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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 are markers for neural tube defects in the amniotic cavity? CSF?
Mesoderm
Branchial arch 2
Diencephalon
Increased AFP and acetycholinesterase (not ACh!) in CSF

2. What are two common findings in pyloric stenosis?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
ACE inhibitors - HCTZ
Cerebellar tonsillar herniation through foramen magnum
Increased AFP and acetycholinesterase (not ACh!) in CSF

3. Which branchial apparatus develops into the thymus?
Week 4; week 3
Endoderm - floor of primitive pharynx
Membrane - all 3 from 1st appartus
3rd pouch

4. what closes the interventricular foramen?
Lithium
Foramen cecum and terminal sulus
Yolk sac; 3rd week
Physiologic incomplete muscular ventricular septum

5. From where did a branchial cleft cyst arise if it found?
Prosencephalon
Failure to recanalize; 21
5th
Found in lateral neck; from no obliteration of 2-4th clefts

6. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
Endoderm
not covered
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
hypospadias

7. What day is the chorion formed?
3
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Foramen cecum and terminal sulus
ACE inhibitors - HCTZ

8. Which parts of the pancreas contribute to the head - uncinate process and main pancreatic duct?
mesodermal
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Dorsal and ventral buds
Aminoglycosides

9. From What embryonic layer does the lens of the eye arise?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Surface ectoderm
Mesencephalon
Bones - cartilage - and nerves

10. From What embryonic layer does bone of the skulls arise?
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Mesencephalon
Neural crest cells
Base of limbs in the zone of polarizing activity; ant - post

11. Cleft palate is a failure of formation of the...
Persistent connection between amniotic cavity and spinal canal; low folic acid
Where the epiblast and hypoblast fuse
Neuroectoderm
secondary palate

12. What embryological structures give rise to the SVC?
Right common cardinal vein and right anterior cardinal vein
Membrane - all 3 from 1st appartus
Mesoderm
Neuroectoderm

13. What does the midgut form? hindgut?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Spinothalamic first
Duodenum to transverse colon; distal transverse colon to rectum
Fetal alcohol syndrome; mental retardation

14. Which branchial apparatus develops into the inferior parathyroids?
Mesdoerm
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Neural crest cells
3rd pouch

15. What causes the transposition of the great vessels? What does it result in?
StyloPharyngeus
Decidual basalis
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
During; instrinsic

16. What is Treacher Collins syndrome? What is the result?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Synctiotrophoblast; outer; no
Excessive resorption of septum primum or secondum (or both)

17. What is the Eisenmeger complex?
Surface ectoderm
When left to right shunting switching to right to left shunting
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Epiblast

18. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
DiGeorge
hypospadias
28 week onward
Turners; inferior

19. What causes the increase in left atrial pressure to close the fossa ovale?
Decreased pulmonary resistance in the pulmonary vasculature
Failure of bony spinal canal to fuse; no; lower vertebral levels
Rhombencephalon
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells

20. what muscles are derived from branchial arch 3?
StyloPharyngeus
6-30
Upper 1/3; urogenital sinus
Synctiotrophoblast; outer; no

21. What can vit A in excess cause in the fetus?
5th
Lots - cleft palate/lip
Neural crest cells
VACTERL; OCPs and maternal diabetes

22. what separates the atria from the ventricles?
Neural crest cells
Endocardial cushions
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Decreases

23. what bone/cartilage and nerves are derived from branchial arch 3?
Greater horn of hyoid; CN IX (styloPharyngeus)
StyloPharyngeus
Telencephalon
Oxygenated; placenta to fetus (IVC)

24. From what branchial derivative do the parafollicular cells arise?
6-30
Failure of the urachus to obliterate; outpouching of the bladder
Neural crest cells
4th/5th branchial pouches

25. What effect does warfarin have on the fetus?
Mesoderm
Hemorrhage - bone deformities
Nutrient and gas for exchange; endometrium
Endoderm

26. From What embryonic layer do the astrocytes arise?
6-30
Vascular accident intra uterine; apple peel atresia
Neuroectoderm
1st cleft/groove (Ectoderm)

27. What is the notochord? What does the notochord later become?
Nutrient and gas exchange
Ectoderm
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Mesoderm; nucleous pulposos

28. How do you differentiate a thyroglossal duct cyst from a persistent cervical sinus?
Thalidomide; nausea
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Week 8

29. From What embryonic layer is the bladder and urethra from?
Mesoderm
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Epispadias
Sperm plus egg

30. What is the most common autopsy finding in brains of premature infants?
Folate antagonists
Incomplete; yes
Increase in oxygen concentration which decreases prostaglandin concentration
Germinal matrix hemorrhage

31. What is the mcc of renovascular hypertension in children? What does this predispose to?
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Renal artery stenosis;
Muscles and arteries
Maternally derived; meconium

32. What components do the neural crest cells of the branchial arches give rise to?
Week 3; primitive streak formation from the epiblast makes the three layers
Bones - cartilage - and nerves
Foramen cecum and terminal sulus
Umbilical - midgut herniates through umbilical ring; SMA

33. What are the clinical symptoms that present with syringomelia?
Wolffian; mullerian
Sperm plus egg
VSD
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

34. What components do the mesoderm of the branchial arches give rise to?
Muscles and arteries
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Pulm art (prox) and ductus arteriosus
From teh lung;blood from IVC in RA to LA; fossa ovalis

35. From What embryonic layer are the melanocytes from?
Grooves/clefts; arches; pouches
Neural crest cells
Neuroectoderm
Right horn of the SV

36. From What embryonic layer is the spleen from?
80%
mesodermal
Mesoderm
Ectoderm

37. which teratogen can cause Ebsteins anomaly in the fetus?
Lithium
arnold chiari associated with thoraclumbar myelomeningocele
Respiratory distress syndrome
Turners; inferior

38. From where does the medulla form?
Dorsal; sensory
Bulbos Cordis; right ventricle entirely
Embryonic period; 1st trimester
Myelencephalon

39. The spinal cord is made from...
3
DiGeorge
T neuroectoderm
Amniotic epithelium

40. What is a syrinx? Where is it found in syringomelia? What is it associated with?
3 -4 -6
Sperm plus egg
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

41. What causes tetralogy of Fallot?
Scrotum; labia majora
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)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Skewed development of AP septum

42. Which branchial derivative creates the epithelial lining of the palatine tonsils?
Prenatal and perinatal
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
2nd pouch
Amniotic cavity and yolk sac

43. By what week is the neural tube supposed to be closed? when did it start forming?
Obliterated; forms tunica vaginalis
primary palate
Week 4; week 3
Pulm art (prox) and ductus arteriosus

44. Which is more common - epispadias or hypospadias?
Neural crest cells
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Ventral ; motor
Hypospadias

45. What axis is Wnt 7 responsible for developing?
arnold chiari associated with thoraclumbar myelomeningocele
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Surface ectoderm
Dorsal ventral axis

46. What do the arches of the branchial apparatus correlate to?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Mesdoerm
mesodermal

47. Which cranial nerve innervates the motor function of the tongue?
XII
Neuroectoderm
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

48. what bone/cartilage and nerves are derived from branchial arch 1?
Hemorrhage - bone deformities
Mid gut to yolk sac; omphalomesenteric duct; 7th week
DiGeorge
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

49. What causes the obstruction in pyloric stenosis? treatment?
Obliterated; forms tunica vaginalis
Week 4
Week 3-8
Hypertrophy of muscularis externis of pylorus; surgical incision

50. what week do the genitalia start to have male/female characteristics? What trimester is that?
Left horn of the sinus venosus
Week 10-12; end of 1st trimester
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Mesoderm