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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 gene is produced in the zone of polarizing activity?
Sonic Hedgehog
3rd and 4th arches
Neural crest cells
OCPS and maternal diabetes

2. What does the first branchial pouch create?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
is no longer intact
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Partial AP septum development; one large vessel leaves the heart - Right to left shunt

3. What teratogens can cause discolored teeth?
Vascular accident intra uterine; apple peel atresia
Tetracyclines
4th/5th branchial pouches
Endocardial cushions

4. From What embryonic layer is aorticopulmonary septum from ?
Endoderm
Neural crest cells
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Ectoderm; endoderm

5. what bone/cartilage and nerves are derived from branchial arch 2?
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Mesoderm; epiblast
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Telencephalon

6. From What embryonic layer does the oligodendrocytes 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
Neuroectoderm
Common carotid and internal carotid
Spinothalamic first

7. From What embryonic layer do chromaffin cells arise?
OCPS and maternal diabetes
Endoderm - floor of primitive pharynx
Hemorrhage - bone deformities
Neural crest cells

8. From What embryonic layer does the lens of the eye arise?
Spinothalamic first
Endoderm
Mesoderm; epiblast
Surface ectoderm

9. Which arches form the posterior 1/3 of the tongue?
Arches 3 and 4
Oligohydramnios
Oxygenated; placenta to fetus (IVC)
Amniotic epithelium

10. What is used to keep the PDA open?
elevated AFP
can make cells
Prostaglandins
Right common cardinal vein and right anterior cardinal vein

11. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Cytotrophoblast and synctiotrophoblast
Neuroectoderm
...
Turners; inferior

12. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
Epispadias
Nicotine; preterm labor
Embryonic period; 1st trimester
Dorsal and ventral buds

13. From what does bicornuate uterus arise? What is it associated with?
Neuroectoderm
Midgut; 10th week
Bone/cartilage and nerves
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility

14. Which branchial derivative accounts for the sensation and taste in the posterior 2/3 of the tongue? how about the very back?
Neuroectoderm
Fluid filled syrinx causes expansion and degeneration of cord tracts
4th arch; 6th arch
IMA

15. From what are the umbilical arteries and veins derived from?
Synctiotrophoblast; outer; no
Allantois
Failure to recanalize; 21
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

16. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
not covered
blood entering the RA
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Neuroectoderm

17. Which branchial apparatus develops into the inferior parathyroids?
Mesoderm
Renal artery stenosis;
3rd pouch
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

18. From What embryonic layer does the brain arise?
hypertrophy
Neuroectoderm
pyloric stenosis
2nd pouch

19. what junction is the last to canalize? what implications does this have down the line?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Week 2; bilaminar disk; epiblast and hypoblast
Primitive atrium
Valproate acid

20. What part of the gut rotates around the SMA? and At what point?
Midgut; 10th week
Arches 3 and 4
Pataus; fetal alcohol syndrome
Stapedius and hyoid artery

21. what muscles are derived from branchial arch 3?
StyloPharyngeus
Nutrient and gas for exchange; endometrium
Maternally derived; meconium
Left horn of the sinus venosus

22. WithIn what week does gastrulation occur? What is gastrulation?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Tunica vaginalis not fully fused
Week 3; primitive streak formation from the epiblast makes the three layers
Neuroectoderm

23. What axis is Wnt 7 responsible for developing?
Prosencephalon - mesencephalon - rhombencephalon
External auditory meatus
Dorsal ventral axis
Surface ectoderm

24. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Truncus arteriosus; pulmonary trunk
Nutrient and gas exchange
Ventral bud

25. What is the effect of teratogens before week 3?
Vascular accident intra uterine; apple peel atresia
All or none
Obliterated; forms tunica vaginalis
Week 2; bilaminar disk; epiblast and hypoblast

26. What can vit A in excess cause in the fetus?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Lots - cleft palate/lip
Neural crest cells
Surface ectoderm

27. Where is the most common ectopic thyroid tissue?
Tongue
Branchial arch 2
Mid gut to yolk sac; omphalomesenteric duct; 7th week
3rd; proximal part of the internal carotid artery

28. The spleen is ____________ in origin and supplied by a foregut artery
Duodenum to transverse colon; distal transverse colon to rectum
mesodermal
Indomethacin; blocks PG production
Ventral; failure of urogenital folds to close

29. From What embryonic lare are the odontoblasts from?
Stapedius and hyoid artery
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Ventral bud
Neural crest cells

30. From What embryonic layer does connective tissue and muscle arise?
Neural crest cells
Maxillary
Mesoderm
Neuroectoderm

31. What are the clinical symptoms that present with syringomelia?
Neural crest cells
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
6th aortic arch
Fallopian tube - uterus - upper 1/3 of vagina

32. Where does fertilization occur?
Mesoderm; 3 week
2; 1
Stapedius and hyoid artery
Ampulla

33. From What embryonic layer do the parafollicular cells of the thyroid arise?
Allantois
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Neural crest cells

34. What are the two components of the fetal component of the placenta?
Mesoderm
Cytotrophoblast and synctiotrophoblast
Physiologic incomplete muscular ventricular septum
Aminoglycosides

35. From where do the three different kidneys come from? Which is the earliest one? is it located most cranially or caudally?
3rd; proximal part of the internal carotid artery
Pronephros - mesonephros - metanephros; pronephros; most cranially
Week 8
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'

36. Cleft lip is a failure of formation of the...
Foramen cecum and terminal sulus
Right common cardinal vein and right anterior cardinal vein
Day 6; with implantation
primary palate

37. What do the groove/clefts of the branchial apparatus correlate to?
Ectoderm
Medial palatine processes
1st
Endoderm - floor of primitive pharynx

38. From What embryonic layer does the spinal cord arise?
Wolffian; mullerian
...
Neuroectoderm
Obliterated; forms tunica vaginalis

39. What is the most common autopsy finding in brains of premature infants?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Germinal matrix hemorrhage
Alkylating agents
Cranio - caudal; segmental

40. What artery is derived branchial (aortic) arch 1?
DiGeorge
not covered
Maxillary
Endoderm

41. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
Sperm plus egg
Fetal and maternal
T neuroectoderm
Week 2; bilaminar disk; epiblast and hypoblast

42. From what aortic arch does the first part of the maxillary artery arise?
Stapedius and hyoid artery
Neural crest cells
1st
Metencephalon; cerebellum

43. During what week does the heart begin to beat?
Mesoderm
Sperm plus egg
Week 4
After; extrinsic

44. During what months is the fetus most susceptible to teratogens? What trimester?
2; 1
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
Embryonic period; 1st trimester
Decidual basalis

45. What does the ureteric bud interact with and What does it induce it to become?
Grooves/clefts; arches; pouches
All 3
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
4th pouch

46. What separated myometrium of the uterus from the blastocyst?
6-30
Decidual basalis
OCPS and maternal diabetes
Respiratory distress syndrome

47. How many umbilical arteries are there? How many umbilical veins?
Decreases
Mesoderm; epiblast
2; 1
Mesoderm; 3 week

48. What do the 2nd through 4th clefts of the branchial apparatus correlate to?
Day 6; maintains corpus luteum; 1st trimester
Temporary cervical sinus
External auditory meatus
Ectoderm

49. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
First branchial pouch
Bulbos Cordis; right ventricle entirely
Pataus; fetal alcohol syndrome
Primitive ventricle

50. failure to close of what fold results in sternal defects? omphalocele? gastrochisis? bladder extrosphy?
3rd; proximal part of the internal carotid artery
Respiratory distress syndrome
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Neural crest cells