The Arrangement Of The Cardiovascular System

The cardiovascular system has two primary components: the heart and blood vessels. A third component, the lymphatic system, does not contain blood, but nonetheless serves an important exchange function in conjunction with blood vessels.

The heart can be viewed functionally as two pumps with the pulmonary and systemic circulations situated between the two pumps (Fig. 1-1). The pulmonary circulation is the blood flow within the lungs that is involved in the exchange of gases between the blood and alveoli. The systemic circulation is comprised of all the blood vessels within and outside of organs excluding the lungs. The right side of the heart comprises the right atrium and the right ventricle. The right atrium receives venous blood from the systemic circulation and the right

The Arteries Systemic Circulation

FIGURE 1-1 Overview of the cardiovascular system. The right side of the heart, pulmonary circulation, left side of the heart, and systemic circulation are arranged in series. RA, right atrium; RV, right ventricle; PA, pulmonary artery; Ao, aorta; LA, left atrium; LV, left ventricle.

Systemic Circulation

FIGURE 1-1 Overview of the cardiovascular system. The right side of the heart, pulmonary circulation, left side of the heart, and systemic circulation are arranged in series. RA, right atrium; RV, right ventricle; PA, pulmonary artery; Ao, aorta; LA, left atrium; LV, left ventricle.

ventricle pumps it into the pulmonary circulation where oxygen and carbon dioxide are exchanged between the blood and alveolar gases. The left side of the heart comprises the left atrium and the left ventricle. The blood leaving the lungs enters the left atrium by way of the pulmonary veins. Blood then flows from the left atrium into the left ventricle. The left ventricle ejects the blood into the aorta, which then distributes the blood to all the organs via the arterial system. Within the organs, the vas-culature branches into smaller and smaller vessels, eventually forming capillaries, which are the primary site of exchange. Blood flow from the capillaries enters veins, which return blood flow to the right atrium via large systemic veins (the superior and inferior vena cava).

As blood flows through organs, some of the fluid, along with electrolytes and small amounts of protein, leaves the circulation and enters the tissue interstitium (a process termed fluid filtration). The lymphatic vessels, which are closely associated with small blood vessels within the tissue, collect the excess fluid that filters from the vasculature and transport it back into the venous circulation by way of lymphatic ducts that empty into large veins (subclavian veins) above the right atrium.

It is important to note the overall arrangement of the cardiovascular system. First, the right and left sides of the heart, which are separated by the pulmonary and systemic circula tions, are in series with each other (see Fig. 1-1). Therefore, all of the blood that is pumped from the right ventricle enters into the pulmonary circulation and then into the left side of the heart from where it is pumped into the systemic circulation before returning to the heart. This in-series relationship of the two sides of the heart and the pulmonary and systemic circulations requires that the output (volume of blood ejected per unit time) of each side of the heart closely matches the output of the other so that there are no major blood volume shifts between the pulmonary and systemic circulations. Second, most of the major organ systems of the body receive their blood from the aorta, and the blood leaving these organs enters into the venous system (superior and inferior vena cava) that returns the blood to the heart. Therefore, the circulations of most major organ systems are in parallel as shown in Figure 1-2. One major exception is the liver, which receives a large fraction of its blood supply from the venous circulation of the intestinal tract that drains into the hepatic portal system to supply the liver. The liver also receives blood from the aorta via the hepatic artery. Therefore, most of the liver circulation is in series with the intestinal circulation, while some of the liver circulation is in parallel with the intestinal circulation.

This parallel arrangement has significant hemodynamic implications as described in Chapter 5. Briefly, the parallel arrangement of

Hepatic Circulation

FIGURE 1-2 Parallel arrangement of organs within the body. One major exception is the hepatic (liver) circulation, which is both in series with the gastrointestinal circulation (Gl) by the hepatic portal circulation and in parallel by the hepatic artery, which supplies part of the hepatic circulation. SVC, superior vena cava; IVC, inferior vena cava.

FIGURE 1-2 Parallel arrangement of organs within the body. One major exception is the hepatic (liver) circulation, which is both in series with the gastrointestinal circulation (Gl) by the hepatic portal circulation and in parallel by the hepatic artery, which supplies part of the hepatic circulation. SVC, superior vena cava; IVC, inferior vena cava.

major vascular beds prevents blood flow changes in one organ from significantly affecting blood flow in other organs. In contrast, when vascular beds are in series, blood flow changes in one vascular bed significantly alters blood flow to the other vascular bed.

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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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Responses

  • teemu
    How pulmonary and systemic circulation arranged in series?
    8 years ago
  • erik
    What is the arrangement of the cardiovascular system?
    10 months ago
  • posco
    How is the cardiovascular system arranged?
    1 month ago
  • angela
    Where does blood from PA to RA to RV in circulation?
    9 days ago

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