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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 olfactory epithelium arise?
Surface ectoderm
Excessive resorption of septum primum or secondum (or both)
V3; VII
4th/5th branchial pouches

2. On what side is the abnormal opening in epispadias? What causes it?
Dorsal; faulty positioning of genital tubercle
Neural crest cells
secondary palate
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule

3. From What embryonic layer does the lens of the eye arise?
Endoderm
Temporary cervical sinus
Surface ectoderm
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

4. From What embryonic layer is the spleen from?
Hypospadias
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Tongue
Mesoderm

5. Which arches form the posterior 1/3 of the tongue?
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Maternally derived; meconium
Arches 3 and 4
septum primum and/or secundum

6. By what week is there fetal movement?
Week 8
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
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Ectoderm

7. By what week is the neural tube supposed to be closed? when did it start forming?
Ampulla
Week 4; week 3
Failure of the urachus to obliterate
Endoderm

8. Which branchial apparatus develops into the superior parathyroids?
Dorsal ventral axis
Obliterated
4th pouch
Neural crest cells

9. Other than not having a brain - what else is a symptom of anencephaly? why? hint: think about amniotic fluid
Polyhydramnios
Aminoglycosides
Mesoderm
Mesoderm

10. As a horseshoe kidney ascends during kidney development - What do they get trapped under?
IMA
Mesoderm
80%
Vascular accident intra uterine; apple peel atresia

11. Which branchial derivative accounts for the posterior 2/3 of the tongue?
3rd and 4th arches
Fluid filled syrinx causes expansion and degeneration of cord tracts
4th/5th branchial pouches
Mesoderm

12. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Indomethacin; blocks PG production
Neural crest cells
DES
Failure to recanalize; 21

13. Which is more common - epispadias or hypospadias?
Spinothalamic first
4th week
Failure of the urachus to obliterate; outpouching of the bladder
Hypospadias

14. What are the aspects of fetal alcohol syndrome?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Neural crest cells
Mental retardation - holoprosencephaly - facial features - fistulas
They are the edge of neural plate folding; all over the body

15. Which branchial apparatus derivative makes the tympanic membrane of the ear?
2; 1
Cleft lip/palate
Membrane - all 3 from 1st appartus
Failure to recanalize; 21

16. What type of blood do umbilical arteries carry? From where to where?
Aortic arch and prox part of subclavian
Mesoderm
8
Deoxygenated blood; fetal internal iliac arteries to placenta

17. What is DiGeorge syndrome and What does it result in?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Neural crest cells
Neuroectoderm

18. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Obliterated
Valproate acid
Lacunae in between the chorionic villi
Epiblast

19. What is the memranous interventricular formaen made from?
Embryonic period; 1st trimester
Neural crest cells
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

20. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
Mesoderm
Neuroectoderm
DiGeorge
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

21. From What embryonic layer is the kidney and the adrenal cortex from?
Mesoderm
6-30
Neural crest cells
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

22. What does DHT turn the urogenital folds into? estrogen?
Primitive atrium
Maxillary
Truncus arteriosus; pulmonary trunk
Ventral shaft of penis (penile urethra); labia minora

23. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Maternally derived; meconium
Endoderm
2; 1
Maxillary

24. From What embryonic layer does the brain arise?
Dorsal ventral axis
Neural crest cells
Neuroectoderm
Turners; inferior

25. What are the two components of the placenta? From What do they form? which one secreted hcG?
...
DHT; estrogen
External auditory meatus
pyloric stenosis

26. From what region does the cerebral hemisphere form?
Neural crest cells
Muscular ventricular septum; no
Telencephalon
1st branchial arch

27. What is associated with only one umbilical artery?
Endocardial cushions
Congenital and chromosomal abnormalities
When left to right shunting switching to right to left shunting
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

28. What is the effect of teratogens before week 3?
All or none
Nutrient and gas for exchange; endometrium
Decreased pulmonary resistance in the pulmonary vasculature
Cytotrophoblast

29. What separated myometrium of the uterus from the blastocyst?
Mesoderm
Decidual basalis
Mesoderm
Sonic Hedgehog

30. Where does fertilization occur?
StyloPharyngeus
3
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Ampulla

31. What is the homeobox gene responsible in developing? (What axis)
Cranio - caudal; segmental
Scrotum; labia majora
After; extrinsic
Temporary cervical sinus

32. What are the two components of the fetal component of the placenta?
Week 8
3rd pouch
Cytotrophoblast and synctiotrophoblast
Prosencephalon

33. What are the three regions of the brain (in order of cranial to caudal)?
Prosencephalon - mesencephalon - rhombencephalon
Prostaglandins
Neuroectoderm
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

34. From where does the medulla form?
Myelencephalon
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Week 8
Week 8

35. What does DHT turn the urogenital sinus into? estrogen?
Week 4
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
XII

36. What teratogens can cause renal damage in the fetus?
ACE inhibitors - HCTZ
Neural crest cells
Wolffian; mullerian
Thyroid - cricoid - arytenoids - corniculate cuneiform

37. How many umbilical arteries are there? How many umbilical veins?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Mesoderm
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
2; 1

38. Monochorionic - ___________ twins are conjoined
monoamniotic
Myelencephalon
3rd pouch
Branchial arch 2

39. What do membranous interventricular septal defect cause? What does this lead to?
Membrane - all 3 from 1st appartus
Initial left to right shunting - then switches
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Cerebral hemisphere - thalami

40. Where is the FGF gene produced? What is it responsible for - How does it do this?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Persistent connection between amniotic cavity and spinal canal; low folic acid
Neuroectoderm
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

41. From what germ layer does the primitive heart tube arise?
2; 1
Bone/cartilage and nerves
Aminoglycosides
Mesoderm

42. is epispadias or hypospadias associated with exstrophy of the bladder?
Left horn of the sinus venosus
Foramen cecum and terminal sulus
Oxygenated; placenta to fetus (IVC)
Epispadias

43. Before birth - blood entering the LA is less than...
Greater horn of hyoid; CN IX (styloPharyngeus)
4th/5th branchial pouches
Neuroectoderm
blood entering the RA

44. what junction is the last to canalize? what implications does this have down the line?
Fetal alcohol syndrome; mental retardation
DiGeorge
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
3rd pouch

45. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
Dorsal and ventral buds
Neural crest cells
Neural crest cells
Aortic arch (from left side); right subclavian (on the right)

46. what chemo drugs can cause neural tube defects in the fetus?
Folate antagonists
Respiratory distress syndrome
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
Endoderm

47. From What embryonic layer does the sensory organs of the ear arise?
Surface ectoderm
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Spinothalamic first
Muscular ventricular septum; no

48. What teratogens can cause discolored teeth?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Tetracyclines
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Arches 3 and 4

49. What is a zygote?
Congenital and chromosomal abnormalities
Sperm plus egg
Foregut; dorsal mesentery (mesodermal)
28 week onward

50. What is the most common autopsy finding in brains of premature infants?
Duodenum to transverse colon; distal transverse colon to rectum
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Germinal matrix hemorrhage
Ventral; failure of urogenital folds to close