the secretory cell cytoplasm pinches off and enters the lumen
apocrine sweat? odor
initally odorless until contacts normal bacterial flora and odor develops
chromohidrosis
colored sweat
disorder of apocrine glands
lipofuscin pigment is responsible for colored sweat
what accounts for lipofuscin color in chromohidrosis?
various oxidative states - yellow / green / blue / black
treatment for chromohidrosis?
none
apoeccrine glands -
hybrid sweat glands found chiefly in axilla
anatomy of apoeccrine?
small diameter portion - similar to eccrine
larger diameter portion - similar to apocrine
apoeccrine glands respond to?
cholinergic - similar to eccrine
where to apoeccrine glands empty
directly on to skin surface
relative sweat secretion of apoeccrine glands vs eccrine?
secrete nearly ten times as much sweat as eccrine
hyperhidrosis involves which glands?
eccrine and or apoeccrine
new and exciting treatment for hyperhidrosis?
BOTOX
blocks the release of acetylcholine - thereby blocking the stimulus for sweat production
apocrine glands before puberty
small and nonfunctional
Caused by a mutation in EDA gene
severely decreased sweating
poor temp regulation
sparse hair / abnormal teeth
diagnosis?
anhidrotic ectodermal dysplasia
acquired disorder of eccrine function?
miliaria
anhidrotic ectodermal dysplasia is what type of disorder of eccrine function?
congenital
in contrast to miliaria - which is acquired
blocked sweat ducts
prickly heat
febrile babies
sweat in dermis :(
what is your diagnosis?
miliaria -
acquired disorder of eccrine function
classic acquired disorder of sweating?
heat shock
are eccrine glands from PEG
NO!
from eccrine germ (unique)
Quintessentail holocrine glands?
sebaceous
What determines which of the three cycles of hair growth hairs are in?
randomly engaged in 1/3 cycles
cycles of hair growth rule of three/
anagen - 3 years
telogen - 3 months
catagen - 3 weeks
catagen =
involution
itch =
pruritis
4 commons causes of itch
dry skin (xerosis)
infection (HIV)
infestation (scabies / lice)
metabolic disorders (renal failure)
two important types of nerve fibers to be aware of?
Type A - heavily myelinated - conduct rapidly
Type C - unmyelinate - conduct slowly
Typa A alpha fibers?
propioception - large motor units
largest
Type A beta fibers
carries touch
Type A gamma fibers
spindle organs in the muscle stretch receptor
Type A delta fibers
fast localizing initial component of pain
Type C fibers
convey sensation of diffuse, dull, non-localized
temperature and itch
common causes of vasculitis?
drug hypersensitivity
infection
neoplastic disorder
collagen vascular disease
congenital problemos of ground substance/
none
ground substance is glued together with
fibronectins
glycosaminoglycans of ground substance
hyaluronic acid
dermatan sulphate
net result of pseudoxanthoma elasticum?
calcified brittle elastic fibers
plucked chicken skin
systemic hypertension
arterial rupture (particularly eye)
acquired disorder of elastic tissue?
solar elastosis
congenital disorder of elastic tissue
pseudoxanthoma elasticum
acquired disorder of collagen?
Scurvy
congential disorder of collagen?
EDS
Characteristic clinical signs of scurvy?
corkscrew hairs with perifollicular hemorrhage
keratotic plugging of hairs
hemorrhagic gingivitis
why does hemorrhage occur in scurvy?
lack of collage support for blood vessels
where is procollagen synthesized
within fibroblasts
