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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 embryonic layer does the epithelial linings of the oral cavity arise?
Neural crest cells
Neural crest cells
Neural crest cells
Surface ectoderm

2. What is annular pancreas associated with in infants?
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Ampulla
XII
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum

3. From where does the medulla form?
Vascular accident intra uterine; apple peel atresia
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)
Myelencephalon
Week 10-12; end of 1st trimester

4. What part of the fetal comp of the placenta secretes hCG? is this part on the inner or outer layer of the chorionic villi? does it make cells?
Synctiotrophoblast; outer; no
Mesoderm
Obliterated
Mesoderm

5. From what branchial derivative do the parafollicular cells arise?
Neuroectoderm
4th/5th branchial pouches
Mesoderm
...

6. What is perinauds syndrome?
...
Excessive resorption of septum primum or secondum (or both)
blood entering the RA
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)

7. From What embryonic layer does the oligodendrocytes arise?
28 week onward
Surface ectoderm
Neuroectoderm
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)

8. What causes tetralogy of Fallot?
Endoderm
Skewed development of AP septum
Surface ectoderm
Persistent connection between amniotic cavity and spinal canal; low folic acid

9. in hypospadias - on which side is the abnormal opening? What causes it?
VACTERL; OCPs and maternal diabetes
Increased AFP and acetycholinesterase (not ACh!) in CSF
Ventral; failure of urogenital folds to close
From endocardial cushions (ventral and dorsal meet each other)

10. What are the two components of the fetal component of the placenta?
Neuroectoderm
Myelencephalon
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Cytotrophoblast and synctiotrophoblast

11. What does the first cleft/groove of the branchial apparatus develop into?
Aortic arch (from left side); right subclavian (on the right)
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Neural crest cells
External auditory meatus

12. What teratogens can cause discolored teeth?
Neuroectoderm
Mesoderm
Tetracyclines
Hepatic circulation; ligamentum venosum

13. What teratogen can cause inhibition of intestinal folate absorption and thus neural tube defects?
Valproate acid
Umbilical - midgut herniates through umbilical ring; SMA
3rd and 4th arches
Cerebral hemisphere - thalami

14. What components do the neural crest cells of the branchial arches give rise to?
Alkylating agents
lumbosacral
Mesoderm; 3 week
Bones - cartilage - and nerves

15. What is the primitive streak? From what layer does it form?
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
2nd pouch
Mesoderm; epiblast
Neuroectoderm

16. What type of - amnios does bilateral agenesis form? What three symptoms does this cause?
Oligohydramnios
mesoderm
Mesoderm
Neuroectoderm

17. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
Mesoderm
Arnold chiari; syringomyelia
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
1st branchial arch

18. The inner layer of the chorionic villi...
Mesoderm
can make cells
Increased AFP and acetycholinesterase (not ACh!) in CSF
Fallopian tube - uterus - upper 1/3 of vagina

19. From What embryonic layer does the sensory organs of the ear arise?
Neuroectoderm
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
Surface ectoderm
Pataus; fetal alcohol syndrome

20. When does the neural tube form and From what does it form?
Neural plate; closes by week 4
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Apical ectodermal ridge
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'

21. Monochorionic - ___________ twins are conjoined
monoamniotic
Aminoglycosides
Telencephalon
mesodermal

22. What is the Eisenmeger complex?
When left to right shunting switching to right to left shunting
Maxillary
Sperm plus egg
IMA

23. From What embryonic layer are the schwann cells from ?
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
Neural crest cells
OCPS and maternal diabetes
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)

24. Which CN accounts for the anterior 2/3 of the tongues sensation and pain? how about taste?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
V3; VII
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems

25. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
Outgrowth of mesonephric as ureteric bud; most caudal
Midgut; 10th week
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

26. How does annular pancreas present in children?
Post. sup wall; luteal phase
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Bone/cartilage and nerves
Mesoderm

27. WithIn what week does gastrulation occur? What is gastrulation?
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Week 3; primitive streak formation from the epiblast makes the three layers
6-30
Endoderm - floor of primitive pharynx

