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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. From what region of the brain does the lateral ventricles and the 3rd ventricle form?
can make cells
Pulm art (prox) and ductus arteriosus
Prosencephalon
4th week

2. What axis does the basal plate form? what neural system does it become?
Ventral ; motor
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Surface ectoderm
Endoderm

3. _____________is common in 1st born males
pyloric stenosis
Lacunae in between the chorionic villi
Apical ectodermal ridge
Bulbos Cordis; right ventricle entirely

4. From which myotomes are muscles of the tongue derived from?
Occiptal
Mid gut to yolk sac; omphalomesenteric duct; 7th week
All 3
Mesoderm

5. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Endoderm - floor of primitive pharynx
Oxygenated; placenta to fetus (IVC)
Valproate acid

6. What causes the degeneration of the spinal cord in syringomelia?
Fluid filled syrinx causes expansion and degeneration of cord tracts
XII
Week 3; primitive streak formation from the epiblast makes the three layers
Ampulla

7. What are the aspects of fetal alcohol syndrome?
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
Ectoderm
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Mental retardation - holoprosencephaly - facial features - fistulas

8. What embryological structure gives rise to the trabeculated parts of the left and right ventricle?
Sperm plus egg
Synctiotrophoblast
Primitive ventricle
From endocardial cushions (ventral and dorsal meet each other)

9. What causes the increase in left atrial pressure to close the fossa ovale?
Decreased pulmonary resistance in the pulmonary vasculature
Endoderm
Ventral bud
Muscular ventricular septum; no

10. What do membranous interventricular septal defect cause? What does this lead to?
Prosencephalon - mesencephalon - rhombencephalon
Folate antagonists
DiGeorge
Initial left to right shunting - then switches

11. What arises from the fourth aortic arch?
Endoderm
Aortic arch (from left side); right subclavian (on the right)
Initial left to right shunting - then switches
Common carotid and internal carotid

12. What artery is derived branchial (aortic) arch 2?
Thalidomide; nausea
Failure of bony spinal canal to fuse; no; lower vertebral levels
Stapedius and hyoid artery
Neuroectoderm

13. How many umbilical arteries are there? How many umbilical veins?
Decreases
Indomethacin; blocks PG production
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
2; 1

14. What do the arches of the branchial apparatus correlate to?
IMA
Mesdoerm
Allantois
From endocardial cushions (ventral and dorsal meet each other)

15. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
During; instrinsic
IX; X
Epispadias
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

16. What do the groove/clefts of the branchial apparatus correlate to?
pyloric stenosis
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Ectoderm
Absent cerebellar vermis; cystic enlargement of 4th ventricle

17. What is the primitive streak? From what layer does it form?
5th
Mesoderm; epiblast
Fallopian tube - uterus - upper 1/3 of vagina
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

18. What is another name for the mesonephric duct? paramesonephric?
80%
Wolffian; mullerian
Duodenum to transverse colon; distal transverse colon to rectum
DES

19. What causes meconium discharge from the umbilicus?
Decreases
OCPS and maternal diabetes
A vitelline fistula - failure of vitelline duct to close
First branchial pouch

20. What does the vitelline duct connect? What is it also known as? when should it obliterate?
Day 6; with implantation
Week 10-12; end of 1st trimester
Endoderm - floor of primitive pharynx
Mid gut to yolk sac; omphalomesenteric duct; 7th week

21. What is the physiological herniation that occurs at the 6th week - what herniates out of the umbilical ring? when it comes back in the 10th week - What does it rotate around?
Scrotum; labia majora
Pulm art (prox) and ductus arteriosus
Umbilical - midgut herniates through umbilical ring; SMA
Mesonephros; male genital system

22. From what region of the brain does the fourth ventricle form?
Rhombencephalon
Hemorrhage - bone deformities
Amniotic cavity and yolk sac
Surface ectoderm

23. During what week does the heart begin to beat?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Week 4
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

24. What two cavities also form during the second week?
Neuroectoderm
Neuroectoderm
Amniotic cavity and yolk sac
Fallopian tube - uterus - upper 1/3 of vagina

