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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. From what region of the brain does the fourth ventricle form?
Sonic Hedgehog
Rhombencephalon
Synctiotrophoblast; outer; no
6-30

2. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
Epiblast
Lacunae in between the chorionic villi
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Where the epiblast and hypoblast fuse

3. When does hcG get secreted? What does it do?up until when ?
Mesoderm; nucleous pulposos
Day 6; maintains corpus luteum; 1st trimester
8
Ventral shaft of penis (penile urethra); labia minora

4. Which part of pancreas contribute to body? tail? isthmus? accessory pancreatic duct?
Spinothalamic first
Ventral bud
Persistent connection between amniotic cavity and spinal canal; low folic acid
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

5. When is most important to take folic acid to prevent neural tube defects?
Embryonic period; 1st trimester
Before getting pregnant!
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Muscular ventricular septum; no

6. What is omphalocele? In What trisomies is it seen?
Fluid filled syrinx causes expansion and degeneration of cord tracts
2nd; 2nd
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

7. What artery is derived branchial (aortic) arch 6?
Decreased separation of hemispheres across midline; cyclopia
Amniotic epithelium
Pulm art (prox) and ductus arteriosus
3rd pouch

8. What is contained in the umbilical cord?
Thyroid - cricoid - arytenoids - corniculate cuneiform
Increased AFP and acetycholinesterase (not ACh!) in CSF
Endoderm
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus

9. From where did a branchial cleft cyst arise if it found?
2nd; 2nd
Found in lateral neck; from no obliteration of 2-4th clefts
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Left horn of the sinus venosus

10. ______________ is associated with ventral curvature of the penis
OCPS and maternal diabetes
hypospadias
XII
Decreases

11. From What embryonic layer does connective tissue and muscle arise?
Mesoderm
Lots - cleft palate/lip
Maternally derived; meconium
Nicotine; preterm labor

12. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Cerebral hemisphere - thalami
Week 2; bilaminar disk; epiblast and hypoblast
Embryonic period; 1st trimester

13. What is the effect of teratogens after week 8?
Right common cardinal vein and right anterior cardinal vein
Deformation
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Umbilical - midgut herniates through umbilical ring; SMA

14. When does hCG secretion take place? with what event?
When left to right shunting switching to right to left shunting
Day 6; with implantation
Spinothalamic first
Aortic arch (from left side); right subclavian (on the right)

15. From which myotomes are muscles of the tongue derived from?
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
3rd; proximal part of the internal carotid artery
Occiptal
Maxillary and medial nasal processes

16. 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?
Nutrient and gas for exchange; endometrium
ACE inhibitors - HCTZ
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
80%

17. What type of radiation is teratogenic ?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Polyhydramnios
Greater horn of hyoid; CN IX (styloPharyngeus)
Ionizing

18. From What embryonic layer does the epithelial linings of the oral cavity arise?
Surface ectoderm
Cerebellar tonsillar herniation through foramen magnum
can make cells
Thickened ectoderm at end of each developing limb

19. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Vascular accident intra uterine; apple peel atresia
Rhombencephalon
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
4th/5th branchial pouches

20. Which branchial apparatus develops into the superior parathyroids?
From endocardial cushions (ventral and dorsal meet each other)
4th pouch
Lithium
pyloric stenosis

21. What role does the placenta have?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Muscular ventricular septum; no
Wolffian; mullerian
Nutrient and gas exchange

22. what closes the interventricular foramen?
Hypospadias
Physiologic incomplete muscular ventricular septum
No more umbilical circulation emptying into RA
OCPS and maternal diabetes

23. From What embryonic layer is aorticopulmonary septum from ?
Neural crest cells
Synctiotrophoblast
4th arch; 6th arch
Mesoderm

24. What are the two walls of the prosencephalon and What do they become?
Increase in oxygen concentration which decreases prostaglandin concentration
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Arnold chiari; syringomyelia
Cerebral hemisphere - thalami

