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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 does the ductus venosus shunt blood away from? What is its remnant?
Persistent connection between amniotic cavity and spinal canal; low folic acid
6th aortic arch
Neuroectoderm
Hepatic circulation; ligamentum venosum

2. What secretes hCG?
6-30
Ventral; failure of urogenital folds to close
Synctiotrophoblast
2; 1

3. What is the prochordal plate?
Where the epiblast and hypoblast fuse
Synctiotrophoblast
Tunica vaginalis not fully fused
Endoderm

4. What is the defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Tunica vaginalis not fully fused
Failure of bony spinal canal to fuse; no; lower vertebral levels
...
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

5. What is the Eisenmeger complex?
Endoderm
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
When left to right shunting switching to right to left shunting
After; extrinsic

6. Where is the FGF gene produced? What is it responsible for - How does it do this?
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Primitive atrium
LH
Prosencephalon

7. what separates the atria from the ventricles?
Midgut; 10th week
Endocardial cushions
Neuroectoderm
Neural crest cells

8. The notochord is...
Muscles and arteries
Synctiotrophoblast; outer; no
mesoderm
Neural crest cells

9. From where does the permanent kidney for? is it most caudal or most cranial?
Neural crest cells
Arches 3 and 4
Outgrowth of mesonephric as ureteric bud; most caudal
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum

10. From What embryonic layer does bone of the skulls arise?
Germinal matrix hemorrhage
Neural crest cells
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
IX; X

11. When does hcG get secreted? What does it do?up until when ?
After; extrinsic
Day 6; maintains corpus luteum; 1st trimester
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
IX; X

12. What are the three regions of the brain (in order of cranial to caudal)?
Deformation
4th week
Neuroectoderm
Prosencephalon - mesencephalon - rhombencephalon

13. From which myotomes are muscles of the tongue derived from?
Ebsteins anomaly; tricuspid atresia
IX; X
Prenatal and perinatal
Occiptal

14. When does hCG secretion take place? with what event?
Neuroectoderm
Day 6; with implantation
Failure of the urachus to obliterate
Yolk sac; 3rd week

15. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Pulm art (prox) and ductus arteriosus
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Medial palatine processes
Scrotum; labia majora

16. From what region does the midbrain form from?
Decidual basalis
Metencephalon; cerebellum
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Mesencephalon

17. What are the two components of the placenta? From What do they form? which one secreted hcG?
Endoderm
Cleft lip/palate
...
Upper 1/3; urogenital sinus

18. What does the midgut form? hindgut?
Neuroectoderm
Epispadias
A vitelline fistula - failure of vitelline duct to close
Duodenum to transverse colon; distal transverse colon to rectum

19. From What embryonic layer is the bladder and urethra from?
Amniotic cavity and yolk sac
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Mesoderm
Week 3; primitive streak formation from the epiblast makes the three layers

20. From What embryonic layer is aorticopulmonary septum from ?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Neural crest cells
3rd; proximal part of the internal carotid artery
Obliterated; forms tunica vaginalis

21. From What embryonic lare are the odontoblasts from?
...
Ampulla
Decreased pulmonary resistance in the pulmonary vasculature
Neural crest cells

22. What hormone is hcG structurally similar too?
Hemorrhage - bone deformities
LH
Week 4
Left horn of the sinus venosus

23. What teratogens can cause CN VIII toxicity in the fetus?
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Aminoglycosides
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

24. What axis does the basal plate form? what neural system does it become?
monoamniotic
Aortic arch and prox part of subclavian
Ventral ; motor
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont

25. failure to close of what fold results in sternal defects? omphalocele? gastrochisis? bladder extrosphy?
4th arch; 6th arch
Branchial arch 2
A vitelline fistula - failure of vitelline duct to close
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

26. In anencephaly you see...
Polyhydramnios
Neuroectoderm
elevated AFP
Stapedius and hyoid artery

27. From which germlayer does the thyroid develop?? From what structure exactly?
Mesoderm; epiblast
Failure of the urachus to obliterate; outpouching of the bladder
Excessive resorption of septum primum or secondum (or both)
Endoderm - floor of primitive pharynx

28. From where does the ureteric bud arise? What does it give rise to?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Neural crest cells
Respiratory distress syndrome
Maxillary

29. What is omphalocele? In What trisomies is it seen?
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
2; 1
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Right common cardinal vein and right anterior cardinal vein

30. From What embryonic layer do the parafollicular cells of the thyroid arise?
Endoderm
Neural crest cells
Right common cardinal vein and right anterior cardinal vein
Renal artery stenosis;

31. From What embryonic layer does the parathyroid arise ?
3 -4 -6
Endoderm
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
80%

32. What arises from the fourth aortic arch?
Rhombencephalon
Pataus; fetal alcohol syndrome
Renal artery stenosis;
Aortic arch (from left side); right subclavian (on the right)

33. 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?
Maxillary and medial nasal processes
Excessive resorption of septum primum or secondum (or both)
Umbilical - midgut herniates through umbilical ring; SMA
Mesoderm

34. What congenital abnormality forms a 'double bubble' on xray?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Annular pancrease
Fluid filled syrinx causes expansion and degeneration of cord tracts
Germinal matrix hemorrhage

35. From where did a branchial cleft cyst arise if it found?
Found in lateral neck; from no obliteration of 2-4th clefts
Endoderm
3rd pouch
Aortic arch (from left side); right subclavian (on the right)

36. From What embryonic layer are the schwann cells from ?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Neural crest cells
Allantois

37. What is holoprosencephaly? what eye disorder does it result in?
DES
Nutrient and gas exchange
Decreased separation of hemispheres across midline; cyclopia
Week 3-8

38. By when are the neuropores supposed to fuse?
secondary palate
blood entering the RA
4th week
ACE inhibitors - HCTZ

39. What is germinal matrix hemorrhage associated with?
Rhombencephalon
Respiratory distress syndrome
Mesoderm
Lacunae in between the chorionic villi

40. What happens in pancreas divisum? what results?
From endocardial cushions (ventral and dorsal meet each other)
Nutrient and gas for exchange; endometrium
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

41. What is a zygote?
Sperm plus egg
Germinal matrix hemorrhage
Indomethacin; blocks PG production
Thyroid - cricoid - arytenoids - corniculate cuneiform

42. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
DiGeorge
...
Prenatal and perinatal
Female; paramesonephric; mesonephric

43. what closes the ductus arteriousus?
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Week 3-8
Increase in oxygen concentration which decreases prostaglandin concentration
Neural plate; closes by week 4

44. From What embryonic layer do CNS neurons arise?
Neuroectoderm
blood entering the RA
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Endoderm

45. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
Truncus arteriosus; pulmonary trunk
Week 4
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Upper 1/3; urogenital sinus

46. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Week 2; bilaminar disk; epiblast and hypoblast
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Endoderm

47. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Valproate acid
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Neural plate; closes by week 4

48. What do the groove/clefts of the branchial apparatus correlate to?
Endometrium
Ectoderm
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Endoderm

49. From What embryonic layer does the lens of the eye arise?
Week 4; week 3
Synctiotrophoblast
Surface ectoderm
Thalidomide; nausea

50. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Upper 1/3; urogenital sinus
Oligohydramnios
XII
Hepatic circulation; ligamentum venosum