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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. Which branchial apparatus develops into the thymus?
3rd pouch
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
First branchial pouch
Hepatic circulation; ligamentum venosum

2. Which branchial apparatus makes the external auditory meatus?
From endocardial cushions (ventral and dorsal meet each other)
2; 1
lumbosacral
1st cleft/groove (Ectoderm)

3. From What embryonic layer are the melanocytes from?
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Fetal alcohol syndrome; mental retardation
3rd; proximal part of the internal carotid artery
Neural crest cells

4. From what region do the thalami form?
Embryonic period; 1st trimester
not covered
Diencephalon
Mesencephalon

5. What causes meconium discharge from the umbilicus?
Tunica vaginalis not fully fused
Ventral ; motor
Week 8
A vitelline fistula - failure of vitelline duct to close

6. What results in annular pancreas? How does it happen?
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Mesoderm
Endoderm - floor of primitive pharynx
Ionizing

7. From What embryonic layer is the kidney and the adrenal cortex from?
Mesoderm
Renal artery stenosis;
Maxillary and medial nasal processes
Neuroectoderm

8. failure to close of what fold results in sternal defects? omphalocele? gastrochisis? bladder extrosphy?
Aminoglycosides
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

9. what separates the atria from the ventricles?
Mental retardation - holoprosencephaly - facial features - fistulas
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Endocardial cushions
Week 3-8

10. What causes the decrease in Right atrial pressure to close the fossa ovale?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
No more umbilical circulation emptying into RA
6th aortic arch
Thyroid - cricoid - arytenoids - corniculate cuneiform

11. The notochord is...
Mesoderm
mesoderm
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
secondary palate

12. Which branchial derivative accounts for the sensation and taste in the posterior 2/3 of the tongue? how about the very back?
Neuroectoderm
Ectoderm; endoderm
4th arch; 6th arch
Surface ectoderm

13. Where does fertilization occur?
Neural crest cells
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Neural crest cells
Ampulla

14. What is the Eisenmeger complex?
Persistent connection between amniotic cavity and spinal canal; low folic acid
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
When left to right shunting switching to right to left shunting
Neural crest cells

15. By what week is the neural tube supposed to be closed? when did it start forming?
septum primum and/or secundum
Annular pancrease
All 3
Week 4; week 3

16. From What embryonic layer do the ANS arise?
Turners; inferior
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Surface ectoderm
Neural crest cells

17. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
Neuroectoderm
Neural crest cells
Female; paramesonephric; mesonephric
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

18. When does erythropoeisis begin in the bone marow?
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
28 week onward
4th/5th branchial pouches

19. What gene is produced in the zone of polarizing activity?
Neuroectoderm
Sonic Hedgehog
Thickened ectoderm at end of each developing limb
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

20. What is annular pancreas associated with in infants?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Thalidomide; nausea
Fetal alcohol syndrome; mental retardation
not covered

21. Where is the FGF gene produced? What is it responsible for - How does it do this?
Outgrowth of mesonephric as ureteric bud; most caudal
Sperm plus egg
Neuroectoderm
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

22. Where is the most common ectopic thyroid tissue?
Tongue
Vascular accident intra uterine; apple peel atresia
Day 6; with implantation
hypertrophy

23. which teratogen can cause Ebsteins anomaly in the fetus?
Endoderm - floor of primitive pharynx
T neuroectoderm
6th aortic arch
Lithium

24. What artery is derived branchial (aortic) arch 2?
Stapedius and hyoid artery
Left horn of the sinus venosus
Foramen cecum and terminal sulus
Ampulla

25. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
Where the epiblast and hypoblast fuse
Nutrient and gas exchange
Persistent connection between amniotic cavity and spinal canal; low folic acid
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

26. From What embryonic layer is the vagina from? testes? ovaries?
Mesoderm
Renal artery stenosis;
First branchial pouch
Failure to recanalize; 21

27. What embryological structure gives rise to the coronary sinus?
Polyhydramnios
...
Arches 3 and 4
Left horn of the sinus venosus

28. What layer is the epiblast? hypoblast?
Pulm art (prox) and ductus arteriosus
Ectoderm; endoderm
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Neuroectoderm

29. What does the midgut form? hindgut?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Duodenum to transverse colon; distal transverse colon to rectum

30. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
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
Neural crest cells
DiGeorge
Incomplete; yes

31. From where does the ureteric bud arise? What does it give rise to?
3rd pouch
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Mesoderm; 3 week
2nd; 2nd

32. what invaginates to form the primitive streak?
monoamniotic
Epiblast
Maxillary
During; instrinsic

33. what drug is used to help close a PDA? what else does this drug treat?
Surface ectoderm
Indomethacin; blocks PG production
Neural crest migration - they then cause spiral
Endoderm

34. Blood coming in the umbilical vein is ____ saturated
80%
OCPS and maternal diabetes
Decreased pulmonary resistance in the pulmonary vasculature
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

35. When does hCG secretion take place? with what event?
Epispadias
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Day 6; with implantation
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

36. What day is the chorion formed?
Hypospadias
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
Myelencephalon
3

37. Septum primum (patent foramen oval) caused by excessive resorption of...
Fetal and maternal
Embryonic period; 1st trimester
Neuroectoderm
septum primum and/or secundum

38. is epispadias or hypospadias associated with exstrophy of the bladder?
Epispadias
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Arches 3 and 4
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

39. What teratogens can cause CN VIII toxicity in the fetus?
can make cells
Amniotic epithelium
Neural plate; closes by week 4
Aminoglycosides

40. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
Endoderm
Lots - cleft palate/lip
Dorsal; faulty positioning of genital tubercle
During; instrinsic

41. In what chromosomal disorder is horseshoe kidney commonly seen? what poles of the kidneys fuse?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Prenatal and perinatal
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Turners; inferior

42. What causes a vesicourachal diverticulum? What is it?
Neural crest cells
Failure of the urachus to obliterate; outpouching of the bladder
Endoderm
Ampulla

43. 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?
Synctiotrophoblast; outer; no
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Deoxygenated blood; fetal internal iliac arteries to placenta
Ventral bud

44. What weeks are considered the 'embryonic period'?
Week 3-8
Arches 3 and 4
Incomplete; yes
Outgrowth of mesonephric as ureteric bud; most caudal

45. During what week does the heart begin to beat?
Spinothalamic first
Week 4
2; 1
External auditory meatus

46. What is a syrinx? Where is it found in syringomelia? What is it associated with?
Pataus; fetal alcohol syndrome
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Endometrium
...

47. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Deformation
Surface ectoderm
3rd; proximal part of the internal carotid artery
1st cleft/groove (Ectoderm)

48. From where does the pulmonary arteries and the ductus arteriosus arise?
Truncus arteriosus; pulmonary trunk
Bones - cartilage - and nerves
elevated AFP
6th aortic arch

49. From What embryonic layer does a craniopharygioma arise?
Incomplete; yes
LH
primary palate
Surface ectoderm

50. From where is amniotic fluid produced? other than electrolytes and carbs - what else does it contain?
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Neural crest cells
OCPS and maternal diabetes
Maternally derived; meconium