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USMLE Embryo

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. what results if they dont? What can increase the risks of this?
1st
Persistent connection between amniotic cavity and spinal canal; low folic acid
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Hemorrhage - bone deformities

2. What germ layer correlates with the branchial pouches?
Endoderm
secondary palate
Rhombencephalon
Before getting pregnant!

3. What is a syrinx? Where is it found in syringomelia? What is it associated with?
Membrane - all 3 from 1st appartus
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
4th arch; 6th arch
Neuroectoderm

4. Pyloric stenosis is characterized by _____________ of muscularis externis in the sphincter
hypertrophy
Endoderm
2nd pouch
Mesoderm

5. Where is erythropoeisis in the weeks 3-8 of fetal development? Where does it occur after that? until when?
Ebsteins anomaly; tricuspid atresia
Ventral shaft of penis (penile urethra); labia minora
Folate antagonists
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)

6. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
StyloPharyngeus
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Grooves/clefts; arches; pouches
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

7. From which myotomes are muscles of the tongue derived from?
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Occiptal
Cleft lip/palate
Neuroectoderm

8. Other than not having a brain - what else is a symptom of anencephaly? why? hint: think about amniotic fluid
Primitive atrium
Polyhydramnios
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Upper 1/3; urogenital sinus

9. Which branchial derivative creates the epithelial lining of the palatine tonsils?
Mesoderm
2nd pouch
Failure of the urachus to obliterate; outpouching of the bladder
DES

10. What teratogens can cause CN VIII toxicity in the fetus?
Truncus arteriosus; pulmonary trunk
Deoxygenated blood; fetal internal iliac arteries to placenta
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Aminoglycosides

11. From What embryonic layer are the schwann cells from ?
Day 6; maintains corpus luteum; 1st trimester
Neural crest cells
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)

12. what else is the caudal regression known as? What two teratogen can cause this in the fetus?
VACTERL; OCPs and maternal diabetes
Medial palatine processes
Week 3-8
Tongue

13. From What embryonic layer does the olfactory epithelium arise?
XII
Surface ectoderm
Sperm plus egg
Folate antagonists

14. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
Amniotic epithelium
Mesencephalon
4th week
Female; paramesonephric; mesonephric

15. what invaginates to form the primitive streak?
can make cells
Decreases
Epiblast
Excessive resorption of septum primum or secondum (or both)

16. What is the prochordal plate?
Lacunae in between the chorionic villi
Endoderm
Where the epiblast and hypoblast fuse
Oxygenated; placenta to fetus (IVC)

17. What two cavities also form during the second week?
Endoderm
Telencephalon
Amniotic cavity and yolk sac
Prevent recurrent UTIs

18. When does hCG secretion take place? with what event?
Embryonic period; 1st trimester
Day 6; with implantation
Urachus/median umbilical ligament; bladder and yolk sac
DiGeorge

19. Blood coming in the umbilical vein is ____ saturated
80%
6th aortic arch
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
IMA

20. Which CN allows for taste and sensation in the posterior 1/3 of the tongue? how about the very back ?
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Aortic arch (from left side); right subclavian (on the right)
IX; X
Transposition of great vessels (failure to spiral)- right to left shunt; tetralogy of Fallout (right to left shunt caused by skewed development of septum); persistent TA (partial septum development - also right to left shunt)

21. By when are the neuropores supposed to fuse?
OCPS and maternal diabetes
4th week
Maxillary and medial nasal processes
Surface ectoderm

22. what junction is the last to canalize? what implications does this have down the line?
lumbosacral
1st branchial arch
Grooves/clefts; arches; pouches
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus

23. What is annular pancreas associated with in infants?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Decreased separation of hemispheres across midline; cyclopia
Neuroectoderm

24. What is the leading cause of birth defects in the US? what else is this perpetrator the leading cause of?
Fetal alcohol syndrome; mental retardation
Lacunae in between the chorionic villi
Renal artery stenosis;
IMA

25. Septum primum (patent foramen oval) caused by excessive resorption of...
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Prosencephalon - mesencephalon - rhombencephalon
septum primum and/or secundum

