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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 is the mnueomonic for the mesodermal defects? What does it stand for?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
blood entering the RA
Allantois

2. From what region does the cerebral hemisphere form?
...
Week 8
Telencephalon
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

3. From What embryonic lare are the odontoblasts from?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Neural crest cells
Week 4
2nd; 2nd

4. From What embryonic layer does the pineal gland arise?
3
Neuroectoderm
Increased AFP and acetycholinesterase (not ACh!) in CSF
Tunica vaginalis not fully fused

5. From where does the pulmonary arteries and the ductus arteriosus arise?
Failure of bony spinal canal to fuse; no; lower vertebral levels
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
6th aortic arch
Fetal alcohol syndrome; mental retardation

6. What is holoprosencephaly? what eye disorder does it result in?
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Increase in oxygen concentration which decreases prostaglandin concentration
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Decreased separation of hemispheres across midline; cyclopia

7. From What embryonic layer is the spleen from?
Hypertrophy of muscularis externis of pylorus; surgical incision
Foregut; dorsal mesentery (mesodermal)
Mesoderm
Ovarian ligament and round ligament of uterus; anchors testes within scrotum

8. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Surface ectoderm
Obliterated
Increased AFP and acetycholinesterase (not ACh!) in CSF
Myelencephalon

9. How many umbilical arteries are there? How many umbilical veins?
2; 1
Thalidomide; nausea
elevated AFP
6-30

10. What causes the degeneration of the spinal cord in syringomelia?
Fluid filled syrinx causes expansion and degeneration of cord tracts
pyloric stenosis
Week 8
Decreased separation of hemispheres across midline; cyclopia

11. In anencephaly you see...
elevated AFP
4th/5th branchial pouches
Germinal matrix hemorrhage
Day 6; with implantation

12. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
3rd pouch
Week 8
Week 4; week 3
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

13. From What embryonic layer does the epidermis arise?
Common carotid and internal carotid
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Surface ectoderm

14. What is DiGeorge syndrome and What does it result in?
4th/5th branchial pouches
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
From endocardial cushions (ventral and dorsal meet each other)

15. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Deoxygenated blood; fetal internal iliac arteries to placenta
Arches 3 and 4
Ectoderm
...

16. During what months is the fetus most susceptible to teratogens? What trimester?
Outgrowth of mesonephric as ureteric bud; most caudal
Female; paramesonephric; mesonephric
Neural crest cells
Embryonic period; 1st trimester

17. What is the notochord? What does the notochord later become?
Mesoderm; nucleous pulposos
Greater horn of hyoid; CN IX (styloPharyngeus)
2; 1
All or none

18. Which branchial apparatus derivative makes the tympanic membrane of the ear?
Dorsal; faulty positioning of genital tubercle
Decreased separation of hemispheres across midline; cyclopia
Mesoderm
Membrane - all 3 from 1st appartus

19. From What embryonic layer does the olfactory epithelium arise?
Surface ectoderm
Nutrient and gas for exchange; endometrium
secondary palate
Endoderm

20. What two cavities also form during the second week?
can make cells
No more umbilical circulation emptying into RA
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Amniotic cavity and yolk sac

21. What is congenital pharyngocutaneous fistula? and How does it occur?
Neural crest cells
Fluid filled syrinx causes expansion and degeneration of cord tracts
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Neural crest cells

22. What embryological structure gives rise to the trabeculated part of the left and right atrium?
Primitive atrium
When left to right shunting switching to right to left shunting
Duodenum to transverse colon; distal transverse colon to rectum
Mesoderm

23. The spinal cord is made from...
3 -4 -6
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Neural crest cells
T neuroectoderm

24. From What embryonic layer does bone arise ?
Common carotid and internal carotid
Mesencephalon
pyloric stenosis
Mesoderm

25. 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?
Right common cardinal vein and right anterior cardinal vein
Diencephalon
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
First branchial pouch

