Development of the Heart and Great Vessels Flashcards

1
Q

Explain what happens after the lateral plate mesoderm divides into visceral and somatic layers

A
  • in visceral layer angiogenic cell clusters called blood islands appear
  • these cells will differentiate into primordial vascular system, heart tube, vessels and primordial erythrocytes
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2
Q

Explain how the right and left heart tubes form from blood islands

A
  • blood islands coalesce and give rise to right and left endocardial tubes and dorsal aorta
  • meanwhile part of mesoderm differentiates into cardiomyocytes
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3
Q

Explain folding of the embryo

A
  • day 20, visceral layers of lateral plate mesoderm approach each other
  • folds fuse along ventral midline
  • space between visceral and somatic mesoderm becomes intraembryonic coelom which later becomes the pericardial cavity
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4
Q

Explain how the right and left endocardial tubes fuse together after folding of the embryo

A
  • endocardial tubes and surrounding cardiogenic mesoderm come together in thoracic region
  • right and left endocardial tubes fuse to form primary heart tube, anterior to gut tube
  • myocardium invests cardiac jelly and the endocardial heart tube
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5
Q

What are the different parts of the heart tube from top to bottom?

A
  • 1st aortic arch coming off aortic sac
  • bulbus cordia
  • primordial ventricle
  • primordial atrium
  • sinus venosus (where vitelline vein, umbilical vein and cardinal vein come off)
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6
Q

What do vitelline veins drain?

A

yolk sac

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7
Q

What do cardinal veins drain (x2)?

A

trunk and head region

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8
Q

What are the 2 parts of the bulbus cordis?

A
  • conus cordis: proximal outflow tract to aorta

- truncus arteriosus: distal outflow tract to pulmonary trunk

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9
Q

Describe the looping and folding of the heart tube

A
  • the 2 ends fold towards each other and to the right
  • pushing the apex of the loop to the left
  • and rotating slightly so that the right side of the heart tends to be more anterior
  • if the ends fold to the left, the developing heart is pushed to the right
  • the developing heart pushes into the pericardial sac and the ventricles start to trabeculate
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10
Q

Describe the layers of the lumen of the heart tube

A
  • called common AV canal
  • surrounded by dense mesenchymal tissue called cardiac jelly
  • produced and replaced by myocardium
  • myocardium derived from a mass of splanchnic mesoderm
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11
Q

Explain how the valves form

A
  • mitral and tricuspid: endocardial cushion growth and cavitation to form papillary muscles and chordae tendineae
  • pulmonary and aortic: hollowing og endocardial tubercles
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12
Q

Explain the formation of the interventricular septum

A
  • while AV canal is formed, IV septum grows towards the endocardial cushion between right and left AV canals
  • doesn’t extend all the way to the endocardial cushion
  • extension of endocardial cushion that fills the gap forms membranous part of IV septum
  • full formation of IV septum separates the primordial ventricle to become left ventricle from the bulbus cordis which will become right ventricle
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13
Q

Explain how the IA septum begins to form

A
  • septum primum starts to grow inferiorly from the roof towards the endocardial cushion
  • forms interatrial septum that separates left and right atria
  • to allow blood to circulate, ostium primum forms to allow flow between atrias
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14
Q

Explain the final division of the atria

A
  • before septum primum completely builds IA septum, a second hole appears high on it called ostium secundum
  • new septum grows down from roof on right side of septum primum called septum secundum which is the wall of the sinus venosus that invaginates into right side of primordial atria
  • once IA septum is done the primordial atria is separated into left and right atria
  • foramen ovale provides the connection between them
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15
Q

What does the left and right atria receive after division?

A
  • left atrium receives pulmonary veins

- right atrium receives sinus venosus which differentiates to SVC and IVC

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16
Q

Explain the formation of the membranous IV septum

A

endocardial cushion sends extension towards muscular part of IV septum and separation of the ventricles is complete

17
Q

Explain the partitioning of conus cordis and truncus arteriosus to form the pulmonaryt trunk and aorta

A
  • conus cordis and truncus arteriosus straddle the IV septum
  • the part of conus cordis that will become the aortic vestibule is on the left side connected to the left ventricle
  • the part of conus cordis that will become the infundibulum is on the right side connected to the right ventricle
  • truncus arteriosus then forms the pulmonary trunk and aorta
  • within conus cordis and truncus arteriosus swellings appear and meet to form a septum called aortico-pulmonary septum that spirals
18
Q

What would the consequence be if the aortico-pulomary septum didn’t spiral?

A

left ventricle would pump blood to the pulmonary artery and the right ventricle would pump blood to the aorta

19
Q

What are the 3 structures that must fuse for complete ventricular separation?

A
  • endocardial cushions
  • IV septum
  • spiral septum
20
Q

Explain the formation of the great vessels to the degeneration of the first 2 aortic arches

A
  • 1st and 2nd aortic arch arteries have developed leading to dorsal aortae
  • branches from left and right dorsal aortae start to develop forming intersegmental arteries
  • 3rd and 4th aortic arches develop and 1st and 2nd degenerate
  • meanwhile bridge like anastomotic vessel starts to appear between first 7 intersegmental arteries
21
Q

What happens after the formation of the of the anastomotic bridge-like vessel between the first 7 intersegmental arteries to the formation of the common and internal carotid arteries?

A
  • dorsal aorta between 3rd and 4th aortic arches start to degenerate so 3rd aortic arch loses its connection with dorsal aorta
  • 4th still connected
  • 6th aortic arch develops close to developing lung buds
  • bridge-like anastomotic artery keeps growing
  • 7th intersegmental artery start’s to grow outward
  • 3rd arch then forms common and internal carotid arteries
22
Q

Explain what happens after the formation of the common and internal carotid arteries to the final formation of the great vessels

A
  • 6th aortic arch sends little branch to developing lung buds which become pulmonary arteries
  • 1-6 intersegmental branches degenerate
  • 7th becomes subclavian artery
  • bridge-like anastomotic artery becomes vertebral artery
  • right dorsal aorta degenerates, left stays and is connected to descending aorta
  • conus cordis and truncus arteriosus partitions to form aorta and pulmonary trunk
  • 6th aortic arch retains connection with left dorsal aorta forming ductus arteriosus
23
Q

What is the function of the sinus venosus?

A

at caudal end receives blood from umbilical, vitelline and cardinal veins