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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 defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Failure of bony spinal canal to fuse; no; lower vertebral levels
When left to right shunting switching to right to left shunting
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
DiGeorge

2. Which part of the chorionic villi can make cells?
3rd and 4th arches
Cytotrophoblast
Mesoderm; nucleous pulposos
Before getting pregnant!

3. From What embryonic layer does the adenohypophysis arise?
Day 6; maintains corpus luteum; 1st trimester
Decidual basalis
Surface ectoderm
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

4. What is an arnold chiari II malformation? through what hole does it herniate?
Arnold chiari; syringomyelia
Cerebellar tonsillar herniation through foramen magnum
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
StyloPharyngeus

5. Where is the apical ectodermal ridge?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Cranio - caudal; segmental
Cerebellar tonsillar herniation through foramen magnum
Thickened ectoderm at end of each developing limb

6. From What embryonic layer is aorticopulmonary septum from ?
4th arch; 6th arch
Neural crest cells
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Metencephalon; cerebellum

7. What axis does the basal plate form? what neural system does it become?
Ectoderm; endoderm
Ventral ; motor
Telencephalon
Diencephalon

8. ______________ is associated with ventral curvature of the penis
hypospadias
Respiratory distress syndrome
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
monoamniotic

9. What is the effect of teratogens after week 8?
Deformation
Increase in oxygen concentration which decreases prostaglandin concentration
...
Mesoderm

10. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
Dorsal and ventral buds
monoamniotic
Neuroectoderm
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

11. What components do the mesoderm of the branchial arches give rise to?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Muscles and arteries
Persistent connection between amniotic cavity and spinal canal; low folic acid

12. What are the aspects of fetal alcohol syndrome?
Mental retardation - holoprosencephaly - facial features - fistulas
Neural crest migration - they then cause spiral
Decreases
3rd pouch

13. From What embryonic layer do the astrocytes arise?
Lots - cleft palate/lip
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Neuroectoderm
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

14. what structures are the derivatives of the neural crest cells in branchial arches?
Epiblast
Foramen cecum and terminal sulus
Bone/cartilage and nerves
Occiptal

15. What role does the placenta have?
elevated AFP
Nutrient and gas exchange
Scrotum; labia majora
Where the epiblast and hypoblast fuse

16. What causes meconium discharge from the umbilicus?
From endocardial cushions (ventral and dorsal meet each other)
pyloric stenosis
A vitelline fistula - failure of vitelline duct to close
Surface ectoderm

17. From what arches are the neural crest cells that form the aorticpulmonary septum derived?
3 -4 -6
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
IX; X
Midgut; 10th week

18. Pyloric stenosis is characterized by _____________ of muscularis externis in the sphincter
hypertrophy
Mesoderm
Hemorrhage - bone deformities
Ectoderm

19. What artery is derived branchial (aortic) arch 2?
3
Prosencephalon
Stapedius and hyoid artery
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility

20. From What embryonic layer does the olfactory epithelium arise?
Hypospadias
Ventral; failure of urogenital folds to close
Surface ectoderm
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII

21. Which branchial apparatus develops into the thymus?
Endoderm
3rd pouch
Neural crest cells
Surface ectoderm

22. What does the mullerian duct develop into? wollffian?
Thyroid - cricoid - arytenoids - corniculate cuneiform
Week 3-8
Fallopian tube - uterus - upper 1/3 of vagina
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility

23. From What embryonic layer does bone of the skulls arise?
Branchial arch 2
Neural crest cells
Sonic Hedgehog
Ectoderm

24. From What embryonic lare are the odontoblasts from?
Midgut; 10th week
6th aortic arch
When left to right shunting switching to right to left shunting
Neural crest cells

25. From what aortic arch does the common carotid artery arise? what else arises from this arch?
3rd; proximal part of the internal carotid artery
Ebsteins anomaly; tricuspid atresia
Week 4; week 3
1st cleft/groove (Ectoderm)

