5 - Development of the Skin and it's Derivatives Flashcards
The skin developes from what two early embryonic tissues? What is critical in directing the formation of all components of the skin?
Epithelium and mesenchyme.
Inductive interactions between these tissues at the epithelial-mesenchyme interface are critical in directing formation of all components of the skin.
What does the epidermis form from?
The surface or non-neural ectoderm covering the embryo.
What cells enter the epidemris? What is their derivation?
Melanocytes - neural crest
Langerhans - bone marrow
Merkel cells - epidermal stem cells in the basal layer
The dermis is derived from what?
Mesenchyme of regional origin.
During skin development, what cross-signaling is cessential?
Ectoderm-mesenchyme
What protects the skin from amniotic fluid?
The vernix caseosa.
Hair follicles, sweat glands, and nails are dervied from what?
Epidermal buds that extend into the forming dermis.
The initial downy, _______ hair is replated near birth by ______ hair.
Lanugo hair is replaced by course hair
What are nails derived from?
Epidermal thickenings at the tips of the digits.
What is piebaldism caused by?
An absence of melanocytes in affected skin and hair follicles caused by an aut. dominant mutation of the KIT proto-oncogene.
What are clinical manifestations of piebaldism?
- Depigmented patches (congenital - seen at birth) often with speckles within - often appear heart-shaped
- Stable spots, non-progressive
- White forelock typical (melanocytes dont make it to this location)
What helps distinguish vitiligo from piebaldism?
History.
What is the cause of Waardenburg syndrome?
Rare disease; multiple genes implicated, resulting in abnormal development of melanocytes (as opposed to a migration problem seen in piebaldism).
What are the clinical manifestations of Waardenburg Syndrome?
Achromia (white patches of skin or hair) with
- deafness
- heterochromia irides (eyes are 2 colors)
- dystopia canthorum (wide distance between eyes)
What is a port-wine stain? How common are they? Do they change?
Malformed, ectatic, dilated capillary to venule sized blood vessels.
- Always present at birth
- Occur in about 0.3-0.6% of newborns
- Tend to darken and thicken over time
What are three potential distributions of facial port-wine stains?
- V1-Ophthalmic Branch: may extend to ocular conjunctive
- V2-Maxillary branch
- V3-mendibular branch: may extend to oral mucosa
Capillary malformations (port-wine stains) in the V1 distribution can be associated with what? What are common findings?
Sturge-Weber syndrome.
Seizures, developmental delay, migraines, and tram track calcifications.
Ocular findings such as congenital glaucoma and increased choroidal vascularity (tomato ketchup spot).
What isthe most common vascular tumor? What is it composed of?
Infantile hemangioma (incidence 4-5%)
Composed of proliferating endothelial-like cells that become clinically visible within first month of life.
How do infantile hemangiomas change over time?
Appear as white flat patch with fine pink-red vessels.
The pallor may be due to local vasoconstriction.
1-2 wks of age proliferation begins; growth phase 3-9 months and then it slowly involutes.
What clinical findings are associated with PHACE syndrome?
P: posterior fossa abnormailities
H: hemangioma (segmental)
A: arterial anomolies
C: cardiac anomolies
E: eye anomolies
S: sternal clefting/supraumbilicant raphe
What causes hypohidrotric ectodermal dysplasia (HED)?
Most ofetn X linked recessive.
Most common form of ectodermal dysplasia.
Multiple genes can cause the condition and they are found in the ectodysplasin signaling pathway.
What are the clinical manifestations of hypohidrotic ectodermal dysplasia (HED)?
- Squareforhead with frontal bossing.
- Flattened nasal bridge (saddle-nose)
- Low-lying ears
- Skin is thin and dry
- Sparse hair
- Hypo-anodontia/Peg teeth
- Decreased ability to sweat
Patients with hypohidrotic ectodermal dysplasia have impaired ability to ______ and can _______.
Impaired ability to sweat and can overheat
