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USMLE Embryo

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Answer 50 questions in 15 minutes.
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1. Where does the blastocyst implant in the uterus? During what phase of the menstrual cycle?
Epiblast
Neural crest cells
Excessive resorption of septum primum or secondum (or both)
Post. sup wall; luteal phase

2. From what does bicornuate uterus arise? What is it associated with?
Surface ectoderm
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Persistent connection between amniotic cavity and spinal canal; low folic acid

3. From What embryonic layer does the olfactory epithelium arise?
Surface ectoderm
Neural crest cells
Embryonic period; 1st trimester
Respiratory distress syndrome

4. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
Duodenum to transverse colon; distal transverse colon to rectum
Upper 1/3; urogenital sinus
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
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

5. What causes a vesicourachal diverticulum? What is it?
Fallopian tube - uterus - upper 1/3 of vagina
Failure of the urachus to obliterate; outpouching of the bladder
4th pouch
Endoderm - floor of primitive pharynx

6. What is another name for the mesonephric duct? paramesonephric?
Cerebellar tonsillar herniation through foramen magnum
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
mesodermal
Wolffian; mullerian

7. To what germ layer does the branchial pouches correlate to?
Aortic arch and prox part of subclavian
Endoderm
Tunica vaginalis not fully fused
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'

8. What causes the obstruction in pyloric stenosis? treatment?
Neural crest cells
Failure to recanalize; 21
Mesdoerm
Hypertrophy of muscularis externis of pylorus; surgical incision

9. What causes urine discharge from the umbilicus?
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
Failure of bony spinal canal to fuse; no; lower vertebral levels
Failure of the urachus to obliterate

10. From What embryonic layer do the salivary - sweat and mammary glands arise?
Week 10-12; end of 1st trimester
Ventral ; motor
Prevent recurrent UTIs
Surface ectoderm

11. what week do the genitalia start to have male/female characteristics? What trimester is that?
secondary palate
Week 10-12; end of 1st trimester
pyloric stenosis
Week 2; bilaminar disk; epiblast and hypoblast

12. What happens in pancreas divisum? what results?
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Surface ectoderm
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)

13. From What embryonic layer does the brain arise?
pyloric stenosis
Epispadias
not covered
Neuroectoderm

14. What teratogens can cause renal damage in the fetus?
ACE inhibitors - HCTZ
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
can make cells
Fetal and maternal

15. What is the female remnant of processus vaginalis? male remnant?
Obliterated; forms tunica vaginalis
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
During; instrinsic
Dorsal; faulty positioning of genital tubercle

16. From What embryonic layer does the gut tube epithelium arise?
V3; VII
Endoderm
Neural crest cells
1st

17. From What embryonic layer does the neurohypophysis arise?
Neural crest cells
Mesoderm
arnold chiari associated with thoraclumbar myelomeningocele
Neuroectoderm

18. From which germlayer does the thyroid develop?? From what structure exactly?
4th arch; 6th arch
3rd pouch
Endoderm - floor of primitive pharynx
Surface ectoderm

19. Which part of the branchial apparatus makes up membranes?
All 3
Truncus arteriosus; pulmonary trunk
Mesoderm
8

20. From What embryonic layer are the pia and arachnoid from?
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Neural crest cells
Thyroid - cricoid - arytenoids - corniculate cuneiform

21. By what week is the neural tube supposed to be closed? when did it start forming?
Week 4; week 3
elevated AFP
Prostaglandins
Excessive resorption of septum primum or secondum (or both)

22. Monochorionic - ___________ twins are conjoined
Endoderm
Upper 1/3; urogenital sinus
Stapedius and hyoid artery
monoamniotic

23. which teratogen can cause Ebsteins anomaly in the fetus?
Telencephalon
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Lacunae in between the chorionic villi
Lithium

24. Septum primum (patent foramen oval) caused by excessive resorption of...
septum primum and/or secundum
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Dorsal; faulty positioning of genital tubercle
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

25. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
Membrane - all 3 from 1st appartus
Endoderm
Muscles and arteries
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum

26. What is duodenal atresia usually due to? What trisomy is it most often seen in?
All or none
Failure to recanalize; 21
Epiblast
Aortic arch and prox part of subclavian

27. What embryologic structure provides the aorticpulmonary septum?
Week 2; bilaminar disk; epiblast and hypoblast
Spinothalamic first
Epispadias
Neural crest migration - they then cause spiral

28. What causes a patent foramen ovale?
Cerebral hemisphere - thalami
Excessive resorption of septum primum or secondum (or both)
Skewed development of AP septum
Decreased pulmonary resistance in the pulmonary vasculature

29. What artery is derived branchial (aortic) arch 1?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Maxillary
Endoderm
3rd and 4th arches

30. what muscles are derived from branchial arch 1?
DiGeorge
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
Yolk sac; 3rd week
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

31. In both meningocele and myelomeningocele the dura...
Nutrient and gas exchange
is no longer intact
Mesoderm
Absent cerebellar vermis; cystic enlargement of 4th ventricle

32. Blood coming in the umbilical vein is ____ saturated
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
Ventral; failure of urogenital folds to close
Tongue
80%

33. What congenital abnormality forms a 'double bubble' on xray?
Annular pancrease
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
Mesoderm; 3 week
Oxygenated; placenta to fetus (IVC)

34. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
Physiologic incomplete muscular ventricular septum
Mid gut to yolk sac; omphalomesenteric duct; 7th week
DES
secondary palate

35. What does DHT turn the genital tubercle into? estrogen?
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Failure to recanalize; 21
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)

36. is epispadias or hypospadias associated with exstrophy of the bladder?
Neural crest cells
Pataus; fetal alcohol syndrome
Epispadias
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

37. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
During; instrinsic
Surface ectoderm
DES
Ventral shaft of penis (penile urethra); labia minora

38. From what region does the midbrain form from?
Mesencephalon
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Truncus arteriosus; pulmonary trunk
Increase in oxygen concentration which decreases prostaglandin concentration

39. Where is the FGF gene produced? What is it responsible for - How does it do this?
VSD
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Mesoderm

40. What axis is Wnt 7 responsible for developing?
Week 8
A vitelline fistula - failure of vitelline duct to close
Mesoderm
Dorsal ventral axis

41. From What embryonic layer does the thyroid follicular cells arise?
Prosencephalon - mesencephalon - rhombencephalon
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Endoderm
Failure to recanalize; 21

42. When does hcG get secreted? What does it do?up until when ?
Neuroectoderm
Alkylating agents
Base of limbs in the zone of polarizing activity; ant - post
Day 6; maintains corpus luteum; 1st trimester

43. What does the first cleft/groove of the branchial apparatus develop into?
Synctiotrophoblast
5th
Sonic Hedgehog
External auditory meatus

44. From What embryonic layer does the parathyroid arise ?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
arnold chiari associated with thoraclumbar myelomeningocele
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Endoderm

45. How do adults with annular pancreas present? and At What age?
Thickened ectoderm at end of each developing limb
DES
Right common cardinal vein and right anterior cardinal vein
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

46. what junction is the last to canalize? what implications does this have down the line?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
6th aortic arch
Annular pancrease
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction

47. what bone/cartilage and nerves are derived from branchial arch 1?
Mesdoerm
IMA
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

48. From where is the allantois formed? During what week?
Week 3; primitive streak formation from the epiblast makes the three layers
Dorsal; faulty positioning of genital tubercle
OCPS and maternal diabetes
Yolk sac; 3rd week

49. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
...
Mental retardation - holoprosencephaly - facial features - fistulas
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Dorsal; sensory

50. What results in annular pancreas? How does it happen?
hypertrophy
Endoderm
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
primary palate

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USMLE Embryo

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