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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 embryological structure gives rise to the smooth part of the right atrium?
Right horn of the SV
Aminoglycosides
Folate antagonists
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

2. Cleft lip is a failure of fusion of ________ and ______.
Temporary cervical sinus
Endoderm
Bone/cartilage and nerves
Maxillary and medial nasal processes

3. From which myotomes are muscles of the tongue derived from?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Occiptal
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Nutrient and gas exchange

4. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Neural crest cells
No more umbilical circulation emptying into RA
Failure to recanalize; 21
Rhombencephalon

5. what week do the genitalia start to have male/female characteristics? What trimester is that?
Week 10-12; end of 1st trimester
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
...
Right common cardinal vein and right anterior cardinal vein

6. What is the prochordal plate?
When left to right shunting switching to right to left shunting
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Where the epiblast and hypoblast fuse
Arches 3 and 4

7. When does hcG get secreted? What does it do?up until when ?
Day 6; maintains corpus luteum; 1st trimester
Surface ectoderm
Muscles and arteries
Truncus arteriosus; pulmonary trunk

8. From What embryonic layer is the bladder and urethra from?
Mesoderm
Bulbos Cordis; right ventricle entirely
Wolffian; mullerian
Cytotrophoblast and synctiotrophoblast

9. From What embryonic layer are the melanocytes from?
Neural crest cells
Polyhydramnios
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont

10. From where does the prostate develop? seminal vesicles? fallopian tube? lower 2/3 of the vagina? ejaculatory duct? epididymis? uterus? upper 1/3 of the vagina?
Hepatic circulation; ligamentum venosum
Before getting pregnant!
Mesoderm
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian

11. What is a teratogen that causes Ebsteins anomaly? What is ebsteins anomaly?

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12. From which germlayer does the thyroid develop?? From what structure exactly?
Ampulla
Endoderm - floor of primitive pharynx
Arnold chiari; syringomyelia
Amniotic cavity and yolk sac

13. From where is the pancreas derived? the spleen?
Surface ectoderm
Maxillary and medial nasal processes
Foregut; dorsal mesentery (mesodermal)
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

14. During what week do the limbs begin to form?
Week 4
...
hypospadias
Cerebral hemisphere - thalami

15. The inner layer of the chorionic villi...
Week 2; bilaminar disk; epiblast and hypoblast
Right common cardinal vein and right anterior cardinal vein
can make cells
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

16. what muscles are derived from branchial arch 6? CN?
Neuroectoderm
Germinal matrix hemorrhage
Endocardial cushions
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)

17. which tracts are damaged first in syringomelia? What tract is preserved?
Mesoderm; epiblast
Spinothalamic first
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

18. Before birth - blood entering the LA is less than...
Telencephalon
Prosencephalon
blood entering the RA
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

19. What are the three results of having pathology in the aorticopulmonary septum?
Mesoderm
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)
No more umbilical circulation emptying into RA
pyloric stenosis

20. what separates the atria from the ventricles?
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Branchial arch 2
Thyroid - cricoid - arytenoids - corniculate cuneiform
Endocardial cushions

21. What causes the increase in left atrial pressure to close the fossa ovale?
Decreased pulmonary resistance in the pulmonary vasculature
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Nicotine; preterm labor
Mesoderm; nucleous pulposos

22. What part of the vagina does the mullerian duct form? Where does the rest come from?
Upper 1/3; urogenital sinus
Bulbos Cordis; right ventricle entirely
Mesdoerm
Fetal alcohol syndrome; mental retardation

23. what drug is used to help close a PDA? what else does this drug treat?
Indomethacin; blocks PG production
Cerebellar tonsillar herniation through foramen magnum
After; extrinsic
Metencephalon; cerebellum

24. What causes the degeneration of the spinal cord in syringomelia?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Week 8
Mesoderm
Initial left to right shunting - then switches

25. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Surface ectoderm
Neural crest cells
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

26. From What embryonic layer does the gut tube epithelium arise?
Pataus; fetal alcohol syndrome
Endoderm
V3; VII
Neuroectoderm

27. Which part of the chorionic villi can make cells?
Cytotrophoblast
Dorsal; faulty positioning of genital tubercle
Outgrowth of mesonephric as ureteric bud; most caudal
Ventral ; motor

28. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Neural crest cells
Prenatal and perinatal
Pataus; fetal alcohol syndrome
3rd; proximal part of the internal carotid artery

29. From where did a branchial cleft cyst arise if it found?
Spinothalamic first
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Found in lateral neck; from no obliteration of 2-4th clefts
Hepatic circulation; ligamentum venosum

30. From What embryonic layer do the salivary - sweat and mammary glands arise?
8
Surface ectoderm
3
Cerebellar tonsillar herniation through foramen magnum

31. From What embryonic layer are the schwann cells from ?
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Yolk sac; 3rd week
Deformation
Neural crest cells

32. Which branchial derivative creates the epithelial lining of the palatine tonsils?
Duodenum to transverse colon; distal transverse colon to rectum
Respiratory distress syndrome
Wolffian; mullerian
2nd pouch

33. What day is the amnion formed?
Neuroectoderm
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Germinal matrix hemorrhage
8

34. What do the arches of the branchial apparatus correlate to?
IX; X
Mesdoerm
Female; paramesonephric; mesonephric
Where the epiblast and hypoblast fuse

35. When does the notochord form? and When does the neural plate form?
Failure of the urachus to obliterate; outpouching of the bladder
Mesoderm; 3 week
Endoderm
Failure of bony spinal canal to fuse; no; lower vertebral levels

36. From what branchial derivative do the parafollicular cells arise?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Failure of the urachus to obliterate; outpouching of the bladder
Fetal and maternal
4th/5th branchial pouches

37. From What embryonic layer do the parafollicular cells of the thyroid arise?
3rd; proximal part of the internal carotid artery
Week 4
Neural crest cells
Surface ectoderm

38. How do AV canals form?
6-30
Neuroectoderm
...
From endocardial cushions (ventral and dorsal meet each other)

39. ______________ is associated with ventral curvature of the penis
hypospadias
Mesoderm; nucleous pulposos
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Mesoderm

40. What is associated with only one umbilical artery?
Congenital and chromosomal abnormalities
28 week onward
Neural plate; closes by week 4
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

41. What hormone is hcG structurally similar too?
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
LH
Neural plate; closes by week 4

42. What part of the gut rotates around the SMA? and At what point?
External auditory meatus
Mesoderm; epiblast
Midgut; 10th week
Neural crest cells

43. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
Nutrient and gas for exchange; endometrium
Bone/cartilage and nerves
Neural crest cells
DES

44. Which branchial apparatus develops into the inferior parathyroids?
Scrotum; labia majora
3rd pouch
Foramen cecum and terminal sulus
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)

45. Which branchial apparatus makes the external auditory meatus?
Neural crest cells
1st cleft/groove (Ectoderm)
Epispadias
Maxillary

46. Which part of the branchial apparatus makes up membranes?
Neural plate; closes by week 4
All 3
Neuroectoderm
Pronephros - mesonephros - metanephros; pronephros; most cranially

47. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
Greater horn of hyoid; CN IX (styloPharyngeus)
Female; paramesonephric; mesonephric
Obliterated; forms tunica vaginalis
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)

48. What embryological structure gives rise to the coronary sinus?
Hepatic circulation; ligamentum venosum
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Left horn of the sinus venosus
6th aortic arch

49. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
XII
Dorsal; sensory
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Failure of bony spinal canal to fuse; no; lower vertebral levels

50. What two things cause VACTERL syndrome?
Neural crest cells
not covered
OCPS and maternal diabetes
Endoderm