Embryology III: Cardiovascular development Study Aid
10/04/2009 Nickalus Khan
Questions (1-56)
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Where is the first evidence of heart formation?
What type of cells are within the splanchnic mesoderm?
What are these cells derived from?
What do blood islands in the same region form?
Where does the future heart begin?
What is the cardiogenic field?
What is above the cardiogenic field?
What brings the heart into its natural anatomical position?
What forms the two endothelial lined tubes on both sides of the heart?
What happens to these tubes?
What surrounds tube (cell type)?
What surrounds the tube and eventually disappears, & serves no function?
List the invaginations of the endocardial tube.
What will each of these invaginations ultimately form?
How does blood enter the primitive heart ? (Before Atria/Ventricle portioning)
How are the atria and ventricles partitioned?
Describe the formation of the AV valves
What direction is blood originally shunted in atria?
What is the crescent shape fold that grows down from the roof of the atria initially in atrial
Septation.
What does this form at the bottom of the atria?
What happens after this is formed at the top of the crescent shape fold?
What is the second structure that grows downward from the roof of the atria?
What develops in this structure?
What now causes blood to be shunted from RA to LA?
What happens after birth in the case of question #24?
What is the function of the ductus arteriosus?
What is the muscular part of the two ventricles derived from?
What forms the membranous part of the two ventricles?
What is probe patency of foramen ovale?
Describe the condition of excessive resorption of septum primum.
Describe the condition of absence of septum secundum.
What is a common atrium?
Describe defects in ventricular septum.
Defects in Septation of truncus arteriosus , describe Tetralogy of Fallot.
Describe persistent truncus arteriosus
Describe transposition of the great vessels.
Describe patent ductus arteriosus.
38. Before birth the ductus arteriosus provides communication between what two
structures?
Embryology III: Cardiovascular development Study Aid
10/04/2009 Nickalus Khan
39. The initial two endothelial tubes that fuse to form the heart develop in what layer?
40. Before birth, what structure overlaps the ostium secundum and appears to close it?
41. What causes tetralogy of fallot?
42. Which of the aortic arches gives rise to the pulmonary arteries?
43. Just before birth, all blood from the placenta goes through the liver. Describe its course
through this organ.
44. How many aorta’s does a developing embryo have ?
45. How does blood exit the heart?
46. Describe the aortic arches
47. What does arch 1-6 give rise to?
48. Why is the r. recurrent laryngeal n superior to the left?
49. What is preductal coartication of aorta?
50. What forms the common cardial vein?
51. What do the vitelline veins form?
52. What happens to the R. umbilical vein?
53. What does the L. umbilical vein extend through the liver as?
54. What does the sinus venosus become?
55. What does the superior and inf. Parts of the vitelline veins become?
56. Describe pre-natal circulation.
57. What does the umbilical arteries and veins atrophy to?
Embryology III: Cardiovascular development Study Aid
10/04/2009 Nickalus Khan
Answers:
1. Splanchnic layer of lateral plate mesoderm (just said splanchnic layer in class)
2. Cardiac Myoblasts
3. Cardiac Progenitor cells induced by underlying pharyngeal endoderm
4. Endothelial lined tubes and transitory blood vessels, definitive blood cells come from mesoderm
around aorta later from liver even later from bone marrow
5. Cranial part of embryo, Buccopharyngeal membrane is landmark for this, it its just cranial to the
buccopharyngeal membrane
6. Endothelial lined tubes and myoblasts formed by the previous blood islands, just cranial to the
buccopharyngeal membrane
7. Pericardial cavity which is derived from the embryonic cavity
8. Cranial and caudal folding of the embryo brings the heart into the thoracic region
9. Blood islands produce angiogenic cells that dissolve into these endothelial lined tubes, they
eventually become endocardial regions of the heart
10. Fold into the midline and fuse to form a single endocardial tube
11. Myoblasts that will become the myocardium of the heart
12. Cardiac Jelly
13. Truncus arteriosus, bulbus cordis, primordial ventricles, primordial atria, sinus venosus
14. Truncus arteriosus  aorta and pulmonary trunk, Bulbus cordis inf. Part of aorta and
pulmonary trunk & adjacent parts of two ventricles, Primordial ventricles  ventricles,
primordial atria  atria, sinus venosus Right horn becomes right atrium, left becomes
coronary sinus
15. Sinus venosus
16. Endocardial cushions grow towards each other, partitions atria from vessels and ventricles
(produces a pattern with two holes penetrating septum that divides atria from ventricles)
17. Dense mesenchyme and myoblasts present, cavitation occurs and cells die, some are replaced
by connective tissue which becomes chordate tendinae
18. From right to left (mix of oxygenated and deoxygenated blood)
19. Septum primum
20. Osteum primum
21. Osteum secundum (maintains shunting after closure of osteum primum)
22. Septum secundum
23. Foramen ovale
24. Pressure in RA is higher than left, pushes blood through foramen ovale into LA
25. Pressure changes , LA is higher and maintains valve closure if it already has not fused
26. Short circuits lungs, sends oxygengated blood from RA directly into the aorta
27. Develops from a ridge between the two ventricles
28. Cotruncal (spiral ) septum descending to meet the endocardial cushion in the muscular ridge
29. Foramen ovale did not fuse, no effect because it is a one way valve, present in 25% of pop.
30. Causes L to R shunt
31. Again, L to R shunt
Embryology III: Cardiovascular development Study Aid
10/04/2009 Nickalus Khan
32. No attempt at partitioning of atria at all, causes L to R severe shunting
33. Occur in membranous part of septum, systemic blood goes back into pulmonary circuit, too
much blood pushing through pulmonary trunk  increased resistance  hypertrophy of RV 
shunts blood from R to L  cyanosis called Eisenmenger complex
34. Aortic arch and pulmonary trunk are shifted to the R, pulmonary trunk is smaller than usual and
aorta is a lot larger. Causes eisenmenger complex and cyanosis
35. No Septation of aorta and pulmonary trunk, only one vessel leaving heart, causes cyanosis
always accompanied by membranous ventricular defect.
36. Open into wrong chambers, causes R to L shunt and cyanosis occurs when AP septum fails to
spiral
37. Blood goes into pulmonary trunk and gets into aorta from ductus arteriosus, can lead to
eisenmenger syndrome leads to cyanosis more quickly than atrial defects
38. Pulmonary Trunk and Aorta
39. Splanchnic mesoderm
40. Septum secundum
41. A misaligned AP septum
42. 6th aortic arch
43. Passes directly through via the ductus venosus
44. Two pairs of dorsal aorta’s
45. Through an aortic sac ( has l and r divisions, forms 6 arches)
46. Anteriorly they communicate with a horn like structure and loop out from dorsal aorta
to this structure
47. 1,2 disappear, 3  common carotid and internal carotid a. , 4 R. subclavian, and arch
of aorta from l. common carotid to l. subclavian, 6 L and R pulmonary arteries and
ductus arteriosus
48. A portion of aortic arch 6 disappears on the R side, on the L side the ductus arteriosus
remains
49. Narrowing of aorta prior to the ductus arteriosus, => ductus arteriosus remains patent,
if post ductal ductus arteriosus atrophies
50. Anterior and post. Cardinal veins, the common cardinal vein also receives umbilical
veinand two vitelline veins, sinus venosus receives common cardinal v.
51. Hepatic sinusoids, hepatic portal v. , hepatic veins, hepatic IVC
52. Atrophies
53. Ductus venosus
54. Hepatic portion of IVC (later he says that the vitelline veins actually forms this,
somewhat misleading from his lecture)
55. Hepatic and renal veins, respectively
56. Path 1: Umbilical v ductus venosus  IVC  foramen ovale  LA,LV  aorta 
systemic  umbilical a.
Path 2: SVC  RA RV  Aorta (mixes oxygenated from path 1 with deoxygenated ) 
systemic  umbilical a.
57. Umbilical v.  ligamentum teres hepatis
a. Umblicial artery  medial umbilical ligaments