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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. When does the notochord form? and When does the neural plate form?
3rd pouch
Mesoderm; 3 week
Tetracyclines
can make cells

2. Only _______________________________ are associated with neural tube defects
Ventral ; motor
arnold chiari associated with thoraclumbar myelomeningocele
OCPS and maternal diabetes
Hypospadias

3. What weeks are considered the 'embryonic period'?
IX; X
Week 3-8
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Medial palatine processes

4. what else is the caudal regression known as? What two teratogen can cause this in the fetus?
VACTERL; OCPs and maternal diabetes
mesodermal
Increased AFP and acetycholinesterase (not ACh!) in CSF
Where the epiblast and hypoblast fuse

5. What arises from the fourth aortic arch?
Prosencephalon
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
6-30
Aortic arch (from left side); right subclavian (on the right)

6. What effect does warfarin have on the fetus?
Hemorrhage - bone deformities
Apical ectodermal ridge
Neural crest migration - they then cause spiral
6-30

7. In both meningocele and myelomeningocele the dura...
DiGeorge
Deformation
Umbilical - midgut herniates through umbilical ring; SMA
is no longer intact

8. The inner layer of the chorionic villi...
can make cells
From teh lung;blood from IVC in RA to LA; fossa ovalis
Surface ectoderm
Endoderm

9. What trisomy is associated with holoprosencephaly? What teratogen?
Surface ectoderm
Upper 1/3; urogenital sinus
Pataus; fetal alcohol syndrome
Mesoderm; 3 week

10. What day is the chorion formed?
6-30
3
Mesoderm
Surface ectoderm

11. How do AV canals form?
Cytotrophoblast and synctiotrophoblast
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
From endocardial cushions (ventral and dorsal meet each other)
Surface ectoderm

12. From What embryonic layer does the skin dermis arise?
Mesoderm
Rhombencephalon
Endoderm
Mesdoerm

13. What embryological structure gives rise to the coronary sinus?
Neural crest cells
Left horn of the sinus venosus
Lots - cleft palate/lip
Temporary cervical sinus

14. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Neuroectoderm
During; instrinsic
DiGeorge

15. What part of the vagina does the mullerian duct form? Where does the rest come from?
Neural crest cells
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Upper 1/3; urogenital sinus
Mesoderm; epiblast

16. To what germ layer does the branchial pouches correlate to?
Spinothalamic first
Week 10-12; end of 1st trimester
Endoderm
...

17. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
Lithium
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
8
Base of limbs in the zone of polarizing activity; ant - post

18. What axis does the alar plate form? what neural system does it become?
Rhombencephalon
Base of limbs in the zone of polarizing activity; ant - post
Dorsal; sensory
3 -4 -6

19. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Endoderm
Oligohydramnios
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
2nd pouch

20. what muscles are derived from branchial arch 2?
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
LH
Polyhydramnios
Cytotrophoblast and synctiotrophoblast

21. what bone/cartilage and nerves are derived from branchial arch 1?
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Nutrient and gas for exchange; endometrium
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Vascular accident intra uterine; apple peel atresia

22. What is the female remnant of the gubernaculum? male remnant?
Surface ectoderm
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Muscular ventricular septum; no
From endocardial cushions (ventral and dorsal meet each other)

23. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
V3; VII
Mesoderm
elevated AFP
Endoderm

24. What part of the gut rotates around the SMA? and At what point?
Embryonic period; 1st trimester
4th arch; 6th arch
Midgut; 10th week
Congenital and chromosomal abnormalities

25. What does the foramen ovale shunt blood from - to where? What is its remnant?
Germinal matrix hemorrhage
From teh lung;blood from IVC in RA to LA; fossa ovalis
Hemorrhage - bone deformities
Neuroectoderm

26. From What embryonic layer does the retina arise?
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Neural crest cells
Increased AFP and acetycholinesterase (not ACh!) in CSF
Neuroectoderm

