Embryology - Formation of cardiac septa Flashcards

1
Q

describe the formation of atrial septum and the mode of septation

A
  • passive expansion of atria and endocardial cushion fusion
    DAY 30
    1. Septum primum and endocardial cushion gap: ostium primum
    2. upper portion of septum primum: cavities: coalesce: ostium secundum
    3. closure of ostium primum by anterior growth of endocardial cushion

DAY 35
1. atrial expansion = invagination of muscular atrial roof = septum secundum
2. septum secundum free end: covers ostium secundum
= only opening: foramen ovale
3. regression of the upper septum primum, remaining = valve of oval foramen
birth, LA pressure greater, valve closes agains the septum secundum, foramen ovale shut

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2
Q

what is the role of foramen ovale in utero

A

allow passage of blood from RA to LA (placental blood into RA via superior and inferior VC)

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3
Q

what is the cause and outcome of atrial septal defect

A
  1. excessive resorption of septum prima
  2. insufficient development of septum secundum
  3. absence of both septum primum and secundum

outcome: right to left shunt
female more than male

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4
Q

what is the AV canal and the endocardial cushion

A
  • AV canal is the internal connection between atrial and ventricle space
  • endocardial cushion: found in AV canal, anterior, posterior left and right
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5
Q

describe the blood flow route at this stage of development

- explain why no outflow, why RV no blood

A

placenta - superior inferior VC - RA - LA - LV - no outflow yet

  1. AV canal not on the right side, so RV no blood received from RA
  2. no outflow as the truncus arteriosus is blocked by the bulboventricular flange
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6
Q

describe the process of AV canal septation, completes by 5th week

A
  1. endocardial cushion fusion: posterior and anterior cushion fuse. L R AV canal formed. Also reposition so each is aligned to the L R atria and ventricle
  2. regression of the bulboventricuar flange to allow out flow
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7
Q

describe the formation of AV valve

A

AV canal surronded by local proliferation of mesenchymal cells

  • blood hollows and thins the mesenchymal cells, valve formed.
  • attached to muscular cords on ventricles initially, those generate and replaced by cordae
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8
Q

what is tricuspid atresia

A

obliteration of AV canal: so no/ fusion of tricuspid valve

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9
Q

describe process of aortico-pumonary septation

A
  1. both the truncus arteriosus and conus cordis seperated by CONOTRUNCAL SEPTUM
  2. swellings arise in the truncus arteriosus: grow towardss each other and towards atria. Fuse and twist in right handed manner
  3. inferior to truncus swellings: conus swellings, aslo fuse
  4. fusion of conus septum and aorticopulmonary septum = conotruncal septum
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10
Q

name the 3 sections on the bulbus cordis

A
  1. truncus arteriosus (actual tube tract)
  2. conus cordis
  3. tuberculated part of RV
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11
Q

describe the formation of membranous inter-ventricular septum

A

fusion of posterior AV cusion and conotruncal sepum = membranous part of interventricular septum

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12
Q

describe the formation of semilunar valve

A

before the truncal swellings fuse:

  • small tubercles arise, 3 in each pulmonic and aortic channels
  • blood hollows out these tubercle (top of it) = valve formed
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