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High in the upper part of the left atrium is a muscular ear-shaped pouch – the left atrial appendage (LAA) (lat: auricula atrii sinistra), which has a tubular trabeculated structure. [9] LAA anatomy as seen in a CT scan is characterized as being in one of four groups: chicken wing (48%), cactus (30%), windsock (19%), and cauliflower(3%).
When the ventricles of the heart contract in ventricular systole, the increased blood pressures in both chambers push the AV valves to close simultaneously, preventing the backflow of blood into the atria. Since the blood pressure in the atria is much lower than that in the ventricles, the flaps attempt to evert to the low pressure regions.
The anchored and electrically inert collagen framework of the four valves allows normal anatomy to house the atrioventricular node (AV node) in its center. The AV node is the only electrical conduit from the atria to the ventricles through the cardiac skeleton, which is why atrial fibrillation can never degrade into ventricular fibrillation.
The atrioventricular septum is a septum of the heart between the right atrium (RA) and the left ventricle (LV). [1] [2]Although the name "atrioventricular septum" implies any septum between an atrium and a ventricle, in practice the divisions from RA to RV and from LA to LV are mediated by valves, not by septa.
The atrial portion starts moving in a cephalically and then moves to the left from its original position. This curved shape approaches the heart and finishes its growth on day 28. The conduit forms the atrial and ventricular junctions which connect the common atrium and the common ventricle in the early embryo.
The SA node is located in the wall of the right atrium, laterally to the entrance of the superior vena cava in a region called the sinus venarum (hence sino-+ atrial). [5] It is positioned roughly between a groove called the crista terminalis located on the internal surface of the heart and the corresponding sulcus terminalis , on the external ...
Bachmann's bundle receives its blood supply from the sinoatrial nodal artery (right, left or both). [4]Besides Bachmann's bundle, the other three conduction tracts that constitute the atrial conduction system are known as the anterior, middle, and posterior tracts, which run from the sinoatrial node to the atrioventricular node, converging in the region near the coronary sinus.
Early ventricular diastole is the filling of blood from the atria (from the left atrium shown in pink, and from the right atrium shown in blue) that weakly contract letting blood fill into the ventricles; in late ventricular diastole, the two atria begin to contract (atrial systole), forcing additional blood flow into the ventricles.