27. What is associated with only one umbilical artery?
3 -4 -6
Germinal matrix hemorrhage
Congenital and chromosomal abnormalities
Obliterated

28. From What embryonic layer does the parathyroid arise ?
not covered
Allantois
Tunica vaginalis not fully fused
Endoderm

29. From What embryonic layer does the thyroid follicular cells arise?
Renal artery stenosis;
Endoderm
Week 4; week 3
Failure of the urachus to obliterate; outpouching of the bladder

30. Most myelomeningoceles present in the _______ region
lumbosacral
Vascular accident intra uterine; apple peel atresia
3rd and 4th arches
Muscles and arteries

31. By when are the neuropores supposed to fuse?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
DHT; estrogen
4th week
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

32. During what week does the heart begin to beat?
Neural plate; closes by week 4
Initial left to right shunting - then switches
Week 3; primitive streak formation from the epiblast makes the three layers
Week 4

33. What is the female remnant of processus vaginalis? male remnant?
Obliterated; forms tunica vaginalis
Hypospadias
First branchial pouch
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

34. Weeks _______ erythropoiesis takes place in the liver
Allantois
Nutrient and gas for exchange; endometrium
Day 6; with implantation
6-30

35. Where is the mothers blood located in the placenta?
mesoderm
Lacunae in between the chorionic villi
28 week onward
Ectoderm; endoderm

36. From what does bicornuate uterus arise? What is it associated with?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
4th pouch
Dorsal; faulty positioning of genital tubercle
Cytotrophoblast

37. What are the three regions of the brain (in order of cranial to caudal)?
Prosencephalon - mesencephalon - rhombencephalon
Failure of the urachus to obliterate; outpouching of the bladder
Week 8
Decreased separation of hemispheres across midline; cyclopia

38. From What embryonic layer do the parafollicular cells of the thyroid arise?
80%
Midgut; 10th week
8
Neural crest cells

39. which tracts are damaged first in syringomelia? What tract is preserved?
All 3
Stapedius and hyoid artery
Spinothalamic first
Week 4; week 3

40. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Left horn of the sinus venosus
Cleft lip/palate
Increased AFP and acetycholinesterase (not ACh!) in CSF
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

41. what results if they dont? What can increase the risks of this?
Hepatic circulation; ligamentum venosum
Persistent connection between amniotic cavity and spinal canal; low folic acid
A vitelline fistula - failure of vitelline duct to close
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

42. From where is amniotic fluid produced? other than electrolytes and carbs - what else does it contain?
4th arch; 6th arch
Dorsal ventral axis
Cerebellar tonsillar herniation through foramen magnum
Maternally derived; meconium

43. What causes the obstruction in pyloric stenosis? treatment?
Fetal and maternal
Mesoderm; epiblast
not covered
Hypertrophy of muscularis externis of pylorus; surgical incision

44. what muscles are derived from branchial arch 1?
Mesoderm
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
Lots - cleft palate/lip
Right horn of the SV

45. From What embryonic layer does the epidermis arise?
Renal artery stenosis;
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Surface ectoderm
Week 2; bilaminar disk; epiblast and hypoblast

46. What gene is produced in the zone of polarizing activity?
Annular pancrease
Hypospadias
mesodermal
Sonic Hedgehog

47. What causes persistent Truncus Arteriosus? What does it result in?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Medial palatine processes
Physiologic incomplete muscular ventricular septum
Week 8

48. What surrounds the umbilical cord?
2nd pouch
3 -4 -6
Amniotic epithelium
Duodenum to transverse colon; distal transverse colon to rectum

49. What does the ductus venosus shunt blood away from? What is its remnant?
Allantois
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Hepatic circulation; ligamentum venosum
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)

50. What are the neural crest cells and where do they come form? where do they go?
4th week
Mesoderm
Ventral shaft of penis (penile urethra); labia minora
They are the edge of neural plate folding; all over the body