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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. From what region of the brain does the fourth ventricle form?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Rhombencephalon
5th
3

2. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Dorsal ventral axis
Oligohydramnios
Arnold chiari; syringomyelia
Dorsal and ventral buds

3. From What embryonic layer does the oligodendrocytes arise?
mesoderm
Neural crest cells
XII
Neuroectoderm

4. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Obliterated
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Week 4
All or none

5. When is most important to take folic acid to prevent neural tube defects?
Surface ectoderm
Before getting pregnant!
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Neuroectoderm

6. Which branchial apparatus develops into the thymus?
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
3rd pouch
Endoderm

7. From What embryonic layer does the lens of the eye arise?
They are the edge of neural plate folding; all over the body
Cerebellar tonsillar herniation through foramen magnum
Surface ectoderm
Found in lateral neck; from no obliteration of 2-4th clefts

8. From what region do the thalami form?
Temporary cervical sinus
Mesencephalon
Diencephalon
Persistent connection between amniotic cavity and spinal canal; low folic acid

9. From What embryonic layer is the bladder and urethra from?
Surface ectoderm
Mesoderm
Week 10-12; end of 1st trimester
Mid gut to yolk sac; omphalomesenteric duct; 7th week

10. What is the effect of teratogens before week 3?
All or none
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)
Surface ectoderm
elevated AFP

11. Septum primum (patent foramen oval) caused by excessive resorption of...
septum primum and/or secundum
Neuroectoderm
hypospadias
Prosencephalon

12. From where does the medulla form?
Myelencephalon
Dorsal; sensory
Surface ectoderm
Skewed development of AP septum

13. How does annular pancreas present in children?
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Mesoderm
Initial left to right shunting - then switches
Spinothalamic first

14. What is the memranous interventricular formaen made from?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII

15. what closes the interventricular foramen?
Physiologic incomplete muscular ventricular septum
Respiratory distress syndrome
Mesoderm
4th/5th branchial pouches

16. What is contained in the umbilical cord?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Yolk sac; 3rd week
Week 4
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus

17. How many umbilical arteries are there? How many umbilical veins?
Ectoderm
A vitelline fistula - failure of vitelline duct to close
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
2; 1

18. What is the notochord? What does the notochord later become?
Mesoderm; nucleous pulposos
Nicotine; preterm labor
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont

19. which tracts are damaged first in syringomelia? What tract is preserved?
Deformation
Spinothalamic first
Week 8
Increase in oxygen concentration which decreases prostaglandin concentration

20. What does the foramen ovale shunt blood from - to where? What is its remnant?
All or none
Left horn of the sinus venosus
From teh lung;blood from IVC in RA to LA; fossa ovalis
Mesoderm

21. Which branchial apparatus makes the external auditory meatus?
Mesoderm; 3 week
1st cleft/groove (Ectoderm)
Cytotrophoblast
lumbosacral

22. From What embryonic layer is the eustachian tube from?
blood entering the RA
Bone/cartilage and nerves
Oligohydramnios
Mesoderm

23. What is the initial step to interventricular septum development? is it complete?
Muscular ventricular septum; no
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
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
Mesoderm

24. From which germlayer does the thyroid develop?? From what structure exactly?
Turners; inferior
Muscular ventricular septum; no
Endoderm - floor of primitive pharynx
Embryonic period; 1st trimester

25. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Aortic arch and prox part of subclavian
Dorsal and ventral buds

26. From where does the prostate develop? seminal vesicles? fallopian tube? lower 2/3 of the vagina? ejaculatory duct? epididymis? uterus? upper 1/3 of the vagina?
Primitive ventricle
Increased AFP and acetycholinesterase (not ACh!) in CSF
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian

27. What can vit A in excess cause in the fetus?
Indomethacin; blocks PG production
Foregut; dorsal mesentery (mesodermal)
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Lots - cleft palate/lip

28. What is a syrinx? Where is it found in syringomelia? What is it associated with?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Sperm plus egg
Initial left to right shunting - then switches
Lithium

29. From What embryonic layer does a craniopharygioma arise?
Congenital and chromosomal abnormalities
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Surface ectoderm
not covered

30. The spinal cord is made from...
Synctiotrophoblast; outer; no
Neural crest cells
T neuroectoderm
Surface ectoderm

31. What teratogens can cause CN VIII toxicity in the fetus?
Neural crest cells
Embryonic period; 1st trimester
Aminoglycosides
hypertrophy

32. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
XII
Bulbos Cordis; right ventricle entirely
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

33. what separates the atria from the ventricles?
Neural crest cells
Endocardial cushions
Stapedius and hyoid artery
Week 8

34. Which arches form the posterior 1/3 of the tongue?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Branchial arch 2
Arches 3 and 4
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

35. From what region of the brain does the lateral ventricles and the 3rd ventricle form?
Mesdoerm
Maternally derived; meconium
Nutrient and gas exchange
Prosencephalon

36. From What embryonic layer do chromaffin cells arise?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Neural crest cells
Week 2; bilaminar disk; epiblast and hypoblast
Neuroectoderm

37. Blood coming in the umbilical vein is ____ saturated
Prosencephalon
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
80%
Upper 1/3; urogenital sinus

38. From where do the three different kidneys come from? Which is the earliest one? is it located most cranially or caudally?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Pronephros - mesonephros - metanephros; pronephros; most cranially
Yolk sac; 3rd week
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

39. Before birth - blood entering the LA is less than...
blood entering the RA
Endometrium
Dorsal; faulty positioning of genital tubercle
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

40. What causes persistent Truncus Arteriosus? What does it result in?
Common carotid and internal carotid
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Neural crest cells
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

41. What is annular pancreas associated with in infants?
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
mesodermal
V3; VII

42. What causes tetralogy of Fallot?
primary palate
Surface ectoderm
Skewed development of AP septum
IMA

43. What part of the gut rotates around the SMA? and At what point?
Failure of bony spinal canal to fuse; no; lower vertebral levels
Prostaglandins
Midgut; 10th week
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)

44. The spleen is ____________ in origin and supplied by a foregut artery
pyloric stenosis
mesodermal
Endoderm
Ionizing

45. what closes the ductus arteriousus?
Hypertrophy of muscularis externis of pylorus; surgical incision
Increase in oxygen concentration which decreases prostaglandin concentration
Week 4
Where the epiblast and hypoblast fuse

46. what muscles are derived from branchial arch 3?
6-30
Week 10-12; end of 1st trimester
StyloPharyngeus
3rd pouch

47. what muscles are derived from branchial arch 4? CN?
Pataus; fetal alcohol syndrome
Skewed development of AP septum
Right common cardinal vein and right anterior cardinal vein
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

48. failure to close of what fold results in sternal defects? omphalocele? gastrochisis? bladder extrosphy?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Fluid filled syrinx causes expansion and degeneration of cord tracts
Germinal matrix hemorrhage
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

49. What effect does warfarin have on the fetus?
monoamniotic
Failure of bony spinal canal to fuse; no; lower vertebral levels
Synctiotrophoblast; outer; no
Hemorrhage - bone deformities

50. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Ectoderm
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
...
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)