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USMLE Embryo

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Answer 50 questions in 15 minutes.
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1. Most myelomeningoceles present in the _______ region
Common carotid and internal carotid
Greater horn of hyoid; CN IX (styloPharyngeus)
lumbosacral
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

2. Before birth - blood entering the LA is less than...
blood entering the RA
Mesoderm
Skewed development of AP septum
Day 6; maintains corpus luteum; 1st trimester

3. What weeks are considered the 'embryonic period'?
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Bone/cartilage and nerves
Week 3-8
All 3

4. what invaginates to form the primitive streak?
4th pouch
Epiblast
Decidual basalis
Foregut; dorsal mesentery (mesodermal)

5. ______________ is associated with ventral curvature of the penis
hypospadias
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Increase in oxygen concentration which decreases prostaglandin concentration
Mesoderm

6. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Surface ectoderm
Scrotum; labia majora
Ventral; failure of urogenital folds to close
Vascular accident intra uterine; apple peel atresia

7. What is congenital pharyngocutaneous fistula? and How does it occur?
Tetracyclines
Right common cardinal vein and right anterior cardinal vein
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

8. which teratogen can cause Ebsteins anomaly in the fetus?
Neuroectoderm
Lithium
Maxillary
Truncus arteriosus; pulmonary trunk

9. What causes tetralogy of Fallot?
Stapedius and hyoid artery
Skewed development of AP septum
...
Day 6; with implantation

10. Cleft palate is a failure of formation of the...
Neural crest migration - they then cause spiral
monoamniotic
After; extrinsic
secondary palate

11. From What embryonic layer do CNS neurons arise?
Surface ectoderm
Neuroectoderm
Sonic Hedgehog
Week 4; week 3

12. From what region of the brain does the aqueduct form?
Scrotum; labia majora
Week 8
Rhombencephalon
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

13. What does the midgut form? hindgut?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Outgrowth of mesonephric as ureteric bud; most caudal
Duodenum to transverse colon; distal transverse colon to rectum
Obliterated; forms tunica vaginalis

14. What is the memranous interventricular formaen made from?
Endoderm
Skewed development of AP septum
Bones - cartilage - and nerves
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

15. What does the ductus venosus shunt blood away from? What is its remnant?
After; extrinsic
Hepatic circulation; ligamentum venosum
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Prosencephalon

16. From What embryonic layer are the schwann cells from ?
Surface ectoderm
Neural crest cells
Persistent connection between amniotic cavity and spinal canal; low folic acid
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

17. Where is the mothers blood located in the placenta?
Allantois
VACTERL; OCPs and maternal diabetes
Ebsteins anomaly; tricuspid atresia
Lacunae in between the chorionic villi

18. From What embryonic layer do the parafollicular cells of the thyroid arise?
Week 8
4th week
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)
Neural crest cells

19. what happens in hydrocele?
Mesoderm
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Tunica vaginalis not fully fused
Endoderm

20. What do the 2nd through 4th clefts of the branchial apparatus correlate to?
Deoxygenated blood; fetal internal iliac arteries to placenta
Mesoderm
Temporary cervical sinus
Absent cerebellar vermis; cystic enlargement of 4th ventricle

21. What is the homeobox gene responsible in developing? (What axis)
Cranio - caudal; segmental
Nutrient and gas for exchange; endometrium
Endoderm - floor of primitive pharynx
Week 3; primitive streak formation from the epiblast makes the three layers

22. From What embryonic layer do the astrocytes arise?
Neuroectoderm
Stapedius and hyoid artery
Prenatal and perinatal
Synctiotrophoblast

23. What artery is derived branchial (aortic) arch 3?
Dorsal; sensory
IMA
Common carotid and internal carotid
Endoderm - floor of primitive pharynx

24. What is perinauds syndrome?
lumbosacral
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Fallopian tube - uterus - upper 1/3 of vagina
Neuroectoderm

