Dermis and Adnexal Flashcards
What is contained within the dermis? (3)
blood vessels
nerves
appendageal strutures (hair / glands / etc)
what provides the major tensile strength of the skin?
the dermis
Thickness of the dermis
varies by local (1-4 mm)
Where does the dermis lie?
between the epidermis and sub-cu
what are the appendageal structures ?
hair
sweat gland
sebaceous gland
vessels and nerves
what are the two major zones of the dermis?
papillary
reticular
papillary dermis -
location?
content?
interlocks with?
upper layer of dermis
thin collagen bundles
interlocks with epidermal rete
the interlocking of the dermis with the epidermal rete increases (2)
strength and surface area
reticular dermis
location?
content?
deeper layer
thick collagen bundles
visible eslatic fibers
what are the three building blocks of the dermis?
collagen
elastic fibers
ground substance
structure of collagen in the skin ?
alpha helical
Gly-X-Y
X = proline
Y = hydroxyproline
How many types of collagen are synthesized in the body
> 25
G-X-Y of collagen
what are X and Y
X proline
Y hydroxyproline
Which collagen is in greatest abundance in the skin?
collagen I
what percent of the adult dermis (wt) is collagen I
85%
which collagen is largest part of fetal dermis
III
Which collagen makes up the BM
IV
Which collagen is responsible for anchoring fibrils
VII
_________________ are characteristic of mature collagen?
“pretty” 68nm bands
Where is PROcollagen synthesized?
within firboblasts
What happens to PROcollagen?
excreted extracellularly
What happens once PROcollagen is excreted extracellularly
it is enzymatically cleaved to TROPOcollagen
What happens once TROPOcollagen is produced in ECM?
It aggregates and becomes crosslinked
Cross-linking of Tropo-collagen is dependent on?
Vitamin C
What results from VitC deficiency
Scurvy
decreased mature collagen
What would we call VitC
Cofactor
How long does it take to manifest sign/symptom of VITC deprivation?
1-3 months
Key findings of scurvy?
keratotic plugging of hairs
perifollicular hemorrhage
“corkscrew hairs”
hemorrhagic gingivitis
weakened / delayed healing
Why does hemorrhage occur in scurvy?
Lack of collagen support for blood vessels leads to rupture and hemorrhage (same for gums)
What kind of disease of collagen production would we call scurvy?
acquired
What is a congenital problem of collagen disease?
Ehlers Danlos Syndrome
Ehlers-Danlos Syndrome
family of disorders based upon?
erroneous collagen synthesis
mutation at various stages of collagen production
Ehlers-Danlos Syndrome - mutations at various stages of collagen production yield findings such as… (4)
hyperextensible skin
hyperextensible joints
fragile blood vessels
poor wound healing
What might you be tempted to think Ehlers Danlos is a disorder of?
Elastic fibers! But resist the temptation! It is a disorder of collagen production
Gordin’s sign
characteristic of EDS - touch tip of tongue to nose
Molluscoid pseudotumors
characteristic of EDS
Absence of the inferior labial frenulum can often be seen in
EDS
Elastic fibers - constitution of dermis? function size? distribution? visualized?
minor constituent of dermis
provide resliency
thin fibers (1-3 micro-meter)
intertwined among collagen bundles
special stains are required to visualize (VVG)
Our example of acquired disorder of elastic fiber
Solar elastosis
Solar elastosis
acquired disorder of elastic fiber
solar elastosis visualizing ?
basophilic (blue) material within superficial dermis
If we see basophilic material within superficial dermis - this is a histologic clue that we are observing?
Tissue from an older person in sun-exposed skin - Solar elastosis (sun damaged elastic fibers) - we would not expect to see this in children
What is an example (We discussed) of an acquired disorder of elastic tissue?
pseudoxanthoma elasticum
-
pseudoxanthoma elasticum is caused by a mutation in?
