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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 are the two walls of the prosencephalon and What do they become?
Cerebral hemisphere - thalami
Ventral ; motor
hypospadias
Ectoderm

2. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Annular pancrease
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Oligohydramnios
Arnold chiari; syringomyelia

3. Cleft palate is a failure of formation of the...
Week 2; bilaminar disk; epiblast and hypoblast
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
No organ in each; agenesis no primordial tissue
secondary palate

4. What do the groove/clefts of the branchial apparatus correlate to?
Ectoderm
Primitive atrium
6th aortic arch
Neural crest migration - they then cause spiral

5. From where does the permanent kidney for? is it most caudal or most cranial?
Outgrowth of mesonephric as ureteric bud; most caudal
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
8
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

6. What does the midgut form? hindgut?
Neural crest cells
Primitive ventricle
Duodenum to transverse colon; distal transverse colon to rectum
Dorsal and ventral buds

7. What hormone is hcG structurally similar too?
Prosencephalon
LH
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Tetracyclines

8. From which germlayer does the thyroid develop?? From what structure exactly?
Epispadias
Telencephalon
28 week onward
Endoderm - floor of primitive pharynx

9. From What embryonic layer does the thyroid follicular cells arise?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Umbilical - midgut herniates through umbilical ring; SMA
Muscular ventricular septum; no
Endoderm

10. What happens in pancreas divisum? what results?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Folate antagonists
Polyhydramnios
Annular pancrease

11. What is the mnueomonic for the mesodermal defects? What does it stand for?
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Scrotum; labia majora
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Thalidomide; nausea

12. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
Stapedius and hyoid artery
Wolffian; mullerian
...
Bulbos Cordis; right ventricle entirely

13. Where is the decidua basalis derived from?
Hemorrhage - bone deformities
Endometrium
Telencephalon
28 week onward

14. From What embryonic layer do the ependymal cells arise?
Neuroectoderm
hypertrophy
Pulm art (prox) and ductus arteriosus
T neuroectoderm

15. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
Obliterated
Synctiotrophoblast
DES
3 -4 -6

16. At what week does the fetus look like a baby?
Mesencephalon
Week 8
All or none
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

17. What components do the neural crest cells of the branchial arches give rise to?
Neural crest cells
Allantois
Bones - cartilage - and nerves
Endoderm

18. What is perinauds syndrome?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Mesoderm
Prostaglandins
Cranio - caudal; segmental

19. From what arches are the neural crest cells that form the aorticpulmonary septum derived?
3 -4 -6
Hepatic circulation; ligamentum venosum
Endoderm
They are the edge of neural plate folding; all over the body

20. What axis is Wnt 7 responsible for developing?
mesodermal
Dorsal ventral axis
...
pyloric stenosis

21. Which branchial apparatus makes the external auditory meatus?
Week 8
1st cleft/groove (Ectoderm)
Rhombencephalon
Fetal and maternal

22. What teratogens can cause renal damage in the fetus?
Duodenum to transverse colon; distal transverse colon to rectum
External auditory meatus
ACE inhibitors - HCTZ
Hemorrhage - bone deformities

23. What is the difference between agenesis and aplasia?
Week 10-12; end of 1st trimester
Cerebral hemisphere - thalami
Respiratory distress syndrome
No organ in each; agenesis no primordial tissue

24. What is the Eisenmeger complex?
When left to right shunting switching to right to left shunting
Foregut; dorsal mesentery (mesodermal)
4th/5th branchial pouches
DiGeorge

25. What is the primitive streak? From what layer does it form?
Bone/cartilage and nerves
Mesoderm; epiblast
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
4th week

26. what separates the atria from the ventricles?
Endocardial cushions
IMA
Nicotine; preterm labor
5th

27. From What embryonic layer does the skin dermis arise?
Duodenum to transverse colon; distal transverse colon to rectum
4th/5th branchial pouches
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Mesoderm

28. What does the foramen ovale shunt blood from - to where? What is its remnant?
Neural plate; closes by week 4
From teh lung;blood from IVC in RA to LA; fossa ovalis
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Surface ectoderm

29. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Oligohydramnios
Ventral shaft of penis (penile urethra); labia minora
After; extrinsic

30. During what week does the heart begin to beat?
Lots - cleft palate/lip
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Week 4
blood entering the RA

31. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
Dorsal; faulty positioning of genital tubercle
T neuroectoderm
V3; VII
OCPS and maternal diabetes

32. What teratogens can cause discolored teeth?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Folate antagonists
hypospadias
Tetracyclines

33. What day is the chorion formed?
Congenital and chromosomal abnormalities
Bulbos Cordis; right ventricle entirely
Endoderm - floor of primitive pharynx
3

34. From What embryonic layer does the lens of the eye arise?
Surface ectoderm
VACTERL; OCPs and maternal diabetes
Muscular ventricular septum; no
Primitive atrium

35. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
Scrotum; labia majora
not covered
Week 3-8
Prenatal and perinatal

36. What embryological structure gives rise to the trabeculated part of the left and right atrium?
Primitive atrium
T neuroectoderm
Folate antagonists
Branchial arch 2

37. During what periods do the damages that cerebral palsy causes occur?
Cerebellar tonsillar herniation through foramen magnum
Prenatal and perinatal
Nicotine; preterm labor
Mesoderm; nucleous pulposos

38. From What embryonic layer does the adenohypophysis arise?
8
Surface ectoderm
VACTERL; OCPs and maternal diabetes
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

39. What artery is derived branchial (aortic) arch 1?
VACTERL; OCPs and maternal diabetes
Maxillary
Skewed development of AP septum
Yolk sac; 3rd week

40. What causes tetralogy of Fallot?
Nutrient and gas exchange
Skewed development of AP septum
hypospadias
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

41. What does DHT turn the genital tubercle into? estrogen?
2; 1
IMA
Valproate acid
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

42. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Valproate acid
Mesdoerm
Failure of bony spinal canal to fuse; no; lower vertebral levels
Umbilical - midgut herniates through umbilical ring; SMA

43. what drug is used to help close a PDA? what else does this drug treat?
Indomethacin; blocks PG production
monoamniotic
From endocardial cushions (ventral and dorsal meet each other)
Nutrient and gas exchange

44. Which branchial apparatus develops into the inferior parathyroids?
3rd pouch
Duodenum to transverse colon; distal transverse colon to rectum
Week 8
From endocardial cushions (ventral and dorsal meet each other)

45. What part of the vagina does the mullerian duct form? Where does the rest come from?
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Upper 1/3; urogenital sinus
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
During; instrinsic

46. What are the neural crest cells and where do they come form? where do they go?
Folate antagonists
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
blood entering the RA
They are the edge of neural plate folding; all over the body

47. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
is no longer intact
Umbilical - midgut herniates through umbilical ring; SMA
monoamniotic
Truncus arteriosus; pulmonary trunk

48. Where is the most common ectopic thyroid tissue?
Amniotic epithelium
Tongue
Week 8
Arnold chiari; syringomyelia

49. What does the mullerian duct develop into? wollffian?
Fallopian tube - uterus - upper 1/3 of vagina
Bones - cartilage - and nerves
Neuroectoderm
Thalidomide; nausea

50. From What embryonic layer are the dorsal root and celiac ganglion from?
During; instrinsic
Neural crest cells
Week 3; primitive streak formation from the epiblast makes the three layers
VACTERL; OCPs and maternal diabetes