The microvascular architecture of the rat submaxillary gland: possible relationship to secretory mechanisms

Injections of various opaque materials including latex, India ink, and silicone rubber were used to examine microscopic sections and whole specimens of the rat submaxillary gland. An excretory duct, several large collecting ducts and a complex system of blood vessels occupy the central areas of the gland, surrounded by connective tissue. A major bifurcation of these central structures occurs approximately 1 3 into the gland. Excretory, collecting and striated ducts are well supplied with a thick capillary network which is connected to an extensive secondary network of metarteriole-sized vessels. Thus, a total of three different strata of blood vessels accompany the excretory and central collecting ducts: (1) the intramural extensive network of capillaries of the ducts themselves, (2) an outermost layer of one, two or three large arteries and veins, and (3) a middle area of intermediate sized vessels (intermediate arteriolar plexus). These latter vessels connect the large vessels with the ductal network, and supply capillaries of the connective tissue in the area and vasa vasorum; this intermediate arteriolar plexus also shows connections between larger vessels which may represent an A-V shunt system. The granular ducts and acini appear to be served by the same capillary bed, which is rather sparse compared to that of the more distal striated, collecting and excretory ducts. These acinar capillary beds are composed of end capillaries of the arteries which accompany the collecting ducts as they enter the lobules, the vessels branching together with the ducts to the most proximal parenchymal areas containing the acini. The venous drainage of these areas also parallels the ducts.