Blood Vessel Pathways and Divisions

Blood Vessel Pathways and Divisions

The blood vessel pathways make up the vascularsystem, which is divided into the systemic and­pulmonary circulation systems. Each of these two systems has its own unique arteries, capillaries, and veins. The systemic circulation is much larger than the pulmonary circulation and receives blood from the heart via just one systemic artery: the aorta (­FIGURE 19-8). This differs from the pulmonary­ cir-culation, in which the heart receives returning blood via two terminal veins: the superior and inferior vena cava. 

The only exception is the blood coming from the myocardium that is collected by the cardiac veins. It reenters the right atrium through the coro-nary sinus. The three major differences between sys-temic blood vessels are as follows:

■■ The arteries are deep, whereas the veins are either deep or superficial: The deep veins run similarly to the course of the arteries. Names of both the systemic arteries and the systemic deep veins are similar. Because there are superficial systemic veins but no such arteries, their names do not correspond to those of any arteries.

■■ Veins have more interconnections than arteries: Therefore, many veins are made up by two vessels with similar names and are more difficult to follow than arteries.

■■ Unique drainage systems exist in the brain and digestive system: Blood draining from the brain goes into the large dural venous sinuses instead of typical veins. Blood draining from the digestive system enters the hepatic portal system, moving through the liver, and then reentering the general systemic circulation.

Systemic Arteries

Systemic arteries begin from the aorta and its branches. Figure 19-8 illustrates an overview of the systemic arterial system, and localizes the major systemic arteries.