Flashcards in Embryology Deck (86)
Defective sonic hedgehog gene?
-gene is involved in patterning along anterior-posterior axis
-defect assoc with holoprosencephaly (forebrain fails to develop into 2 hemispheres; have 1 central eye...)
Defect in FGF gene?
-involved in lengthening of limbs
-defect --> Achondroplasia
Hox genes: -what do they code for? if defective?
-code for DNA-binding transcription factors; involved in segmental organization of embryo in a cranio-caudal direction
-Hox mutations--> appendages in wrong locations (ie extra fused digit between 3rd and 4th fingers)
When is embryo most susceptible to teratogens?
between 3-8 weeks, embryonically (so, 5-10 weeks of pregnancy) = "embryonic period" (b/c this is when organogenesis occurs)
***note: before week 3: all-or-none (miscarriage or nothing)
***after week 8: growth and function are affected
What week, embryologically, does the heart begin to beat?
When is it "embryo"? "fetus"?
-"embryo"--> weeks 3-8
-"fetus"--> at week 8, on
When does hCG secretion begin?
within 1 week after fertilization
What week does the neural tube close?
Neural tube formed by neuroectoderm and closes by week 4 (this is why MUST already be taking folic acid prior to pregnancy, b/c spinal development occurs within the first 4 weeks!)
Adenohypophysis arises from which embryologic derivative/germ layer?
Adenohypophysis = Ant pituitary; arises from Rathke's pouch, from Surface Ectoderm
Neurohypophysis arises from which embryologic germ layer/derivative?
Neural Crest derivatives:
-dorsal root ganglia
-chromaffin cells of adrenal medulla
-parafollicular (C) cells of thyroid
-pia and arachnoid
-bones of skull
-odontoblasts (teeth-->crest toothpaste!)
-aorticopulmonary septum (spiral septum of heart)
Which germ layer does the spleen arise from?
Nucleus pulposus is derived from?
Notochord; Notochord induces ectoderm to differentiate into neuroectoderm and form the neural plate; neural plate gives rise to neural tube and neural crest cells; notochord becomes the nucleus pulposus of the intervertebral disk in adults
Agenesis vs Hypoplasia vs Aplasia
Agenesis: No primordial tissue, so no organ
Hypoplasia: Primordial tissue present, but incomplete organ development
Aplasia: Primordial tissue present, but no organ
Malformation vs Deformation
Malformation: Intrinsic disruption (like a teratogen); occurs during embryonic period (3-8 weeks)
Deformation: extrinsic disruption; occurs after embryonic period (after week 8)
teratogenic effect of aminoglycosides?
CN VIII toxicity (hearing problems)
teratogenic effect of DES (diethylstilbestrol), a synthetic estrogen
Vaginal clear cell adenocarcinoma (in female fetuses, when older)
Ebstein's anomaly (enlarged Right atrium; small Right ventricle) - assoc with which teratogen?
Neural tube defects --> caused by which teratogens?
(Valproate and Carbamazepine decrease folate absorption; so, if pts are taking these drugs during pregnancy, then must take extra folate)
infant with flat nasal bridge, "railroad track" ears, thin upper limb, small palpebral fissures, epicanthal folds, upturned nose, smooth philtrum (space from nose to upper lip)... may be caused by which teratogen?
Alcohol (Fetal Alcohol Syndrome)
Which fetal structure secretes hCG?
Syncytiotrophoblast (outer layer of chorionic villi)
maternal component of the placenta; derived from the endometrium; if absent, get placenta accreta (placenta attaches to myometrium instead of to endometrium; so, no separation of placenta after birth; get massive bleeding after delivery)
How many umbilical artery/ies? Vein/s?
2 umbilical arteries
1 umbilical vein
*both are derived from the allantois
Urachal duct: what is it? what's it formed from? what if duct fails to obliterate?
During 3rd week: yolk sac forms allantois, which extends into urogenital sinus; allantois becomes urachus, which is a duct between bladder and yolk sac (so, connects fetal bladder to maternal system)
*If urachus does not obliterate after birth:
-patent urachus --> urine discharge from umbilicus
-vesicourachal diverticulum --> outpouching of bladder; asymptomatic
urine discharge from umbilicus in neonate: what's the cause/abnormality?
-Failure of urachal duct to obliterate (urachal duct connects fetal bladder to maternal system in utero)
Vitelline duct: What is it? Abnormalities associated with it?
-Vitelline duct = omphalomesenteric duct --> connects yolk sac to midgut lumen
--> obliterated at 7th week
-Vitelline fistula = failure of duct to close; get meconium discharge from umbilicus
-Meckel's diverticulum = partial closure of duct, may have portion attached to ileum; may have ectopic gastric mucosa --> melena and periumbilical pain
meconium discharge from umbilicus: what abnormality caused this?
Vitelline fistula (failure of the vitalline/omphalomesenteric duct to close)
Meckel's diverticulum cause?
Due to partial closure of the Vitelline duct (instead of full closure)
Truncus Arteriosus: What does it give rise to?
Pathologies associated with abnormal formation?
Gives rise to ascending aorta and pulmonary trunk:
-Have neural crest migration --> truncal and bulbar ridges that spiral and fuse to form the aorticopulmonary septum --> ascending aorta and pulmonary trunk
-Transposition of great vessels (failure to spiral)
-TOF (skewed AP septum development)
-Persistent TA (from partial AP septum development)