26. What is perinauds syndrome?
Yolk sac; 3rd week
Incomplete; yes
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Nicotine; preterm labor

27. What part of the fetal comp of the placenta secretes hCG? is this part on the inner or outer layer of the chorionic villi? does it make cells?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Synctiotrophoblast; outer; no
3 -4 -6

28. What does the mullerian duct develop into? wollffian?
Fallopian tube - uterus - upper 1/3 of vagina
6th aortic arch
Fluid filled syrinx causes expansion and degeneration of cord tracts
Decreases

29. What are the neural crest cells and where do they come form? where do they go?
External auditory meatus
They are the edge of neural plate folding; all over the body
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
arnold chiari associated with thoraclumbar myelomeningocele

30. In what chromosomal disorder is horseshoe kidney commonly seen? what poles of the kidneys fuse?
Neural crest migration - they then cause spiral
Neural plate; closes by week 4
Membrane - all 3 from 1st appartus
Turners; inferior

31. What teratogens can cause flipper limbs (limb defects)? What is this drug used for?
Aminoglycosides
Decidual basalis
Mesoderm; nucleous pulposos
Thalidomide; nausea

32. What does DHT turn the urogenital folds into? estrogen?
Decreases
Base of limbs in the zone of polarizing activity; ant - post
Ventral shaft of penis (penile urethra); labia minora
Stapedius and hyoid artery

33. What does DHT turn the genital tubercle into? estrogen?
T neuroectoderm
Endoderm
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
No more umbilical circulation emptying into RA

34. which tracts are damaged first in syringomelia? What tract is preserved?
Thalidomide; nausea
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Spinothalamic first

35. Name a syndrome cleft palate is often seen in
Endocardial cushions
DiGeorge
Fallopian tube - uterus - upper 1/3 of vagina
Neural crest cells

36. When is most important to take folic acid to prevent neural tube defects?
Bones - cartilage - and nerves
5th
Before getting pregnant!
Failure to recanalize; 21

37. What do membranous interventricular septal defect cause? What does this lead to?
Initial left to right shunting - then switches
Telencephalon
Right common cardinal vein and right anterior cardinal vein
DiGeorge

38. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
Primitive atrium
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Female; paramesonephric; mesonephric
DES

39. What causes the transposition of the great vessels? What does it result in?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
mesoderm
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

40. What is meckel's diverticulum? What is it associated with? What does that cause?
Midgut; 10th week
They are the edge of neural plate folding; all over the body
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

41. What gene is produced in the zone of polarizing activity?
Truncus arteriosus; pulmonary trunk
Occiptal
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Sonic Hedgehog

42. Which branchial apparatus develops into the thymus?
Pataus; fetal alcohol syndrome
3rd pouch
Mesonephros; male genital system
Failure to recanalize; 21

43. What teratogens can cause discolored teeth?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Prenatal and perinatal
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Tetracyclines

44. From where did a branchial cleft cyst arise if it found?
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
hypertrophy
Found in lateral neck; from no obliteration of 2-4th clefts
2nd pouch

45. What is the effect of teratogens before week 3?
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
All or none
Ebsteins anomaly; tricuspid atresia
4th/5th branchial pouches

46. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Neuroectoderm
Week 3-8
Valproate acid

47. For what reason do hypospadias need to be fixed?
Found in lateral neck; from no obliteration of 2-4th clefts
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Prevent recurrent UTIs
Branchial arch 2

48. From What embryonic layer does the lens of the eye arise?
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Neural crest cells
Surface ectoderm
Rhombencephalon

49. From where is the pancreas derived? the spleen?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Scrotum; labia majora
Mesencephalon
Foregut; dorsal mesentery (mesodermal)

50. ______________ is associated with ventral curvature of the penis
6th aortic arch
hypospadias
No more umbilical circulation emptying into RA
Day 6; maintains corpus luteum; 1st trimester