USMLE Embryo

Instructions:

• Answer 50 questions in 15 minutes.
• If you are not ready to take this test, you can study here.
• Match each statement with the correct term.
• Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. To what germ layer does the branchial pouches correlate to?
Sonic Hedgehog
Prosencephalon - mesencephalon - rhombencephalon
Endoderm
No organ in each; agenesis no primordial tissue


2. What is the effect of teratogens before week 3?
All or none
Hypertrophy of muscularis externis of pylorus; surgical incision
Germinal matrix hemorrhage
secondary palate


3. From What embryonic layer does the neurohypophysis arise?
Neuroectoderm
Synctiotrophoblast; outer; no
Turners; inferior
Pronephros - mesonephros - metanephros; pronephros; most cranially


4. From What embryonic layer are the pia and arachnoid from?
Yolk sac; liver (weeks 6-30) and spleen (9-28 weeks)
Skewed development of AP septum
Endoderm
Neural crest cells


5. How do AV canals form?
From endocardial cushions (ventral and dorsal meet each other)
Dorsal ventral axis
Thickened ectoderm at end of each developing limb
OCPS and maternal diabetes


6. Which branchial apparatus develops into the thymus?
3rd pouch
T neuroectoderm
...
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum


7. From what aortic arch does the stapedial artery arise? the hyoid?
Week 3-8
Bulbos Cordis; right ventricle entirely
2nd; 2nd
From teh lung;blood from IVC in RA to LA; fossa ovalis


8. What type of blood do umbilical veins carry? From where to where?
Allantois
ACE inhibitors - HCTZ
Oxygenated; placenta to fetus (IVC)
Tongue


9. What day is the amnion formed?
Neuroectoderm
monoamniotic
8
Excessive resorption of septum primum or secondum (or both)


10. From where does the permanent kidney for? is it most caudal or most cranial?
Week 8
Tunica vaginalis not fully fused
All 3
Outgrowth of mesonephric as ureteric bud; most caudal


11. What happens in pancreas divisum? what results?
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
6-30
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)


12. From what region does the cerebral hemisphere form?
Deoxygenated blood; fetal internal iliac arteries to placenta
Temporary cervical sinus
Endoderm
Telencephalon


13. Which branchial derivative accounts for taste in the ant 2/3?
Branchial arch 2
secondary palate
Metanephric mesenchyme; differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Ventral; failure of urogenital folds to close


14. What are the two walls of the prosencephalon and What do they become?
Temporary cervical sinus
mesoderm
is no longer intact
Cerebral hemisphere - thalami


15. When is most important to take folic acid to prevent neural tube defects?
Before getting pregnant!
Stapedius and hyoid artery
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
Neuroectoderm


16. From what aortic arch does the first part of the maxillary artery arise?
Umbilical - midgut herniates through umbilical ring; SMA
1st
Failure of the urachus to obliterate; outpouching of the bladder
XII


17. What teratogens can cause flipper limbs (limb defects)? What is this drug used for?
Thalidomide; nausea
Mesoderm; nucleous pulposos
Allantois
Aortic arch (from left side); right subclavian (on the right)


18. _____________is common in 1st born males
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain
Surface ectoderm
pyloric stenosis
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)


19. Where is the mothers blood located in the placenta?
Telencephalon
Lacunae in between the chorionic villi
Prevent recurrent UTIs
Allantois


20. What artery is derived branchial (aortic) arch 6?
Polyhydramnios
not covered
Endoderm
Pulm art (prox) and ductus arteriosus


21. From What embryonic layer does the brain arise?
Foregut; dorsal mesentery (mesodermal)
Neuroectoderm
Surface ectoderm
Endoderm


22. From what region do the thalami form?
Fetal alcohol syndrome; mental retardation
No organ in each; agenesis no primordial tissue
Diencephalon
Neural crest cells


23. By when are the neuropores supposed to fuse?
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Skewed development of AP septum
4th week


24. What teratogens can cause renal damage in the fetus?
ACE inhibitors - HCTZ
Neural crest migration - they then cause spiral
Amniotic cavity and yolk sac
Neuroectoderm


25. what muscles are derived from branchial arch 3?
Endoderm
StyloPharyngeus
Increased AFP and acetycholinesterase (not ACh!) in CSF
primary palate


26. which tracts are damaged first in syringomelia? What tract is preserved?
T neuroectoderm
Renal artery stenosis;
Spinothalamic first
Outgrowth of mesonephric as ureteric bud; most caudal