26. From What embryonic layer does the epithelial linings of the oral cavity arise?
Endoderm - floor of primitive pharynx
Dorsal ventral axis
Surface ectoderm
Common carotid and internal carotid

27. What is duodenal atresia usually due to? What trisomy is it most often seen in?
3rd and 4th arches
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Failure to recanalize; 21

28. As a horseshoe kidney ascends during kidney development - What do they get trapped under?
IMA
3
Female; paramesonephric; mesonephric
Week 8

29. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Neuroectoderm
Obliterated
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)

30. Monochorionic - ___________ twins are conjoined
monoamniotic
No more umbilical circulation emptying into RA
Mesoderm
Neuroectoderm

31. From which germlayer does the thyroid develop?? From what structure exactly?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Endoderm - floor of primitive pharynx
Neuroectoderm
hypertrophy

32. From What embryonic layer does the neurohypophysis arise?
Day 6; with implantation
Umbilical - midgut herniates through umbilical ring; SMA
Neuroectoderm
First branchial pouch

33. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
3rd; proximal part of the internal carotid artery
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
Nicotine; preterm labor
LH

34. What causes a patent foramen ovale?
Day 6; with implantation
Endoderm - floor of primitive pharynx
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Excessive resorption of septum primum or secondum (or both)

35. From What embryonic layer is the eustachian tube from?
From teh lung;blood from IVC in RA to LA; fossa ovalis
Prostaglandins
VSD
Mesoderm

36. What is associated with only one umbilical artery?
Ventral shaft of penis (penile urethra); labia minora
Congenital and chromosomal abnormalities
Thyroid - cricoid - arytenoids - corniculate cuneiform
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects

37. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Annular pancrease
Mesoderm
Failure of bony spinal canal to fuse; no; lower vertebral levels
Mid gut to yolk sac; omphalomesenteric duct; 7th week

38. From where does pons form from? what else forms from there?
Telencephalon
Maternally derived; meconium
Surface ectoderm
Metencephalon; cerebellum

39. _____________is common in 1st born males
Lots - cleft palate/lip
pyloric stenosis
IMA
Fallopian tube - uterus - upper 1/3 of vagina

40. WithIn what week does gastrulation occur? What is gastrulation?
Initial left to right shunting - then switches
Fluid filled syrinx causes expansion and degeneration of cord tracts
Week 3; primitive streak formation from the epiblast makes the three layers
Mesoderm

41. From What embryonic layer does the pineal gland arise?
Tetracyclines
Neuroectoderm
A vitelline fistula - failure of vitelline duct to close
Female; paramesonephric; mesonephric

42. What components do the neural crest cells of the branchial arches give rise to?
Bones - cartilage - and nerves
V3; VII
Maxillary
Alkylating agents

43. Which branchial apparatus develops into the inferior parathyroids?
Fallopian tube - uterus - upper 1/3 of vagina
is no longer intact
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
3rd pouch

44. By what week is there fetal movement?
Week 3; primitive streak formation from the epiblast makes the three layers
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Week 8
septum primum and/or secundum

45. what separates the atria from the ventricles?
Endocardial cushions
secondary palate
Metencephalon; cerebellum
Physiologic incomplete muscular ventricular septum

46. What is holoprosencephaly? what eye disorder does it result in?
Ampulla
Decreased separation of hemispheres across midline; cyclopia
Surface ectoderm
3 -4 -6

47. What results in annular pancreas? How does it happen?
Surface ectoderm
Polyhydramnios
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

48. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
DHT; estrogen
Arnold chiari; syringomyelia
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII

49. From What embryonic layer does the thyroid follicular cells arise?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Aortic arch (from left side); right subclavian (on the right)
Decreases
Endoderm

50. From what branchial derivative do the parafollicular cells arise?
4th/5th branchial pouches
Ventral; failure of urogenital folds to close
3
Neural crest cells