Three-Dimensional Vascular Architecture of the Dog Heart as Revealed by Injection Replica Scanning Electron Microscopy

The three-dimensional vascular architecture of the dog myocardium was investigated by means of injection replica scanning electron microscopy.
Coronary arteries entered into myocardial wall at almost right angle. They repeated bicornal divisions and run toward endocardium. The arterioles and precapillary arterioles branched in bicornal, tricornal or multicornal fashions. These branches were arranged usually in a plane in short distances. Capillaries were arranged parallel to the myocardial cells and had many anastomotic channels. The branching of the capillaries was usually Y-, T-, H- or K-shape, and Y-shape was the most common. Many anastomotic channels between precapillary arterioles were recognized just under the endocardiurn, while same connections were very difficult to identify in the myocardial wall. Numerous venous capillaries joined together with postcapillary venules and collecting venules almost exclusively in a plane parallel to the capillary sheets. Junctional architecture of these capillaries and venules was usually fan-shaped, finger-shaped or feather-shaped in appearance. The postcapillary venules and collecting venules were oriented usually perpendicular to the muscle fiber or capillary direction. The orifices of Thebesian veins, arterio-luminal vessels and arterio-sinusoidal vessels were observed between ventricular trabeculae as small masses of injected resin. The number of these orifices were more abundant in the right ventricular wall than in the left.