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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. which teratogen can cause Ebsteins anomaly in the fetus?
Nicotine; preterm labor
Congenital and chromosomal abnormalities
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Lithium

2. What artery is derived branchial (aortic) arch 6?
Renal artery stenosis;
Pulm art (prox) and ductus arteriosus
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Dorsal; faulty positioning of genital tubercle

3. what muscles are derived from branchial arch 6? CN?
Mesoderm
Folate antagonists
Surface ectoderm
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)

4. What axis is Wnt 7 responsible for developing?
Nutrient and gas for exchange; endometrium
Fetal and maternal
Dorsal ventral axis
Fallopian tube - uterus - upper 1/3 of vagina

5. When does organogenesis occur?
Diencephalon
3rd pouch
Week 3-8
2; 1

6. What is congenital pharyngocutaneous fistula? and How does it occur?
Metencephalon; cerebellum
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Occiptal
Apical ectodermal ridge

7. What are the three regions of the brain (in order of cranial to caudal)?
Prosencephalon - mesencephalon - rhombencephalon
Neuroectoderm
VSD
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)

8. What causes the degeneration of the spinal cord in syringomelia?
Maternally derived; meconium
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Fluid filled syrinx causes expansion and degeneration of cord tracts
Greater horn of hyoid; CN IX (styloPharyngeus)

9. what else is the caudal regression known as? What two teratogen can cause this in the fetus?
Cytotrophoblast and synctiotrophoblast
Sonic Hedgehog
VACTERL; OCPs and maternal diabetes
Endoderm

10. failure to close of what fold results in sternal defects? omphalocele? gastrochisis? bladder extrosphy?
arnold chiari associated with thoraclumbar myelomeningocele
Urachus/median umbilical ligament; bladder and yolk sac
VSD
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

11. What can vit A in excess cause in the fetus?
Lots - cleft palate/lip
Hepatic circulation; ligamentum venosum
Myelencephalon
Epiblast

12. Which branchial apparatus makes the external auditory meatus?
T neuroectoderm
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
1st cleft/groove (Ectoderm)
Maxillary and medial nasal processes

13. What type of blood do umbilical veins carry? From where to where?
Neuroectoderm
Base of limbs in the zone of polarizing activity; ant - post
Oxygenated; placenta to fetus (IVC)
Ventral shaft of penis (penile urethra); labia minora

14. From What embryonic layer does the oligodendrocytes arise?
Tongue
Neuroectoderm
From teh lung;blood from IVC in RA to LA; fossa ovalis
All 3

15. From What embryonic layer do the salivary - sweat and mammary glands arise?
Surface ectoderm
Mesonephros; male genital system
Deformation
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)

16. what week do the genitalia start to have male/female characteristics? What trimester is that?
Week 10-12; end of 1st trimester
lumbosacral
Neural crest cells
Ventral shaft of penis (penile urethra); labia minora

17. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
is no longer intact
Mesoderm
During; instrinsic
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)

18. What is used to keep the PDA open?
Week 4
Prostaglandins
Greater horn of hyoid; CN IX (styloPharyngeus)
Initial left to right shunting - then switches

19. What does the first branchial pouch create?
Prevent recurrent UTIs
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Dorsal and ventral buds
Bulbos Cordis; right ventricle entirely

20. What do the 2nd through 4th clefts of the branchial apparatus correlate to?
Temporary cervical sinus
Arnold chiari; syringomyelia
Turners; inferior
Where the epiblast and hypoblast fuse

21. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
DiGeorge
mesodermal
Muscular ventricular septum; no
Endoderm

22. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Thalidomide; nausea
Vascular accident intra uterine; apple peel atresia
3rd; proximal part of the internal carotid artery

23. Septum primum (patent foramen oval) caused by excessive resorption of...
Neuroectoderm
septum primum and/or secundum
Week 4
Thickened ectoderm at end of each developing limb

24. What embryological structure gives rise to the trabeculated part of the left and right atrium?
Failure to recanalize; 21
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
...
Primitive atrium