25. During what periods do the damages that cerebral palsy causes occur?
Prenatal and perinatal
Rhombencephalon
Allantois
Tetracyclines

26. From What embryonic layer do the ependymal cells arise?
Neuroectoderm
4th/5th branchial pouches
Muscular ventricular septum; no
Base of limbs in the zone of polarizing activity; ant - post

27. What causes a vesicourachal diverticulum? What is it?
Failure of the urachus to obliterate; outpouching of the bladder
Alkylating agents
Ventral ; motor
Prosencephalon - mesencephalon - rhombencephalon

28. What causes a patent foramen ovale?
Aortic arch and prox part of subclavian
4th pouch
Excessive resorption of septum primum or secondum (or both)
Mesoderm; epiblast

29. From What embryonic layer does the thyroid follicular cells arise?
Endoderm
Myelencephalon
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
2nd; 2nd

30. From What embryonic layer does a craniopharygioma arise?
Maternally derived; meconium
Cytotrophoblast and synctiotrophoblast
pyloric stenosis
Surface ectoderm

31. From What embryonic layer does connective tissue and muscle arise?
Ventral shaft of penis (penile urethra); labia minora
arnold chiari associated with thoraclumbar myelomeningocele
Mesoderm
Week 8

32. What components do the mesoderm of the branchial arches give rise to?
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)
Endoderm
Muscles and arteries
Respiratory distress syndrome

33. What is meckel's diverticulum? What is it associated with? What does that cause?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Ectoderm
Ionizing
Endoderm

34. What does the first branchial pouch create?
primary palate
Maxillary and medial nasal processes
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
DHT; estrogen

35. which genital embryology is default? From what duct? what duct degenerates without signal to stay?
Failure of bony spinal canal to fuse; no; lower vertebral levels
Female; paramesonephric; mesonephric
Week 2; bilaminar disk; epiblast and hypoblast
T neuroectoderm

36. To what germ layer does the branchial pouches correlate to?
Endoderm
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Neuroectoderm
Occiptal

37. Weeks _______ erythropoiesis takes place in the liver
Mesoderm
6-30
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Aminoglycosides

38. On what side is the abnormal opening in epispadias? What causes it?
Mental retardation - holoprosencephaly - facial features - fistulas
5th
Week 8
Dorsal; faulty positioning of genital tubercle

39. What day is the chorion formed?
Neuroectoderm
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
3
Surface ectoderm

40. From where did a branchial cleft cyst arise if it found?
Mental retardation - holoprosencephaly - facial features - fistulas
Found in lateral neck; from no obliteration of 2-4th clefts
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
secondary palate

41. What part of the gut rotates around the SMA? and At what point?
Midgut; 10th week
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Failure of bony spinal canal to fuse; no; lower vertebral levels
Excessive resorption of septum primum or secondum (or both)

42. How do AV canals form?
From endocardial cushions (ventral and dorsal meet each other)
Post. sup wall; luteal phase
Oxygenated; placenta to fetus (IVC)
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility

43. What is the effect of teratogens before week 3?
Metencephalon; cerebellum
All or none
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks

44. From What embryonic layer is the bladder and urethra from?
Left horn of the sinus venosus
Arches 3 and 4
Mesoderm
Neural crest cells

45. The notochord is...
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Week 4
mesoderm
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck

46. What separated myometrium of the uterus from the blastocyst?
Decidual basalis
Oligohydramnios
5th
Mesdoerm

47. How do you differentiate a thyroglossal duct cyst from a persistent cervical sinus?
4th week
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Decreased separation of hemispheres across midline; cyclopia
Vascular accident intra uterine; apple peel atresia

48. What is jejunal - ileal - colonic atresia usually due to? What do you see on x ray?
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Hemorrhage - bone deformities
Vascular accident intra uterine; apple peel atresia
VSD

49. What teratogens can cause discolored teeth?
Umbilical - midgut herniates through umbilical ring; SMA
Tetracyclines
Maternally derived; meconium
Week 4

50. What does the mullerian duct develop into? wollffian?
Fallopian tube - uterus - upper 1/3 of vagina
Dorsal; faulty positioning of genital tubercle
Increased AFP and acetycholinesterase (not ACh!) in CSF
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)