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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. From What embryonic layer does the neurohypophysis arise?
Prenatal and perinatal
Neuroectoderm
3rd; proximal part of the internal carotid artery
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus

2. what muscles are derived from branchial arch 1?
Apical ectodermal ridge
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
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
pyloric stenosis

3. What teratogens can cause CN VIII toxicity in the fetus?
Pulm art (prox) and ductus arteriosus
Aminoglycosides
Renal artery stenosis;
Surface ectoderm

4. From where is amniotic fluid produced? other than electrolytes and carbs - what else does it contain?
Maternally derived; meconium
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
3rd; proximal part of the internal carotid artery
Week 8

5. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
Sperm plus egg
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Nicotine; preterm labor

6. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
Bone/cartilage and nerves
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
...
Neuroectoderm

7. What separates the ant 1/3 and post 2/3 of tongue?
XII
Foramen cecum and terminal sulus
Cytotrophoblast and synctiotrophoblast
VSD

8. what separates the atria from the ventricles?
Ebsteins anomaly; tricuspid atresia
Maxillary and medial nasal processes
Congenital and chromosomal abnormalities
Endocardial cushions

9. What layer is the epiblast? hypoblast?
Decreased pulmonary resistance in the pulmonary vasculature
Myelencephalon
lumbosacral
Ectoderm; endoderm

10. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Obliterated
Telencephalon
Fetal alcohol syndrome; mental retardation
Apical ectodermal ridge

11. What artery is derived branchial (aortic) arch 6?
Yolk sac; 3rd week
Pulm art (prox) and ductus arteriosus
1st branchial arch
3rd and 4th arches

12. What surrounds the umbilical cord?
Amniotic epithelium
Occiptal
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Truncus arteriosus; pulmonary trunk

13. what junction is the last to canalize? what implications does this have down the line?
3 -4 -6
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
All 3
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

14. From What embryonic layer do the parafollicular cells of the thyroid arise?
Base of limbs in the zone of polarizing activity; ant - post
Neural crest cells
Female; paramesonephric; mesonephric
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts

15. What is hypoplasia? is primordial tissue present?
Ectoderm; endoderm
Neural crest cells
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Incomplete; yes

16. What is an arnold chiari II malformation? through what hole does it herniate?
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Mesonephros; male genital system
Rhombencephalon
Cerebellar tonsillar herniation through foramen magnum

17. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
Greater horn of hyoid; CN IX (styloPharyngeus)
External auditory meatus
Valproate acid
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

18. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Hepatic circulation; ligamentum venosum
Valproate acid
Thalidomide; nausea
Bones - cartilage - and nerves

19. what bone/cartilage and nerves are derived from branchial arch 3?
Greater horn of hyoid; CN IX (styloPharyngeus)
Oxygenated; placenta to fetus (IVC)
Neural crest cells
Endoderm

20. From where to Where is the foregut derivative? midgut? hindgut?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Obliterated; forms tunica vaginalis
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum

21. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Mesoderm
Neural crest cells
Lots - cleft palate/lip
Endometrium

22. How do adults with annular pancreas present? and At What age?
DiGeorge
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Hepatic circulation; ligamentum venosum
Maternally derived; meconium

23. What hormone is hcG structurally similar too?
Failure of the urachus to obliterate; outpouching of the bladder
Neural crest cells
...
LH

24. Does deformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
Thickened ectoderm at end of each developing limb
Tunica vaginalis not fully fused
After; extrinsic
Fetal alcohol syndrome; mental retardation

25. Where is the decidua basalis derived from?
Endometrium
Nutrient and gas exchange
Apical ectodermal ridge
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

26. What components do the mesoderm of the branchial arches give rise to?
Muscles and arteries
Upper 1/3; urogenital sinus
primary palate
hypospadias

27. What is DiGeorge syndrome and What does it result in?
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Mesdoerm
Week 4

28. The notochord is...
Decreases
Surface ectoderm
Mesoderm; 3 week
mesoderm

29. What is the leading cause of birth defects in the US? what else is this perpetrator the leading cause of?
Scrotum; labia majora
Neural crest cells
Fetal alcohol syndrome; mental retardation
Week 4

30. What axis is Wnt 7 responsible for developing?
Ventral shaft of penis (penile urethra); labia minora
Dorsal ventral axis
Prosencephalon
Ionizing

31. What axis does the basal plate form? what neural system does it become?
Valproate acid
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Mesoderm
Ventral ; motor

32. During what week do the limbs begin to form?
Week 4
Prosencephalon - mesencephalon - rhombencephalon
mesoderm
Tetracyclines

33. Cleft lip is a failure of fusion of ________ and ______.
Neuroectoderm
2nd pouch
Maxillary and medial nasal processes
IX; X

34. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
1st cleft/groove (Ectoderm)
Outgrowth of mesonephric as ureteric bud; most caudal
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Muscles and arteries

35. What does the maternal component of the placenta provide? Where is it derived from?
XII
Pronephros - mesonephros - metanephros; pronephros; most cranially
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Nutrient and gas for exchange; endometrium

36. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
Surface ectoderm
elevated AFP
V3; VII
3

37. What is the allantois become? What is this duct connected to ( on both ends)?
Arnold chiari; syringomyelia
Fallopian tube - uterus - upper 1/3 of vagina
Urachus/median umbilical ligament; bladder and yolk sac
Nicotine; preterm labor

38. What are the neural crest cells and where do they come form? where do they go?
Post. sup wall; luteal phase
They are the edge of neural plate folding; all over the body
Dorsal ventral axis
4th week

39. Which branchial apparatus develops into the inferior parathyroids?
3rd pouch
Pulm art (prox) and ductus arteriosus
Truncus arteriosus; pulmonary trunk
Decreased separation of hemispheres across midline; cyclopia

40. what closes the ductus arteriousus?
When left to right shunting switching to right to left shunting
Week 8
Prosencephalon - mesencephalon - rhombencephalon
Increase in oxygen concentration which decreases prostaglandin concentration

41. From What embryonic layer does the pineal gland arise?
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
Fluid filled syrinx causes expansion and degeneration of cord tracts
Neuroectoderm
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

42. What two things cause VACTERL syndrome?
Lacunae in between the chorionic villi
OCPS and maternal diabetes
Maxillary
Nutrient and gas for exchange; endometrium

43. What day is the amnion formed?
mesoderm
8
Endoderm
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

44. Which branchial apparatus develops into the superior parathyroids?
Wolffian; mullerian
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
4th pouch

45. What artery is derived branchial (aortic) arch 1?
Sonic Hedgehog
8
Failure to recanalize; 21
Maxillary

46. What is a zygote?
Cytotrophoblast and synctiotrophoblast
Cranio - caudal; segmental
Dorsal; sensory
Sperm plus egg

47. What is the mcc of renovascular hypertension in children? What does this predispose to?
Renal artery stenosis;
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Maternally derived; meconium
Synctiotrophoblast

48. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
All 3
ACE inhibitors - HCTZ
Synctiotrophoblast; outer; no
Truncus arteriosus; pulmonary trunk

49. For what reason do hypospadias need to be fixed?
Muscular ventricular septum; no
Prevent recurrent UTIs
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Week 4

50. what muscles are derived from branchial arch 2?
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Right common cardinal vein and right anterior cardinal vein
Indomethacin; blocks PG production
Congenital and chromosomal abnormalities