How long is the cardiovascular system

The cardiovascular system is sometimes called the blood - vascular , or simply the circulatory, system. It consists of the heart , which is a muscular pumping device, and a closed system of vessels called arteries , veins , and capillaries. In pulmonary circulation, though, the roles are switched. It is the pulmonary artery that brings oxygen-poor blood into your lungs and the pulmonary vein that brings oxygen-rich blood back to your heart.

In the diagram, the vessels that carry oxygen-rich blood are colored red, and the vessels that carry oxygen-poor blood are colored blue. Click on Related Links for detailed views of the heart and cardiovascular system. Twenty major arteries make a path through your tissues, where they branch into smaller vessels called arterioles. The heart is the key organ in the circulatory system. As a hollow, muscular pump, its main function is to propel blood throughout the body.

It usually beats from 60 to times per minute, but can go much faster when necessary. It beats about , times a day, more than 30 million times per year, and about 2. The heart has four chambers that are enclosed by thick, muscular walls. It lies between the lungs and just to the left of the middle of the chest cavity.

The bottom part of the heart is divided into two chambers called the right and left ventricles, which pump blood out of the heart. A wall called the interventricular septum divides the ventricles. The upper part of the heart is made up of the other two chambers of the heart, the right and left atria. The right and left atria receive the blood entering the heart.

A wall called the interatrial septum divides the right and left atria, which are separated from the ventricles by the atrioventricular valves. The tricuspid valve separates the right atrium from the right ventricle, and the mitral valve separates the left atrium and the left ventricle. Two other cardiac valves separate the ventricles and the large blood vessels that carry blood leaving the heart. Arteries carry blood away from the heart. They are the thickest blood vessels, with muscular walls that contract to keep the blood moving away from the heart and through the body.

In the systemic circulation, oxygen-rich blood is pumped from the heart into the aorta. This huge artery curves up and back from the left ventricle, then heads down in front of the spinal column into the abdomen. Two coronary arteries branch off at the beginning of the aorta and divide into a network of smaller arteries that provide oxygen and nourishment to the muscles of the heart.

From the right ventricle, the pulmonary artery divides into right and left branches, on the way to the lungs where blood picks up oxygen. As they get farther from the heart, the arteries branch out into arterioles, which are smaller and less elastic.

Veins carry blood back to the heart. Veins have the same three layers that arteries do, but are thinner and less flexible. The two largest veins are the superior and inferior vena cavae. A network of tiny capillaries connects the arteries and veins. In addition, waste products such as carbon dioxide are also removed by the capillaries.

The circulatory system works closely with other systems in our bodies. It supplies oxygen and nutrients to our bodies by working with the respiratory system. At the same time, the circulatory system helps carry waste and carbon dioxide out of the body. Hormones — produced by the endocrine system — are also transported through the blood in the circulatory system. A unique electrical conduction system in the heart causes it to beat in its regular rhythm.

The sinoatrial or SA node, a small area of tissue in the wall of the right atrium, sends out an electrical signal to start the contracting of the heart muscle. This node is called the pacemaker of the heart because it sets the rate of the heartbeat and causes the rest of the heart to contract in its rhythm. These electrical impulses cause the atria to contract first, and then travel down to the atrioventricular or AV node, which acts as a kind of relay station. From here the electrical signal travels through the right and left ventricles, causing them to contract and forcing blood out into the major arteries.

In the systemic circulation, blood travels out of the left ventricle, to the aorta, to every organ and tissue in the body, and then back to the right atrium. The arteries, capillaries, and veins of the systemic circulatory system are the channels through which this long journey takes place. The circulatory system includes the heart, blood vessels and blood, and is vital for fighting diseases and maintaining homeostasis proper temperature and pH balance.

The system's main function is to transport blood, nutrients, gases and hormones to and from the cells throughout the body. Here are 11 fun, interesting and perhaps surprising facts about the circulatory system that you may not know.

If you were to lay out all of the arteries, capillaries and veins in one adult, end-to-end, they would stretch about 60, miles , kilometers. What's more, the capillaries, which are the smallest of the blood vessels, would make up about 80 percent of this length. By comparison, the circumference of the Earth is about 25, miles 40, km. That means a person's blood vessels could wrap around the planet approximately 2. Red blood cells are about the same size as the capillaries through which they travel, so these cells must move in single-file lines.

Some capillaries, however, are slightly smaller in diameter than blood cells, forcing the cells to distort their shapes to pass through. Across the animal kingdom, heart rate is inversely related to body size: In general, the bigger the animal, the slower its resting heart rate. An adult human has an average resting heart rate of about 75 beats per minute, the same rate as an adult sheep. But a blue whale's heart is about the size of a compact car, and only beats five times per minute.

A shrew, on the other hand, has a heart rate of about 1, beats per minute.