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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 does the ductus arteriosus shunt blood away from - to where? What is its remnant?
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Germinal matrix hemorrhage
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

2. From what aortic arch does the common carotid artery arise? what else arises from this arch?
3rd; proximal part of the internal carotid artery
Failure of the urachus to obliterate; outpouching of the bladder
After; extrinsic
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian

3. From What embryonic layer does connective tissue and muscle arise?
mesoderm
Mesoderm
DHT; estrogen
Week 4

4. Which part of pancreas contribute to body? tail? isthmus? accessory pancreatic duct?
6th aortic arch
Ventral bud
Ampulla
DiGeorge

5. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
Cytotrophoblast
Pulm art (prox) and ductus arteriosus
not covered
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

6. What is the prochordal plate?
Congenital and chromosomal abnormalities
Ventral; failure of urogenital folds to close
Greater horn of hyoid; CN IX (styloPharyngeus)
Where the epiblast and hypoblast fuse

7. What are the three regions of the brain (in order of cranial to caudal)?
Mesoderm
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Prosencephalon - mesencephalon - rhombencephalon
Dorsal and ventral buds

8. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
Allantois
Neural crest cells
Ampulla
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

9. What does the first cleft/groove of the branchial apparatus develop into?
External auditory meatus
Mesoderm; epiblast
Neural crest cells
Cerebral hemisphere - thalami

10. What congenital abnormality forms a 'double bubble' on xray?
Hypospadias
Prosencephalon - mesencephalon - rhombencephalon
Surface ectoderm
Annular pancrease

11. From What embryonic layer do the parafollicular cells of the thyroid arise?
4th/5th branchial pouches
Neural crest cells
mesodermal
Pataus; fetal alcohol syndrome

12. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Mesoderm
Increased AFP and acetycholinesterase (not ACh!) in CSF
monoamniotic
...

13. What are the three results of having pathology in the aorticopulmonary septum?
Turners; inferior
not covered
Endoderm
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)

14. What axis does the alar plate form? what neural system does it become?
Dorsal; sensory
Aortic arch (from left side); right subclavian (on the right)
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Maxillary and medial nasal processes

15. What are the two walls of the prosencephalon and What do they become?
Muscular ventricular septum; no
Cerebral hemisphere - thalami
Grooves/clefts; arches; pouches
IX; X

16. What do the groove/clefts of the branchial apparatus correlate to?
Surface ectoderm
Ectoderm
Mesoderm
80%

17. What are the clinical symptoms that present with syringomelia?
Cerebral hemisphere - thalami
Tetracyclines
Lithium
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

18. Monochorionic - ___________ twins are conjoined
monoamniotic
80%
1st
Ventral shaft of penis (penile urethra); labia minora

19. From What embryonic layer is the eustachian tube from?
Mesoderm
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Sonic Hedgehog
Aortic arch and prox part of subclavian

20. What weeks are considered the 'embryonic period'?
Decreased pulmonary resistance in the pulmonary vasculature
Week 3-8
T neuroectoderm
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

21. What is the effect of teratogens after week 8?
Neural crest cells
Metencephalon; cerebellum
Germinal matrix hemorrhage
Deformation

22. What does the midgut form? hindgut?
Duodenum to transverse colon; distal transverse colon to rectum
Week 3; primitive streak formation from the epiblast makes the three layers
OCPS and maternal diabetes
6-30

23. During what months is the fetus most susceptible to teratogens? What trimester?
Hepatic circulation; ligamentum venosum
Embryonic period; 1st trimester
2nd pouch
Mesoderm

24. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
Arnold chiari; syringomyelia
Occiptal
Fluid filled syrinx causes expansion and degeneration of cord tracts
Cranio - caudal; segmental

25. Septum primum (patent foramen oval) caused by excessive resorption of...
septum primum and/or secundum
Muscles and arteries
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Right common cardinal vein and right anterior cardinal vein

26. What artery is derived branchial (aortic) arch 4?
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Ectoderm; endoderm
Hemorrhage - bone deformities
Aortic arch and prox part of subclavian

27. What causes the decrease in Right atrial pressure to close the fossa ovale?
Ebsteins anomaly; tricuspid atresia
lumbosacral
Mesoderm
No more umbilical circulation emptying into RA

28. What does the ureteric bud interact with and What does it induce it to become?
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
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
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

29. From What embryonic layer do CNS neurons arise?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Urachus/median umbilical ligament; bladder and yolk sac
Neuroectoderm

30. How do you differentiate a thyroglossal duct cyst from a persistent cervical sinus?
...
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Muscles and arteries
Mesoderm

31. What type of blood do umbilical veins carry? From where to where?
Cerebellar tonsillar herniation through foramen magnum
From endocardial cushions (ventral and dorsal meet each other)
Neural crest cells
Oxygenated; placenta to fetus (IVC)

32. From What embryonic layer is the kidney and the adrenal cortex from?
Tunica vaginalis not fully fused
Mesoderm
4th pouch
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric

33. What hormone is hcG structurally similar too?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
LH
All 3

34. From What embryonic layer does the gut tube epithelium arise?
Endoderm
From endocardial cushions (ventral and dorsal meet each other)
Turners; inferior
Week 8

35. What is the defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Failure of bony spinal canal to fuse; no; lower vertebral levels
Surface ectoderm
Fetal alcohol syndrome; mental retardation
Surface ectoderm

36. From What embryonic layer do the astrocytes arise?
DES
Ebsteins anomaly; tricuspid atresia
...
Neuroectoderm

37. What are the two components of the placenta? From What do they form? which one secreted hcG?
is no longer intact
Neural crest cells
...
Muscles and arteries

38. What is germinal matrix hemorrhage associated with?
Primitive atrium
Nicotine; preterm labor
Respiratory distress syndrome
Neural crest cells

39. what invaginates to form the primitive streak?
Epiblast
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
...
Day 6; with implantation

40. What causes the degeneration of the spinal cord in syringomelia?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Medial palatine processes
Week 8
Initial left to right shunting - then switches

41. What causes a vesicourachal diverticulum? What is it?
Failure of the urachus to obliterate; outpouching of the bladder
can make cells
Hypospadias
Dorsal; faulty positioning of genital tubercle

42. what closes the interventricular foramen?
Physiologic incomplete muscular ventricular septum
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Germinal matrix hemorrhage
Failure to recanalize; 21

43. What components do the neural crest cells of the branchial arches give rise to?
Epiblast
Fetal and maternal
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Bones - cartilage - and nerves

44. Which branchial derivative creates the middle ear cavity - eustachian tube and mastoid air cells?
Neural crest cells
XII
Excessive resorption of septum primum or secondum (or both)
First branchial pouch

45. What trisomy is associated with holoprosencephaly? What teratogen?
Neuroectoderm
Deoxygenated blood; fetal internal iliac arteries to placenta
...
Pataus; fetal alcohol syndrome

46. What embryologic structure provides the aorticpulmonary septum?
Neural crest migration - they then cause spiral
Neuroectoderm
Muscles and arteries
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

47. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
DHT; estrogen
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
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
Deoxygenated blood; fetal internal iliac arteries to placenta

48. What is the primitive streak? From what layer does it form?
Renal artery stenosis;
When left to right shunting switching to right to left shunting
3 -4 -6
Mesoderm; epiblast

49. From What embryonic layer is the vagina from? testes? ovaries?
Truncus arteriosus; pulmonary trunk
Primitive ventricle
primary palate
Mesoderm

50. From what region does the cerebral hemisphere form?
2; 1
Tunica vaginalis not fully fused
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Telencephalon