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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 embryological structures give rise to the SVC?
After; extrinsic
Right common cardinal vein and right anterior cardinal vein
No more umbilical circulation emptying into RA
Failure to recanalize; 21

2. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
4th week
Valproate acid
3
Alkylating agents

3. What teratogens can cause renal damage in the fetus?
Base of limbs in the zone of polarizing activity; ant - post
ACE inhibitors - HCTZ
Lacunae in between the chorionic villi
Lithium

4. What does the first cleft/groove of the branchial apparatus develop into?
Thyroid - cricoid - arytenoids - corniculate cuneiform
Ventral shaft of penis (penile urethra); labia minora
External auditory meatus
Persistent connection between amniotic cavity and spinal canal; low folic acid

5. From where to Where is the foregut derivative? midgut? hindgut?
1st cleft/groove (Ectoderm)
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Cleft lip/palate

6. What is the effect of teratogens before week 3?
can make cells
All or none
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
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)

7. ______________ is associated with ventral curvature of the penis
Neuroectoderm
hypospadias
Primitive atrium
IX; X

8. What do membranous interventricular septal defect cause? What does this lead to?
Endoderm
Hemorrhage - bone deformities
monoamniotic
Initial left to right shunting - then switches

9. What day is the amnion formed?
Ectoderm; endoderm
Physiologic incomplete muscular ventricular septum
can make cells
8

10. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Mesoderm
Nicotine; preterm labor
Endoderm
First branchial pouch

11. 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?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
8
Nutrient and gas exchange
Aortic arch (from left side); right subclavian (on the right)

12. From What embryonic layer does the retina arise?
Neuroectoderm
Branchial arch 2
After; extrinsic
IX; X

13. What is the homeobox gene responsible in developing? (What axis)
Ectoderm; endoderm
Cranio - caudal; segmental
...
DiGeorge

14. What are the three regions of the brain (in order of cranial to caudal)?
Oxygenated; placenta to fetus (IVC)
Prosencephalon - mesencephalon - rhombencephalon
Surface ectoderm
primary palate

15. From where did a branchial cleft cyst arise if it found?
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Outgrowth of mesonephric as ureteric bud; most caudal
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Found in lateral neck; from no obliteration of 2-4th clefts

16. What teratogens can cause flipper limbs (limb defects)? What is this drug used for?
Neural crest cells
Surface ectoderm
Thalidomide; nausea
Hepatic circulation; ligamentum venosum

17. what bone/cartilage and nerves are derived from branchial arch 3?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Neuroectoderm
1st
Greater horn of hyoid; CN IX (styloPharyngeus)

18. What teratogens can cause CN VIII toxicity in the fetus?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Branchial arch 2
Aminoglycosides
StyloPharyngeus

19. From what region of the brain does the lateral ventricles and the 3rd ventricle form?
Mesoderm
Alkylating agents
Week 8
Prosencephalon

20. What teratogens can cause discolored teeth?
Tetracyclines
Ectoderm; endoderm
Neuroectoderm
Cranio - caudal; segmental

21. From What embryonic layer do the ANS arise?
Stapedius and hyoid artery
Neural crest cells
Mesoderm; nucleous pulposos
Arches 3 and 4

22. From What embryonic layer does the epidermis arise?
Greater horn of hyoid; CN IX (styloPharyngeus)
Surface ectoderm
Muscular ventricular septum; no
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts

23. What three components make up the branchial/pharyngeal apparatus?
Surface ectoderm
Failure of the urachus to obliterate; outpouching of the bladder
Mesoderm
Grooves/clefts; arches; pouches

24. What embryological structure gives rise to the smooth part of the right atrium?
Right horn of the SV
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Duodenum to transverse colon; distal transverse colon to rectum
Neural plate; closes by week 4

25. How many umbilical arteries are there? How many umbilical veins?
2; 1
mesodermal
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Neural crest cells

26. What is the memranous interventricular formaen made from?
Tunica vaginalis not fully fused
2nd; 2nd
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

