The Circulatory System of the Cat

The circulatory system of the cat is comprised of the heart, a network of arteries and veins, and the spleen (which serves as a blood reservoir). A cat's heart rate, beating from 110 to 140 times a minute, is almost twice the normal heart rate of a human. The cat's  body contains half a pint of blood, and this blood is circulated through the body once every 11 seconds. The blood, which is initially blue, goes through the heart to the lungs where it changes color, becoming crimson. The iron atoms in the blood discharge their carbon dioxide and grab some oxygen, which has been freshly inhaled through the lungs.

With the pulmonary part of its journey complete, the blood launches itself on a path through the body. It moves into the aorta and then into the smaller arteries that filter throughout the entire body. The blood slows slightly as it enters even the even smaller arterioles which regulate blood flow to the tissues of the body.

By the time the blood reaches the metarterioles (the conduits between arterioles and capillaries), the blood is moving at its slowest pace. The blood is now a purplish red after being stripped of most of its oxygen. The blood exits the capillaries through venules (little tiny veins) and begins its journey back to the heart. All this takes only 11 seconds.

The bloodstream is important, and not only because it allows for the exchange of oxygen and carbon dioxide throughout the body. The bloodstream is also responsible for the creation of the clots that patch up tears, control osmotic pressure, and adjust the cat's thermostat when the cat is either too warm or too cold by moving heat to other areas of the body. Excess heat is expelled from the body also thanks to the bloodstream. Blood is even responsible for shivering and the warming of the body. The bloodstream defends the cat against disease, helps with digestion after meals, and even helps the cat catch his breath after exertion. In other words, the circulatory system of the cat is perhaps one of the most important systems of all, and not just because it circulates blood.