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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. Only _______________________________ are associated with neural tube defects
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
arnold chiari associated with thoraclumbar myelomeningocele
Prenatal and perinatal
...

2. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Neuroectoderm
Week 3; primitive streak formation from the epiblast makes the three layers
Mid gut to yolk sac; omphalomesenteric duct; 7th week
blood entering the RA

3. What does the first cleft/groove of the branchial apparatus develop into?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Medial palatine processes
External auditory meatus
Tetracyclines

4. From What embryonic layer is the vagina from? testes? ovaries?
Week 3-8
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Mesoderm
Tunica vaginalis not fully fused

5. What type of blood do umbilical arteries carry? From where to where?
Failure to recanalize; 21
Deoxygenated blood; fetal internal iliac arteries to placenta
Thyroid - cricoid - arytenoids - corniculate cuneiform
Fetal alcohol syndrome; mental retardation

6. From where do the three different kidneys come from? Which is the earliest one? is it located most cranially or caudally?
2nd; 2nd
Pronephros - mesonephros - metanephros; pronephros; most cranially
Oxygenated; placenta to fetus (IVC)
Week 3; primitive streak formation from the epiblast makes the three layers

7. What does DHT turn the genital tubercle into? estrogen?
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Neural crest cells
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Neural crest migration - they then cause spiral

8. From What embryonic layer does the parathyroid arise ?
not covered
Endoderm
Muscular ventricular septum; no
Aortic arch (from left side); right subclavian (on the right)

9. what muscles are derived from branchial arch 4? CN?
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Oligohydramnios
Female; paramesonephric; mesonephric
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

10. When does organogenesis occur?
Week 3-8
Neural crest cells
Cerebral hemisphere - thalami
Maxillary and medial nasal processes

11. What is the mcc of renovascular hypertension in children? What does this predispose to?
Renal artery stenosis;
not covered
Neuroectoderm
Surface ectoderm

12. From What embryonic layer does the epidermis arise?
Female; paramesonephric; mesonephric
Surface ectoderm
...
Day 6; with implantation

13. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
DES
Week 4
Arnold chiari; syringomyelia
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

14. By what week is the neural tube supposed to be closed? when did it start forming?
Oligohydramnios
Week 4; week 3
Telencephalon
Upper 1/3; urogenital sinus

15. When does hCG secretion take place? with what event?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Physiologic incomplete muscular ventricular septum
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
Day 6; with implantation

16. What are the two walls of the prosencephalon and What do they become?
6-30
Cerebral hemisphere - thalami
Prosencephalon
Ionizing

17. What can vit A in excess cause in the fetus?
Lots - cleft palate/lip
mesoderm
Surface ectoderm
Midgut; 10th week

18. What are the three results of having pathology in the aorticopulmonary septum?
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)
Scrotum; labia majora
Neural crest migration - they then cause spiral
Decreased separation of hemispheres across midline; cyclopia

19. The notochord is...
Truncus arteriosus; pulmonary trunk
mesoderm
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Neuroectoderm

20. From where is amniotic fluid produced? other than electrolytes and carbs - what else does it contain?
Maternally derived; meconium
Cleft lip/palate
not covered
Lacunae in between the chorionic villi

21. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
V3; VII
Oligohydramnios
Week 2; bilaminar disk; epiblast and hypoblast
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus

22. From What embryonic layer are the melanocytes from?
Surface ectoderm
arnold chiari associated with thoraclumbar myelomeningocele
DiGeorge
Neural crest cells

23. Pyloric stenosis is characterized by _____________ of muscularis externis in the sphincter
arnold chiari associated with thoraclumbar myelomeningocele
hypertrophy
Found in lateral neck; from no obliteration of 2-4th clefts
Bone/cartilage and nerves

24. From What embryonic layer does bone arise ?
Mesoderm
From endocardial cushions (ventral and dorsal meet each other)
mesodermal
3 -4 -6

25. When does erythropoeisis begin in the bone marow?
Thyroid - cricoid - arytenoids - corniculate cuneiform
Ectoderm
28 week onward
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

26. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Failure to recanalize; 21
Neuroectoderm
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Pulm art (prox) and ductus arteriosus

27. Which branchial derivative accounts for taste in the ant 2/3?
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Branchial arch 2
Right horn of the SV
Endoderm

28. From where is the pancreas derived? the spleen?
IX; X
Foregut; dorsal mesentery (mesodermal)
Day 6; with implantation
Epiblast

29. Other than not having a brain - what else is a symptom of anencephaly? why? hint: think about amniotic fluid
hypertrophy
not covered
Polyhydramnios
Embryonic period; 1st trimester

30. What is holoprosencephaly? what eye disorder does it result in?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Turners; inferior
Decreased separation of hemispheres across midline; cyclopia
Ampulla

31. What does the ureteric bud interact with and What does it induce it to become?
Increase in oxygen concentration which decreases prostaglandin concentration
Epiblast
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

32. The inner layer of the chorionic villi...
Ventral bud
can make cells
Fluid filled syrinx causes expansion and degeneration of cord tracts
3rd; proximal part of the internal carotid artery

33. Which cranial nerve innervates the motor function of the tongue?
XII
OCPS and maternal diabetes
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Cerebellar tonsillar herniation through foramen magnum

34. Cleft palate is a failure of formation of the...
secondary palate
mesodermal
Amniotic cavity and yolk sac
Mesencephalon

35. What causes the increase in left atrial pressure to close the fossa ovale?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
DHT; estrogen
Decreased pulmonary resistance in the pulmonary vasculature
1st cleft/groove (Ectoderm)

36. From What embryonic layer is the spleen from?
ACE inhibitors - HCTZ
Endoderm
Aortic arch and prox part of subclavian
Mesoderm

37. What is the prochordal plate?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
septum primum and/or secundum
Where the epiblast and hypoblast fuse
Indomethacin; blocks PG production

38. What role does the placenta have?
monoamniotic
4th pouch
Nutrient and gas exchange
Mesoderm

39. What gene is produced in the zone of polarizing activity?
Week 4
Mesencephalon
Prevent recurrent UTIs
Sonic Hedgehog

40. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Maxillary and medial nasal processes
Indomethacin; blocks PG production
Primitive ventricle
Valproate acid

41. What day is the amnion formed?
8
Week 8
Hemorrhage - bone deformities
Epispadias

42. What teratogens can cause CN VIII toxicity in the fetus?
Sonic Hedgehog
Aminoglycosides
Bulbos Cordis; right ventricle entirely
hypospadias

43. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
Branchial arch 2
Metencephalon; cerebellum
Neuroectoderm
not covered

44. 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)
Ectoderm
Maternally derived; meconium
Amniotic cavity and yolk sac

45. Which branchial derivative accounts for the posterior 2/3 of the tongue?
LH
A vitelline fistula - failure of vitelline duct to close
Left horn of the sinus venosus
3rd and 4th arches

46. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Ventral shaft of penis (penile urethra); labia minora
Oligohydramnios
Hypospadias
Endoderm

47. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
8
Bulbos Cordis; right ventricle entirely
Embryonic period; 1st trimester
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

48. What part of the gut rotates around the SMA? and At what point?
Found in lateral neck; from no obliteration of 2-4th clefts
Midgut; 10th week
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Week 3-8

49. What axis does the basal plate form? what neural system does it become?
Ampulla
Ventral ; motor
Amniotic cavity and yolk sac
5th

50. Which branchial arch derivative is obliterated?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
5th
When left to right shunting switching to right to left shunting
Initial left to right shunting - then switches