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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 components do the mesoderm of the branchial arches give rise to?
Sperm plus egg
hypospadias
Muscles and arteries
Outgrowth of mesonephric as ureteric bud; most caudal

2. what happens in hydrocele?
A vitelline fistula - failure of vitelline duct to close
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Umbilical - midgut herniates through umbilical ring; SMA
Tunica vaginalis not fully fused

3. From what are the umbilical arteries and veins derived from?
Ventral ; motor
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Allantois
Week 2; bilaminar disk; epiblast and hypoblast

4. From where is the pancreas derived? the spleen?
Foregut; dorsal mesentery (mesodermal)
Valproate acid
VSD
Prostaglandins

5. During what week do the limbs begin to form?
Dorsal; faulty positioning of genital tubercle
Primitive atrium
Week 4
80%

6. Which branchial derivative accounts for the sensation and taste in the posterior 2/3 of the tongue? how about the very back?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
4th arch; 6th arch

7. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
From endocardial cushions (ventral and dorsal meet each other)
Ectoderm; endoderm
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Rhombencephalon

8. What is germinal matrix hemorrhage associated with?
Mesoderm
Respiratory distress syndrome
Mesoderm
Thickened ectoderm at end of each developing limb

9. Which branchial derivative accounts for taste in the ant 2/3?
Branchial arch 2
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Endoderm
monoamniotic

10. Which branchial arch derivative is obliterated?
Week 4; week 3
Surface ectoderm
5th
Obliterated; forms tunica vaginalis

11. What is the female remnant of the gubernaculum? male remnant?
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Dorsal ventral axis
Week 4; week 3

12. Which part of the branchial apparatus makes up membranes?
arnold chiari associated with thoraclumbar myelomeningocele
Neuroectoderm
can make cells
All 3

13. Does deformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
After; extrinsic
Outgrowth of mesonephric as ureteric bud; most caudal
Mesoderm; epiblast
Lots - cleft palate/lip

14. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
DHT; estrogen
Neural crest cells
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

15. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Ectoderm
From teh lung;blood from IVC in RA to LA; fossa ovalis
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Prevent recurrent UTIs

16. From What embryonic layer does the sensory organs of the ear arise?
Surface ectoderm
Germinal matrix hemorrhage
Mesonephros; male genital system
Stapedius and hyoid artery

17. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
XII
Endocardial cushions
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

18. What congenital abnormality forms a 'double bubble' on xray?
Nutrient and gas exchange
Mesoderm
Annular pancrease
Initial left to right shunting - then switches

19. What does DHT turn the genital tubercle into? estrogen?
Cerebral hemisphere - thalami
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Muscles and arteries
Rhombencephalon

20. From which branchial derivative does the anterior 2/3 of the tongue develop?
Surface ectoderm
1st branchial arch
Renal artery stenosis;
Mesencephalon

21. What is a zygote?
T neuroectoderm
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Sperm plus egg
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)

22. When does the neural tube form and From what does it form?
Neural plate; closes by week 4
Mesoderm; epiblast
Neuroectoderm
Mid gut to yolk sac; omphalomesenteric duct; 7th week

23. What causes the transposition of the great vessels? What does it result in?
Neuroectoderm
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Oligohydramnios
A vitelline fistula - failure of vitelline duct to close

24. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Amniotic cavity and yolk sac
Oligohydramnios
Mesonephros; male genital system
When left to right shunting switching to right to left shunting

25. Name two endocardial cushion defects.
Sonic Hedgehog
...
Ebsteins anomaly; tricuspid atresia
No more umbilical circulation emptying into RA

26. When does organogenesis occur?
Right common cardinal vein and right anterior cardinal vein
After; extrinsic
Week 3-8
Decreased pulmonary resistance in the pulmonary vasculature

27. What secretes hCG?
Neural crest cells
Upper 1/3; urogenital sinus
Surface ectoderm
Synctiotrophoblast

28. What type of blood do umbilical arteries carry? From where to where?
Surface ectoderm
Dorsal and ventral buds
Deoxygenated blood; fetal internal iliac arteries to placenta
Aminoglycosides

29. What results in annular pancreas? How does it happen?
Scrotum; labia majora
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
primary palate

30. From What embryonic layer does the gut tube epithelium arise?
Mesoderm
Oxygenated; placenta to fetus (IVC)
Endoderm
Maxillary and medial nasal processes

31. _____________is common in 1st born males
pyloric stenosis
Neuroectoderm
Ebsteins anomaly; tricuspid atresia
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

32. What are markers for neural tube defects in the amniotic cavity? CSF?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Myelencephalon
Spinothalamic first
4th week

33. What does the foramen ovale shunt blood from - to where? What is its remnant?
Muscular ventricular septum; no
Wolffian; mullerian
...
From teh lung;blood from IVC in RA to LA; fossa ovalis

34. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Failure to recanalize; 21
Decreased separation of hemispheres across midline; cyclopia
From teh lung;blood from IVC in RA to LA; fossa ovalis
Obliterated; forms tunica vaginalis

35. What axis does the alar plate form? what neural system does it become?
Before getting pregnant!
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Dorsal; sensory
Mesoderm

36. Cleft palate is a failure of formation of the...
Prevent recurrent UTIs
Alkylating agents
secondary palate
arnold chiari associated with thoraclumbar myelomeningocele

37. What is the 'fetal period'- ie When is it?
Mesoderm; epiblast
Surface ectoderm
Prostaglandins
Week 8

38. From What embryonic layer does the skin dermis arise?
Respiratory distress syndrome
Mesoderm
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Neuroectoderm

39. What does the RET gene encode? what neoplasias is it associated with?
Obliterated; forms tunica vaginalis
3 -4 -6
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Neural crest migration - they then cause spiral

40. What is congenital pharyngocutaneous fistula? and How does it occur?
1st
Epiblast
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Neuroectoderm

41. From What embryonic layer is aorticopulmonary septum from ?
Indomethacin; blocks PG production
Neural crest cells
Week 3-8
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

42. What germ layer correlates with the branchial pouches?
Umbilical - midgut herniates through umbilical ring; SMA
Neural crest cells
DiGeorge
Endoderm

43. From What embryonic lare are the odontoblasts from?
Maxillary and medial nasal processes
Neural crest cells
not covered
Decreased separation of hemispheres across midline; cyclopia

44. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
Sonic Hedgehog
Arnold chiari; syringomyelia
Female; paramesonephric; mesonephric
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

45. From What embryonic layer does the adenohypophysis arise?
Surface ectoderm
Found in lateral neck; from no obliteration of 2-4th clefts
Folate antagonists
From endocardial cushions (ventral and dorsal meet each other)

46. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
Prosencephalon
V3; VII
Dorsal and ventral buds
No organ in each; agenesis no primordial tissue

47. From What embryonic layer does the retina arise?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Neuroectoderm
blood entering the RA

48. Which is more common - epispadias or hypospadias?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Hypospadias
Apical ectodermal ridge
Neural crest cells

49. What type of radiation is teratogenic ?
Mesoderm
Ionizing
primary palate
Week 3; primitive streak formation from the epiblast makes the three layers

50. What artery is derived branchial (aortic) arch 3?
Common carotid and internal carotid
During; instrinsic
Pronephros - mesonephros - metanephros; pronephros; most cranially
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects