DEVELOPMENT OF BLOOD SUPPLY IN RAT HEART

The development of the cardiac vessels was studied histologically by means of gelatine-Indian ink injections in 379 rat hearts (aged between the 9th embryonic day and the 6th month of life). Up to the 12th embryonic day the nutrition of the myocardium takes place by diffusion; following this stage a venous supply system develops. It consists of 1. sinusoids, which from the 11th embryonic day onwards can be demonstrated as indentations between the trabeculae of the ventricle wall; 2. capillaries, the first rudiments of which are observed on the 13th embryonic day either as protuberances of the ventricular endocardium at the cardiac base and the ventricular septum; or as fissure formations in the myocardium of the bulbar wall. These initially blind ending vessels anastomose from the 14th embryonic day onwards to form capillary nets, which communicated with the ventricular sinusoids; 3. veins, which originate from protuberances of the coronary sinus and which fuse with the capillaries. This sinusoid-venous system is initially restricted to the ventricular septum and the cardiac base; later on, however, it is found in the entire heart. Between the 16th and 17th embryonic day the coronary arteries are formed as protuberances of the aortic sinus. They fuse with already existing capillaries; part of these capillaries is converted into arterioles, arteries, veins, and venules. By the 3rd day of life the definite coronary vascular system is formed. In addition the capillary system as such is being re-organized at this stage. The number of capillaries increases, they form a fine net-work and orientate like the musculature in a longitudinal fashion on the inside and outside of the ventricular wall, and in a circular manner in the centre. At approximately the 18th embryonic day, the sinusoids are transformed to Thebesius' veins, capillary-like vascular-luminar anastomoses and intermediary forms. The auricular walls obtain their vessels partly from the extra-coronary (mediastinum), partly from the coronary circulatory system, as well as directly from the auricular lumen. © 1969 Springer-Verlag.