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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 branchial apparatus develops into the superior parathyroids?
8
4th pouch
Neural crest cells
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)

2. What is the effect of teratogens before week 3?
Duodenum to transverse colon; distal transverse colon to rectum
All or none
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Grooves/clefts; arches; pouches

3. which posterior fossa malformation results in aqueductal stenosis and hydrocephaly? what other spinal cord lesion does this malformation present with?
Bone/cartilage and nerves
Arnold chiari; syringomyelia
Surface ectoderm
Fallopian tube - uterus - upper 1/3 of vagina

4. What components do the neural crest cells of the branchial arches give rise to?
Week 8
V3; VII
Bones - cartilage - and nerves
Telencephalon

5. What is the initial step to interventricular septum development? is it complete?
Ectoderm
Prosencephalon
Primitive atrium
Muscular ventricular septum; no

6. How is amniontic fluid excreted? How is amniotic fluid resorped?
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood
can make cells
Wolffian; mullerian
Endoderm

7. From where does the permanent kidney for? is it most caudal or most cranial?
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Renal artery stenosis;
2nd; 2nd
Outgrowth of mesonephric as ureteric bud; most caudal

8. From What embryonic layer does the skin dermis arise?
Week 4
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Neural plate; closes by week 4
Mesoderm

9. At what week does the fetus look like a baby?
1st branchial arch
not covered
Week 8
Fetal kidney; fetal swallows - absorbs - and then removed from placental blood

10. what other facial defect other than cyclopia is associated with holoprosencephaly?
Tetracyclines
Cytotrophoblast
Cleft lip/palate
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'

11. ______________ is associated with ventral curvature of the penis
hypospadias
Failure to spiral (aorta coming out of RV and PA coming out of left ventricle)- two completely separate systems
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
VACTERL- vertebral defect - anal atresia - cardiac defects - tracheo - esophageal fistula - renal defects - limb defects

12. What is duodenal atresia usually due to? What trisomy is it most often seen in?
DiGeorge
Failure to recanalize; 21
Neural crest cells
Epiblast

13. From What embryonic layer does the parathyroid arise ?
All 3
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
hypospadias
Endoderm

14. From What embryonic layer does the brain arise?
Mesoderm
Initial left to right shunting - then switches
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Neuroectoderm

15. During what week does the heart begin to beat?
Week 4
Aminoglycosides
ACE inhibitors - HCTZ
Post. sup wall; luteal phase

16. 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
Maxillary
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18

17. What is an arnold chiari II malformation? through what hole does it herniate?
Cerebellar tonsillar herniation through foramen magnum
Surface ectoderm
Stapedius and hyoid artery
From endocardial cushions (ventral and dorsal meet each other)

18. As a horseshoe kidney ascends during kidney development - What do they get trapped under?
DHT; estrogen
IMA
1st cleft/groove (Ectoderm)
Arnold chiari; syringomyelia

19. By what week is the neural tube supposed to be closed? when did it start forming?
Endoderm
Week 4; week 3
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Medial palatine processes

20. What components do the mesoderm of the branchial arches give rise to?
Muscles and arteries
LH
Mesoderm
Surface ectoderm

21. What causes a patent foramen ovale?
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II
Tetracyclines
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Excessive resorption of septum primum or secondum (or both)

22. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Ionizing
DiGeorge
3rd; proximal part of the internal carotid artery
4th arch; 6th arch

23. What separated myometrium of the uterus from the blastocyst?
Muscles and arteries
Cerebral hemisphere - thalami
Bulbos Cordis; right ventricle entirely
Decidual basalis

24. What day is the chorion formed?
Failure of the urachus to obliterate
3
3 -4 -6
Fallopian tube - uterus - upper 1/3 of vagina

25. What does the RET gene encode? what neoplasias is it associated with?
Excessive resorption of septum primum or secondum (or both)
DES
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Failure of bony spinal canal to fuse; no; lower vertebral levels

26. what results if they dont? What can increase the risks of this?
Vascular accident intra uterine; apple peel atresia
Persistent connection between amniotic cavity and spinal canal; low folic acid
Umbilical - midgut herniates through umbilical ring; SMA
Thalidomide; nausea

