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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 is the allantois become? What is this duct connected to ( on both ends)?
V3; VII
Endoderm
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Urachus/median umbilical ligament; bladder and yolk sac

2. From What embryonic layer is the bladder and urethra from?
Polyhydramnios
Mesoderm
Endoderm
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

3. From What embryonic layer is the eustachian tube from?
Mesoderm
Before getting pregnant!
Mental retardation - holoprosencephaly - facial features - fistulas
3

4. From what region does the midbrain form from?
Valproate acid
Mesencephalon
Excessive resorption of septum primum or secondum (or both)
IMA

5. What is the defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Neural crest cells
Cytotrophoblast and synctiotrophoblast
Failure of bony spinal canal to fuse; no; lower vertebral levels
Mesonephros; male genital system

6. What artery is derived branchial (aortic) arch 1?
Maxillary
After; extrinsic
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Telencephalon

7. From What embryonic layer is the spleen from?
Neural crest cells
80%
Mesoderm
Tetracyclines

8. From What embryonic layer do chromaffin cells arise?
Fetal and maternal
Primitive atrium
Grooves/clefts; arches; pouches
Neural crest cells

9. what week do the genitalia start to have male/female characteristics? What trimester is that?
3rd; proximal part of the internal carotid artery
Week 2; bilaminar disk; epiblast and hypoblast
Week 10-12; end of 1st trimester
Muscles and arteries

10. From What embryonic layer does the retina arise?
Ampulla
Obliterated; forms tunica vaginalis
Duodenum to transverse colon; distal transverse colon to rectum
Neuroectoderm

11. What is used to keep the PDA open?
Decidual basalis
Amniotic cavity and yolk sac
Fetal and maternal
Prostaglandins

12. At what week does the fetus look like a baby?
Midgut; 10th week
Week 8
Obliterated; forms tunica vaginalis
Failure of the urachus to obliterate

13. Cleft lip is a failure of formation of the...
secondary palate
Upper 1/3; urogenital sinus
primary palate
80%

14. From where is the pancreas derived? the spleen?
Aminoglycosides
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Rhombencephalon
Foregut; dorsal mesentery (mesodermal)

15. What is the primitive streak? From what layer does it form?
Mesoderm; epiblast
Week 8
Endoderm - floor of primitive pharynx
Arnold chiari; syringomyelia

16. What germ layer correlates with the branchial pouches?
Rhombencephalon
Day 6; with implantation
Endoderm
Scrotum; labia majora

17. What causes a vesicourachal diverticulum? What is it?
6th aortic arch
Neuroectoderm
Failure of the urachus to obliterate; outpouching of the bladder
They are the edge of neural plate folding; all over the body

18. From What embryonic layer does the skin dermis arise?
Mesoderm
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
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
Renal artery stenosis;

19. What is an arnold chiari II malformation? through what hole does it herniate?
arnold chiari associated with thoraclumbar myelomeningocele
Cerebellar tonsillar herniation through foramen magnum
Myelencephalon
Midgut; 10th week

20. What is the notochord? What does the notochord later become?
28 week onward
Prostaglandins
Mesoderm; nucleous pulposos
Midgut; 10th week

21. From What embryonic layer is the vagina from? testes? ovaries?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Decreased pulmonary resistance in the pulmonary vasculature
Mesoderm

22. What causes the degeneration of the spinal cord in syringomelia?
Prenatal and perinatal
XII
Neural crest cells
Fluid filled syrinx causes expansion and degeneration of cord tracts

23. On what side is the abnormal opening in epispadias? What causes it?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Neuroectoderm
StyloPharyngeus
Dorsal; faulty positioning of genital tubercle

24. From What embryonic layer does the inner arise?
Right horn of the SV
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Neural crest cells
...

25. Before birth - blood entering the LA is less than...
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
blood entering the RA
Neuroectoderm

26. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Week 2; bilaminar disk; epiblast and hypoblast
Nicotine; preterm labor
Hypertrophy of muscularis externis of pylorus; surgical incision

27. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
3rd pouch
IX; X
Ampulla
Nicotine; preterm labor

28. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Failure to recanalize; 21
A vitelline fistula - failure of vitelline duct to close
Prosencephalon

29. From What embryonic layer does a craniopharygioma arise?
V3; VII
Surface ectoderm
2nd; 2nd
VSD

30. What part of the fetal comp of the placenta secretes hCG? is this part on the inner or outer layer of the chorionic villi? does it make cells?
2nd; 2nd
Week 10-12; end of 1st trimester
Ventral; failure of urogenital folds to close
Synctiotrophoblast; outer; no

31. what muscles are derived from branchial arch 1?
Week 3; primitive streak formation from the epiblast makes the three layers
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
Decreased separation of hemispheres across midline; cyclopia
Surface ectoderm

32. What does DHT turn the urogenital sinus into? estrogen?
Mesoderm
Fetal alcohol syndrome; mental retardation
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

33. In both meningocele and myelomeningocele the dura...
When left to right shunting switching to right to left shunting
Surface ectoderm
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
is no longer intact

34. From What embryonic layer does the sensory organs of the ear arise?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Week 4
Surface ectoderm
Increase in oxygen concentration which decreases prostaglandin concentration

35. is epispadias or hypospadias associated with exstrophy of the bladder?
Folate antagonists
Epispadias
Cytotrophoblast and synctiotrophoblast
Branchial arch 2

36. What are the neural crest cells and where do they come form? where do they go?
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
6-30
They are the edge of neural plate folding; all over the body
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

37. What teratogens can cause renal damage in the fetus?
Aminoglycosides
ACE inhibitors - HCTZ
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Hypospadias

38. What part of the vagina does the mullerian duct form? Where does the rest come from?
Tongue
Upper 1/3; urogenital sinus
No organ in each; agenesis no primordial tissue
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

39. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Amniotic epithelium
1st
Nutrient and gas exchange

40. The spleen is ____________ in origin and supplied by a foregut artery
Myelencephalon
mesodermal
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Valproate acid

41. What causes persistent Truncus Arteriosus? What does it result in?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Primitive ventricle
Apical ectodermal ridge
Turners; inferior

42. From What embryonic layer does connective tissue and muscle arise?
Increase in oxygen concentration which decreases prostaglandin concentration
Mesoderm
Hypertrophy of muscularis externis of pylorus; surgical incision
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus

43. What are the two components of the fetal component of the placenta?
Neural crest cells
Surface ectoderm
Cytotrophoblast and synctiotrophoblast
3rd pouch

44. What components do the mesoderm of the branchial arches give rise to?
Muscles and arteries
Common carotid and internal carotid
Cytotrophoblast and synctiotrophoblast
Failure of the urachus to obliterate; outpouching of the bladder

45. From What embryonic layer do the astrocytes arise?
Cytotrophoblast and synctiotrophoblast
Cerebellar tonsillar herniation through foramen magnum
Neuroectoderm
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

46. From What embryonic layer does bone arise ?
Neural crest cells
Mesoderm
Maxillary
No more umbilical circulation emptying into RA

47. What day is the amnion formed?
Neural crest migration - they then cause spiral
Increased AFP and acetycholinesterase (not ACh!) in CSF
8
Failure to recanalize; 21

48. what bone/cartilage and nerves are derived from branchial arch 1?
hypertrophy
Mesoderm
External auditory meatus
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

49. 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)
Decidual basalis
Neural plate; closes by week 4
Urachus/median umbilical ligament; bladder and yolk sac

50. What does the RET gene encode? what neoplasias is it associated with?
T neuroectoderm
Lots - cleft palate/lip
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Pataus; fetal alcohol syndrome