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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. Which cranial nerve innervates the motor function of the tongue?
XII
Midgut; 10th week
Dorsal; sensory
Arnold chiari; syringomyelia

2. WithIn what week does gastrulation occur? What is gastrulation?
3rd and 4th arches
Arnold chiari; syringomyelia
Week 3; primitive streak formation from the epiblast makes the three layers
Ectoderm; endoderm

3. What is the female remnant of the gubernaculum? male remnant?
Neural plate; closes by week 4
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Nutrient and gas for exchange; endometrium
Week 3-8

4. What causes the transposition of the great vessels? What does it result in?
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
Arches 3 and 4
During; instrinsic
Neural plate; closes by week 4

5. What is the neural plate and From what does it form?
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Week 10-12; end of 1st trimester
1st branchial arch
Ectoderm

6. From What embryonic layer is the spleen from?
2nd pouch
Mesoderm
From endocardial cushions (ventral and dorsal meet each other)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm

7. What is a teratogen that causes Ebsteins anomaly? What is ebsteins anomaly?

8. What is another name for the mesonephric duct? paramesonephric?
Neuroectoderm
Dorsal and ventral buds
Wolffian; mullerian
Annular pancrease

9. From what aortic arch does the first part of the maxillary artery arise?
IMA
1st
Fetal and maternal
Neural crest migration - they then cause spiral

10. what else is the caudal regression known as? What two teratogen can cause this in the fetus?
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Failure to recanalize; 21
Obliterated
VACTERL; OCPs and maternal diabetes

11. From where does the ureteric bud arise? What does it give rise to?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Mesoderm
Week 3-8

12. Which branchial derivative accounts for the posterior 2/3 of the tongue?
Spinothalamic first
3rd and 4th arches
Muscular ventricular septum; no
Mesonephros; male genital system

13. Which branchial apparatus develops into the inferior parathyroids?
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Neuroectoderm
3rd pouch
Neuroectoderm

14. From What embryonic layer does the oligodendrocytes arise?
Neuroectoderm
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Outgrowth of mesonephric as ureteric bud; most caudal
Cytotrophoblast and synctiotrophoblast

15. What is the female remnant of processus vaginalis? male remnant?
Obliterated; forms tunica vaginalis
Outgrowth of mesonephric as ureteric bud; most caudal
Mesoderm
6-30

16. Cleft lip is a failure of fusion of ________ and ______.
Thyroid - cricoid - arytenoids - corniculate cuneiform
Maxillary and medial nasal processes
arnold chiari associated with thoraclumbar myelomeningocele
Before getting pregnant!

17. In anencephaly you see...
4th/5th branchial pouches
Muscles of facial expression - stapedius - stylohyoid - posterior belly of the digastric
Synctiotrophoblast; outer; no
elevated AFP

18. What artery is derived branchial (aortic) arch 1?
Neuroectoderm
Maxillary
Grooves/clefts; arches; pouches
Endoderm

19. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
1st
5th
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Mental retardation - holoprosencephaly - facial features - fistulas

20. By when are the neuropores supposed to fuse?
4th week
Left horn of the sinus venosus
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Amniotic cavity and yolk sac

21. Other than not having a brain - what else is a symptom of anencephaly? why? hint: think about amniotic fluid
Ectoderm
Rhombencephalon
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Polyhydramnios

22. Which part of the branchial apparatus makes up membranes?
1st
All 3
Neural crest cells
Female; paramesonephric; mesonephric

23. What surrounds the umbilical cord?
Amniotic epithelium
Increased AFP and acetycholinesterase (not ACh!) in CSF
Surface ectoderm
Neural crest cells

24. Name two endocardial cushion defects.
Neuroectoderm
Tongue
Ebsteins anomaly; tricuspid atresia
Dorsal; faulty positioning of genital tubercle

25. What causes the increase in left atrial pressure to close the fossa ovale?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Decreased pulmonary resistance in the pulmonary vasculature
Foregut; dorsal mesentery (mesodermal)

26. From What embryonic layer does the epithelial linings of the oral cavity arise?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
External auditory meatus
Aminoglycosides
Surface ectoderm

27. What is the effect of teratogens before week 3?
Wolffian; mullerian
Sonic Hedgehog
All or none
Sperm plus egg

28. From What embryonic layer does the brain arise?
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
DiGeorge
Neuroectoderm
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont

29. From What embryonic layer does the olfactory epithelium arise?
2nd pouch
Surface ectoderm
4th/5th branchial pouches
Bulbos Cordis; right ventricle entirely

30. What axis does the alar plate form? what neural system does it become?
Mesoderm
Neuroectoderm
Dorsal; sensory
Lacunae in between the chorionic villi

31. From What embryonic layer is the vagina from? testes? ovaries?
Dorsal and ventral buds
Mesonephros; male genital system
Epispadias
Mesoderm

32. Which branchial derivative accounts for taste in the ant 2/3?
Branchial arch 2
Week 10-12; end of 1st trimester
Neural crest cells
Endoderm

33. failure to close of what fold results in sternal defects? omphalocele? gastrochisis? bladder extrosphy?
Surface ectoderm
Synctiotrophoblast; outer; no
Ventral shaft of penis (penile urethra); labia minora
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

34. which tracts are damaged first in syringomelia? What tract is preserved?
Respiratory distress syndrome
Endoderm
Spinothalamic first
ACE inhibitors - HCTZ

35. what muscles are derived from branchial arch 4? CN?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Thalidomide; nausea
Endometrium
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)

36. what chemo drugs can cause neural tube defects in the fetus?
Folate antagonists
All or none
External auditory meatus
They are the edge of neural plate folding; all over the body

37. What is the notochord? What does the notochord later become?
Neuroectoderm
Mesoderm; nucleous pulposos
From endocardial cushions (ventral and dorsal meet each other)
Absent cerebellar vermis; cystic enlargement of 4th ventricle

38. Septum primum (patent foramen oval) caused by excessive resorption of...
septum primum and/or secundum
Dorsal ventral axis
Neural crest cells
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18

39. From What embryonic layer does the skin dermis arise?
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Tetracyclines
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

40. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Synctiotrophoblast
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Skewed development of AP septum

41. what bone/cartilage and nerves are derived from branchial arch 3?
Female; paramesonephric; mesonephric
Mesoderm; nucleous pulposos
3rd pouch
Greater horn of hyoid; CN IX (styloPharyngeus)

42. Weeks _______ erythropoiesis takes place in the liver
Week 4; week 3
6-30
Thyroid - cricoid - arytenoids - corniculate cuneiform
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

43. What does the midgut form? hindgut?
Day 6; maintains corpus luteum; 1st trimester
Dorsal ventral axis
3
Duodenum to transverse colon; distal transverse colon to rectum

44. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
Surface ectoderm
Umbilical artery - vein; and whartons jelly (mucus connective tissue) - urachus
V3; VII
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

45. what bone/cartilage and nerves are derived from branchial arch 1?
Amniotic epithelium
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3

46. What are the neural crest cells and where do they come form? where do they go?
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Lacunae in between the chorionic villi
They are the edge of neural plate folding; all over the body
Rhombencephalon

47. How is amniontic fluid excreted? How is amniotic fluid resorped?
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

48. What is associated with only one umbilical artery?
Cytotrophoblast
Ampulla
6th aortic arch
Congenital and chromosomal abnormalities

49. What is Treacher Collins syndrome? What is the result?
Mental retardation - holoprosencephaly - facial features - fistulas
Endoderm
Thickened ectoderm at end of each developing limb
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)

50. From where did a branchial cleft cyst arise if it found?
No organ in each; agenesis no primordial tissue
Sonic Hedgehog
Pulm art (prox) and ductus arteriosus
Found in lateral neck; from no obliteration of 2-4th clefts