27. What arises from the fourth aortic arch?
Week 4
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Aortic arch (from left side); right subclavian (on the right)
Cleft lip/palate

28. What do the arches of the branchial apparatus correlate to?
From teh lung;blood from IVC in RA to LA; fossa ovalis
Midgut; 10th week
Folate antagonists
Mesdoerm

29. Cleft palate is a failure of fusion of the lateral palatine processes - the nasal septum and or the ________?
4th arch; 6th arch
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Surface ectoderm
Medial palatine processes

30. What is the effect of teratogens after week 8?
Female; paramesonephric; mesonephric
Deformation
Decreased separation of hemispheres across midline; cyclopia
Congenital and chromosomal abnormalities

31. What does the midgut form? hindgut?
Prostaglandins
primary palate
Duodenum to transverse colon; distal transverse colon to rectum
Incomplete; yes

32. What does DHT turn the genital tubercle into? estrogen?
OCPS and maternal diabetes
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
During; instrinsic

33. From What embryonic layer does the epidermis arise?
Dorsal; sensory
Surface ectoderm
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Muscles and arteries

34. What embryologic structure provides the aorticpulmonary septum?
Neural crest migration - they then cause spiral
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Cranio - caudal; segmental
Left horn of the sinus venosus

35. What part of the vagina does the mullerian duct form? Where does the rest come from?
Surface ectoderm
Endoderm
6-30
Upper 1/3; urogenital sinus

36. Weeks _______ erythropoiesis takes place in the liver
Week 8
Grooves/clefts; arches; pouches
Cranio - caudal; segmental
6-30

37. What surrounds the umbilical cord?
Neural crest cells
Amniotic epithelium
Mesoderm
Hemorrhage - bone deformities

38. what muscles are derived from branchial arch 3?
Neuroectoderm
StyloPharyngeus
Embryonic period; 1st trimester
First branchial pouch

39. 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?
Right common cardinal vein and right anterior cardinal vein
2; 1
4th arch; 6th arch
Umbilical - midgut herniates through umbilical ring; SMA

40. From What embryonic layer do CNS neurons arise?
Mullerian inhibitory factor from Sertoli cells; increased androgen from Leydig cells
Week 3-8
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Neuroectoderm

41. From What embryonic layer are the schwann cells from ?
Ectoderm; endoderm
Neural crest cells
5th
Amniotic cavity and yolk sac

42. What is germinal matrix hemorrhage associated with?
Mesoderm
Female; paramesonephric; mesonephric
Wolffian; mullerian
Respiratory distress syndrome

43. What do membranous interventricular septal defect cause? What does this lead to?
8
Initial left to right shunting - then switches
Thalidomide; nausea
1st branchial arch

44. From where does the ureteric bud arise? What does it give rise to?
The caudal end mesonephros; the ureter - pelvis - calyces - collecting ducts
Aortic arch and prox part of subclavian
Arches 3 and 4
Polyhydramnios

45. What happens in pancreas divisum? what results?
Aortic arch and prox part of subclavian
Ampulla
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Surface ectoderm

46. What are the two walls of the prosencephalon and What do they become?
Neural crest cells
Thyroglossal duct cysts will move with swallowing while persistent cervical sinuses in lateral neck wont
Cerebral hemisphere - thalami
Mesonephros; male genital system

47. From What embryonic layer does the adenohypophysis arise?
Uretopelvis; most common site for obstruction (hydronephrosis) in fetus
Surface ectoderm
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Thalidomide; nausea

48. By what week is there fetal movement?
Week 8
Cerebral hemisphere - thalami
Bones - cartilage - and nerves
Decreased separation of hemispheres across midline; cyclopia

49. What are markers for neural tube defects in the amniotic cavity? CSF?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Amniotic epithelium
Aortic arch (from left side); right subclavian (on the right)
Surface ectoderm

50. Which branchial derivative accounts for the posterior 2/3 of the tongue?
Neuroectoderm
Post. sup wall; luteal phase
3rd and 4th arches
Fetal and maternal