28. What are the three results of having pathology in the aorticopulmonary septum?
Physiologic incomplete muscular ventricular septum
Maternally derived; meconium
Germinal matrix hemorrhage
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)

29. From where does pons form from? what else forms from there?
Stapedius and hyoid artery
Metencephalon; cerebellum
...
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum

30. What do the groove/clefts of the branchial apparatus correlate to?
T neuroectoderm
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Ectoderm
Failure of bony spinal canal to fuse; no; lower vertebral levels

31. Which CN allows for taste and sensation in the posterior 1/3 of the tongue? how about the very back ?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
IX; X
Aortic arch and prox part of subclavian
Neural crest cells

32. What are markers for neural tube defects in the amniotic cavity? CSF?
Mesoderm
Nutrient and gas exchange
1st cleft/groove (Ectoderm)
Increased AFP and acetycholinesterase (not ACh!) in CSF

33. what bone/cartilage and nerves are derived from branchial arch 1?
Meckels cartilage: mandible - malleus - INCUS - sphenoMandibular ligament; CN V2 and V3
After; extrinsic
Mesoderm
Pulm art (prox) and ductus arteriosus

34. Septum primum (patent foramen oval) caused by excessive resorption of...
septum primum and/or secundum
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Folate antagonists
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

35. Name two endocardial cushion defects.
8
Ebsteins anomaly; tricuspid atresia
DiGeorge
Hemorrhage - bone deformities

36. On what side is the abnormal opening in epispadias? What causes it?
Failure to recanalize; 21
Dorsal; faulty positioning of genital tubercle
4th pouch
Obliterated

37. By what week is there fetal movement?
Week 8
Neuroectoderm
From endocardial cushions (ventral and dorsal meet each other)
Alkylating agents

38. What does the first branchial pouch create?
4th week
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
From endocardial cushions (ventral and dorsal meet each other)
Ventral; failure of urogenital folds to close

39. What is the female remnant of processus vaginalis? male remnant?
Obliterated; forms tunica vaginalis
hypertrophy
Thickened ectoderm at end of each developing limb
Post. sup wall; luteal phase

40. what junction is the last to canalize? what implications does this have down the line?
Right common cardinal vein and right anterior cardinal vein
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus

41. From What embryonic layer is the eustachian tube from?
Hepatic circulation; ligamentum venosum
Skewed development of AP septum
Mesoderm
No more umbilical circulation emptying into RA

42. From What embryonic layer does bone arise ?
Mesoderm
Mesoderm; 3 week
Maxillary and medial nasal processes
Stapedius and hyoid artery

43. From What embryonic layer do chromaffin cells arise?
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Cerebral hemisphere - thalami
Neural plate; closes by week 4
Neural crest cells

44. With the first breath the infant take - pulmonary vasculature resistance _______ which causes an increase in left atrial pressure
mesodermal
During; instrinsic
From endocardial cushions (ventral and dorsal meet each other)
Decreases

45. From What embryonic layer does the adenohypophysis arise?
Surface ectoderm
Skewed development of AP septum
Neural crest cells
mesoderm

46. What type of blood do umbilical arteries carry? From where to where?
Deoxygenated blood; fetal internal iliac arteries to placenta
Increased AFP and acetycholinesterase (not ACh!) in CSF
blood entering the RA
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

47. From what region of the brain does the aqueduct form?
Rhombencephalon
Ionizing
Endometrium
Decidual basalis

48. What do membranous interventricular septal defect cause? What does this lead to?
Initial left to right shunting - then switches
Dorsal; faulty positioning of genital tubercle
VSD
Epiblast

49. Where is the decidua basalis derived from?
DiGeorge
Endometrium
Neural crest migration - they then cause spiral
Mesoderm

50. What does the midgut form? hindgut?
Primitive atrium
Duodenum to transverse colon; distal transverse colon to rectum
Mesoderm
Rhombencephalon