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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 layer is the epiblast? hypoblast?
Yolk sac; 3rd week
Thickened ectoderm at end of each developing limb
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Ectoderm; endoderm

2. What are the two walls of the prosencephalon and What do they become?
Cerebral hemisphere - thalami
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Upper 1/3; urogenital sinus
Bulbos Cordis; right ventricle entirely

3. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Mesoderm
Failure to recanalize; 21
blood entering the RA
Base of limbs in the zone of polarizing activity; ant - post

4. In order to survive tricuspid atresia - What do you need?
VSD
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Nicotine; preterm labor
4th arch; 6th arch

5. What does the ductus venosus shunt blood away from? What is its remnant?
Neural crest cells
Failure of bony spinal canal to fuse; no; lower vertebral levels
Hepatic circulation; ligamentum venosum
XII

6. ______________ is associated with ventral curvature of the penis
Base of limbs in the zone of polarizing activity; ant - post
Ionizing
hypospadias
Muscular ventricular septum; no

7. what muscles are derived from branchial arch 2?
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Fetal and maternal
Mesoderm
Dorsal; faulty positioning of genital tubercle

8. what muscles are derived from branchial arch 4? CN?
Found in lateral neck; from no obliteration of 2-4th clefts
All 3
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Cytotrophoblast and synctiotrophoblast

9. From What embryonic layer does the neurohypophysis arise?
Week 2; bilaminar disk; epiblast and hypoblast
Neuroectoderm
DiGeorge
Endoderm - floor of primitive pharynx

10. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
Cerebral hemisphere - thalami
All 3
Deoxygenated blood; fetal internal iliac arteries to placenta
DHT; estrogen

11. What are the three results of having pathology in the aorticopulmonary septum?
Ventral; failure of urogenital folds to close
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)
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
28 week onward

12. When does the neural tube form and From what does it form?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
All or none
Synctiotrophoblast; outer; no
Neural plate; closes by week 4

13. what invaginates to form the primitive streak?
Myelencephalon
Lots - cleft palate/lip
2nd; 2nd
Epiblast

14. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
Common carotid and internal carotid
Neuroectoderm
Annular pancrease
DES

15. what other facial defect other than cyclopia is associated with holoprosencephaly?
Cleft lip/palate
Failure to recanalize; 21
Neuroectoderm
4th/5th branchial pouches

16. What are the three regions of the brain (in order of cranial to caudal)?
Prosencephalon - mesencephalon - rhombencephalon
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
1st cleft/groove (Ectoderm)
Endoderm

17. By what week is there fetal movement?
Decreased separation of hemispheres across midline; cyclopia
monoamniotic
Surface ectoderm
Week 8

18. what junction is the last to canalize? what implications does this have down the line?
Bulbos Cordis; right ventricle entirely
Hepatic circulation; ligamentum venosum
Prosencephalon
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus

19. What is the prochordal plate?
Metencephalon; cerebellum
After; extrinsic
Where the epiblast and hypoblast fuse
Ectoderm

20. Which branchial derivative creates the epithelial lining of the palatine tonsils?
2nd pouch
Bone/cartilage and nerves
Duodenum to transverse colon; distal transverse colon to rectum
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

21. From What embryonic layer does the olfactory epithelium arise?
Surface ectoderm
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
5th

22. What is the neural plate and From what does it form?
Week 3-8
Before getting pregnant!
Ectoderm
Deformation

23. Septum primum (patent foramen oval) caused by excessive resorption of...
septum primum and/or secundum
Week 10-12; end of 1st trimester
Aortic arch and prox part of subclavian
Prostaglandins

24. What congenital abnormality forms a 'double bubble' on xray?
Annular pancrease
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Increase in oxygen concentration which decreases prostaglandin concentration

25. What is used to keep the PDA open?
Prostaglandins
Hemorrhage - bone deformities
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Pataus; fetal alcohol syndrome

