Test your basic knowledge |

USMLE Embryo

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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 role does the placenta have?
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
1st
Nutrient and gas exchange
Cytotrophoblast and synctiotrophoblast

2. What happens in pancreas divisum? what results?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Surface ectoderm
4th arch; 6th arch

3. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Valproate acid
Neural crest cells
Week 10-12; end of 1st trimester
Mesoderm

4. What two cavities also form during the second week?
Amniotic cavity and yolk sac
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Maxillary
Rhombencephalon

5. What is the most common autopsy finding in brains of premature infants?
Germinal matrix hemorrhage
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
From endocardial cushions (ventral and dorsal meet each other)
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

6. From what branchial derivative do the parafollicular cells arise?
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Week 8
4th/5th branchial pouches
Base of limbs in the zone of polarizing activity; ant - post

7. what junction is the last to canalize? what implications does this have down the line?
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
3rd pouch
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Absent cerebellar vermis; cystic enlargement of 4th ventricle

8. From What embryonic layer do the ANS arise?
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Neural crest cells
Lithium
Neural plate; closes by week 4

9. From What embryonic layer is the bladder and urethra from?
Valproate acid
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Mesoderm
secondary palate

10. What causes the degeneration of the spinal cord in syringomelia?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Increase in oxygen concentration which decreases prostaglandin concentration
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
IX; X

11. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
Arnold chiari; syringomyelia
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Pronephros - mesonephros - metanephros; pronephros; most cranially
Outgrowth of mesonephric as ureteric bud; most caudal

12. What causes a patent foramen ovale?
Umbilical - midgut herniates through umbilical ring; SMA
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Excessive resorption of septum primum or secondum (or both)
Ampulla

13. From what arches are the neural crest cells that form the aorticpulmonary septum derived?
3 -4 -6
Deoxygenated blood; fetal internal iliac arteries to placenta
VACTERL; OCPs and maternal diabetes
Neural crest cells

14. From where is the allantois formed? During what week?
Neural crest migration - they then cause spiral
Oligohydramnios
Yolk sac; 3rd week
Mesencephalon

15. What embryological structure gives rise to the smooth part of the right atrium?
Right common cardinal vein and right anterior cardinal vein
First branchial pouch
Right horn of the SV
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

16. What do the arches of the branchial apparatus correlate to?
Sperm plus egg
is no longer intact
Mesdoerm
Mesoderm; nucleous pulposos

17. By what week is the neural tube supposed to be closed? when did it start forming?
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
Week 4; week 3
Surface ectoderm
DHT; estrogen

18. The inner layer of the chorionic villi...
Week 3-8
Alkylating agents
can make cells
Excessive resorption of septum primum or secondum (or both)

19. What are the aspects of fetal alcohol syndrome?
Day 6; with implantation
Occiptal
3rd pouch
Mental retardation - holoprosencephaly - facial features - fistulas

20. What is the allantois become? What is this duct connected to ( on both ends)?
Urachus/median umbilical ligament; bladder and yolk sac
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Female; paramesonephric; mesonephric
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects

21. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
Day 6; with implantation
4th/5th branchial pouches
Neural crest cells
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

22. What does the RET gene encode? what neoplasias is it associated with?
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Branchial arch 2
They are the edge of neural plate folding; all over the body
Endoderm

23. Which branchial derivative accounts for the posterior 2/3 of the tongue?
All or none
3rd and 4th arches
Mesoderm; epiblast
6th aortic arch

24. From What embryonic layer does the sensory organs of the ear arise?
Decidual basalis
Surface ectoderm
Mesoderm
Persistent connection between amniotic cavity and spinal canal; low folic acid

25. What is perinauds syndrome?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
XII
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Failure of bony spinal canal to fuse; no; lower vertebral levels

26. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Ectoderm
hypertrophy
Metencephalon; cerebellum
3rd; proximal part of the internal carotid artery

27. What are the three results of having pathology in the aorticopulmonary septum?
Week 10-12; end of 1st trimester
Folate antagonists
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)
Sperm plus egg

28. What part of the gut rotates around the SMA? and At what point?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Stapedius and hyoid artery
Midgut; 10th week

29. What is DiGeorge syndrome and What does it result in?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Persistent connection between amniotic cavity and spinal canal; low folic acid
Left horn of the sinus venosus
Fetal alcohol syndrome; mental retardation

30. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
Mesoderm
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Neural crest migration - they then cause spiral
is no longer intact

31. Where is the mothers blood located in the placenta?
Bones - cartilage - and nerves
Lacunae in between the chorionic villi
3rd and 4th arches
VSD

32. What is the mcc of renovascular hypertension in children? What does this predispose to?
Neural plate; closes by week 4
From teh lung;blood from IVC in RA to LA; fossa ovalis
Renal artery stenosis;
No more umbilical circulation emptying into RA

33. What does DHT turn the urogenital sinus into? estrogen?
Endoderm
Amniotic cavity and yolk sac
Nicotine; preterm labor
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

34. What embryologic structure provides the aorticpulmonary septum?
Neural crest migration - they then cause spiral
blood entering the RA
mesoderm
Primitive ventricle

35. What is the 'fetal period'- ie When is it?
Outgrowth of mesonephric as ureteric bud; most caudal
Week 8
Endoderm
Primitive atrium

36. Name a syndrome cleft palate is often seen in
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
DiGeorge
Endoderm

37. What is the kidney that functions at the interim kidney in the 1st trimester? What does it later contribute to?
Umbilical - midgut herniates through umbilical ring; SMA
Mesonephros; male genital system
Tetracyclines
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

38. Where is the FGF gene produced? What is it responsible for - How does it do this?
Oxygenated; placenta to fetus (IVC)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Ectoderm

39. What does the first branchial pouch create?
Neuroectoderm
Greater horn of hyoid; CN IX (styloPharyngeus)
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Post. sup wall; luteal phase

40. Cleft lip is a failure of fusion of ________ and ______.
Maxillary and medial nasal processes
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Amniotic cavity and yolk sac
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

41. What is the difference between agenesis and aplasia?
Cranio - caudal; segmental
Synctiotrophoblast; outer; no
Excessive resorption of septum primum or secondum (or both)
No organ in each; agenesis no primordial tissue

42. What artery is derived branchial (aortic) arch 4?
Aortic arch and prox part of subclavian
Neuroectoderm
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Stapedius and hyoid artery

43. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
is no longer intact
Rhombencephalon
Neural crest cells
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

44. Which branchial apparatus makes the external auditory meatus?
All 3
Initial left to right shunting - then switches
4th arch; 6th arch
1st cleft/groove (Ectoderm)

45. Where is Wnt 7 gene produced?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Folate antagonists
Base of limbs in the zone of polarizing activity; ant - post
Apical ectodermal ridge

46. what muscles are derived from branchial arch 4? CN?
Failure of the urachus to obliterate; outpouching of the bladder
Mesoderm
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Neural crest cells

47. From What embryonic layer does connective tissue and muscle arise?
Mesoderm
Prosencephalon
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Week 2; bilaminar disk; epiblast and hypoblast

48. What is the prochordal plate?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Telencephalon
Where the epiblast and hypoblast fuse
Dorsal ventral axis

49. From where does pons form from? what else forms from there?
Metencephalon; cerebellum
Cytotrophoblast
Ectoderm
not covered

50. When does organogenesis occur?
Obliterated
Allantois
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Week 3-8