Detailed Cardiac - Atrioventricular Canal
|Embryology - 26 Nov 2020 Expand to Translate|
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|Detailed Cardiac: Systemic Venous Sinus | Pulmonary Vein | Superior Interatrial Fold | Atrioventricular Cushions | Atrioventricular Canal | Interventricular Communication | Subpulmonary Infundibulum | Arterial Roots | Intrapericardial Arterial Trunks | Extrapericardial Arterial Channels | Sinus Node | Atrioventricular Conduction Axis|
Expansion of the Atrioventricular Canal
As indicated above, the next crucial event in cardiac development is rightward expansion of the atrioventricular canal. It was rightward shift of the systemic venous tributaries that brought all the blood from the developing embryo back to the right half of the common atrial chamber. The rightward expansion of the atrioventricular canal, occurring during the latter half of the fifth week of development in the human, and early on E11.5 in the mouse, now brings the cavity of the right atrium into direct continuity with the right ventricle, and thus produces the right ventricular inlet component (Figure 12).
Fig. 12. The left hand image is from an episcopic dataset prepared from a developing mouse embryo early on E11.5. The section is taken in so-called “four chamber” plane. The atrioventricular canal has expanded rightward so that the right atrium is now in direct continuity (white arrow) with the developing right ventricle (RV). There has also been growth of the primary atrial septum, with the primary foramen now seen between its leading edge, which is capped by mesenchyme, and the cranial margin of the inferior atrioventricular (AV) cushions. Note that there is also a space between the caudal edge of the cushion and the crest of the muscular ventricular septum. This is the reorientated embryonic interventricular foramen. The right hand panel is a histological section, again taken in the so-called “four chamber plane”, from a human embryo at Carnegie stage 16, representing the end of the fifth week of development. As can be seen, it is directly comparable with the situation as shown in the mouse heart. The section in the human heart is taken between the atrioventricular cushions, which have yet to fuse at this stage of development. This shows that there is a large defect, well described as an atrioventricular septal defect, through which all four cardiac chambers are in free communication.
Cite this page: Hill, M.A. (2020, November 26) Embryology Detailed Cardiac - Atrioventricular Canal. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Detailed_Cardiac_-_Atrioventricular_Canal
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G