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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. Where is the apical ectodermal ridge?
Thickened ectoderm at end of each developing limb
Endocardial cushions
Surface ectoderm
can make cells

2. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
3rd; proximal part of the internal carotid artery
mesodermal
During; instrinsic
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

3. What components do the mesoderm of the branchial arches give rise to?
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Muscles and arteries
Increase in oxygen concentration which decreases prostaglandin concentration

4. What is the defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Surface ectoderm
Failure of bony spinal canal to fuse; no; lower vertebral levels
Truncus arteriosus; pulmonary trunk
Left horn of the sinus venosus

5. What teratogens can cause CN VIII toxicity in the fetus?
Primitive atrium
Incomplete; yes
Aminoglycosides
Week 8

6. What is a zygote?
Apical ectodermal ridge
Sperm plus egg
Lithium
Failure to recanalize; 21

7. What causes meconium discharge from the umbilicus?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Nutrient and gas exchange
Myelencephalon
A vitelline fistula - failure of vitelline duct to close

8. Cleft lip is a failure of fusion of ________ and ______.
Prenatal and perinatal
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Spinothalamic first
Maxillary and medial nasal processes

9. From What embryonic layer does the oligodendrocytes arise?
Neuroectoderm
6-30
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Oxygenated; placenta to fetus (IVC)

10. What do the arches of the branchial apparatus correlate to?
Urachus/median umbilical ligament; bladder and yolk sac
Mesdoerm
80%
Decreased separation of hemispheres across midline; cyclopia

11. From What embryonic layer does the brain arise?
Mesonephros; male genital system
Decreased pulmonary resistance in the pulmonary vasculature
Neuroectoderm
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

12. What do the groove/clefts of the branchial apparatus correlate to?
Ionizing
After; extrinsic
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Ectoderm

13. The notochord is...
Neuroectoderm
ACE inhibitors - HCTZ
mesoderm
can make cells

14. From What embryonic layer does the lens of the eye arise?
Week 3-8
Surface ectoderm
Endometrium
Mesonephros; male genital system

15. What does the midgut form? hindgut?
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Duodenum to transverse colon; distal transverse colon to rectum
Surface ectoderm
Deoxygenated blood; fetal internal iliac arteries to placenta

16. What causes the decrease in Right atrial pressure to close the fossa ovale?
Amniotic epithelium
Mesoderm; nucleous pulposos
No more umbilical circulation emptying into RA
Apical ectodermal ridge

17. From which germlayer does the thyroid develop?? From what structure exactly?
Neural crest cells
Mesoderm; nucleous pulposos
Primitive atrium
Endoderm - floor of primitive pharynx

18. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
From teh lung;blood from IVC in RA to LA; fossa ovalis
Mesoderm; epiblast
Fetal alcohol syndrome; mental retardation
Week 2; bilaminar disk; epiblast and hypoblast

19. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Prenatal and perinatal
Duodenum to transverse colon; distal transverse colon to rectum
Neural crest cells
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

20. Which branchial apparatus develops into the thymus?
3rd pouch
Fetal and maternal
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Failure of bony spinal canal to fuse; no; lower vertebral levels

21. What type of radiation is teratogenic ?
Ionizing
Week 2; bilaminar disk; epiblast and hypoblast
Primitive atrium
Turners; inferior

22. What surrounds the umbilical cord?
Physiologic incomplete muscular ventricular septum
Medial palatine processes
Amniotic epithelium
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

23. From which myotomes are muscles of the tongue derived from?
Mesoderm
Myelencephalon
Neural crest cells
Occiptal

24. The inner layer of the chorionic villi...
Day 6; maintains corpus luteum; 1st trimester
Mesencephalon
can make cells
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

25. What are the three results of having pathology in the aorticopulmonary septum?
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)
No organ in each; agenesis no primordial tissue
VACTERL; OCPs and maternal diabetes
Foramen cecum and terminal sulus

