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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 part of the vagina does the mullerian duct form? Where does the rest come from?
Neural crest cells
Day 6; maintains corpus luteum; 1st trimester
Upper 1/3; urogenital sinus
Neural crest migration - they then cause spiral

2. How do AV canals form?
Before getting pregnant!
From endocardial cushions (ventral and dorsal meet each other)
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
IMA

3. From What embryonic layer are the cardiovascular - lymphatics and blood from?
Mesoderm
Fetal alcohol syndrome; mental retardation
Mental retardation - holoprosencephaly - facial features - fistulas
No organ in each; agenesis no primordial tissue

4. When does erythropoeisis begin in the bone marow?
Thickened ectoderm at end of each developing limb
28 week onward
Neuroectoderm
Membrane - all 3 from 1st appartus

5. Pyloric stenosis is characterized by _____________ of muscularis externis in the sphincter
Primitive ventricle
Mesoderm
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
hypertrophy

6. How does annular pancreas present in children?
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Surface ectoderm
Truncus arteriosus; pulmonary trunk
Neuroectoderm

7. What causes the transposition of the great vessels? What does it result in?
Endoderm
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont

8. What is contained in the umbilical cord?
can make cells
Tetracyclines
Neural crest cells
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus

9. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
V3; VII
Ebsteins anomaly; tricuspid atresia
External auditory meatus
Vascular accident intra uterine; apple peel atresia

10. Cleft palate is a failure of fusion of the lateral palatine processes - the nasal septum and or the ________?
Medial palatine processes
3 -4 -6
Greater horn of hyoid; CN IX (styloPharyngeus)
Endoderm

11. From What embryonic layer does bone of the skulls arise?
Neural crest cells
Sperm plus egg
3rd; proximal part of the internal carotid artery
Metencephalon; cerebellum

12. 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?
Bulbos Cordis; right ventricle entirely
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Apical ectodermal ridge
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

13. What does the first branchial pouch create?
Thyroid - cricoid - arytenoids - corniculate cuneiform
Embryonic period; 1st trimester
All or none
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells

14. what muscles are derived from branchial arch 4? CN?
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
All or none
Obliterated

15. When is most important to take folic acid to prevent neural tube defects?
Mesoderm
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Before getting pregnant!
IX; X

16. What is the difference between agenesis and aplasia?
Neuroectoderm
Ionizing
No organ in each; agenesis no primordial tissue
Temporary cervical sinus

17. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Urachus/median umbilical ligament; bladder and yolk sac
After; extrinsic
Mesoderm
Vascular accident intra uterine; apple peel atresia

18. What role does the placenta have?
Mesoderm
Nutrient and gas exchange
Amniotic cavity and yolk sac
monoamniotic

19. What does DHT turn the urogenital sinus into? estrogen?
ACE inhibitors - HCTZ
Telencephalon
Mesoderm; 3 week
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

20. Where is the apical ectodermal ridge?
Stapedius and hyoid artery
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Thickened ectoderm at end of each developing limb
DiGeorge

21. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
External auditory meatus
Week 10-12; end of 1st trimester
1st cleft/groove (Ectoderm)
not covered

22. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
DES
Embryonic period; 1st trimester
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Occiptal

23. What causes persistent Truncus Arteriosus? What does it result in?
Synctiotrophoblast; outer; no
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
First branchial pouch
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

24. How many umbilical arteries are there? How many umbilical veins?
When left to right shunting switching to right to left shunting
2; 1
Synctiotrophoblast
can make cells

25. What are the clinical symptoms that present with syringomelia?
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Mesdoerm
Neuroectoderm
Congenital and chromosomal abnormalities

26. When does the neural tube form and From what does it form?
DHT; estrogen
3rd; proximal part of the internal carotid artery
Week 4; week 3
Neural plate; closes by week 4

27. Where is the FGF gene produced? What is it responsible for - How does it do this?
Week 8
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Neuroectoderm
Myelencephalon

28. What teratogens can cause renal damage in the fetus?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Mesoderm; nucleous pulposos
Mesoderm
ACE inhibitors - HCTZ

29. When does the notochord form? and When does the neural plate form?
6th aortic arch
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Mesoderm; 3 week
They are the edge of neural plate folding; all over the body

30. What effect does warfarin have on the fetus?
Hemorrhage - bone deformities
Base of limbs in the zone of polarizing activity; ant - post
Foregut; dorsal mesentery (mesodermal)
Failure to recanalize; 21

31. What are two common findings in pyloric stenosis?
Oxygenated; placenta to fetus (IVC)
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Renal artery stenosis;
Neuroectoderm

32. What is the memranous interventricular formaen made from?
Week 8
3rd pouch
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

33. From What embryonic layer do the ANS arise?
Neural crest cells
Fallopian tube - uterus - upper 1/3 of vagina
Arnold chiari; syringomyelia
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

34. What are the three results of having pathology in the aorticopulmonary septum?
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)
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Upper 1/3; urogenital sinus
Ventral; failure of urogenital folds to close

35. What weeks are considered the 'embryonic period'?
Maxillary
Indomethacin; blocks PG production
Foramen cecum and terminal sulus
Week 3-8

36. What surrounds the umbilical cord?
Base of limbs in the zone of polarizing activity; ant - post
Amniotic epithelium
lumbosacral
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells

37. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Mesdoerm
Cytotrophoblast
...
Endocardial cushions

38. What causes the increase in left atrial pressure to close the fossa ovale?
Foregut; dorsal mesentery (mesodermal)
Decreased pulmonary resistance in the pulmonary vasculature
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Ventral bud

39. Which branchial apparatus develops into the thymus?
Fallopian tube - uterus - upper 1/3 of vagina
3rd pouch
Maternally derived; meconium
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

40. Which part of the chorionic villi can make cells?
Surface ectoderm
Cytotrophoblast
Cerebral hemisphere - thalami
secondary palate

41. From what does bicornuate uterus arise? What is it associated with?
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Prevent recurrent UTIs
Ectoderm; endoderm
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)

42. From What embryonic layer does connective tissue and muscle arise?
4th week
Endoderm
Prevent recurrent UTIs
Mesoderm

43. What separated myometrium of the uterus from the blastocyst?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Week 10-12; end of 1st trimester
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Decidual basalis

44. Which part of pancreas contribute to body? tail? isthmus? accessory pancreatic duct?
Mesoderm
Wolffian; mullerian
Ventral bud
Right horn of the SV

45. What embryological structure gives rise to the coronary sinus?
From teh lung;blood from IVC in RA to LA; fossa ovalis
4th week
Fetal and maternal
Left horn of the sinus venosus

46. What is the effect of teratogens after week 8?
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Neuroectoderm
Deformation
Synctiotrophoblast

47. What is an example of a syndrome that can cause abnormal neural crest migration and thus CV abnormalities?
DiGeorge
LH
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Urachus/median umbilical ligament; bladder and yolk sac

48. From What embryonic layer does the epidermis arise?
Surface ectoderm
Incomplete; yes
V3; VII
Prenatal and perinatal

49. How many components are there to the placenta? What are they called?
Fetal and maternal
No organ in each; agenesis no primordial tissue
Branchial arch 2
Neuroectoderm

50. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Initial left to right shunting - then switches
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Maternally derived; meconium
Neuroectoderm