Skin Devo Flashcards
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
Melanocyte
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