MDR gene
pseudoxanthoma elasticum results in
calcified, brittle elastic fibers
which disease is associated wtih
- plucked chicken skin
pseudoxanthoma elasticum
pseudoxanthoma elasticum is associated wtih
skin finding?
system finding?
eye finding?
plucked chicken skin
systemic hypertension - with arterial rupture (particularly eye)
angioid streaks in the retina
Ground substance - made up of?
protein-sugar moieties (glycosaminoglycans) - hyaluronic acid and dermatan sulphate
what glues together the protein-sugar moeities of the ground substance?
fibronectin
what is an acquired disorder of ground substance? stretch
cosmetic hyaluronic acid filler may (Sometimes) represent an acquired disorder of ground substance
what congenital problems do we see with ground substance?
none
Blood vessels in the epidermis
none
where does epidermis get its nutrient / oxygen supply?
depends entirely on the dermis via diffusion
Two plexi of skin vessels?
superficial plexus (goes in dermal papillary loop) deep plexus (with perforating arterioles)
disorders of capillary loops?
dilated, torturous capillaries are noted with diseases with increased epidermal turnover - psoriasis / verruca
when do we see dilated capillaries (which recall are in dermis) with epidermal diseases?
diseases with increased epidermal turnover - e.g. psoriasis / verruca (warts)
what causes vasculitis
inflammation of capillaries and venules due to immune complexes depositing in small vessel walls
immune complexes in vasculitis may result from?
drug hypersensitivity
infection
neoplasm
collagen vascular disease
what type of immune reaction is vasculitis of the dermal capillaries?
type III - antibody mediated so will positive coomb
What notable finding will we often see with vasculitis?
palpable purpura
what is palpable purpura -
combination of inflammation and hemorrhage that manifests frequently with vasculitis of the dermal capillaries - extravasation can also contribute to palpableness :)
Nervous tissue of the dermis?
job?
inform and protect
nerves traverse the dermis to end as?
specialized nerve structures (Meissner / Pacinian)
free nerve endings
Two important types of nerve fibers to be aware of?
A and C
Type A nerve fibers
characteristic
heavily myelinated and conduct rapidly
Type C nerve fibers characteristic
unmyelinated and conducts slowly
Four types of A fibers?
A -alpha –
A - beta
A - gamma
A - delta
A-alpha fibers
proprioception and large motor units (largest)
A-beta fibers
carries touch
A-gamma fibers
spindle organs in teh muscle stretch receptors
A-delta fibers
smallest - fast localizing initial component of pain
Type C fibers job
convey sensation of diffuse, dull, non-localizing / temp and itch sensations
what is itch called?
pruritis
4 common causes of itch
Dry skin (xerosis)
Infection (HIV)
Infestation (scabies / lice)
metabolic disorders (renal failure)
Meissner’s corpuscles
pine-cone like structures located near the DEJ inovlved in fine touch, highest density on the pulps of digits
Pacinian Corpuscles
onion like - structures located in the dermis, involved in pressure and vibration - highest in the genitals
Adnexal structures (5)
hair follicles eccrine glands apocrine glands apoeccrine glandes sebaceous glands
Basics of hair
Types of hair (2)
terminal
vellus
terminal hair
dark / thick / course
vellus hair
fine / thin / apigmented
Hair follicle anatomy is divided into 3 regions
infundibulum / isthmus / matrical region
from bottom to top
Which fibers are responsible for itch?
Type C fibers
Embryologic origin of hair?
Primitive ectodermal germ (PEG)
Classic induction
Embryologic origin of hair - induction?
mesenchyme induces the overlying neuroectoderm –> downward bud with 3 bulges
hair gland 3 bulges?
upper - apocrine (+/-)
middle - sebaceous gland
lower - attachment arector pillori
How many hairs does the normal scalp contain
> 100,000
3 cycles of hair
anagen (growth) 85%
telogen (rest) 10-15%
catagen (involution) 1-5%
3 cycles of hair and the rule of three?
anagen - 3 years
telogen - 3 months
catagen - 3 weeks or less
androgenic (androgenetic) hair loss?
