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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 arises from the fourth aortic arch?
Dorsal and ventral buds
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Aortic arch (from left side); right subclavian (on the right)
Left horn of the sinus venosus

2. _____________is common in 1st born males
pyloric stenosis
Neural crest migration - they then cause spiral
Excessive resorption of septum primum or secondum (or both)
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

3. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
StyloPharyngeus
4th pouch
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
not covered

4. What is an arnold chiari II malformation? through what hole does it herniate?
...
Cerebellar tonsillar herniation through foramen magnum
Decreases
Nutrient and gas for exchange; endometrium

5. What components do the neural crest cells of the branchial arches give rise to?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Bones - cartilage - and nerves
Failure of bony spinal canal to fuse; no; lower vertebral levels
LH

6. What is another name for the mesonephric duct? paramesonephric?
Surface ectoderm
Wolffian; mullerian
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Foregut; dorsal mesentery (mesodermal)

7. From What embryonic layer do the astrocytes arise?
Primitive atrium
Neuroectoderm
Stapedius and hyoid artery
Mesoderm

8. What two things cause VACTERL syndrome?
OCPS and maternal diabetes
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
Week 2; bilaminar disk; epiblast and hypoblast
Bones - cartilage - and nerves

9. What is the Eisenmeger complex?
Epispadias
Bone/cartilage and nerves
Grooves/clefts; arches; pouches
When left to right shunting switching to right to left shunting

10. What is the neural plate and From what does it form?
Ectoderm
Mid gut to yolk sac; omphalomesenteric duct; 7th week
6-30
Neuroectoderm

11. During what months is the fetus most susceptible to teratogens? What trimester?
Fetal and maternal
Embryonic period; 1st trimester
Upper 1/3; urogenital sinus
Mesoderm

12. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Prevent recurrent UTIs
Day 6; with implantation
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Neural crest cells

13. From What embryonic layer do CNS neurons arise?
First branchial pouch
Neural crest migration - they then cause spiral
Neuroectoderm
Occiptal

14. Which branchial apparatus develops into the inferior parathyroids?
Endoderm
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
3rd pouch
Failure of the urachus to obliterate

15. what week do the genitalia start to have male/female characteristics? What trimester is that?
Surface ectoderm
Post. sup wall; luteal phase
Week 10-12; end of 1st trimester
Dorsal and ventral buds

16. what structures are the derivatives of the neural crest cells in branchial arches?
80%
Bone/cartilage and nerves
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
All 3

17. From What embryonic layer does the adenohypophysis arise?
Surface ectoderm
Indomethacin; blocks PG production
Tongue
Synctiotrophoblast; outer; no

18. How do adults with annular pancreas present? and At What age?
hypospadias
Neuroectoderm
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Tongue

19. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
Nutrient and gas exchange
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Absent cerebellar vermis; cystic enlargement of 4th ventricle

20. What does the RET gene encode? what neoplasias is it associated with?
Increased AFP and acetycholinesterase (not ACh!) in CSF
StyloPharyngeus
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Week 4

21. What is Treacher Collins syndrome? What is the result?
5th
Ventral bud
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Neural crest migration - they then cause spiral

22. What are two common findings in pyloric stenosis?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
6-30
Neural crest cells

23. What are the clinical symptoms that present with syringomelia?
Prenatal and perinatal
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Prosencephalon
Absent cerebellar vermis; cystic enlargement of 4th ventricle

24. Which cranial nerve innervates the motor function of the tongue?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
1st
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
XII

25. What is perinauds syndrome?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Surface ectoderm
DHT; estrogen

26. What components do the mesoderm of the branchial arches give rise to?
Allantois
Muscles and arteries
primary palate
Endoderm

27. The notochord is...
Outgrowth of mesonephric as ureteric bud; most caudal
Thalidomide; nausea
1st cleft/groove (Ectoderm)
mesoderm

28. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Mesoderm
secondary palate
Nicotine; preterm labor
blood entering the RA

29. From where is the pancreas derived? the spleen?
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
mesoderm
Foregut; dorsal mesentery (mesodermal)

30. What causes the decrease in Right atrial pressure to close the fossa ovale?
No more umbilical circulation emptying into RA
Mesoderm
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells

31. what invaginates to form the primitive streak?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Epiblast
OCPS and maternal diabetes
Increase in oxygen concentration which decreases prostaglandin concentration

32. From What embryonic layer is the bladder and urethra from?
Temporary cervical sinus
Mesoderm
No organ in each; agenesis no primordial tissue
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule

33. what bone/cartilage and nerves are derived from branchial arch 3?
hypertrophy
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Greater horn of hyoid; CN IX (styloPharyngeus)
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)

34. What causes tetralogy of Fallot?
Skewed development of AP septum
Metencephalon; cerebellum
4th arch; 6th arch
Nutrient and gas exchange

35. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Embryonic period; 1st trimester
During; instrinsic
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

36. What embryological structures give rise to the SVC?
Neuroectoderm
Midgut; 10th week
Right common cardinal vein and right anterior cardinal vein
1st cleft/groove (Ectoderm)

37. What is omphalocele? In What trisomies is it seen?
2nd; 2nd
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Mesdoerm
Endometrium

38. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
Respiratory distress syndrome
Ventral ; motor
Nicotine; preterm labor
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'

39. From what region of the brain does the lateral ventricles and the 3rd ventricle form?
Prosencephalon
No more umbilical circulation emptying into RA
ACE inhibitors - HCTZ
Ebsteins anomaly; tricuspid atresia

40. From What embryonic layer does bone arise ?
Week 10-12; end of 1st trimester
Surface ectoderm
Mesoderm
...

41. What is the difference between agenesis and aplasia?
No organ in each; agenesis no primordial tissue
Week 3; primitive streak formation from the epiblast makes the three layers
Mental retardation - holoprosencephaly - facial features - fistulas
Branchial arch 2

42. From What embryonic layer does the retina arise?
Neuroectoderm
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Failure of bony spinal canal to fuse; no; lower vertebral levels
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

43. When is most important to take folic acid to prevent neural tube defects?
Before getting pregnant!
Neural crest migration - they then cause spiral
2nd pouch
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

44. what closes the interventricular foramen?
Physiologic incomplete muscular ventricular septum
Lithium
Duodenum to transverse colon; distal transverse colon to rectum
secondary palate

45. From What embryonic layer does the gut tube epithelium arise?
Tongue
Oxygenated; placenta to fetus (IVC)
Endoderm
Allantois

46. How is amniontic fluid excreted? How is amniotic fluid resorped?
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Neuroectoderm
External auditory meatus
Mesoderm; 3 week

47. What does DHT turn the urogenital folds into? estrogen?
Week 2; bilaminar disk; epiblast and hypoblast
Turners; inferior
Incomplete; yes
Ventral shaft of penis (penile urethra); labia minora

48. What secretes hCG?
Telencephalon
Hypertrophy of muscularis externis of pylorus; surgical incision
Right horn of the SV
Synctiotrophoblast

49. What can vit A in excess cause in the fetus?
Lots - cleft palate/lip
Oxygenated; placenta to fetus (IVC)
Surface ectoderm
Maternally derived; meconium

50. Where is the FGF gene produced? What is it responsible for - How does it do this?
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Aortic arch and prox part of subclavian
Failure of the urachus to obliterate
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm