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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 gut tube epithelium arise?
3 -4 -6
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Endoderm
Rhombencephalon

2. What is DiGeorge syndrome and What does it result in?
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
LH
Hypertrophy of muscularis externis of pylorus; surgical incision
Renal artery stenosis;

3. Which part of the branchial apparatus makes up membranes?
All 3
Tunica vaginalis not fully fused
Endoderm
Bone/cartilage and nerves

4. Where does the blastocyst implant in the uterus? During what phase of the menstrual cycle?
Surface ectoderm
Post. sup wall; luteal phase
StyloPharyngeus
Fluid filled syrinx causes expansion and degeneration of cord tracts

5. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
Valproate acid
Mesoderm; 3 week
Week 2; bilaminar disk; epiblast and hypoblast
Ventral shaft of penis (penile urethra); labia minora

6. From where to Where is the foregut derivative? midgut? hindgut?
Pharynx to duodenum; duodenum to transverse colon; distal transverse colon to rectum
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Fallopian tube - uterus - upper 1/3 of vagina
Amniotic epithelium

7. From what aortic arch does the common carotid artery arise? what else arises from this arch?
3rd; proximal part of the internal carotid artery
Week 3-8
VSD
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari

8. What causes tetralogy of Fallot?
StyloPharyngeus
Ventral shaft of penis (penile urethra); labia minora
Skewed development of AP septum
Post. sup wall; luteal phase

9. What connects the thyroid to the tongue? when happens if it doesnt obliterate?
DiGeorge
IX; X
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct
Before getting pregnant!

10. What is holoprosencephaly? what eye disorder does it result in?
Temporary cervical sinus
Mesoderm
Decreased separation of hemispheres across midline; cyclopia
Ventral ; motor

11. What embryological structure gives rise to the coronary sinus?
Nutrient and gas for exchange; endometrium
Primitive atrium
Hypertrophy of muscularis externis of pylorus; surgical incision
Left horn of the sinus venosus

12. What is the memranous interventricular formaen made from?
Ectoderm
Mesoderm
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian

13. From What embryonic layer does the spinal cord arise?
V3; VII
Neuroectoderm
Failure of the urachus to obliterate
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain

14. From What embryonic layer does the retina arise?
T neuroectoderm
Before getting pregnant!
Deformation
Neuroectoderm

15. From What embryonic layer does the epithelial linings of the oral cavity arise?
DiGeorge
Duodenum to transverse colon; distal transverse colon to rectum
Maxillary and medial nasal processes
Surface ectoderm

16. What is the notochord? What does the notochord later become?
Surface ectoderm
Obliterated
Mesoderm; nucleous pulposos
Absent cerebellar vermis; cystic enlargement of 4th ventricle

17. When does hcG get secreted? What does it do?up until when ?
Day 6; maintains corpus luteum; 1st trimester
Synctiotrophoblast
mesodermal
1st

18. How many components are there to the placenta? What are they called?
Fetal and maternal
Hepatic circulation; ligamentum venosum
LH
Neural crest cells

19. What is an arnold chiari II malformation? through what hole does it herniate?
Cerebellar tonsillar herniation through foramen magnum
Bones - cartilage - and nerves
Aberrant development of 3rd and 4th pouches; t cell def (thymic aplasia) - hypocalcemia (failure of parathyroid development) - CF and CV defects
can make cells

20. From What embryonic layer does the epidermis arise?
Week 3-8
Excessive resorption of septum primum or secondum (or both)
pyloric stenosis
Surface ectoderm

21. In order to survive tricuspid atresia - What do you need?
Germinal matrix hemorrhage
Nutrient and gas exchange
VSD
Tetracyclines

22. What is the Eisenmeger complex?
Failure of the urachus to obliterate
Common carotid and internal carotid
When left to right shunting switching to right to left shunting
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

23. What is perinauds syndrome?
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Hemorrhage - bone deformities

24. From What embryonic layer does the olfactory epithelium arise?
Week 4; week 3
Surface ectoderm
Endoderm
Germinal matrix hemorrhage

25. What do membranous interventricular septal defect cause? What does this lead to?
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
Obliterated; forms tunica vaginalis
ACE inhibitors - HCTZ
Initial left to right shunting - then switches

26. What is the female remnant of the gubernaculum? male remnant?
IMA
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Hemorrhage - bone deformities
Surface ectoderm

