Pulmonary Circuit
The pulmonary circuit consists of vessels that carry blood from the heart to the lungs and then back to the heart. As blood flows through the pulmonary trunk, it enters the pulmonary circuit. About 5 centimeters above where it begins, the pulmonary trunk divides into the right and left pulmonary arteries, which are responsible for supplying blood to the lungs. These arteries later divide into arterioles and also capillaries. All of these blood vessels lead to the alveoli in the lungs, where gas is exchanged. The pulmonary capillaries supply blood to the venules, which come together to form veins. The human body contains four pulmonary veins, which return blood to the left atrium from the lungs. |
Systemic Circuit
The systemic circuit consists of blood vessels that transport oxygenated blood from the left ventricle throughout the body. This includes the aorta, the largest-diameter artery in the body, which branches off into smaller blood vessels, reaching all tissues of the body. To complete the circuit, a system of veins returns blood from body tissues to the right atrium. |
Aorta
The first part of the aorta, coming out of the heart, is called the ascending aorta. At the base of it by the heart, there are three cusps of the aortic valve, which help in regulating blood flow out of the heart through the rest of the body. The right and left coronary arteries also originate from this location. The arch of the aorta, called the aortic arch, is the starting point for three major arteries: the brachiocephalic artery, the left common carotid artery, and the left subclavian artery. The upper portion of the descending aorta is located in front of the vertebral column. Above the diaphragm this is called the thoracic aorta, while below the diaphragm it is called the abdominal aorta. The abdominal aorta has many arteries branching off of it, which supply blood to the surrounding organs. Some of the most important ones include the celiac artery, which provides blood to the gastric, splenic, and hepatic arteries, as well as the mesenteric arteries, which circulates blood to the small and large intestines. |