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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 meconium discharge from the umbilicus?
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Ionizing
Rhombencephalon
A vitelline fistula - failure of vitelline duct to close

2. What embryologic structure provides the aorticpulmonary septum?
Neural crest migration - they then cause spiral
Neuroectoderm
Neural crest cells
Hypospadias

3. What is DiGeorge syndrome and What does it result in?
3rd pouch
XII
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII

4. What does DHT turn the genital tubercle into? estrogen?
4th/5th branchial pouches
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Week 3-8
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

5. What day is the amnion formed?
8
Hepatic circulation; ligamentum venosum
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Bones - cartilage - and nerves

6. What components do the neural crest cells of the branchial arches give rise to?
Embryonic period; 1st trimester
Increase in oxygen concentration which decreases prostaglandin concentration
Bones - cartilage - and nerves
Failure of the urachus to obliterate

7. What two cavities also form during the second week?
Amniotic cavity and yolk sac
Ectoderm
Endometrium
Incomplete; yes

8. What axis does the alar plate form? what neural system does it become?
Decidual basalis
1st branchial arch
4th arch; 6th arch
Dorsal; sensory

9. Where does fertilization occur?
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Endoderm
Ampulla
Neuroectoderm

10. What axis is Wnt 7 responsible for developing?
Neural crest cells
primary palate
Dorsal ventral axis
6th aortic arch

11. What teratogen can cause an absence of digits amongst other things in the fetus? give an example.
Lacunae in between the chorionic villi
Membrane - all 3 from 1st appartus
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Alkylating agents

12. What does the ductus arteriosus shunt blood away from - to where? What is its remnant?
Occiptal
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Aortic arch and prox part of subclavian
Physiologic incomplete muscular ventricular septum

13. Which cranial nerve innervates the motor function of the tongue?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Surface ectoderm
XII

14. What causes tetralogy of Fallot?
Mesoderm
Endoderm - floor of primitive pharynx
Skewed development of AP septum
Neural crest cells

15. From where does the medulla form?
Myelencephalon
Hemorrhage - bone deformities
Surface ectoderm
Lacunae in between the chorionic villi

16. what muscles are derived from branchial arch 6? CN?
Week 8
Valproate acid
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Mesdoerm

17. what chemo drugs can cause neural tube defects in the fetus?
Week 3-8
Hemorrhage - bone deformities
Folate antagonists
Neural crest cells

18. From What embryonic layer does the epidermis arise?
Surface ectoderm
Neuroectoderm
Week 8
Mesoderm

19. 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?
Occiptal
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian

20. From What embryonic layer do the parafollicular cells of the thyroid arise?
Epiblast
Fetal alcohol syndrome; mental retardation
Excessive resorption of septum primum or secondum (or both)
Neural crest cells

21. What is duodenal atresia usually due to? What trisomy is it most often seen in?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Failure to recanalize; 21
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Arnold chiari; syringomyelia

22. In anencephaly you see...
Fetal and maternal
Ectoderm
elevated AFP
DES

23. From What embryonic layer does the neurohypophysis arise?
Neuroectoderm
Arches 3 and 4
4th arch; 6th arch
Endoderm

24. How does annular pancreas present in children?
Initial left to right shunting - then switches
mesoderm
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
elevated AFP

25. From what region of the brain does the aqueduct form?
Rhombencephalon
elevated AFP
Foramen cecum and terminal sulus
1st

26. From What embryonic layer does the gut tube derivatives arise (lungs liver - pancreas - parathryroid - thyroid follicular cells - thymus)?
Week 4; week 3
Epiblast
Endoderm
Congenital and chromosomal abnormalities

27. Which part of pancreas contribute to body? tail? isthmus? accessory pancreatic duct?
2; 1
Amniotic cavity and yolk sac
Ventral bud
hypospadias

28. Which branchial apparatus develops into the superior parathyroids?
After; extrinsic
Persistent connection between amniotic cavity and spinal canal; low folic acid
4th pouch
Mesonephros; male genital system

29. What is the fate of the cervical sinuses that develop from the 2nd -4th branchial grooves?
Endoderm
Obliterated
Primitive atrium
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule

30. When does organogenesis occur?
pyloric stenosis
Cerebellar tonsillar herniation through foramen magnum
Mesoderm
Week 3-8

31. What does DHT turn the labioscrotal swelling into? estrogen?
Scrotum; labia majora
Right common cardinal vein and right anterior cardinal vein
...
Week 8

32. what muscles are derived from branchial arch 2?
Week 3-8
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Decreases
Oligohydramnios

33. which tracts are damaged first in syringomelia? What tract is preserved?
Failure of bony spinal canal to fuse; no; lower vertebral levels
Spinothalamic first
Failure of the urachus to obliterate; outpouching of the bladder
Surface ectoderm

34. What are the aspects of fetal alcohol syndrome?
monoamniotic
Medial palatine processes
Excessive resorption of septum primum or secondum (or both)
Mental retardation - holoprosencephaly - facial features - fistulas

35. On what side is the abnormal opening in epispadias? What causes it?
Dorsal; faulty positioning of genital tubercle
Greater horn of hyoid; CN IX (styloPharyngeus)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

36. What three layers form during gastrulation? From What do they form? and what week does gastrulation occur?
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Ampulla
Surface ectoderm
Mesencephalon

37. What does the maternal component of the placenta provide? Where is it derived from?
Lots - cleft palate/lip
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Nutrient and gas for exchange; endometrium
Neuroectoderm

38. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Arnold chiari; syringomyelia
Thyroid - cricoid - arytenoids - corniculate cuneiform

39. WithIn what week does gastrulation occur? What is gastrulation?
elevated AFP
Pataus; fetal alcohol syndrome
Deformation
Week 3; primitive streak formation from the epiblast makes the three layers

40. What arises from the fourth aortic arch?
Aortic arch (from left side); right subclavian (on the right)
2nd pouch
Week 10-12; end of 1st trimester
Renal artery stenosis;

41. _____________is common in 1st born males
Mesoderm
pyloric stenosis
Surface ectoderm
During; instrinsic

42. What is the effect of teratogens after week 8?
Sonic Hedgehog
Neuroectoderm
Deformation
Failure of the urachus to obliterate

43. what results if they dont? What can increase the risks of this?
Persistent connection between amniotic cavity and spinal canal; low folic acid
Synctiotrophoblast
Surface ectoderm
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

44. what drug is used to help close a PDA? what else does this drug treat?
From teh lung;blood from IVC in RA to LA; fossa ovalis
Neural crest cells
Indomethacin; blocks PG production
Temporary cervical sinus

45. What congenital abnormality forms a 'double bubble' on xray?
DHT; estrogen
Mental retardation - holoprosencephaly - facial features - fistulas
Annular pancrease
Truncus arteriosus; pulmonary trunk

46. what bone/cartilage and nerves are derived from branchial arch 1?
Left horn of the sinus venosus
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
Aortic arch and prox part of subclavian

47. What is the female remnant of the gubernaculum? male remnant?
Week 8
Temporary cervical sinus
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
...

48. From What embryonic layer is the vagina from? testes? ovaries?
Mesoderm
Amniotic epithelium
Maternally derived; meconium
From endocardial cushions (ventral and dorsal meet each other)

49. what structures are the derivatives of the neural crest cells in branchial arches?
Ventral bud
Oxygenated; placenta to fetus (IVC)
Aortic arch and prox part of subclavian
Bone/cartilage and nerves

50. From What embryonic layer is aorticopulmonary septum from ?
Endoderm
Sperm plus egg
Neural crest cells
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum