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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. During what week does the heart begin to beat?
Neuroectoderm
Week 4
Amniotic cavity and yolk sac
Fluid filled cavity in spinal cord; C8- T1; arnold chiari II

2. Where is the decidua basalis derived from?
Pulm art (prox) and ductus arteriosus
Endometrium
Cranio - caudal; segmental
Surface ectoderm

3. what muscles are derived from branchial arch 1?
IX; X
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
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

4. From what region does the cerebral hemisphere form?
Mesoderm
Telencephalon
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
2nd; 2nd

5. What is a zygote?
1st arch neural crest fails to migrate --> mandibular hypoplasia - facial abnormalities (cleft palate - decreased slanting of palpebral fissures)
Incomplete fusion of paramesonephric ducts; UT abnormalities and infertility
Sperm plus egg
V3; VII

6. From What embryonic layer do the ependymal cells arise?
From the the lung; blood from SVC that went into RV gets shunted from pulm artery to aorta; ligamentum arteriosum
Lithium; valve leaflets attach to domain down low in RV- 'atrialized RV'
Neuroectoderm
Thyroglossal duct; persists as pyramidal lobe of thyroid; foramen cecum on tongue is normal remnant of thyroglossal duct

7. is epispadias or hypospadias associated with exstrophy of the bladder?
Epispadias
2nd; 2nd
Persistance of herniation of abdominal contents into umbilical cord covered by peritoneum; 13 - 18
Telencephalon

8. Where does the blastocyst implant in the uterus? During what phase of the menstrual cycle?
Neuroectoderm
Post. sup wall; luteal phase
Urachus/median umbilical ligament; bladder and yolk sac
All 3

9. From what aortic arch does the common carotid artery arise? what else arises from this arch?
Ventral bud
Fluid filled syrinx causes expansion and degeneration of cord tracts
Caused by compression on trocheal nerve - causes vertical gaze paralysis (associated with arnold chiari)
3rd; proximal part of the internal carotid artery

10. From what branchial derivative do the parafollicular cells arise?
Decreased separation of hemispheres across midline; cyclopia
4th/5th branchial pouches
secondary palate
Annular pancrease

11. What hormones are in charge of external genitalia development in the fetus? (in both male and female)
Scrotum; labia majora
T neuroectoderm
DHT; estrogen
Ionizing

12. Where is the FGF gene produced? What is it responsible for - How does it do this?
Week 3-8
Apical ectodermal ridge; limb lengthening; stimulates mitosis of underlying mesoderm
Sonic Hedgehog
Female; paramesonephric; mesonephric

13. What produces testis determining factor? what cells are produced from this? and What do they secrete? does this result in?
Obliterated; forms tunica vaginalis
Branchial arch 2
SRY gene on Y chromosomes; sertoli and leydi; MIF and androgens; suppression of paramesonephric ducts and dev. of mesonephric (all respectively)
Failure of the urachus to obliterate

14. The spleen is ____________ in origin and supplied by a foregut artery
Polyhydramnios - Down syndrome - Esophageal/duodenal atresia - Imperforate anus - Meckel diverticulum
Primitive atrium
Rhombencephalon
mesodermal

15. What artery is derived branchial (aortic) arch 3?
Mesoderm
Hepatic circulation; ligamentum venosum
Cerebellar tonsillar herniation through foramen magnum
Common carotid and internal carotid

16. From What embryonic layer are the serous linings of the body cavities from? for ex - peritoneum?
Ectoderm
...
Turners; inferior
Scrotum; labia majora

17. What does DHT turn the urogenital sinus into? estrogen?
Fetal and maternal
Persistent connection between amniotic cavity and spinal canal; low folic acid
Endoderm
Bulbourethral glands (of Cowper) and Prostate gland; greater vestibular glands (of Bartholin) and Urethral and paraurethral glands (of Skene)

18. From What embryonic layer does the epidermis arise?
Duodenum to transverse colon; distal transverse colon to rectum
Sperm plus egg
Ectoderm - mesoderm - endoderm; epiblast - primitive streak - hypoblast; week 3
Surface ectoderm

19. From What embryonic layer does the adenohypophysis arise?
Truncus arteriosus; pulmonary trunk
Surface ectoderm
Embryonic period; 1st trimester
Congenital and chromosomal abnormalities

20. In order to survive tricuspid atresia - What do you need?
VSD
can make cells
Annular pancrease
Muscles and arteries

21. What axis does the alar plate form? what neural system does it become?
Sonic Hedgehog
Dorsal; sensory
Gastric outlet obstruction (bilious vomiting - feeding intolerance - abdominal distention)
6-30

22. What arises from the fourth aortic arch?
Aortic arch (from left side); right subclavian (on the right)
Nutrient and gas for exchange; endometrium
Surface ectoderm
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs

23. The inner layer of the chorionic villi...
can make cells
Ventral; failure of urogenital folds to close
20-50yrs - Abdominal pain - Postprandial fullness - Nausea - Peptic ulcers - Pancreatitis - Rarely - biliary obstruction
Dorsal; faulty positioning of genital tubercle

24. Which part of pancreas contribute to body? tail? isthmus? accessory pancreatic duct?
LH
Outgrowth of mesonephric as ureteric bud; most caudal
Ventral bud
Neuroectoderm

25. From What embryonic layer are the melanocytes from?
Oligohydramnios
Prenatal and perinatal
Neural crest cells
Mesoderm

26. What is the most common subtype of tracheoesophageal fistula? name some symptoms (hint: O2 levels - feeding - stomach on CXR - - amnios? - NG tube? - respiratory infection? )
ACE inhibitors - HCTZ
Cleft lip/palate
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
Temporary cervical sinus

27. What is holoprosencephaly? what eye disorder does it result in?
3rd pouch
Decreased separation of hemispheres across midline; cyclopia
Neuroectoderm
Renal artery stenosis;

28. What are the two walls of the prosencephalon and What do they become?
Decreases
Primitive ventricle
Neural crest cells
Cerebral hemisphere - thalami

29. What are the two components of the placenta? From What do they form? which one secreted hcG?
...
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
DHT; estrogen
Ovarian ligament and round ligament of uterus; anchors testes within scrotum

30. what else is the caudal regression known as? What two teratogen can cause this in the fetus?
Obliterated
Glans penis and corpus cavernosum and spongiosum; glans clitoris and vestibular bulbs
Neural crest cells
VACTERL; OCPs and maternal diabetes

31. What causes persistent Truncus Arteriosus? What does it result in?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Embryonic period; 1st trimester
Partial AP septum development; one large vessel leaves the heart - Right to left shunt
They are the edge of neural plate folding; all over the body

32. What causes the degeneration of the spinal cord in syringomelia?
Primitive atrium
mesoderm
pyloric stenosis
Fluid filled syrinx causes expansion and degeneration of cord tracts

33. what bone/cartilage and nerves are derived from branchial arch 3?
All 3
Thickened ectoderm at end of each developing limb
Amniotic cavity and yolk sac
Greater horn of hyoid; CN IX (styloPharyngeus)

34. What separates the ant 1/3 and post 2/3 of tongue?
Hypertrophy of muscularis externis of pylorus; surgical incision
Neural crest cells
Where the epiblast and hypoblast fuse
Foramen cecum and terminal sulus

35. What teratogen can cause vaginal clear cell adenocarcinoma in the fetus?
DES
Nutrient and gas exchange
Reicherts cartilage: Stapes - Styloid process - Lesser horn of hyloid - Stylohyoid ligament and CN VII
When the AP septum meets and fuses with the muscular ventricular septum to form membranous intraventricular septum - closing interventricular foramen

36. The notochord is...
Where the epiblast and hypoblast fuse
pyloric stenosis
Urachus/median umbilical ligament; bladder and yolk sac
mesoderm

37. What is hypoplasia? is primordial tissue present?
Hemorrhage - bone deformities
Hypospadias
Incomplete; yes
Day 6; maintains corpus luteum; 1st trimester

38. What teratogens can cause discolored teeth?
Indomethacin; blocks PG production
Neural crest cells
Tetracyclines
Neural crest migration - they then cause spiral

39. Which branchial apparatus develops into the thymus?
Yolk sac; 3rd week
3rd pouch
Neural crest cells
Surface ectoderm

40. Does malformation occur during or after the embryonic period? is it due to an extrinsic or intrinsic disruption?
Before getting pregnant!
Mesdoerm
During; instrinsic
IMA

41. what muscles are derived from branchial arch 4? CN?
Neuroectoderm
LH
Most pharyngeal constrictors - Cricothyroid - levator veli palatini; CN X (superior laryngeal branch - swallowing)
Neuroectoderm

42. Which branchial apparatus derivative makes the tympanic membrane of the ear?
...
Mesoderm
Endoderm
Membrane - all 3 from 1st appartus

43. Where does fertilization occur?
Prenatal and perinatal
Upper 1/3; urogenital sinus
Neural crest cells
Ampulla

44. From What embryonic layer does the parathyroid arise ?
Endoderm
Upper 1/3; urogenital sinus
Ventral ; motor
mesoderm

45. During what months is the fetus most susceptible to teratogens? What trimester?
Embryonic period; 1st trimester
Endoderm
...
Prosencephalon

46. To what germ layer does the branchial pouches correlate to?
Increased AFP and acetycholinesterase (not ACh!) in CSF
Mesoderm
Endoderm
After; extrinsic

47. What separated myometrium of the uterus from the blastocyst?
Indomethacin; blocks PG production
Ventral; failure of urogenital folds to close
Yolk sac; 3rd week
Decidual basalis

48. What teratogen can cause an absence of digits amongst other things in the fetus? give an example.
Alkylating agents
Blastocyst; epiblast and hypoblast; synctiotrophoblast and cytotrophoblast
4th/5th branchial pouches
Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation

49. What is the effect of teratogens after week 8?
Ectoderm; endoderm
Dorsal ventral axis
Neural crest development; MEN 2A (pheo - PTH tumor - parafollicular cell tumor)
Deformation

50. From which myotomes are muscles of the tongue derived from?
not covered
From teh lung;blood from IVC in RA to LA; fossa ovalis
Occiptal
Right horn of the SV