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USMLE Embryo

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Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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1. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
Blind upper esophagus with lower esophagus connected to trachea; cyanosis - choking and vomiting with feeding; air bubble on CXR; polyhydramnios; failure to pass NG tube; pneumonitis
No more umbilical circulation emptying into RA
Day 6; maintains corpus luteum; 1st trimester
Neuroectoderm

2. Most myelomeningoceles present in the _______ region
Rhombencephalon
Ventral bud
lumbosacral
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum

3. What are two common findings in pyloric stenosis?
During; instrinsic
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Ionizing
80%

4. From What embryonic layer does the gut tube epithelium arise?
Pataus; fetal alcohol syndrome
Endoderm
Nicotine; preterm labor
Surface ectoderm

5. During what week do the limbs begin to form?
StyloPharyngeus
Neural crest cells
Week 4
Ventral bud

6. What do the 2nd through 4th clefts of the branchial apparatus correlate to?
Mesoderm
Week 10-12; end of 1st trimester
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Temporary cervical sinus

7. How many umbilical arteries are there? How many umbilical veins?
Dorsal ventral axis
6-30
3rd pouch
2; 1

8. _____________is common in 1st born males
From endocardial cushions (ventral and dorsal meet each other)
Decreases
Turners; inferior
pyloric stenosis

9. What is Treacher Collins syndrome? What is the result?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Primitive ventricle

10. what closes the interventricular foramen?
Myelencephalon
Folate antagonists
Urachus/median umbilical ligament; bladder and yolk sac
Physiologic incomplete muscular ventricular septum

11. From What embryonic layer does the lens of the eye arise?
4th arch; 6th arch
Persistent connection between amniotic cavity and spinal canal; low folic acid
...
Surface ectoderm

12. From where did a branchial cleft cyst arise if it found?
3
Found in lateral neck; from no obliteration of 2-4th clefts
Bulbos Cordis; right ventricle entirely
Fetal and maternal

13. By what week is the neural tube supposed to be closed? when did it start forming?
Week 4; week 3
Decidual basalis
Allantois
Week 4

14. The notochord is...
28 week onward
mesoderm
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
6-30

15. what week do the genitalia start to have male/female characteristics? What trimester is that?
XII
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Tongue
Week 10-12; end of 1st trimester

16. What is annular pancreas associated with in infants?
Cranio - caudal; segmental
Mesoderm
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Fallopian tube - uterus - upper 1/3 of vagina

17. What teratogens can cause discolored teeth?
Mental retardation - holoprosencephaly - facial features - fistulas
Neuroectoderm
3 -4 -6
Tetracyclines

18. What day is the amnion formed?
8
Amniotic cavity and yolk sac
Epiblast
Lacunae in between the chorionic villi

19. From what region does the cerebral hemisphere form?
Foramen cecum and terminal sulus
3rd and 4th arches
Telencephalon
Neural crest cells

20. What embryological structure gives rise to the coronary sinus?
Neuroectoderm
Surface ectoderm
Left horn of the sinus venosus
Neuroectoderm

21. What is the mnueomonic for the mesodermal defects? What does it stand for?
Neuroectoderm
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Ectoderm
Decreased separation of hemispheres across midline; cyclopia

22. What causes the obstruction in pyloric stenosis? treatment?
not covered
Hypertrophy of muscularis externis of pylorus; surgical incision
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

23. Name two endocardial cushion defects.
Yolk sac; 3rd week
Ebsteins anomaly; tricuspid atresia
Female; paramesonephric; mesonephric
Found in lateral neck; from no obliteration of 2-4th clefts

24. What role does the placenta have?
can make cells
Nutrient and gas exchange
Physiologic incomplete muscular ventricular septum
hypospadias

25. In both meningocele and myelomeningocele the dura...
Temporary cervical sinus
is no longer intact
Mesoderm
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

26. What is the female remnant of the gubernaculum? male remnant?
Mesoderm
Aortic arch (from left side); right subclavian (on the right)
3
Ovarian ligament and round ligament of uterus; anchors testes within scrotum