26. What is the 'fetal period'- ie When is it?
Failure of the urachus to obliterate; outpouching of the bladder
2nd pouch
Week 8
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18

27. From What embryonic layer is the spleen from?
Umbilical - midgut herniates through umbilical ring; SMA
Deoxygenated blood; fetal internal iliac arteries to placenta
Mesoderm
Folate antagonists

28. What results in annular pancreas? How does it happen?
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Mesoderm
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
28 week onward

29. From What embryonic layer is the eustachian tube from?
Sperm plus egg
Deformation
Stapedius and hyoid artery
Mesoderm

30. Which cranial nerve innervates the motor function of the tongue?
XII
Initial left to right shunting - then switches
Aortic arch (from left side); right subclavian (on the right)
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum

31. What are the clinical symptoms that present with syringomelia?
Aortic arch (from left side); right subclavian (on the right)
Surface ectoderm
4th arch; 6th arch
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

32. Cleft palate is a failure of formation of the...
secondary palate
Embryonic period; 1st trimester
Medial palatine processes
primary palate

33. what other facial defect other than cyclopia is associated with holoprosencephaly?
V3; VII
Neural crest cells
Neuroectoderm
Cleft lip/palate

34. From What embryonic layer does the epidermis arise?
Surface ectoderm
Ectoderm; endoderm
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)

35. What are the aspects of fetal alcohol syndrome?
Oxygenated; placenta to fetus (IVC)
Mental retardation - holoprosencephaly - facial features - fistulas
monoamniotic
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

36. Name a syndrome cleft palate is often seen in
Common carotid and internal carotid
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Cranio - caudal; segmental
DiGeorge

37. What axis is Wnt 7 responsible for developing?
Mesoderm
Ebsteins anomaly; tricuspid atresia
Dorsal ventral axis
3rd pouch

38. What does the first branchial pouch create?
Endoderm - floor of primitive pharynx
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
...
Endometrium

39. What teratogen can cause an absence of digits amongst other things in the fetus? give an example.
Hemorrhage - bone deformities
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Annular pancrease
Alkylating agents

40. Where is the mothers blood located in the placenta?
Lacunae in between the chorionic villi
Neural crest cells
Dorsal ventral axis
Cleft lip/palate

41. From What embryonic layer do the astrocytes arise?
Neuroectoderm
Left horn of the sinus venosus
Oxygenated; placenta to fetus (IVC)
Fetal and maternal

42. Which CN allows for taste and sensation in the posterior 1/3 of the tongue? how about the very back ?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
IX; X
Neural crest cells
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

43. What role does the placenta have?
Nutrient and gas exchange
Temporary cervical sinus
Endometrium
80%

44. What type of blood do umbilical veins carry? From where to where?
Hemorrhage - bone deformities
Oxygenated; placenta to fetus (IVC)
Dorsal; faulty positioning of genital tubercle
Week 8

45. Which branchial derivative accounts for taste in the ant 2/3?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Branchial arch 2
First branchial pouch
Hypertrophy of muscularis externis of pylorus; surgical incision

46. What does the mullerian duct develop into? wollffian?
Bone/cartilage and nerves
Fallopian tube - uterus - upper 1/3 of vagina
elevated AFP
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

47. What is the female remnant of processus vaginalis? male remnant?
Cerebellar tonsillar herniation through foramen magnum
Ectoderm
Obliterated; forms tunica vaginalis
80%

48. What separates the ant 1/3 and post 2/3 of tongue?
Prosencephalon - mesencephalon - rhombencephalon
2; 1
Foramen cecum and terminal sulus
Week 3; primitive streak formation from the epiblast makes the three layers

49. From What embryonic layer is the vagina from? testes? ovaries?
Mesoderm
Tetracyclines
Muscular ventricular septum; no
...

50. what chemo drugs can cause neural tube defects in the fetus?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Folate antagonists
Medial palatine processes
mesoderm