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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. From What embryonic layer are the dorsal root and celiac ganglion from?
Maternally derived; meconium
From teh lung;blood from IVC in RA to LA; fossa ovalis
Neural crest cells
Endoderm

2. What is annular pancreas associated with in infants?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Hypospadias
Germinal matrix hemorrhage

3. What secretes hCG?
Maxillary
can make cells
Synctiotrophoblast
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast

4. From What embryonic layer does the neurohypophysis arise?
Tunica vaginalis not fully fused
Cerebellar tonsillar herniation through foramen magnum
hypospadias
Neuroectoderm

5. What results in annular pancreas? How does it happen?
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
IX; X
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Neural crest migration - they then cause spiral

6. What is the neural plate and From what does it form?
Dorsal ventral axis
Base of limbs in the zone of polarizing activity; ant - post
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Ectoderm

7. Which is more common - epispadias or hypospadias?
Hypospadias
can make cells
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Membrane - all 3 from 1st appartus

8. The spleen is ____________ in origin and supplied by a foregut artery
mesodermal
Pulm art (prox) and ductus arteriosus
Week 3; primitive streak formation from the epiblast makes the three layers
Fallopian tube - uterus - upper 1/3 of vagina

9. What is congenital pharyngocutaneous fistula? and How does it occur?
Ebsteins anomaly; tricuspid atresia
Day 6; maintains corpus luteum; 1st trimester
Yolk sac; 3rd week
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

10. From what arches are the neural crest cells that form the aorticpulmonary septum derived?
Prenatal and perinatal
3 -4 -6
Neural crest cells
Incomplete; yes

11. From where does the ureteric bud arise? What does it give rise to?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Neural crest cells
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Neuroectoderm

12. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Decreases
V3; VII
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Vascular accident intra uterine; apple peel atresia

13. What is used to keep the PDA open?
Germinal matrix hemorrhage
Prostaglandins
From endocardial cushions (ventral and dorsal meet each other)
From teh lung;blood from IVC in RA to LA; fossa ovalis

14. From What embryonic layer is the spleen from?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Week 8
Bones - cartilage - and nerves
Mesoderm

15. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Annular pancrease
Valproate acid
Week 3-8
Indomethacin; blocks PG production

16. What is hypoplasia? is primordial tissue present?
Right horn of the SV
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Annular pancrease
Incomplete; yes

17. What is the difference between agenesis and aplasia?
Outgrowth of mesonephric as ureteric bud; most caudal
Thalidomide; nausea
No organ in each; agenesis no primordial tissue
OCPS and maternal diabetes

18. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Week 2; bilaminar disk; epiblast and hypoblast
IMA
Surface ectoderm

19. what closes the interventricular foramen?
Physiologic incomplete muscular ventricular septum
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
They are the edge of neural plate folding; all over the body

20. From what region of the brain does the aqueduct form?
8
Decreases
A vitelline fistula - failure of vitelline duct to close
Rhombencephalon

21. What is meckel's diverticulum? What is it associated with? What does that cause?
Mesoderm
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

22. From what branchial derivative do the parafollicular cells arise?
Endoderm
Neuroectoderm
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
4th/5th branchial pouches

23. What teratogens can cause renal damage in the fetus?
Epispadias
Week 3; primitive streak formation from the epiblast makes the three layers
ACE inhibitors - HCTZ
Mesoderm; epiblast

24. What layer is the epiblast? hypoblast?
Epiblast
No organ in each; agenesis no primordial tissue
Ectoderm; endoderm
Left horn of the sinus venosus

25. What does DHT turn the urogenital sinus into? estrogen?
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Mesoderm
...
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian

26. From What embryonic layer does the olfactory epithelium arise?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Cytotrophoblast
Surface ectoderm

27. Before birth - blood entering the LA is less than...
blood entering the RA
Bones - cartilage - and nerves
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Diencephalon

28. From where does the signal come from to suppress paramesonephric ducts? what stimulates development of the mesonephric ducts?
A vitelline fistula - failure of vitelline duct to close
Mesoderm; epiblast
After; extrinsic
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

29. what bone/cartilage and nerves are derived from branchial arch 3?
Greater horn of hyoid; CN IX (styloPharyngeus)
Ventral ; motor
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus

30. What is the effect of teratogens before week 3?
From endocardial cushions (ventral and dorsal meet each other)
Decreased pulmonary resistance in the pulmonary vasculature
All or none
Mesoderm

31. In both meningocele and myelomeningocele the dura...
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Folate antagonists
is no longer intact
6-30

32. What is the mnueomonic for the mesodermal defects? What does it stand for?
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Week 10-12; end of 1st trimester
Where the epiblast and hypoblast fuse
Neural crest cells

33. 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?
Synctiotrophoblast; outer; no
Embryonic period; 1st trimester
Foramen cecum and terminal sulus
Foregut; dorsal mesentery (mesodermal)

34. What two things cause VACTERL syndrome?
OCPS and maternal diabetes
Week 8
arnold chiari associated with thoraclumbar myelomeningocele
Outgrowth of mesonephric as ureteric bud; most caudal

35. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Aortic arch (from left side); right subclavian (on the right)
OCPS and maternal diabetes
Mid gut to yolk sac; omphalomesenteric duct; 7th week

36. How many components are there to the placenta? What are they called?
Fetal and maternal
Increase in oxygen concentration which decreases prostaglandin concentration
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
Dorsal; faulty positioning of genital tubercle

37. With the first breath the infant take - pulmonary vasculature resistance _______ which causes an increase in left atrial pressure
Cranio - caudal; segmental
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Decreases
Where the epiblast and hypoblast fuse

38. When does hCG secretion take place? with what event?
DHT; estrogen
Day 6; with implantation
Bulbos Cordis; right ventricle entirely
Scrotum; labia majora

39. From what region does the midbrain form from?
Where the epiblast and hypoblast fuse
Surface ectoderm
Mesencephalon
Nicotine; preterm labor

40. What weeks are considered the 'embryonic period'?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Failure to recanalize; 21
Ectoderm
Week 3-8

41. From What embryonic layer is the eustachian tube from?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Mesoderm
Deformation
Hypospadias

42. What causes the transposition of the great vessels? What does it result in?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
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)
2; 1
Neuroectoderm

43. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Oligohydramnios
4th pouch
Prosencephalon

44. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Decreased separation of hemispheres across midline; cyclopia
Failure to recanalize; 21
Mesoderm
Membrane - all 3 from 1st appartus

45. What type of radiation is teratogenic ?
Prosencephalon - mesencephalon - rhombencephalon
Ionizing
Surface ectoderm
Right horn of the SV

46. From which germlayer does the thyroid develop?? From what structure exactly?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Annular pancrease
Endoderm - floor of primitive pharynx
Upper 1/3; urogenital sinus

47. What artery is derived branchial (aortic) arch 4?
2nd; 2nd
Aortic arch and prox part of subclavian
Bone/cartilage and nerves
Oligohydramnios

48. what bone/cartilage and nerves are derived from branchial arch 1?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Cranio - caudal; segmental
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

49. From What embryonic layer do chromaffin cells arise?
Neural crest cells
Week 3; primitive streak formation from the epiblast makes the three layers
StyloPharyngeus
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

50. From where is the pancreas derived? the spleen?
Ventral ; motor
StyloPharyngeus
Foregut; dorsal mesentery (mesodermal)
2nd pouch