27. what muscles are derived from branchial arch 1?
80%
Muscles of Mastication: Temporalis - masseter - Lateral and Medila pterygoids - Mylohyoid - anterior belly of the digastric - tensor tympani - tensor veli palatini; ant 2/3 of tongue
lumbosacral
primary palate

28. Which branchial apparatus derivative makes the tympanic membrane of the ear?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Membrane - all 3 from 1st appartus
ACE inhibitors - HCTZ
Pronephros - mesonephros - metanephros; pronephros; most cranially

29. On what side is the abnormal opening in epispadias? What causes it?
3rd; proximal part of the internal carotid artery
Dorsal; faulty positioning of genital tubercle
Excessive resorption of septum primum or secondum (or both)
Decreased pulmonary resistance in the pulmonary vasculature

30. Blood coming in the umbilical vein is ____ saturated
Duodenum to transverse colon; distal transverse colon to rectum
80%
Mesoderm
Neural crest cells

31. what drug is used to help close a PDA? what else does this drug treat?
Thickened ectoderm at end of each developing limb
Indomethacin; blocks PG production
Duodenum to transverse colon; distal transverse colon to rectum
1st cleft/groove (Ectoderm)

32. In order to survive tricuspid atresia - What do you need?
VSD
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Physiologic incomplete muscular ventricular septum
elevated AFP

33. In anencephaly you see...
Hepatic circulation; ligamentum venosum
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
elevated AFP
Endoderm

34. From What embryonic layer is the bladder and urethra from?
...
Epiblast
Cytotrophoblast and synctiotrophoblast
Mesoderm

35. What is the Eisenmeger complex?
When left to right shunting switching to right to left shunting
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

36. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
Week 2; bilaminar disk; epiblast and hypoblast
2; 1
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
is no longer intact

37. What does DHT turn the urogenital folds into? estrogen?
Surface ectoderm
Ventral shaft of penis (penile urethra); labia minora
Nutrient and gas exchange
elevated AFP

38. What is associated with only one umbilical artery?
mesodermal
Week 2; bilaminar disk; epiblast and hypoblast
Congenital and chromosomal abnormalities
pyloric stenosis

39. When does the neural tube form and From what does it form?
Prosencephalon - mesencephalon - rhombencephalon
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Week 8
Neural plate; closes by week 4

40. At what week does the fetus look like a baby?
Allantois
Mesoderm; nucleous pulposos
2nd; 2nd
Week 8

41. what muscles are derived from branchial arch 6? CN?
Endoderm
Folate antagonists
Hypertrophy of muscularis externis of pylorus; surgical incision
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)

42. What gene is produced in the zone of polarizing activity?
Sonic Hedgehog
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Ventral; failure of urogenital folds to close

43. what happens in hydrocele?
primary palate
Fetal alcohol syndrome; mental retardation
Tunica vaginalis not fully fused
Temporary cervical sinus

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

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45. What secretes hCG?
Neural crest migration - they then cause spiral
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Incomplete; yes
Synctiotrophoblast

46. From where is amniotic fluid produced? other than electrolytes and carbs - what else does it contain?
Neuroectoderm
After; extrinsic
Maternally derived; meconium
6-30

47. From What embryonic layer do the parafollicular cells of the thyroid arise?
Maternally derived; meconium
Neural crest cells
Telencephalon
Synctiotrophoblast; outer; no

48. From What embryonic layer does the spinal cord arise?
Cerebellar tonsillar herniation through foramen magnum
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Mesoderm
Neuroectoderm

49. What are the clinical symptoms that present with syringomelia?
External auditory meatus
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Failure of bony spinal canal to fuse; no; lower vertebral levels
Deoxygenated blood; fetal internal iliac arteries to placenta

50. Where is erythropoeisis in the weeks 3-8 of fetal development? Where does it occur after that? until when?
elevated AFP
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Hypospadias
Dorsal; faulty positioning of genital tubercle