“pattern baldness”
characteristic loss
50% population
conversion of testosterone to DHT results in miniaturization of follicle
treatments of hair loss
finasteride (propecia) - selective inhibitor of 5-alpha reductase
- blocks conversion of testosterone to DHT
- works well in prevent loss and “less well” in restoring hair loss IN MEN
Dangerous in women of reproductive age! ?post-menopause
Fiansteride and hair loss
Women?
NO! do not use in women of reproductive age!
- blocks conversion to T to DHT and seems to help men from losing more
What happens to the hair follicle followin finasteride treatement?
follicles go deeper in dermis
Sebaceous glands - purpose?
lubricate thick terminal hairs
acne pathogenesis
disease of?
disease of pilosebaceous unit
acne is a disease of pilosebaceous unit - there is abnormal?
follicular maturation
abnormal follicular maturation in acne causes ?
comedone formation (black-heads / white-heads)
acne - following the comedone formation that resulted from abnormal follicular maturation what happens?
the plugged follicular environment allows overgrowth of P acnes
What does P acnes do in acne?
P acnes liberates FFAs and or rupture follicles –> later events yield dermal inflammation
Holocrine glands -
whole cells are shed and disintegrate, release contents
which are quintessential holocrine glands?
sebaceous glands
Eccrine glands -
odorless watery sweat glands
Eccrine glands are important in -
thermoregulation
where are eccrine glands numerous?
forehead - cutaneous lip - palms/soles
eccrine glands produce what type of secretions
merocrine
what are merocrine secretions?
excreted via exocytosis from secretory cells into an epithelial-walled duct or ducts and thence onto a bodily surface or into the lumen
innervation of eccrine glands?
sympathetic - but use ACh
Are eccrine glands derived from primitive ectodermal germ?
No!
Which glands are derived from PEG (primitive ectodermal germ?)
Upper = apocrine
Middle - sebaceous
Lower - errector pili attachment
Eccrine gland anatomy?
sweat production - beginning is located way down between the junction of the dermis and sub-cu — then travels up long long tube all the way through the dermis and through the epidermis - until it is release onto the skin.
2 acquired disorders of sweating?
heat shock (classic) antiperspirants
Heat shock -
you stop sweating and overheat
How do antiperspirants work?
active agent - AlClOH3, selectively soluble
perspiration raise the pH - insoluble precipitates to block sweat duct
washing with soap raises pH - solublel –> duct is unblocked
What is miliaria?
prickly heat :) / or sweat gland gets ruptured - sweat goes into dermis where it is not supposed to be and causes prickly heat
blocked sweat ducts
miliaria in bambinos –>
febrile
what is an acquired disorder of eccrine function?
miliaria
are there congenital problems of eccrine function?
anhidrotic ectodermal dysplaisa
what is anhidrotic ectodermal dysplaisa?
mutation in EDA gene Aberrant eccrine development severely decreased sweating poor temp regulation other ectodermal problemos - sparse hair / abnormal teeth
If we see someone come in with decreased sweating / temp regulatory problemos / and other ectodermal problems e.g. hair/teeth… what might we consider?
anhidrotic ectodermal dysplasia
apocrine glands are?
outgrowths of the upper bulge of primitive ectodermal germ
where are apocrine glands located?
axillary and anogenital area
when are apocrine glands functional
usually post puberty
specialized apocrine glands (3)
Moll’s (eyelid)
cerumen (external auditory canal)
lactation (boobs)
how do apocrine glands secrete?
decapitation
how is apocrine sweat different than eccrine
stickier (sialomucin)
odor of apocrine sweat?
initially odorless but flora of normal skin make smelly
apoeccrine glands =
hybrid sweat glands
located mainly in axilla
apoecrrine glands - likely play role in?
axillary hyperhidrosis
apoeccrine glands secrete how much sweat relative to eccrine?
nearly 10x
Treatment of hyperhidrosis?
botulinum toxin
How does botox treat hyperhidrosis?
block acetylcholine release - upon which secretion is dependent!
