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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 muscles are derived from branchial arch 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
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Arnold chiari; syringomyelia
Thyroid - cricoid - arytenoids - corniculate cuneiform

2. Where is Wnt 7 gene produced?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Apical ectodermal ridge
Stapedius and hyoid artery
Grooves/clefts; arches; pouches

3. What does the first cleft/groove of the branchial apparatus develop into?
External auditory meatus
Left horn of the sinus venosus
Before getting pregnant!
80%

4. When is most important to take folic acid to prevent neural tube defects?
4th arch; 6th arch
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Surface ectoderm
Before getting pregnant!

5. During what week does the heart begin to beat?
Neural crest cells
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
After; extrinsic
Week 4

6. How many components are there to the placenta? What are they called?
Failure to recanalize; 21
Day 6; with implantation
Primitive ventricle
Fetal and maternal

7. What surrounds the umbilical cord?
First branchial pouch
Fallopian tube - uterus - upper 1/3 of vagina
Amniotic epithelium
Endoderm

8. What germ layer correlates with the branchial pouches?
Oligohydramnios
Surface ectoderm
Endoderm
Surface ectoderm

9. What causes the increase in left atrial pressure to close the fossa ovale?
Urachus/median umbilical ligament; bladder and yolk sac
Decreased pulmonary resistance in the pulmonary vasculature
Fluid filled syrinx causes expansion and degeneration of cord tracts
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

10. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Endoderm
Vascular accident intra uterine; apple peel atresia
Found in lateral neck; from no obliteration of 2-4th clefts
elevated AFP

11. what drug is used to help close a PDA? what else does this drug treat?
Left horn of the sinus venosus
No organ in each; agenesis no primordial tissue
Neuroectoderm
Indomethacin; blocks PG production

12. Where is sonic hedgehog gene produced? What axis is it responsible in patterning?
Cytotrophoblast
Base of limbs in the zone of polarizing activity; ant - post
Endoderm
Surface ectoderm

13. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Mesoderm
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
Amniotic epithelium
Synctiotrophoblast

14. What does the foramen ovale shunt blood from - to where? What is its remnant?
Endoderm
Surface ectoderm
From teh lung;blood from IVC in RA to LA; fossa ovalis
Mesoderm

15. From what does bicornuate uterus arise? What is it associated with?
Neural crest cells
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
1st branchial arch
Synctiotrophoblast

16. From What embryonic layer does the brain arise?
Pulm art (prox) and ductus arteriosus
Mesoderm
Endoderm
Neuroectoderm

17. From where does the prostate develop? seminal vesicles? fallopian tube? lower 2/3 of the vagina? ejaculatory duct? epididymis? uterus? upper 1/3 of the vagina?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
8
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Endoderm

18. What does the maternal component of the placenta provide? Where is it derived from?
Nutrient and gas for exchange; endometrium
Thyroid - cricoid - arytenoids - corniculate cuneiform
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Week 8

19. What is the mcc of renovascular hypertension in children? What does this predispose to?
Wolffian; mullerian
Renal artery stenosis;
Umbilical - midgut herniates through umbilical ring; SMA
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII

20. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
3rd and 4th arches
Mesoderm

21. From What embryonic layer does the lens of the eye arise?
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Common carotid and internal carotid
Where the epiblast and hypoblast fuse
Surface ectoderm

22. Pyloric stenosis is characterized by _____________ of muscularis externis in the sphincter
hypertrophy
Mesoderm
Hepatic circulation; ligamentum venosum
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

23. What causes the obstruction in pyloric stenosis? treatment?
2; 1
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Hypertrophy of muscularis externis of pylorus; surgical incision
Incomplete; yes

24. Septum primum (patent foramen oval) caused by excessive resorption of...
Day 6; maintains corpus luteum; 1st trimester
Neural crest cells
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
septum primum and/or secundum

25. From where is amniotic fluid produced? other than electrolytes and carbs - what else does it contain?
8
Prostaglandins
Allantois
Maternally derived; meconium

26. From What embryonic layer does the pineal gland arise?
Aminoglycosides
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Day 6; maintains corpus luteum; 1st trimester
Neuroectoderm

27. What is the most common autopsy finding in brains of premature infants?
Endoderm
Germinal matrix hemorrhage
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)
primary palate

28. From what region does the cerebral hemisphere form?
Week 3; primitive streak formation from the epiblast makes the three layers
Endometrium
All 3
Telencephalon

29. What artery is derived branchial (aortic) arch 2?
Amniotic cavity and yolk sac
Occiptal
Stapedius and hyoid artery
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

30. What trisomy is associated with holoprosencephaly? What teratogen?
Pataus; fetal alcohol syndrome
Pronephros - mesonephros - metanephros; pronephros; most cranially
Respiratory distress syndrome
Bones - cartilage - and nerves

31. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Synctiotrophoblast
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Neural crest cells
Urachus/median umbilical ligament; bladder and yolk sac

32. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Week 4
Mesoderm
not covered

33. What causes tetralogy of Fallot?
Skewed development of AP septum
Week 2; bilaminar disk; epiblast and hypoblast
Excessive resorption of septum primum or secondum (or both)
Initial left to right shunting - then switches

34. What components do the neural crest cells of the branchial arches give rise to?
Neuroectoderm
Bones - cartilage - and nerves
Allantois
8

35. From What do the embryoblast and trophoblast form from? What does the embryoblast split into? the trophoblast?
Hypospadias
Nutrient and gas exchange
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Cerebral hemisphere - thalami

36. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
septum primum and/or secundum
Tongue
ACE inhibitors - HCTZ
Truncus arteriosus; pulmonary trunk

37. From What embryonic layer do chromaffin cells arise?
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Common carotid and internal carotid
Neural crest cells

38. What is Treacher Collins syndrome? What is the result?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Surface ectoderm
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells

39. WithIn what week does gastrulation occur? What is gastrulation?
Truncus arteriosus; pulmonary trunk
Foramen cecum and terminal sulus
Hypertrophy of muscularis externis of pylorus; surgical incision
Week 3; primitive streak formation from the epiblast makes the three layers

40. From what region do the thalami form?
Diencephalon
After; extrinsic
Neural crest cells
Day 6; with implantation

41. What is the difference between agenesis and aplasia?
Aortic arch and prox part of subclavian
No organ in each; agenesis no primordial tissue
Branchial arch 2
Week 8

42. From where does the ureteric bud arise? What does it give rise to?
Skewed development of AP septum
Scrotum; labia majora
Polyhydramnios
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts

43. What is DiGeorge syndrome and What does it result in?
Mesoderm
Deformation
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Mesoderm

44. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
3rd pouch
Week 2; bilaminar disk; epiblast and hypoblast
Epiblast
Ampulla

45. What embryological structure gives rise to the trabeculated part of the left and right atrium?
Bulbos Cordis; right ventricle entirely
Ventral ; motor
Endoderm
Primitive atrium

46. What is a teratogen that causes Ebsteins anomaly? What is ebsteins anomaly?

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47. When does the neural tube form and From what does it form?
Neural plate; closes by week 4
Annular pancrease
Cytotrophoblast
Surface ectoderm

48. What artery is derived branchial (aortic) arch 1?
Maxillary
Mesoderm
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Deformation

49. What does DHT turn the urogenital folds into? estrogen?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
No more umbilical circulation emptying into RA
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Ventral shaft of penis (penile urethra); labia minora

50. From where is the pancreas derived? the spleen?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
4th/5th branchial pouches
Muscles and arteries
Foregut; dorsal mesentery (mesodermal)