27. From What embryonic layer does the parathyroid arise ?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
V3; VII
Endoderm
Hypertrophy of muscularis externis of pylorus; surgical incision

28. From what branchial derivative do the parafollicular cells arise?
4th/5th branchial pouches
Fetal alcohol syndrome; mental retardation
Week 4
monoamniotic

29. How do adults with annular pancreas present? and At What age?
Failure of the urachus to obliterate
Prostaglandins
Fetal alcohol syndrome; mental retardation
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

30. what chemo drugs can cause neural tube defects in the fetus?
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Folate antagonists
Congenital and chromosomal abnormalities
mesoderm

31. What is omphalocele? In What trisomies is it seen?
DES
hypospadias
Neuroectoderm
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18

32. From What embryonic layer does the epithelial linings of the oral cavity arise?
Surface ectoderm
Hypertrophy of muscularis externis of pylorus; surgical incision
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Week 8

33. From what region does the midbrain form from?
Epispadias
Mesoderm; 3 week
Mesencephalon
3

34. What causes a patent foramen ovale?
Neural crest cells
Excessive resorption of septum primum or secondum (or both)
Lacunae in between the chorionic villi
Cerebellar tonsillar herniation through foramen magnum

35. What separated myometrium of the uterus from the blastocyst?
Aminoglycosides
Decidual basalis
XII
Cerebellar tonsillar herniation through foramen magnum

36. What trisomy is associated with holoprosencephaly? What teratogen?
Tetracyclines
Deoxygenated blood; fetal internal iliac arteries to placenta
Neural crest cells
Pataus; fetal alcohol syndrome

37. What type of blood do umbilical veins carry? From where to where?
Oxygenated; placenta to fetus (IVC)
Fluid filled syrinx causes expansion and degeneration of cord tracts
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Obliterated

38. What are the clinical symptoms that present with syringomelia?
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Dorsal ventral axis
Aminoglycosides
Week 4

39. What embryological structures give rise to the SVC?
Right common cardinal vein and right anterior cardinal vein
Lots - cleft palate/lip
Ampulla
Thyroid - cricoid - arytenoids - corniculate cuneiform

40. From what region of the brain does the fourth ventricle form?
Neural crest cells
Dorsal; faulty positioning of genital tubercle
Neural crest cells
Rhombencephalon

41. What does DHT turn the urogenital folds into? estrogen?
Ventral shaft of penis (penile urethra); labia minora
Increased AFP and acetycholinesterase (not ACh!) in CSF
Week 8
Indomethacin; blocks PG production

42. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
V3; VII
A vitelline fistula - failure of vitelline duct to close
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Neural plate; closes by week 4

43. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
Arnold chiari; syringomyelia
Nicotine; preterm labor
Ventral bud
ACE inhibitors - HCTZ

44. From What embryonic layer does the olfactory epithelium arise?
Right common cardinal vein and right anterior cardinal vein
Allantois
Surface ectoderm
3rd; proximal part of the internal carotid artery

45. What causes persistent Truncus Arteriosus? What does it result in?
When left to right shunting switching to right to left shunting
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Endoderm
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

46. What are markers for neural tube defects in the amniotic cavity? CSF?
Decreases
Increased AFP and acetycholinesterase (not ACh!) in CSF
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Alkylating agents

47. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
Persistent connection between amniotic cavity and spinal canal; low folic acid
Surface ectoderm
...
Bulbos Cordis; right ventricle entirely

48. Weeks _______ erythropoiesis takes place in the liver
OCPS and maternal diabetes
Alkylating agents
2nd pouch
6-30

49. From where is the allantois formed? During what week?
Where the epiblast and hypoblast fuse
Yolk sac; 3rd week
Mesoderm
4th pouch

50. which teratogen can cause Ebsteins anomaly in the fetus?
Lithium
Telencephalon
3rd pouch
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

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