Changes

The primordium of the heart forms in the cardiogenic plate located at the cranial end of the embryo. Angiogenic cell clusters which lie in a horseshoe shape configuration in the plate coalesce to form two endocardial tubes. These tubes are then forced into the thoracic region due to cephalic and lateral foldings where they fuse together forming a single endocardial tube.

The primordium of the heart forms in the cardiogenic plate located at the cranial end of the embryo. Angiogenic cell clusters which lie in a horseshoe shape configuration in the plate coalesce to form two endocardial tubes. These tubes are then forced into the thoracic region due to cephalic and lateral foldings where they fuse together forming a single endocardial tube.

The tube is then subdivided into primordial heart chambers starting caudally at the inflow end: the sinus venosus, primitive atria, ventricle and bulbus cordis.

The tube is then subdivided into primordial heart chambers starting caudally at the inflow end: the sinus venosus, primitive atria, ventricle and bulbus cordis.

The heart tube grows rapidly forcing it to bend upon itself resulting in the bulboventricular loop. Septa begin to grow in the atria, ventricle and bulbus cordis forming right and left atria, right and left ventricles and two great vessels - the pulmonary artery and the aorta.

The heart tube grows rapidly forcing it to bend upon itself resulting in the bulboventricular loop. Septa begin to grow in the atria, ventricle and bulbus cordis forming right and left atria, right and left ventricles and two great vessels - the pulmonary artery and the aorta.

The processes involved in forming a simple heart, such as that in a fish, or a multi-chambered heart, as seen in oxygen-breathing vertebrates, follow similar pathways.

The processes involved in forming a simple heart, such as that in a fish, or a multi-chambered heart, as seen in oxygen-breathing vertebrates, follow similar pathways.