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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 bone/cartilage and nerves are derived from branchial arch 1?
2nd; 2nd
Neural crest migration - they then cause spiral
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Endoderm

2. From What embryonic layer do the ANS arise?
Oxygenated; placenta to fetus (IVC)
Neural crest cells
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Week 4

3. Most myelomeningoceles present in the _______ region
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
mesodermal
lumbosacral
Neural crest migration - they then cause spiral

4. What is the effect of teratogens after week 8?
Ventral; failure of urogenital folds to close
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Deformation
Surface ectoderm

5. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
6th aortic arch
During; instrinsic
Valproate acid

6. What is the memranous interventricular formaen made from?
Synctiotrophoblast
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Mesoderm; nucleous pulposos
DiGeorge

7. which teratogen can cause Ebsteins anomaly in the fetus?
Turners; inferior
Outgrowth of mesonephric as ureteric bud; most caudal
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Lithium

8. The notochord is...
mesoderm
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Fluid filled syrinx causes expansion and degeneration of cord tracts
Ebsteins anomaly; tricuspid atresia

9. From What embryonic layer do chromaffin cells arise?
Tongue
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Foregut; dorsal mesentery (mesodermal)
Neural crest cells

10. What part of the vagina does the mullerian duct form? Where does the rest come from?
Upper 1/3; urogenital sinus
Mesoderm
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Foramen cecum and terminal sulus

11. What is a zygote?
Sperm plus egg
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Tetracyclines
1st cleft/groove (Ectoderm)

12. Which branchial derivative accounts for taste in the ant 2/3?
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Sperm plus egg
1st
Branchial arch 2

13. From what arches are the neural crest cells that form the aorticpulmonary septum derived?
3 -4 -6
Dorsal and ventral buds
Neuroectoderm
Primitive ventricle

14. From What embryonic layer does bone of the skulls arise?
Before getting pregnant!
Indomethacin; blocks PG production
Neural crest cells
Pronephros - mesonephros - metanephros; pronephros; most cranially

15. what closes the ductus arteriousus?
Ventral ; motor
Embryonic period; 1st trimester
Increase in oxygen concentration which decreases prostaglandin concentration
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

16. What does the foramen ovale shunt blood from - to where? What is its remnant?
Myelencephalon
From teh lung;blood from IVC in RA to LA; fossa ovalis
Respiratory distress syndrome
Folate antagonists

17. The inner layer of the chorionic villi...
3rd and 4th arches
Neuroectoderm
can make cells
Synctiotrophoblast

18. what muscles are derived from branchial arch 6? CN?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Primitive ventricle
Medial palatine processes
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells

19. From where do the three different kidneys come from? Which is the earliest one? is it located most cranially or caudally?
Pronephros - mesonephros - metanephros; pronephros; most cranially
secondary palate
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

20. What are the two types of posterior fossa malformations? which one results in a hindbrain crowding? and which results in an enlarged posterior fossa? which one is associated with syringomelia?
Cytotrophoblast
Yolk sac; 3rd week
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

21. What do the arches of the branchial apparatus correlate to?
Mesdoerm
Mental retardation - holoprosencephaly - facial features - fistulas
Ectoderm; endoderm
Vascular accident intra uterine; apple peel atresia

22. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
3rd pouch
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Mesoderm

23. Septum primum (patent foramen oval) caused by excessive resorption of...
Ectoderm
septum primum and/or secundum
Greater horn of hyoid; CN IX (styloPharyngeus)
ACE inhibitors - HCTZ

24. For what reason do hypospadias need to be fixed?
Endoderm
Ectoderm; endoderm
Prevent recurrent UTIs
Neuroectoderm

25. Which is more common - epispadias or hypospadias?
Hypospadias
Bulbos Cordis; right ventricle entirely
Persistent connection between amniotic cavity and spinal canal; low folic acid
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

26. What surrounds the umbilical cord?
3rd and 4th arches
Yolk sac; 3rd week
1st
Amniotic epithelium

27. _____________is common in 1st born males
Ventral bud
pyloric stenosis
During; instrinsic
6th aortic arch

28. As a horseshoe kidney ascends during kidney development - What do they get trapped under?
IMA
...
Valproate acid
Initial left to right shunting - then switches

29. What teratogens can cause renal damage in the fetus?
ACE inhibitors - HCTZ
Skewed development of AP septum
Germinal matrix hemorrhage
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

30. From which branchial derivative does the anterior 2/3 of the tongue develop?
Surface ectoderm
1st branchial arch
pyloric stenosis
Physiologic incomplete muscular ventricular septum

31. From What embryonic layer does the neurohypophysis arise?
V3; VII
Neuroectoderm
3rd pouch
Excessive resorption of septum primum or secondum (or both)

32. What teratogens can cause flipper limbs (limb defects)? What is this drug used for?
Base of limbs in the zone of polarizing activity; ant - post
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Thalidomide; nausea

33. What is the most common autopsy finding in brains of premature infants?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Germinal matrix hemorrhage
Neural plate; closes by week 4
Neural crest cells

34. Cleft palate is a failure of fusion of the lateral palatine processes - the nasal septum and or the ________?
Medial palatine processes
Bone/cartilage and nerves
Week 4
Yolk sac; 3rd week

35. From What embryonic layer does the inner arise?
From endocardial cushions (ventral and dorsal meet each other)
...
Obliterated
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)

36. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
VACTERL; OCPs and maternal diabetes
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Neural crest cells

37. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Ionizing
Base of limbs in the zone of polarizing activity; ant - post
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Endoderm

38. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Prostaglandins
Vascular accident intra uterine; apple peel atresia
Mid gut to yolk sac; omphalomesenteric duct; 7th week

39. What happens in pancreas divisum? what results?
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Mesoderm
Neural crest migration - they then cause spiral
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

40. What is the effect of teratogens before week 3?
Ectoderm
Week 8
All or none
Decreased separation of hemispheres across midline; cyclopia

41. From What embryonic layer does the epidermis arise?
Mesoderm; epiblast
Surface ectoderm
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
Greater horn of hyoid; CN IX (styloPharyngeus)

42. Where does fertilization occur?
Myelencephalon
Ampulla
Tetracyclines
Fallopian tube - uterus - upper 1/3 of vagina

43. Where is the most common ectopic thyroid tissue?
Aortic arch and prox part of subclavian
Cytotrophoblast and synctiotrophoblast
Tongue
Sperm plus egg

44. Before birth - blood entering the LA is less than...
Ectoderm
Lacunae in between the chorionic villi
blood entering the RA
...

45. From What embryonic layer is the spleen from?
A vitelline fistula - failure of vitelline duct to close
Mesoderm
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Failure of bony spinal canal to fuse; no; lower vertebral levels

46. what muscles are derived from branchial arch 1?
Week 4
Bone/cartilage and nerves
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. What artery is derived branchial (aortic) arch 6?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Pulm art (prox) and ductus arteriosus
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Surface ectoderm

48. From where is the pancreas derived? the spleen?
3rd; proximal part of the internal carotid artery
Dorsal ventral axis
Foregut; dorsal mesentery (mesodermal)
3rd pouch

49. what chemo drugs can cause neural tube defects in the fetus?
Folate antagonists
Cerebral hemisphere - thalami
Fetal and maternal
Cytotrophoblast and synctiotrophoblast

50. In anencephaly you see...
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Rhombencephalon
elevated AFP
Mesoderm