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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 2?
Lots - cleft palate/lip
XII
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII

2. From What embryonic layer is the kidney and the adrenal cortex from?
Mesencephalon
Endometrium
Neuroectoderm
Mesoderm

3. WithIn what week does gastrulation occur? What is gastrulation?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Nutrient and gas for exchange; endometrium
Mesonephros; male genital system
Week 3; primitive streak formation from the epiblast makes the three layers

4. In anencephaly you see...
elevated AFP
They are the edge of neural plate folding; all over the body
...
Physiologic incomplete muscular ventricular septum

5. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Increase in oxygen concentration which decreases prostaglandin concentration
hypertrophy
Prostaglandins
Mesoderm

6. Name a syndrome cleft palate is often seen in
Mesencephalon
Maxillary and medial nasal processes
3rd pouch
DiGeorge

7. What are markers for neural tube defects in the amniotic cavity? CSF?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Left horn of the sinus venosus
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

8. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
hypertrophy
not covered
Rhombencephalon
Mesoderm; 3 week

9. what muscles are derived from branchial arch 2?
Rhombencephalon
Prenatal and perinatal
Decreases
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric

10. How is amniontic fluid excreted? How is amniotic fluid resorped?
VACTERL; OCPs and maternal diabetes
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Dorsal; faulty positioning of genital tubercle

11. What causes the obstruction in pyloric stenosis? treatment?
Neuroectoderm
Endometrium
Pataus; fetal alcohol syndrome
Hypertrophy of muscularis externis of pylorus; surgical incision

12. By when are the neuropores supposed to fuse?
4th week
80%
Embryonic period; 1st trimester
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18

13. What causes a vesicourachal diverticulum? What is it?
Arnold chiari; syringomyelia
Failure of the urachus to obliterate; outpouching of the bladder
Day 6; with implantation
Duodenum to transverse colon; distal transverse colon to rectum

14. Only _______________________________ are associated with neural tube defects
arnold chiari associated with thoraclumbar myelomeningocele
Tongue
During; instrinsic
Annular pancrease

15. From where do the three different kidneys come from? Which is the earliest one? is it located most cranially or caudally?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Pronephros - mesonephros - metanephros; pronephros; most cranially
All 3
Week 4

16. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Week 4
3rd pouch
Week 2; bilaminar disk; epiblast and hypoblast

17. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
6th aortic arch
Female; paramesonephric; mesonephric
Indomethacin; blocks PG production
Neural crest cells

18. what drug is used to help close a PDA? what else does this drug treat?
Hepatic circulation; ligamentum venosum
Failure of the urachus to obliterate
Week 3-8
Indomethacin; blocks PG production

19. From What embryonic layer does the epidermis arise?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Week 4
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Surface ectoderm

20. What are the two walls of the prosencephalon and What do they become?
Cerebral hemisphere - thalami
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Pronephros - mesonephros - metanephros; pronephros; most cranially
Bulbos Cordis; right ventricle entirely

21. Which branchial apparatus makes the external auditory meatus?
Endoderm - floor of primitive pharynx
Mesoderm
Aortic arch (from left side); right subclavian (on the right)
1st cleft/groove (Ectoderm)

22. From where did a branchial cleft cyst arise if it found?
All or none
Found in lateral neck; from no obliteration of 2-4th clefts
Decreased pulmonary resistance in the pulmonary vasculature
Endocardial cushions

23. From What embryonic layer is the eustachian tube from?
Week 4
Increase in oxygen concentration which decreases prostaglandin concentration
Failure of the urachus to obliterate
Mesoderm

24. What embryological structure gives rise to the coronary sinus?
Left horn of the sinus venosus
4th arch; 6th arch
Surface ectoderm
DiGeorge

25. How many umbilical arteries are there? How many umbilical veins?
Dorsal and ventral buds
2; 1
All 3
...

26. What is the 'fetal period'- ie When is it?
Week 3-8
Excessive resorption of septum primum or secondum (or both)
4th arch; 6th arch
Week 8

27. What secretes hCG?
arnold chiari associated with thoraclumbar myelomeningocele
4th/5th branchial pouches
Synctiotrophoblast
Hemorrhage - bone deformities

28. From What embryonic layer are the pia and arachnoid from?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Neural crest cells
From endocardial cushions (ventral and dorsal meet each other)
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)

29. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
Hemorrhage - bone deformities
Dorsal; sensory
DiGeorge
3rd pouch

30. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Pronephros - mesonephros - metanephros; pronephros; most cranially
Neuroectoderm
Failure to recanalize; 21
3rd and 4th arches

31. What two cavities also form during the second week?
Deformation
Amniotic cavity and yolk sac
...
Neural crest cells

32. Name two endocardial cushion defects.
Rhombencephalon
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
Ebsteins anomaly; tricuspid atresia
Cytotrophoblast and synctiotrophoblast

33. When does organogenesis occur?
Week 3-8
Ebsteins anomaly; tricuspid atresia
External auditory meatus
First branchial pouch

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

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35. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
They are the edge of neural plate folding; all over the body
During; instrinsic
secondary palate
Week 4

36. What day is the amnion formed?
8
Amniotic cavity and yolk sac
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
secondary palate

37. From What embryonic layer is the spleen from?
Mesoderm
Week 3-8
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Valproate acid

38. From What embryonic layer does the retina arise?
Neuroectoderm
Muscular ventricular septum; no
Mental retardation - holoprosencephaly - facial features - fistulas
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

39. From What embryonic layer does the gut tube epithelium arise?
Spinothalamic first
Yolk sac; 3rd week
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Endoderm

40. From What embryonic layer does bone arise ?
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
Mesoderm
Prostaglandins
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

41. Weeks _______ erythropoiesis takes place in the liver
Failure to recanalize; 21
6-30
Obliterated; forms tunica vaginalis
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

42. From What embryonic layer does the adenohypophysis arise?
Synctiotrophoblast; outer; no
Neuroectoderm
Ampulla
Surface ectoderm

43. What does the first cleft/groove of the branchial apparatus develop into?
Skewed development of AP septum
A vitelline fistula - failure of vitelline duct to close
Mesoderm
External auditory meatus

44. Which branchial derivative accounts for the posterior 2/3 of the tongue?
Ventral; failure of urogenital folds to close
Branchial arch 2
VACTERL; OCPs and maternal diabetes
3rd and 4th arches

45. From what region does the midbrain form from?
Mesencephalon
Surface ectoderm
Neural crest cells
Branchial arch 2

46. From what does bicornuate uterus arise? What is it associated with?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
monoamniotic
Decreased pulmonary resistance in the pulmonary vasculature
Endoderm

47. From what are the umbilical arteries and veins derived from?
Allantois
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
External auditory meatus

48. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Initial left to right shunting - then switches
V3; VII

49. In what chromosomal disorder is horseshoe kidney commonly seen? what poles of the kidneys fuse?
Pataus; fetal alcohol syndrome
Turners; inferior
6th aortic arch
blood entering the RA

50. By what week is the neural tube supposed to be closed? when did it start forming?
not covered
Week 4; week 3
Neural crest cells
4th pouch