27. From where is the pancreas derived? the spleen?
OCPS and maternal diabetes
Dorsal and ventral buds
Surface ectoderm
Foregut; dorsal mesentery (mesodermal)

28. _____________is common in 1st born males
Allantois
pyloric stenosis
Week 3; primitive streak formation from the epiblast makes the three layers
Base of limbs in the zone of polarizing activity; ant - post

29. From What embryonic layer does the brain arise?
Amniotic cavity and yolk sac
Arnold Chiari and Dandy Walker; Arnold Chiari; Dandy Walker; Arnold Chiari
Mid gut to yolk sac; omphalomesenteric duct; 7th week
Neuroectoderm

30. What does the ductus venosus shunt blood away from? What is its remnant?
Ebsteins anomaly; tricuspid atresia
Prenatal and perinatal
Ventral bud
Hepatic circulation; ligamentum venosum

31. What is the female remnant of processus vaginalis? male remnant?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
monoamniotic
Obliterated; forms tunica vaginalis
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3

32. What causes a large posterior fossa in a dandy walker malformation? What is found in this fossa?
1st
Absent cerebellar vermis; cystic enlargement of 4th ventricle
Valproate acid
Tongue

33. What does the maternal component of the placenta provide? Where is it derived from?
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
StyloPharyngeus
Nutrient and gas for exchange; endometrium
Thyroid - cricoid - arytenoids - corniculate cuneiform

34. What are markers for neural tube defects in the amniotic cavity? CSF?
Increased AFP and acetycholinesterase (not ACh!) in CSF
...
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)
Muscles and arteries

35. From where does pons form from? what else forms from there?
Right common cardinal vein and right anterior cardinal vein
Ring of pancreatic tissue can cause duodenal narrowing; ventral pancreatic bud abnormally encircles 2nd part of duodenum
Metencephalon; cerebellum
Pulm art (prox) and ductus arteriosus

36. What causes the obstruction in pyloric stenosis? treatment?
...
Skewed development of AP septum
Hypertrophy of muscularis externis of pylorus; surgical incision
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)

37. What are two common findings in pyloric stenosis?
Week 3-8
Palpable olive mass in epigastric region; nonbilious projectile vomitting @around 2 weeks
Mesdoerm
Dorsal; faulty positioning of genital tubercle

38. What does the RET gene encode? what neoplasias is it associated with?
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Prosencephalon - mesencephalon - rhombencephalon
Urogenital sinus; wolffian duct; mullerian duct; urogenital sinus; wolffian duct; wolffian duct; mullerian; mullerian
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure

39. What is Treacher Collins syndrome? What is the result?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Persistent connection between amniotic cavity and spinal canal; low folic acid

40. What is germinal matrix hemorrhage associated with?
Foregut; dorsal mesentery (mesodermal)
Respiratory distress syndrome
Decreases
VACTERL; OCPs and maternal diabetes

41. Which branchial apparatus makes the external auditory meatus?
XII
1st cleft/groove (Ectoderm)
Rhombencephalon
Nicotine; preterm labor

42. Cleft palate is a failure of formation of the...
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Dorsal ventral axis
secondary palate
Annular pancrease

43. what muscles are derived from branchial arch 1?
Surface ectoderm
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
Mesdoerm
2nd; 2nd

44. What is associated with only one umbilical artery?
DHT; estrogen
Outgrowth of mesonephric as ureteric bud; most caudal
Week 4; week 3
Congenital and chromosomal abnormalities

45. What causes a patent foramen ovale?
Neuroectoderm
Excessive resorption of septum primum or secondum (or both)
Rostral fold closure ; lateral fold closure; lateral fold closure; caudal fold closure
3rd pouch

46. From what aortic arch does the first part of the maxillary artery arise?
1st
Temporary cervical sinus
Nutrient and gas exchange
Endoderm

47. During what months is the fetus most susceptible to teratogens? What trimester?
All 3
Embryonic period; 1st trimester
Oligohydramnios
OCPS and maternal diabetes

48. What is the neural plate and From what does it form?
Week 4
Ectoderm
blood entering the RA
Nicotine; preterm labor

49. What is omphalocele? In What trisomies is it seen?
Oxygenated; placenta to fetus (IVC)
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Excessive resorption of septum primum or secondum (or both)
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis

50. What is the most common autopsy finding in brains of premature infants?
Neural crest cells
Ovarian ligament and round ligament of uterus; anchors testes within scrotum
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Germinal matrix hemorrhage