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MSS Weeks 3-5 > Skin Devo > Flashcards

Flashcards in Skin Devo Deck (22)
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Precursors for Skin

Head - Neural crest & Head mesoderm
Trunks & Limbs - Somatic
Back - Dermatome


What is skin at 3rd week of development?

Single layer of surface ectoderm
Permeable layer that allows fluid to pass through


Periderm & Intermediate layer Formation

At wks 4-8 thin layer of peridermal cells begin to cover surface ectoderm
Peridermal cells develop micorvilli to absorb nutrients from fluid
At wks 11-12: Mitosis from basal to form intermediate layer, skin starts become barrier against amnionic fluid


Definitive layer formation

All the definitive layers form during 4-6 months (Fetal period)
Peridermis goes away, replaced by keratinocyte
Vernix Caseosa - White, sticky covering around fetus, sebaceous secretion


What cells migrate as dermis matures?

Langerhan's Cells - End of fetal period from bone marrow
Merkel cells


Piebaldism (Genetics, Mechanism, Findings)

Autosomal dominant, mutation of the KIT proto-oncogene
Results in impaired migration of melanocytes
Results in depigmented congenital patches often with speckles within, stable, nonprogressive, white forelock of hair is typical
History is what distinguishes with vitiligo


Waardenburg syndrome (Genetics, Mechanisms, Findings)

Rare autosomal dominant, multiple genes implicated
Abnormal development of melanocyte
Results primarily with achromia (White patches of skin/hair)
Also has deafness, heterochromia irides, dystopia canthorum


Developmental history of dermis

Fibroblasts migrate in
Begin to produce collagen
Form papillary and reticular (thicker fibers) regions in dermis


Port-wine stain (Mechanism, Incidence)

Malformed, ectatic, dilated capillary to venule sized blood vessels
Always present at birth
Occur in about 0.3%-0.6%
Tend to darken and thicken over time


Facial Port-wine stain distribution

V1 - Ophthalmic branch: Can extend to conjunctiva
V2 - Maxillary branch: Less risk for complications (watershed risk with lower eyelid)
V3 - Mandibular branch - May extend to oral mucosa


Sturge-Weber Syndrome (Facial Association, Neurologic findings, Occular findings)

V1 dermatome associated
Neurological: Seizures, developmental delay, migraine headaches, tram track calcifications (calcification of the occipital and/or temporal cortex)
Ocular: Congenital glaucoma, increased choroidal vascularity (tomato ketchup spot)


Infantile Hemangioma (Incidence, Appearance, Complication)

Incidence - Most common vascular tumor: 4-5% estimated incidence
Appearance - Endothelial-like proliferating cells that become clinically visible within the first months of life
Complications - Failure to open eye in early months can lead to permanent blindness


Infantile Hemaginoma Growth Cycle

Birth - Appears as a white flat patch with fine, pink-red vessels
Pallor - Due to local vasoconstriction
1-2 wks: Proliferation begins
Growth phase variable: 3-9 months
Slow involution (not resolution)


PHACE Syndrome

Posterior fossa abnormalities
Hemangioma (segmental)
Arterial Anomalies
Cardiac Anomalies
Eye Anomalies
Sternal clefting/supraumbilical raphe


Formation of Hair Follicles

Thickening of epidermis to form hair bud
Extends into the mesenchyme to form hair bulb
Mesenchyme joins to form dermal papilla
Hair forms out
Erector pillae forms from ectoderm


Formation of Sweat gland

Budding from basal layer
Solid cylindrical downgrowth
Form a lumen and a secretory coil

Eccrine - Enters into the surface
Apocrine - Enters into the hair folicle


Eccrine vs Apocrine (Mechanism of secretion and Location)

Eccrine - Merocrine (Cross-membrane) secretion; palms, soles
Apocrine - Apocrine (partial cytoplasm is removed) secretion; axilla, genitalia


Formation of nails

Nail fold surrounds nail field
Nail plate comes underneath and forms eponychium


Ectodermal Dysplasia - Number of types, what structures can be affected

Over 150 rare syndromes altering in 2 or more structures from embryonic ectoderm
Defects in hair, teeth, nails, sweat glands, lens of the eye


Hypohidrotic Ectodermal Dysplasia (Genetics, incidence, pathway)

X-Linked Recessive
Most common form of ED encountered by clinicians
Ectodysplasin Signaling Pathway: Ectodysplasin-A1 (EDA-A1), Eda-A1 receptor (EDAR), EDAR associated death domain


HED Findings

Square forehead with frontal bossing
Flattened nasal bridge
Low-lying ears
Skin is thin and dry
Sparse hair
Hypo-anodontia/Peg Teeth
Decreased ability to sweat


HED Management

Avoid overheating
Consult dentistry
Recommend families to contact National Foundation for Ectodermal Dysplasias