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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. In what chromosomal disorder is horseshoe kidney commonly seen? what poles of the kidneys fuse?
Endoderm
arnold chiari associated with thoraclumbar myelomeningocele
No more umbilical circulation emptying into RA
Turners; inferior

2. Cleft palate is a failure of formation of the...
Mesoderm
secondary palate
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Dorsal ventral axis

3. What does the foramen ovale shunt blood from - to where? What is its remnant?
VSD
From teh lung;blood from IVC in RA to LA; fossa ovalis
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Failure of the urachus to obliterate; outpouching of the bladder

4. What can vit A in excess cause in the fetus?
Oligohydramnios
1st branchial arch
Mesoderm
Lots - cleft palate/lip

5. From What embryonic layer does the adenohypophysis arise?
is no longer intact
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Endoderm
Surface ectoderm

6. What does DHT turn the urogenital folds into? estrogen?
Muscular ventricular septum; no
Day 6; maintains corpus luteum; 1st trimester
Prosencephalon - mesencephalon - rhombencephalon
Ventral shaft of penis (penile urethra); labia minora

7. What are the two walls of the prosencephalon and What do they become?
Midgut; 10th week
...
Apical ectodermal ridge
Cerebral hemisphere - thalami

8. What artery is derived branchial (aortic) arch 3?
Truncus arteriosus; pulmonary trunk
Rhombencephalon
Midgut; 10th week
Common carotid and internal carotid

9. During what week does the heart begin to beat?
Primitive ventricle
...
Ventral shaft of penis (penile urethra); labia minora
Week 4

10. From What embryonic layer does the lens of the eye arise?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Surface ectoderm
Nicotine; preterm labor
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

11. What teratogens can cause renal damage in the fetus?
Wolffian; mullerian
Hepatic circulation; ligamentum venosum
ACE inhibitors - HCTZ
Upper 1/3; urogenital sinus

12. What components do the neural crest cells of the branchial arches give rise to?
DiGeorge
Scrotum; labia majora
Bones - cartilage - and nerves
Thickened ectoderm at end of each developing limb

13. what invaginates to form the primitive streak?
Nutrient and gas for exchange; endometrium
Maxillary and medial nasal processes
Hypertrophy of muscularis externis of pylorus; surgical incision
Epiblast

14. what happens in hydrocele?
Prenatal and perinatal
2; 1
Tunica vaginalis not fully fused
Pronephros - mesonephros - metanephros; pronephros; most cranially

15. What embryological structures give rise to the SVC?
Temporary cervical sinus
Greater horn of hyoid; CN IX (styloPharyngeus)
Mesoderm
Right common cardinal vein and right anterior cardinal vein

16. What does DHT turn the genital tubercle into? estrogen?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Mesoderm
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
T neuroectoderm

17. What hormone is hcG structurally similar too?
2nd pouch
Skewed development of AP septum
LH
Mesoderm

18. What two cavities also form during the second week?
Rhombencephalon
Amniotic cavity and yolk sac
Decreased pulmonary resistance in the pulmonary vasculature
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

19. From What embryonic layer does the skin dermis arise?
Deoxygenated blood; fetal internal iliac arteries to placenta
Mesoderm
Epiblast
6-30

20. What is the physiological herniation that occurs at the 6th week - what herniates out of the umbilical ring? when it comes back in the 10th week - What does it rotate around?
A vitelline fistula - failure of vitelline duct to close
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
Foramen cecum and terminal sulus
Umbilical - midgut herniates through umbilical ring; SMA

21. What teratogens can cause CN VIII toxicity in the fetus?
Maxillary
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Endometrium
Aminoglycosides

22. What are markers for neural tube defects in the amniotic cavity? CSF?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Right common cardinal vein and right anterior cardinal vein
4th pouch
Increased AFP and acetycholinesterase (not ACh!) in CSF

23. What is meckel's diverticulum? What is it associated with? What does that cause?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Neural crest cells

24. what muscles are derived from branchial arch 2?
Ebsteins anomaly; tricuspid atresia
is no longer intact
Neuroectoderm
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric

