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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 muscles are derived from branchial arch 2?
Common carotid and internal carotid
1st cleft/groove (Ectoderm)
Endoderm
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric

2. 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?
No organ in each; agenesis no primordial tissue
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Prevent recurrent UTIs
Synctiotrophoblast; outer; no

3. From What embryonic layer does connective tissue and muscle arise?
Mesoderm
Ebsteins anomaly; tricuspid atresia
Increase in oxygen concentration which decreases prostaglandin concentration
Endoderm

4. From What embryonic layer does the sensory organs of the ear arise?
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Decidual basalis
Surface ectoderm
Primitive atrium

5. On what side is the abnormal opening in epispadias? What causes it?
Dorsal; faulty positioning of genital tubercle
DiGeorge
Cranio - caudal; segmental
Nutrient and gas exchange

6. what closes the interventricular foramen?
Physiologic incomplete muscular ventricular septum
Respiratory distress syndrome
primary palate
Female; paramesonephric; mesonephric

7. What is the memranous interventricular formaen made from?
Pronephros - mesonephros - metanephros; pronephros; most cranially
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Ampulla
Maternally derived; meconium

8. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Neural crest cells
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Respiratory distress syndrome

9. What is the initial step to interventricular septum development? is it complete?
Week 3; primitive streak formation from the epiblast makes the three layers
Muscular ventricular septum; no
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Surface ectoderm

10. what bone/cartilage and nerves are derived from branchial arch 2?
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Failure of the urachus to obliterate
Metencephalon; cerebellum
Neural crest cells

11. At what week does the fetus look like a baby?
Obliterated
Hemorrhage - bone deformities
Week 8
Failure of the urachus to obliterate; outpouching of the bladder

12. Where does the blastocyst implant in the uterus? During what phase of the menstrual cycle?
Post. sup wall; luteal phase
Ionizing
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
...

13. What is an arnold chiari II malformation? through what hole does it herniate?
Fetal alcohol syndrome; mental retardation
Wolffian; mullerian
Cerebellar tonsillar herniation through foramen magnum
Urachus/median umbilical ligament; bladder and yolk sac

14. What causes tetralogy of Fallot?
Skewed development of AP septum
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Week 8
Mesoderm

15. What artery is derived branchial (aortic) arch 6?
Mesoderm
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Neural crest cells
Pulm art (prox) and ductus arteriosus

16. When does erythropoeisis begin in the bone marow?
DES
Neural crest cells
28 week onward
Endoderm

17. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
pyloric stenosis
Valproate acid
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
A vitelline fistula - failure of vitelline duct to close

18. In anencephaly you see...
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Base of limbs in the zone of polarizing activity; ant - post
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
elevated AFP

19. What germ layer correlates with the branchial pouches?
Endoderm
Duodenum to transverse colon; distal transverse colon to rectum
Prosencephalon - mesencephalon - rhombencephalon
...

20. _____________is common in 1st born males
Cleft lip/palate
pyloric stenosis
Aortic arch and prox part of subclavian
LH

21. what separates the atria from the ventricles?
No more umbilical circulation emptying into RA
DiGeorge
Tetracyclines
Endocardial cushions

22. From What embryonic layer does the spinal cord arise?
Umbilical - midgut herniates through umbilical ring; SMA
secondary palate
Cytotrophoblast and synctiotrophoblast
Neuroectoderm

23. How does annular pancreas present in children?
Mesdoerm
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Thickened ectoderm at end of each developing limb
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects

24. What is the primitive streak? From what layer does it form?
Membrane - all 3 from 1st appartus
8
Mesoderm; epiblast
From teh lung;blood from IVC in RA to LA; fossa ovalis

25. From what region of the brain does the aqueduct form?
Initial left to right shunting - then switches
Rhombencephalon
Greater horn of hyoid; CN IX (styloPharyngeus)
hypospadias

26. What is the female remnant of processus vaginalis? male remnant?
Cerebellar tonsillar herniation through foramen magnum
Dorsal; sensory
Obliterated; forms tunica vaginalis
Surface ectoderm

27. what bone/cartilage and nerves are derived from branchial arch 1?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Germinal matrix hemorrhage
lumbosacral

28. What artery is derived branchial (aortic) arch 3?
Week 3; primitive streak formation from the epiblast makes the three layers
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Common carotid and internal carotid
Neuroectoderm

29. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Spinothalamic first
Surface ectoderm
3rd; proximal part of the internal carotid artery
Hemorrhage - bone deformities

30. what drug is used to help close a PDA? what else does this drug treat?
Indomethacin; blocks PG production
Upper 1/3; urogenital sinus
Prostaglandins
Failure of the urachus to obliterate

31. What causes the decrease in Right atrial pressure to close the fossa ovale?
Endoderm
hypospadias
No more umbilical circulation emptying into RA
...

32. Where is erythropoeisis in the weeks 3-8 of fetal development? Where does it occur after that? until when?
...
They are the edge of neural plate folding; all over the body
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

33. What embryological structure gives rise to the smooth part of the right atrium?
Primitive atrium
2; 1
Right horn of the SV
Neural crest cells

34. From What embryonic layer does the pineal gland arise?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Ventral bud
Neuroectoderm
Aminoglycosides

35. During what periods do the damages that cerebral palsy causes occur?
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Surface ectoderm
Prenatal and perinatal
5th

36. What teratogens can cause discolored teeth?
Tetracyclines
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
hypertrophy
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

37. Before birth - blood entering the LA is less than...
6th aortic arch
Week 2; bilaminar disk; epiblast and hypoblast
2nd pouch
blood entering the RA

38. Which branchial derivative accounts for the sensation and taste in the posterior 2/3 of the tongue? how about the very back?
Synctiotrophoblast
4th arch; 6th arch
5th
From teh lung;blood from IVC in RA to LA; fossa ovalis

39. Which branchial arch derivative is obliterated?
5th
Pataus; fetal alcohol syndrome
Membrane - all 3 from 1st appartus
Mesonephros; male genital system

40. When does organogenesis occur?
Week 3-8
2nd; 2nd
Temporary cervical sinus
Mesencephalon

41. How many umbilical arteries are there? How many umbilical veins?
DiGeorge
hypospadias
mesoderm
2; 1

42. What is the notochord? What does the notochord later become?
Mesoderm; nucleous pulposos
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
Common carotid and internal carotid
Right horn of the SV

43. How is amniontic fluid excreted? How is amniotic fluid resorped?
Arches 3 and 4
secondary palate
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Greater horn of hyoid; CN IX (styloPharyngeus)

44. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
Mesoderm
Temporary cervical sinus
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
not covered

45. From What embryonic layer does the lens of the eye arise?
Increase in oxygen concentration which decreases prostaglandin concentration
Scrotum; labia majora
Upper 1/3; urogenital sinus
Surface ectoderm

46. What causes urine discharge from the umbilicus?
3rd pouch
Right horn of the SV
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Failure of the urachus to obliterate

47. Which CN allows for taste and sensation in the posterior 1/3 of the tongue? how about the very back ?
Neural crest cells
Diencephalon
IX; X
T neuroectoderm

48. From where does the pulmonary arteries and the ductus arteriosus arise?
blood entering the RA
1st
Dorsal and ventral buds
6th aortic arch

49. What is perinauds syndrome?
Increase in oxygen concentration which decreases prostaglandin concentration
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Mesoderm
Endoderm

50. What causes a patent foramen ovale?
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Excessive resorption of septum primum or secondum (or both)
Endoderm
Congenital and chromosomal abnormalities