Arteries are one type of blood vessels that transport blood away from the heart and are an integral part of the cardiovascular system. Two different arteries carry de-oxygenated and oxygenated blood to parts of the body and these include the pulmonary arteries and the systemic arteries. Pulmonary arteries are responsible for getting blood to the lungs while the systemic arteries branch out from the main artery in the body, the aorta, and take the oxygenated blood to every part of the body.
As stated before, arteries are blood vessels, meaning that they are hollow tubes through which blood flows. There are two other types of blood vessels in the body and these are the veins and capillaries. If you were to stretch out all of the blood vessels present in an adult in a single line, it would be over 100,000 miles long.
Arteries are composed of three layers which are the tunica intima, the tunica media, and the tunica externa. The innermost layer is the tunica intima and is constructed of layered fat cells which provide a very smooth surface for the blood to flow through. The middle layer is the tunica media which is made of smooth muscle tissue. This layer is very elastic and helps arteries to expand and contract with the pumping of the blood providing an additional push for the blood. The outer layer is the tunica externa and it is mostly constructed out of connective tissue. This layer is responsible for keeping the shape and holding the artery together during the pumping of blood through the artery.
De-oxygenated blood enters the heart from the vena cava into the right atrium, it is pumped into the right ventricle and then through the pulmonary value into the pulmonary arteries. Two arteries branch out from the main pulmonary artery and take the blood to both lungs where the carbon dioxide on the hemoglobin of the blood cells is exchanged with the oxygen in the lungs and thus the blood becomes oxygenated. Since arteries only take blood away from the heart, the pulmonary arteries are not responsible for taking blood back to the heart as that is done by the pulmonary veins.
After the oxygenated blood comes back into the left atrium of the heart, it is then pumped into the left ventricle and then through the aortic valve into the aorta. The aorta is the largest and most important artery in the body. From this artery, oxygenated blood travels to every part of the body. The aorta branches off numerous times and the branches in turn branch out multiple times as well. Each time they branch out, the diameter of the artery gets smaller. This creates a network of arteries traveling through the body to reach the tips of the appendages and head. From the aorta, arteries branch out to the upper portion of the body while the descending or abdominal aorta travels to the lower part of the body branching out several times and finally splitting into two arteries, one for each leg. There are 24 branches coming off of the aorta and descending aorta.
The branching arteries will get smaller in diameter and eventually become arterioles. The arterioles will transfer blood from the larger arteries into the capillaries of the body. The capillaries are another type of blood vessel and are responsible for facilitating the exchange of oxygen for carbon dioxide in the tissue, muscle, and organs of the body. From the capillaries, the de-oxygenated blood will travel to the veins and back into the heart where the process will repeat.