26. From What embryonic layer do the salivary - sweat and mammary glands arise?
Turners; inferior
Ebsteins anomaly; tricuspid atresia
Neural plate; closes by week 4
Surface ectoderm

27. How do you differentiate a thyroglossal duct cyst from a persistent cervical sinus?
Found in lateral neck; from no obliteration of 2-4th clefts
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
4th arch; 6th arch

28. Before birth - blood entering the LA is less than...
Female; paramesonephric; mesonephric
Ventral; failure of urogenital folds to close
blood entering the RA
Dorsal; sensory

29. What are the two components of the placenta? From What do they form? which one secreted hcG?
...
Dorsal; sensory
primary palate
Endoderm

30. From What embryonic layer does the thyroid follicular cells arise?
DHT; estrogen
3rd pouch
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
Endoderm

31. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
Myelencephalon
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
Annular pancrease
Absent cerebellar vermis; cystic enlargement of 4th ventricle

32. What causes persistent Truncus Arteriosus? What does it result in?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Week 8
Deoxygenated blood; fetal internal iliac arteries to placenta

33. The spleen is ____________ in origin and supplied by a foregut artery
Surface ectoderm
mesodermal
Thyroid - cricoid - arytenoids - corniculate cuneiform
Maxillary

34. What axis does the basal plate form? what neural system does it become?
arnold chiari associated with thoraclumbar myelomeningocele
Week 3-8
Ventral ; motor
Urachus/median umbilical ligament; bladder and yolk sac

35. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
Surface ectoderm
During; instrinsic
Decreased pulmonary resistance in the pulmonary vasculature
Neuroectoderm

36. What is the primitive streak? From what layer does it form?
Neural crest cells
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Week 3-8
Mesoderm; epiblast

37. Cleft palate is a failure of formation of the...
Rhombencephalon
secondary palate
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
No more umbilical circulation emptying into RA

38. How do adults with annular pancreas present? and At What age?
Sperm plus egg
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Renal artery stenosis;
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

39. What weeks are considered the 'embryonic period'?
Week 3-8
DES
Lithium
Left horn of the sinus venosus

40. what muscles are derived from branchial arch 6? CN?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Umbilical - midgut herniates through umbilical ring; SMA
Bulbos Cordis; right ventricle entirely

41. What is the difference between agenesis and aplasia?
Hemorrhage - bone deformities
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
No organ in each; agenesis no primordial tissue
Branchial arch 2

42. What is the most common autopsy finding in brains of premature infants?
Germinal matrix hemorrhage
Neuroectoderm
Urachus/median umbilical ligament; bladder and yolk sac
Turners; inferior

43. What is the memranous interventricular formaen made from?
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Fluid filled syrinx causes expansion and degeneration of cord tracts
Female; paramesonephric; mesonephric

44. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
Neuroectoderm
V3; VII
Stapedius and hyoid artery
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'

45. What teratogen can cause IUGR and ADHD in a fetus? what else can this teratogen cause?
Primitive ventricle
Nicotine; preterm labor
1st cleft/groove (Ectoderm)
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

46. Which part of the branchial apparatus makes up membranes?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
From teh lung;blood from IVC in RA to LA; fossa ovalis
Oligohydramnios
All 3

47. From What embryonic layer do the astrocytes arise?
Vascular accident intra uterine; apple peel atresia
Spinothalamic first
Mesoderm
Neuroectoderm

48. Which branchial derivative creates the middle ear cavity - eustachian tube and mastoid air cells?
2; 1
First branchial pouch
When left to right shunting switching to right to left shunting
Week 10-12; end of 1st trimester

49. From What embryonic layer does the spinal cord arise?
can make cells
Neuroectoderm
septum primum and/or secundum
Dorsal ventral axis

50. What embryologic structure gives rise to the smooth outflow tracts of the ventricles? what else does it give rise to?
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
3 -4 -6
Bulbos Cordis; right ventricle entirely
Partial AP septum development; one large vessel leaves the heart - Right to left shunt