The aorta is the main artery of the mammalian circulatory system that supplies oxygenated blood to the other arteries of the body. In humans, the aorta is about one inch in diameter and extends upward from the left ventricle, before arching downward through the chest. An opening in the muscular diaphragm termed the aortic hiatus allows the aorta to enter the abdomen, whence it divides into the paired common iliac arteries that extend into the legs. The wall of the aorta is composed of three tissue layers, the middle of which is thick and elastic. This elasticity enables the aorta to distend enough to accommodate the blood that surges through it as the heart contracts.

A dilation, narrowing, or tear of the aorta can be very serious, as can any loss of aortic elasticity. Some of the conditions that can lead to such an occurrence include hypertension, atherosclerosis, scleroderma or other connective tissue disorders, injury, or certain inherited diseases. Studies with rats and other animal models have been heavily utilized to investigate the effects of various maladies on the aorta and to test the efficacy of potential treatments and preventive measures. Research into this area is of special concern because cardiovascular disease is the leading cause of mortality of American men and women.

The rat aorta tissue section presented in the digital image above was labeled for the filamentous actin cytoskeletal network with Alexa Fluor 568 conjugated to phalloidin, a cyclic peptide produced by the Amanita phalloides mushroom. Cell nuclei were counterstained with Hoechst 33342. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.