25. From What embryonic layer does the sensory organs of the ear arise?
Surface ectoderm
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Foregut; dorsal mesentery (mesodermal)
T neuroectoderm

26. What secretes hCG?
XII
Synctiotrophoblast
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)
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

27. What do membranous interventricular septal defect cause? What does this lead to?
Initial left to right shunting - then switches
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Hypospadias
5th

28. Which branchial apparatus makes the external auditory meatus?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Deoxygenated blood; fetal internal iliac arteries to placenta
Mental retardation - holoprosencephaly - facial features - fistulas
1st cleft/groove (Ectoderm)

29. In both meningocele and myelomeningocele the dura...
is no longer intact
Right horn of the SV
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
lumbosacral

30. What are the aspects of fetal alcohol syndrome?
Mesoderm
Mental retardation - holoprosencephaly - facial features - fistulas
Neuroectoderm
Decreased pulmonary resistance in the pulmonary vasculature

31. Which branchial derivative creates the epithelial lining of the palatine tonsils?
Renal artery stenosis;
Nutrient and gas for exchange; endometrium
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
2nd pouch

32. What arises from the fourth aortic arch?
Annular pancrease
blood entering the RA
Aortic arch (from left side); right subclavian (on the right)
Diencephalon

33. What causes the transposition of the great vessels? What does it result in?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Week 2; bilaminar disk; epiblast and hypoblast
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Medial palatine processes

34. What is perinauds syndrome?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Before getting pregnant!
Absent cerebellar vermis; cystic enlargement of 4th ventricle
When left to right shunting switching to right to left shunting

35. From where is the allantois formed? During what week?
Endoderm
A vitelline fistula - failure of vitelline duct to close
Arnold chiari; syringomyelia
Yolk sac; 3rd week

36. failure to close of what fold results in sternal defects? omphalocele? gastrochisis? bladder extrosphy?
Scrotum; labia majora
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Epispadias

37. Septum primum (patent foramen oval) caused by excessive resorption of...
From teh lung;blood from IVC in RA to LA; fossa ovalis
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
septum primum and/or secundum
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

38. From where does the ureteric bud arise? What does it give rise to?
Dorsal; faulty positioning of genital tubercle
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
3rd and 4th arches
6-30

39. To what germ layer does the branchial pouches correlate to?
Endoderm
Hepatic circulation; ligamentum venosum
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Mesencephalon

40. How is amniontic fluid excreted? How is amniotic fluid resorped?
Endoderm
V3; VII
Amniotic cavity and yolk sac
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

41. What does DHT turn the labioscrotal swelling into? estrogen?
Nicotine; preterm labor
IX; X
Scrotum; labia majora
During; instrinsic

42. What embryological structure gives rise to the smooth part of the right atrium?
Neuroectoderm
Bulbos Cordis; right ventricle entirely
VACTERL; OCPs and maternal diabetes
Right horn of the SV

43. The notochord is...
Mesoderm
Tunica vaginalis not fully fused
Medial palatine processes
mesoderm

44. What is hypoplasia? is primordial tissue present?
Neural crest cells
Day 6; maintains corpus luteum; 1st trimester
Incomplete; yes
Absent cerebellar vermis; cystic enlargement of 4th ventricle

45. What teratogens can cause flipper limbs (limb defects)? What is this drug used for?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Thalidomide; nausea
Neuroectoderm
2; 1

46. From What embryonic layer is the eustachian tube from?
Dorsal and ventral buds
All 3
Mesoderm
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

47. _____________is common in 1st born males
pyloric stenosis
Neural crest cells
Right horn of the SV
Maxillary and medial nasal processes

48. What axis does the alar plate form? what neural system does it become?
Surface ectoderm
Dorsal; sensory
Endoderm
XII

49. Where is the apical ectodermal ridge?
4th pouch
Surface ectoderm
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Thickened ectoderm at end of each developing limb

50. From What embryonic layer does the retina arise?
Telencephalon
Persistent connection between amniotic cavity and spinal canal; low folic acid
Neuroectoderm
monoamniotic