26. What are two common findings in pyloric stenosis?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Endoderm - floor of primitive pharynx
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Mesoderm

27. Which branchial arch derivative is obliterated?
Transposition of great vessels (failure to spiral)- right to left shunt; tetralogy of Fallout (right to left shunt caused by skewed development of septum); persistent TA (partial septum development - also right to left shunt)
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Decidual basalis
5th

28. What are the three results of having pathology in the aorticopulmonary septum?
Neuroectoderm
Found in lateral neck; from no obliteration of 2-4th clefts
Transposition of great vessels (failure to spiral)- right to left shunt; tetralogy of Fallout (right to left shunt caused by skewed development of septum); persistent TA (partial septum development - also right to left shunt)
Persistent connection between amniotic cavity and spinal canal; low folic acid

29. What weeks are considered the 'embryonic period'?
Maxillary and medial nasal processes
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Sonic Hedgehog
Week 3-8

30. From what region of the brain does the fourth ventricle form?
Rhombencephalon
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
can make cells
Endocardial cushions

31. What is contained in the umbilical cord?
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Week 4; week 3
Incomplete; yes

32. What embryological structure gives rise to the smooth part of the right atrium?
Mesoderm
Right horn of the SV
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Synctiotrophoblast; outer; no

33. During what periods do the damages that cerebral palsy causes occur?
Ebsteins anomaly; tricuspid atresia
Cleft lip/palate
6th aortic arch
Prenatal and perinatal

34. From What embryonic layer is aorticopulmonary septum from ?
Excessive resorption of septum primum or secondum (or both)
Hypertrophy of muscularis externis of pylorus; surgical incision
Week 4
Neural crest cells

35. Where is the apical ectodermal ridge?
DHT; estrogen
Initial left to right shunting - then switches
Thickened ectoderm at end of each developing limb
Excessive resorption of septum primum or secondum (or both)

36. From What embryonic layer does the epidermis arise?
Surface ectoderm
Respiratory distress syndrome
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Failure of bony spinal canal to fuse; no; lower vertebral levels

37. Where is the decidua basalis derived from?
Endoderm
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Endometrium
Mesoderm

38. what other facial defect other than cyclopia is associated with holoprosencephaly?
Ectoderm
3rd pouch
Cleft lip/palate
Sperm plus egg

39. From What embryonic layer are the pia and arachnoid from?
Surface ectoderm
Grooves/clefts; arches; pouches
Primitive ventricle
Neural crest cells

40. Which branchial derivative accounts for taste in the ant 2/3?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Found in lateral neck; from no obliteration of 2-4th clefts
Week 3-8
Branchial arch 2

41. What is a zygote?
Sperm plus egg
Polyhydramnios
Neuroectoderm
Foramen cecum and terminal sulus

42. what muscles are derived from branchial arch 6? CN?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Ectoderm
Lacunae in between the chorionic villi
3rd pouch

43. What causes a patent foramen ovale?
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Hepatic circulation; ligamentum venosum
Excessive resorption of septum primum or secondum (or both)

44. What causes tetralogy of Fallot?
Post. sup wall; luteal phase
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Failure to recanalize; 21
Skewed development of AP septum

45. From where does the ureteric bud arise? What does it give rise to?
Decidual basalis
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Mesonephros; male genital system
secondary palate

46. From What embryonic layer are the dorsal root and celiac ganglion from?
Nutrient and gas for exchange; endometrium
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Primitive ventricle
Neural crest cells

47. Which branchial apparatus develops into the thymus?
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Polyhydramnios
3rd pouch
...

48. What artery is derived branchial (aortic) arch 6?
Pulm art (prox) and ductus arteriosus
Surface ectoderm
Foregut; dorsal mesentery (mesodermal)
Alkylating agents

49. What embryological structures give rise to the SVC?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Right common cardinal vein and right anterior cardinal vein
1st
Wolffian; mullerian

50. what bone/cartilage are derived from branchial arch 4-6?
Week 10-12; end of 1st trimester
Thyroid - cricoid - arytenoids - corniculate cuneiform
Surface ectoderm
Mesoderm