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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 causes persistent Truncus Arteriosus? What does it result in?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Endocardial cushions
Neural crest cells
Week 8

2. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
Primitive atrium
Mesoderm
Nicotine; preterm labor
Neural crest cells

3. Which cranial nerve innervates the motor function of the tongue?
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
septum primum and/or secundum
XII
Congenital and chromosomal abnormalities

4. From What embryonic layer does bone arise ?
Week 3; primitive streak formation from the epiblast makes the three layers
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Neuroectoderm
Mesoderm

5. What is the leading cause of birth defects in the US? what else is this perpetrator the leading cause of?
Ventral shaft of penis (penile urethra); labia minora
Fetal alcohol syndrome; mental retardation
Base of limbs in the zone of polarizing activity; ant - post
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

6. What is associated with only one umbilical artery?
Neuroectoderm
Congenital and chromosomal abnormalities
Found in lateral neck; from no obliteration of 2-4th clefts
Alkylating agents

7. From What embryonic layer does bone of the skulls arise?
Neural crest cells
Myelencephalon
Renal artery stenosis;
Epispadias

8. By what week is there fetal movement?
Week 8
Neuroectoderm
Week 4
Cytotrophoblast

9. What do membranous interventricular septal defect cause? What does this lead to?
Endoderm
Initial left to right shunting - then switches
6th aortic arch
1st cleft/groove (Ectoderm)

10. From What do the embryoblast and trophoblast form from? What does the embryoblast split into? the trophoblast?
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Neural crest cells
Increase in oxygen concentration which decreases prostaglandin concentration
Occiptal

11. what closes the ductus arteriousus?
Cerebellar tonsillar herniation through foramen magnum
Increase in oxygen concentration which decreases prostaglandin concentration
Surface ectoderm
Skewed development of AP septum

12. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
not covered
Failure to recanalize; 21
6th aortic arch
Tongue

13. What axis does the alar plate form? what neural system does it become?
Tunica vaginalis not fully fused
Dorsal; sensory
No more umbilical circulation emptying into RA
DES

14. Monochorionic - ___________ twins are conjoined
not covered
Surface ectoderm
monoamniotic
Amniotic cavity and yolk sac

15. With the first breath the infant take - pulmonary vasculature resistance _______ which causes an increase in left atrial pressure
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
Decreases
Endoderm
Aminoglycosides

16. What do the groove/clefts of the branchial apparatus correlate to?
Surface ectoderm
Mesencephalon
Ectoderm
Muscles of Mastication: Temporalis - masseter - Lateral and Medila pterygoids - Mylohyoid - anterior belly of the digastric - tensor tympani - tensor veli palatini; ant 2/3 of tongue

17. From What embryonic layer does a craniopharygioma arise?
Week 4
Decreased separation of hemispheres across midline; cyclopia
Neuroectoderm
Surface ectoderm

18. Cleft lip is a failure of formation of the...
primary palate
Failure of bony spinal canal to fuse; no; lower vertebral levels
DHT; estrogen
Increase in oxygen concentration which decreases prostaglandin concentration

19. From What embryonic layer is the bladder and urethra from?
Surface ectoderm
Valproate acid
Thalidomide; nausea
Mesoderm

20. Which branchial derivative creates the middle ear cavity - eustachian tube and mastoid air cells?
Neuroectoderm
No more umbilical circulation emptying into RA
StyloPharyngeus
First branchial pouch

21. what bone/cartilage and nerves are derived from branchial arch 3?
First branchial pouch
Maxillary
Neural crest cells
Greater horn of hyoid; CN IX (styloPharyngeus)

22. What surrounds the umbilical cord?
Metencephalon; cerebellum
primary palate
Amniotic epithelium
Midgut; 10th week

23. Before birth - blood entering the LA is less than...
Aminoglycosides
blood entering the RA
hypospadias
Oligohydramnios

24. What is the primitive streak? From what layer does it form?
3
Mesoderm
Mesoderm; epiblast
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

25. Which branchial arch derivative is obliterated?
5th
mesoderm
Surface ectoderm
Mesoderm

26. What is the allantois become? What is this duct connected to ( on both ends)?
Urachus/median umbilical ligament; bladder and yolk sac
Mesdoerm
External auditory meatus
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

27. What does DHT turn the labioscrotal swelling into? estrogen?
Scrotum; labia majora
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Cytotrophoblast and synctiotrophoblast
Obliterated

28. In anencephaly you see...
Week 8
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
elevated AFP
Thickened ectoderm at end of each developing limb

29. What is DiGeorge syndrome and What does it result in?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Wolffian; mullerian

30. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Obliterated
1st branchial arch
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

31. From What embryonic layer does connective tissue and muscle arise?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Mesoderm
Female; paramesonephric; mesonephric
Foregut; dorsal mesentery (mesodermal)

32. From What embryonic layer does the inner arise?
Ebsteins anomaly; tricuspid atresia
...
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Arches 3 and 4

33. From which germlayer does the thyroid develop?? From what structure exactly?
Neuroectoderm
Increase in oxygen concentration which decreases prostaglandin concentration
Endoderm - floor of primitive pharynx
Mesoderm

34. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Oligohydramnios
Cerebral hemisphere - thalami
A vitelline fistula - failure of vitelline duct to close
Week 2; bilaminar disk; epiblast and hypoblast

35. Where is the FGF gene produced? What is it responsible for - How does it do this?
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Base of limbs in the zone of polarizing activity; ant - post
Tetracyclines
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

36. what muscles are derived from branchial arch 2?
Prevent recurrent UTIs
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Cytotrophoblast and synctiotrophoblast
OCPS and maternal diabetes

37. The inner layer of the chorionic villi...
Ectoderm
Hypospadias
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
can make cells

38. What embryonic structure gives rise to the ascending aorta? what else does it give rise to?
IMA
Truncus arteriosus; pulmonary trunk
Synctiotrophoblast; outer; no
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

39. From What embryonic layer does the adenohypophysis arise?
Amniotic cavity and yolk sac
Surface ectoderm
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Cytotrophoblast

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

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41. From What embryonic layer is the eustachian tube from?
Mesoderm
No organ in each; agenesis no primordial tissue
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Lots - cleft palate/lip

42. From what branchial derivative do the parafollicular cells arise?
4th/5th branchial pouches
Occiptal
blood entering the RA
lumbosacral

43. 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)
Mesoderm
Bone/cartilage and nerves
Neural crest cells

44. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Female; paramesonephric; mesonephric
Neuroectoderm
Valproate acid

45. What does DHT turn the genital tubercle into? estrogen?
Week 8
Endoderm - floor of primitive pharynx
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Synctiotrophoblast; outer; no

46. When does erythropoeisis begin in the bone marow?
Mesoderm
Nicotine; preterm labor
Decreased separation of hemispheres across midline; cyclopia
28 week onward

47. From What embryonic layer do the ANS arise?
Neural crest cells
Hemorrhage - bone deformities
V3; VII
Primitive ventricle

48. in hypospadias - on which side is the abnormal opening? What causes it?
Fetal and maternal
Endoderm - floor of primitive pharynx
Ventral; failure of urogenital folds to close
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

49. What is meckel's diverticulum? What is it associated with? What does that cause?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Endoderm
OCPS and maternal diabetes
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

50. When is most important to take folic acid to prevent neural tube defects?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Cerebellar tonsillar herniation through foramen magnum
Before getting pregnant!
Mental retardation - holoprosencephaly - facial features - fistulas