25. what bone/cartilage and nerves are derived from branchial arch 3?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Tunica vaginalis not fully fused
Greater horn of hyoid; CN IX (styloPharyngeus)
Mesoderm

26. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Endoderm
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Duodenum to transverse colon; distal transverse colon to rectum
Amniotic epithelium

27. Which branchial derivative accounts for taste in the ant 2/3?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Upper 1/3; urogenital sinus
Branchial arch 2
Mesoderm

28. What arises from the fourth aortic arch?
Found in lateral neck; from no obliteration of 2-4th clefts
Aortic arch (from left side); right subclavian (on the right)
Cytotrophoblast and synctiotrophoblast
Hepatic circulation; ligamentum venosum

29. From which branchial derivative does the anterior 2/3 of the tongue develop?
Midgut; 10th week
4th arch; 6th arch
1st branchial arch
No organ in each; agenesis no primordial tissue

30. What part of the vagina does the mullerian duct form? Where does the rest come from?
Cerebellar tonsillar herniation through foramen magnum
Upper 1/3; urogenital sinus
Lots - cleft palate/lip
Myelencephalon

31. From What embryonic layer does the brain arise?
Metencephalon; cerebellum
Neuroectoderm
Indomethacin; blocks PG production
Cranio - caudal; segmental

32. What artery is derived branchial (aortic) arch 3?
Common carotid and internal carotid
...
elevated AFP
Fetal and maternal

33. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
Mesoderm
Mesoderm; 3 week
Ventral bud
DES

34. What day is the amnion formed?
8
Ebsteins anomaly; tricuspid atresia
Neural crest cells
Prevent recurrent UTIs

35. From What embryonic layer do the ependymal cells arise?
Where the epiblast and hypoblast fuse
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Neuroectoderm
lumbosacral

36. From What embryonic layer does the olfactory epithelium arise?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Grooves/clefts; arches; pouches
StyloPharyngeus
Surface ectoderm

37. What does DHT turn the urogenital sinus into? estrogen?
Surface ectoderm
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

38. From What embryonic layer are the melanocytes from?
Neural crest cells
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Mesdoerm
Decreased pulmonary resistance in the pulmonary vasculature

39. What causes a patent foramen ovale?
4th/5th branchial pouches
Excessive resorption of septum primum or secondum (or both)
Umbilical - midgut herniates through umbilical ring; SMA
Neuroectoderm

40. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Right horn of the SV
First branchial pouch
Mesoderm
Physiologic incomplete muscular ventricular septum

41. What are the two components of the fetal component of the placenta?
4th pouch
Pronephros - mesonephros - metanephros; pronephros; most cranially
Cytotrophoblast and synctiotrophoblast
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian

42. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Mesoderm
Hepatic circulation; ligamentum venosum
Vascular accident intra uterine; apple peel atresia
is no longer intact

43. What type of blood do umbilical arteries carry? From where to where?
Deoxygenated blood; fetal internal iliac arteries to placenta
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
2; 1
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

44. From what does bicornuate uterus arise? What is it associated with?
Surface ectoderm
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Temporary cervical sinus
Hemorrhage - bone deformities

45. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
Nicotine; preterm labor
Right horn of the SV
A vitelline fistula - failure of vitelline duct to close
Mesoderm

46. What two things cause VACTERL syndrome?
OCPS and maternal diabetes
Amniotic cavity and yolk sac
Tunica vaginalis not fully fused
Excessive resorption of septum primum or secondum (or both)

47. When does hCG secretion take place? with what event?
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Day 6; with implantation
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Annular pancrease

48. What is the female remnant of the gubernaculum? male remnant?
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Initial left to right shunting - then switches
Hepatic circulation; ligamentum venosum
Neural crest cells

49. Where is sonic hedgehog gene produced? What axis is it responsible in patterning?
Arnold chiari; syringomyelia
3
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Base of limbs in the zone of polarizing activity; ant - post

50. From what region do the thalami form?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Diencephalon
Hypertrophy of muscularis externis of pylorus; surgical incision
Ventral shaft of penis (penile urethra); labia minora