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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 the obstruction in pyloric stenosis? treatment?
Aortic arch and prox part of subclavian
XII
Hypertrophy of muscularis externis of pylorus; surgical incision
Germinal matrix hemorrhage

2. What is used to keep the PDA open?
Deoxygenated blood; fetal internal iliac arteries to placenta
Right common cardinal vein and right anterior cardinal vein
Prostaglandins
Yolk sac; 3rd week

3. What is perinauds syndrome?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Maternally derived; meconium
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Bone/cartilage and nerves

4. What embryological structure gives rise to the trabeculated part of the left and right atrium?
mesodermal
Primitive atrium
Mesoderm; 3 week
Apical ectodermal ridge

5. What are the two types of posterior fossa malformations? which one results in a hindbrain crowding? and which results in an enlarged posterior fossa? which one is associated with syringomelia?
Muscles and arteries
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Week 4
XII

6. What does the midgut form? hindgut?
Oxygenated; placenta to fetus (IVC)
Valproate acid
Duodenum to transverse colon; distal transverse colon to rectum
Scrotum; labia majora

7. What happens in pancreas divisum? what results?
6-30
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Foregut; dorsal mesentery (mesodermal)
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

8. From where did a branchial cleft cyst arise if it found?
Failure of the urachus to obliterate
Thyroid - cricoid - arytenoids - corniculate cuneiform
Neural crest cells
Found in lateral neck; from no obliteration of 2-4th clefts

9. What is the 'fetal period'- ie When is it?
Midgut; 10th week
Telencephalon
External auditory meatus
Week 8

10. Most myelomeningoceles present in the _______ region
lumbosacral
Spinothalamic first
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Neural crest cells

11. what results if they dont? What can increase the risks of this?
Physiologic incomplete muscular ventricular septum
Dorsal and ventral buds
Outgrowth of mesonephric as ureteric bud; most caudal
Persistent connection between amniotic cavity and spinal canal; low folic acid

12. From What embryonic layer does the epidermis arise?
Surface ectoderm
Cleft lip/palate
Neural crest cells
Cytotrophoblast and synctiotrophoblast

13. From What embryonic layer is the kidney and the adrenal cortex from?
Before getting pregnant!
Branchial arch 2
Mesoderm
Week 4; week 3

14. In order to survive tricuspid atresia - What do you need?
Amniotic epithelium
Primitive ventricle
VSD
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

15. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Endoderm
Oligohydramnios

16. What part of the gut rotates around the SMA? and At what point?
Midgut; 10th week
Truncus arteriosus; pulmonary trunk
80%
Mental retardation - holoprosencephaly - facial features - fistulas

17. During what months is the fetus most susceptible to teratogens? What trimester?
6-30
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
ACE inhibitors - HCTZ
Embryonic period; 1st trimester

18. Cleft palate is a failure of fusion of the lateral palatine processes - the nasal septum and or the ________?
Lots - cleft palate/lip
Prosencephalon - mesencephalon - rhombencephalon
Ebsteins anomaly; tricuspid atresia
Medial palatine processes

19. What arises from the fourth aortic arch?
Decreased separation of hemispheres across midline; cyclopia
Aortic arch (from left side); right subclavian (on the right)
monoamniotic
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

20. What is omphalocele? In What trisomies is it seen?
Apical ectodermal ridge
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Surface ectoderm
Epispadias

21. What artery is derived branchial (aortic) arch 2?
Deformation
Stapedius and hyoid artery
Week 4; week 3
Apical ectodermal ridge

22. From where to Where is the foregut derivative? midgut? hindgut?
Annular pancrease
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum

23. What day is the amnion formed?
Arnold chiari; syringomyelia
mesodermal
Prenatal and perinatal
8

24. What artery is derived branchial (aortic) arch 6?
Endoderm
Pulm art (prox) and ductus arteriosus
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
4th week

25. What causes the increase in left atrial pressure to close the fossa ovale?
Decreased pulmonary resistance in the pulmonary vasculature
6-30
Ampulla
Stapedius and hyoid artery