27. From where is the allantois formed? During what week?
Nicotine; preterm labor
Persistence of 3rd cleft (groove) and pouch causes fistula between tonsillar area and cleft in lateral neck
Mesonephros; male genital system
Yolk sac; 3rd week


28. What is meckel's diverticulum? What is it associated with? What does that cause?
Duodenum to transverse colon; distal transverse colon to rectum
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)
4th week
Partial closure of vitelline duct so that the patent portion is attached to ileum; ectopic gastric mucosa; melena and periumbilical pain


29. What is the memranous interventricular formaen made from?
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen
Dorsal; sensory
Dorsal ventral axis
Ionizing


30. What can vit A in excess cause in the fetus?
Lots - cleft palate/lip
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Persistent connection between amniotic cavity and spinal canal; low folic acid
Foramen cecum and terminal sulus


31. What are the clinical symptoms that present with syringomelia?
Turners; inferior
Neuroectoderm
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
Week 8


32. what muscles are derived from branchial arch 6? CN?
Neural crest cells
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
IX; X
All intrinsic muscles of larynx except cricothyroid; CN X (recurrent laryngeal nerve - speaking)


33. What teratogens can cause CN VIII toxicity in the fetus?
Epiblast
Telencephalon
Aminoglycosides
From teh lung;blood from IVC in RA to LA; fossa ovalis


34. Gastroschisis is extrusion of abdominal contents out of abdominal folds ___________ by peritoneum
not covered
Annular pancrease
Duodenum to transverse colon; distal transverse colon to rectum
Day 6; with implantation


35. What is used to keep the PDA open?
Endoderm lined structures of ear: middle ear cavity - eustacian tube - mastoid air cells
Neuroectoderm
Neural crest cells
Prostaglandins


36. What does the first cleft/groove of the branchial apparatus develop into?
Synctiotrophoblast
Week 4; week 3
2; 1
External auditory meatus


37. Which branchial derivative creates the epithelial lining of the palatine tonsils?
T neuroectoderm
Persistent connection between amniotic cavity and spinal canal; low folic acid
Congenital and chromosomal abnormalities
2nd pouch


38. What is an arnold chiari II malformation? through what hole does it herniate?
Deformation
Dorsal; sensory
Cerebellar tonsillar herniation through foramen magnum
When left to right shunting switching to right to left shunting


39. From What embryonic layer does the epithelial linings of the oral cavity arise?
Ectoderm
Neuroectoderm
Surface ectoderm
Mid gut to yolk sac; omphalomesenteric duct; 7th week


40. What is the effect of teratogens after week 8?
Week 4; week 3
6th aortic arch
Deformation
Yolk sac; 3rd week


41. What does DHT turn the urogenital folds into? estrogen?
Ventral shaft of penis (penile urethra); labia minora
First branchial pouch
Pulm art (prox) and ductus arteriosus
Ovarian ligament and round ligament of uterus; anchors testes within scrotum


42. What is germinal matrix hemorrhage associated with?
Fetal and maternal
1st branchial arch
Pataus; fetal alcohol syndrome
Respiratory distress syndrome


43. When does the blastocyst split into two disks? What is this disk called? What are the two germ layers called?
4th/5th branchial pouches
septum primum and/or secundum
...
Week 2; bilaminar disk; epiblast and hypoblast


44. Septum primum (patent foramen oval) caused by excessive resorption of...
septum primum and/or secundum
1st
Neuroectoderm
Prosencephalon - mesencephalon - rhombencephalon


45. Which part of the branchial apparatus makes up membranes?
Pulm art (prox) and ductus arteriosus
All 3
Neural crest cells
Failure of bony spinal canal to fuse; no; lower vertebral levels


46. Which branchial apparatus develops into the inferior parathyroids?
Epispadias
Neuroectoderm
Neuroectoderm
3rd pouch


47. From where did a branchial cleft cyst arise if it found?
Mesoderm
Found in lateral neck; from no obliteration of 2-4th clefts
Ventral and dorsal parts fail to fuse at 8th week; 2 pancreatic ducts!- more prone to pancreatitis
Foramen cecum and terminal sulus


48. What weeks are considered the 'embryonic period'?
Week 3-8
Metencephalon; cerebellum
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Neuroectoderm


49. What is the defect in spina bifida occulta? is there any structural herniation? where on the spinal cord is it usually seen?
Fluid filled syrinx causes expansion and degeneration of cord tracts
Amniotic cavity and yolk sac
Alkylating agents
Failure of bony spinal canal to fuse; no; lower vertebral levels


50. From What embryonic layer do the salivary - sweat and mammary glands arise?
Endoderm
Surface ectoderm
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Medial palatine processes