25. When does organogenesis occur?
Week 3-8
Folate antagonists
Ectoderm; endoderm
Endoderm

26. What embryologic structure provides the aorticpulmonary septum?
Neural crest migration - they then cause spiral
Neural crest cells
Week 8
Neural crest cells

27. What causes the obstruction in pyloric stenosis? treatment?
Hypertrophy of muscularis externis of pylorus; surgical incision
Fetal alcohol syndrome; mental retardation
Foregut; dorsal mesentery (mesodermal)
Cytotrophoblast and synctiotrophoblast

28. What do the groove/clefts of the branchial apparatus correlate to?
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Ectoderm
Found in lateral neck; from no obliteration of 2-4th clefts
Epispadias

29. Where is the most common ectopic thyroid tissue?
3rd and 4th arches
Tongue
Hepatic circulation; ligamentum venosum
septum primum and/or secundum

30. What is associated with only one umbilical artery?
Failure to recanalize; 21
Found in lateral neck; from no obliteration of 2-4th clefts
Congenital and chromosomal abnormalities
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

31. Monochorionic - ___________ twins are conjoined
Endoderm
monoamniotic
Mesencephalon
Day 6; maintains corpus luteum; 1st trimester

32. What do the 2nd through 4th clefts of the branchial apparatus correlate to?
Medial palatine processes
Neural crest cells
Neural crest cells
Temporary cervical sinus

33. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
lumbosacral
Cytotrophoblast and synctiotrophoblast
Rhombencephalon
Vascular accident intra uterine; apple peel atresia

34. Cleft lip is a failure of formation of the...
Truncus arteriosus; pulmonary trunk
Grooves/clefts; arches; pouches
Dorsal; sensory
primary palate

35. From what aortic arch does the first part of the maxillary artery arise?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
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
From endocardial cushions (ventral and dorsal meet each other)
1st

36. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
DiGeorge
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
External auditory meatus
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)

37. What do the arches of the branchial apparatus correlate to?
3rd pouch
From teh lung;blood from IVC in RA to LA; fossa ovalis
Mesdoerm
Ampulla

38. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
can make cells
80%
Bulbos Cordis; right ventricle entirely
Dorsal and ventral buds

39. Does deformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
8
After; extrinsic
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

40. What is the female remnant of the gubernaculum? male remnant?
Pataus; fetal alcohol syndrome
DHT; estrogen
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Diencephalon

41. From where does the ureteric bud arise? What does it give rise to?
6th aortic arch
Before getting pregnant!
2; 1
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts

42. From What embryonic layer are the pia and arachnoid from?
Decreased separation of hemispheres across midline; cyclopia
Neural crest cells
Ebsteins anomaly; tricuspid atresia
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus

43. what muscles are derived from branchial arch 1?
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
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Synctiotrophoblast
Arnold chiari; syringomyelia

44. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Endoderm
Sperm plus egg
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Obliterated

45. From where is the pancreas derived? the spleen?
Surface ectoderm
Where the epiblast and hypoblast fuse
Synctiotrophoblast
Foregut; dorsal mesentery (mesodermal)

46. What causes meconium discharge from the umbilicus?
A vitelline fistula - failure of vitelline duct to close
Dorsal; faulty positioning of genital tubercle
Increased AFP and acetycholinesterase (not ACh!) in CSF
Folate antagonists

47. What is holoprosencephaly? what eye disorder does it result in?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Decreased separation of hemispheres across midline; cyclopia
Mesoderm
Ectoderm

48. what muscles are derived from branchial arch 3?
Neural crest cells
Ventral shaft of penis (penile urethra); labia minora
StyloPharyngeus
secondary palate

49. When does hcG get secreted? What does it do?up until when ?
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Day 6; maintains corpus luteum; 1st trimester
Surface ectoderm
Aortic arch and prox part of subclavian

50. Which is more common - epispadias or hypospadias?
Nicotine; preterm labor
Hypospadias
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Decreases