26. What is the initial step to interventricular septum development? is it complete?
Muscular ventricular septum; no
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
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Decreases

27. Where is the apical ectodermal ridge?
Amniotic epithelium
secondary palate
Thickened ectoderm at end of each developing limb
Lacunae in between the chorionic villi

28. what muscles are derived from branchial arch 4? CN?
Mesoderm
Mesoderm
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Right common cardinal vein and right anterior cardinal vein

29. What does DHT turn the urogenital sinus into? estrogen?
...
Mesoderm
is no longer intact
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

30. What is a syrinx? Where is it found in syringomelia? What is it associated with?
Indomethacin; blocks PG production
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Medial palatine processes
Neuroectoderm

31. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
DiGeorge
Neural crest cells
Arches 3 and 4
Prevent recurrent UTIs

32. From What embryonic layer do CNS neurons arise?
Ampulla
Neuroectoderm
Endoderm - floor of primitive pharynx
Mesonephros; male genital system

33. What components do the mesoderm of the branchial arches give rise to?
Muscles and arteries
Excessive resorption of septum primum or secondum (or both)
Increase in oxygen concentration which decreases prostaglandin concentration
Week 3-8

34. Where is the FGF gene produced? What is it responsible for - How does it do this?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
2nd pouch
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
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

35. From What embryonic layer does a craniopharygioma arise?
DiGeorge
Surface ectoderm
4th week
Congenital and chromosomal abnormalities

36. Where is the most common ectopic thyroid tissue?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Lacunae in between the chorionic villi
Tongue
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells

37. Which part of pancreas contribute to body? tail? isthmus? accessory pancreatic duct?
Spinothalamic first
After; extrinsic
Ventral bud
3rd; proximal part of the internal carotid artery

38. From What embryonic layer does the adenohypophysis arise?
Surface ectoderm
Mesoderm
Decreased separation of hemispheres across midline; cyclopia
Neuroectoderm

39. What are two common findings in pyloric stenosis?
Turners; inferior
Medial palatine processes
Vascular accident intra uterine; apple peel atresia
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

40. what chemo drugs can cause neural tube defects in the fetus?
Folate antagonists
Decidual basalis
First branchial pouch
Sonic Hedgehog

41. From where does the prostate develop? seminal vesicles? fallopian tube? lower 2/3 of the vagina? ejaculatory duct? epididymis? uterus? upper 1/3 of the vagina?
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
septum primum and/or secundum
No more umbilical circulation emptying into RA
Temporary cervical sinus

42. What hormone is hcG structurally similar too?
Before getting pregnant!
Synctiotrophoblast; outer; no
LH
Greater horn of hyoid; CN IX (styloPharyngeus)

43. Where does the blastocyst implant in the uterus? During what phase of the menstrual cycle?
Dorsal; sensory
Dorsal ventral axis
Post. sup wall; luteal phase
Ventral bud

44. The spleen is ____________ in origin and supplied by a foregut artery
8
mesodermal
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Congenital and chromosomal abnormalities

45. Cleft lip is a failure of formation of the...
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
primary palate
Folate antagonists
Neuroectoderm

46. Which branchial derivative accounts for the posterior 2/3 of the tongue?
Endoderm
Ventral shaft of penis (penile urethra); labia minora
3rd and 4th arches
Persistent connection between amniotic cavity and spinal canal; low folic acid

47. What causes a vesicourachal diverticulum? What is it?
Found in lateral neck; from no obliteration of 2-4th clefts
Failure of the urachus to obliterate; outpouching of the bladder
When left to right shunting switching to right to left shunting
Mesdoerm

48. From What embryonic layer does bone of the skulls arise?
Neural crest cells
Maxillary
Mesoderm; 3 week
Amniotic epithelium

49. When does hcG get secreted? What does it do?up until when ?
Day 6; maintains corpus luteum; 1st trimester
elevated AFP
V3; VII
Primitive ventricle

50. What is associated with only one umbilical artery?
All or none
External auditory meatus
Congenital and chromosomal abnormalities
Bulbos Cordis; right ventricle entirely