Anatomic and hemodynamic characteristics of the blood vessels feeding the cremaster skeletal muscle in the rat.

The anatomic arrangement, pressure distribution, and resting vascular tone of the feed arteries located upstream from the rat cremaster microcirculation were determined to characterize the sites of the vascular resistance in this macrovessel segment of the cremaster circulation. The cremaster microcirculation and its feeding arteries were studied using an intravital video microscopy system. Vascular diameters and pressures were measured with an image shearing monitor and servo-null micropipet system, respectively. The central arteriole of the cremaster muscle was found to be a distal segment of the external spermatic artery which branched from the pudic-epigastric artery that in turn arose from the common iliac artery. Together the length of these vessels, from the aorta to the cremaster muscle, was 37 mm and they accounted for 42% of the total pressure drop across the cremaster vascular network. The largest pressure drop (31 mm Hg) upstream from the cremaster occurred across the external spermatic artery which was also the longest (17.7 mm) feed vessel. Topical application of adenosine (1 X 10(-3) M) significantly dilated the pudic-epigastric artery and the external spermatic artery, indicating that these vessels had significant tone. In summary, our data indicate that the large fraction of network vascular resistance located in the feed vessels upstream from the cremaster is the result of both architectural features and vascular tone.