25. What are two common findings in pyloric stenosis?
Mental retardation - holoprosencephaly - facial features - fistulas
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Aortic arch (from left side); right subclavian (on the right)
No more umbilical circulation emptying into RA

26. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
DES
Surface ectoderm
External auditory meatus
Endoderm

27. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
From teh lung;blood from IVC in RA to LA; fossa ovalis
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Surface ectoderm
Day 6; with implantation

28. What three components make up the branchial/pharyngeal apparatus?
Grooves/clefts; arches; pouches
Duodenum to transverse colon; distal transverse colon to rectum
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
Maxillary and medial nasal processes

29. How do adults with annular pancreas present? and At What age?
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Polyhydramnios
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Decreased separation of hemispheres across midline; cyclopia

30. What causes the degeneration of the spinal cord in syringomelia?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Surface ectoderm
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Pulm art (prox) and ductus arteriosus

31. Only _______________________________ are associated with neural tube defects
arnold chiari associated with thoraclumbar myelomeningocele
When left to right shunting switching to right to left shunting
Post. sup wall; luteal phase
hypertrophy

32. What separates the ant 1/3 and post 2/3 of tongue?
Hemorrhage - bone deformities
Medial palatine processes
Branchial arch 2
Foramen cecum and terminal sulus

33. what closes the ductus arteriousus?
Neural crest cells
Increase in oxygen concentration which decreases prostaglandin concentration
Mesoderm; nucleous pulposos
Ventral shaft of penis (penile urethra); labia minora

34. What is the primitive streak? From what layer does it form?
Mesoderm; epiblast
Stapedius and hyoid artery
OCPS and maternal diabetes
Week 2; bilaminar disk; epiblast and hypoblast

35. What is meckel's diverticulum? What is it associated with? What does that cause?
Foramen cecum and terminal sulus
4th/5th branchial pouches
Mesoderm
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

36. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
1st cleft/groove (Ectoderm)
Aortic arch and prox part of subclavian
V3; VII
Mesoderm

37. During what week do the limbs begin to form?
Cerebral hemisphere - thalami
Neural plate; closes by week 4
Week 2; bilaminar disk; epiblast and hypoblast
Week 4

38. From where does the pulmonary arteries and the ductus arteriosus arise?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
6th aortic arch
ACE inhibitors - HCTZ
Tunica vaginalis not fully fused

39. what bone/cartilage are derived from branchial arch 4-6?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Neural crest cells
Thyroid - cricoid - arytenoids - corniculate cuneiform
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)

40. Weeks _______ erythropoiesis takes place in the liver
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Medial palatine processes
6-30
can make cells

41. From What embryonic layer does the brain arise?
Sonic Hedgehog
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Neuroectoderm
Increased AFP and acetycholinesterase (not ACh!) in CSF

42. What do the groove/clefts of the branchial apparatus correlate to?
Endoderm
Week 3-8
Neuroectoderm
Ectoderm

43. 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
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Epispadias
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)

44. What axis does the basal plate form? what neural system does it become?
Branchial arch 2
Fetal and maternal
...
Ventral ; motor

45. From where do the three different kidneys come from? Which is the earliest one? is it located most cranially or caudally?
Occiptal
Endoderm
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Pronephros - mesonephros - metanephros; pronephros; most cranially

46. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Excessive resorption of septum primum or secondum (or both)
...
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
pyloric stenosis

47. By what week is there fetal movement?
Week 8
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Failure of the urachus to obliterate
Muscular ventricular septum; no

48. what results if they dont? What can increase the risks of this?
IX; X
28 week onward
Failure of bony spinal canal to fuse; no; lower vertebral levels
Persistent connection between amniotic cavity and spinal canal; low folic acid

49. what else is the caudal regression known as? What two teratogen can cause this in the fetus?
Neural crest cells
VACTERL; OCPs and maternal diabetes
Endoderm
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus

50. what closes the interventricular foramen?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
5th
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Physiologic incomplete muscular ventricular septum

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USMLE Embryo

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