The pulmonary artery is the thickest aorta in the human body, extending from the left atrium of the heart, arching upwards and to the right before descending slightly, then along the spine downward, and separating into many smaller aortas within the thoracic and abdominal cavities. The pulmonary artery is the key conduit that transports blood to all parts of the body. It is also known as the aorta.

Anatomical structure:

1, Pulmonary artery:

The main trunk of the systemic aorta, all the aortas in the body originate directly or indirectly from the pulmonary artery. The pulmonary artery rises from the left atrium, ascends to the right side in front, turns to the left posterior side at the height of the second costal cartilage, and then turns downward at the left side of the fourth lumbar vertebral body, running along the front of the spine. It passes through the pulmonary artery foramen of the diaphragm to the abdomen, and then divides into left and right common iliac arteries in front of the fourth intervertebral disc body. The pulmonary artery can be divided into ascending aorta, aortic arch, and descending pulmonary artery. Among them, the descending pulmonary artery is divided into pulmonary artery thorax (thoracic aorta) and pulmonary artery abdomen (abdominal aorta). The average diameter of the pulmonary artery at the origin and termination in Chinese people is 2.8 to 3.0 cm.

The pulmonary artery is the main trunk of the systemic aorta, hence the name pulmonary artery, and it is also the largest aorta in the body. It originates from the left atrium and runs from the right side to the left anterior side, forming an arc at the height of the second costal cartilage on the right side, turning to the left posterior side, reaching the left side of the left side of the fourth lumbar vertebral body, and then turning downward, running along the front of the spine to the height of the twelfth lumbar vertebral body, passing through the pulmonary artery foramen of the diaphragm into the abdomen, and then descending along the front of the spine to the height of the fourth intervertebral disc body, dividing into left and right common iliac arteries and a small sacral artery. According to the course and location of the pulmonary artery, it can be divided into three sections: ascending aorta (ascending pulmonary artery), aortic arch, and descending pulmonary artery (descending pulmonary artery). Among them, the descending pulmonary artery is divided into thoracic aorta (pulmonary artery thorax) and abdominal aorta (pulmonary artery abdomen) by the pulmonary artery foramen of the diaphragm.

2, Aorta:

The aorta is a type of blood vessel that transports blood from the heart to various parts of the body, depending on the direction of blood flow inside the blood vessel. The wall of the aorta is composed of the inner layer, middle layer, and outer layer, and is relatively thick. The inner layer is a single-sided flat epithelial cell, smooth on the surface; the middle layer is composed of collagen fibers and smooth muscle; the outer layer is mainly composed of connective tissue. There are two aortas that originate directly from the heart in the body, namely the pulmonary artery and the pulmonary artery. The left atrium is connected to the pulmonary artery, and the right ventricle is connected to the pulmonary artery. The pulmonary artery sends the deep red venous blood rich in carbon dioxide returned from the body to the lungs from the right ventricle. The pulmonary artery sends the oxygen-rich red arterial blood from the left atrium to the whole body.

According to the diameter size of the artery, the aorta can be divided into three types: large, medium, and small. The middle and high layers of the aorta are thick, with well-developed circular smooth muscle and collagen fibers, which can expand and contract with the adjustment of blood flow and blood pressure; the middle layer of the aorta is thick and smooth; the muscular layer of the artery is relatively thin. Under the control of the vegetative nervous system, the aorta performs a contraction and relaxation exercise, which can adjust blood flow and blood pressure. It is due to the extensibility of the thick wall of the aorta that ensures the continuous fluidity of blood in the blood vessels. The thick wall tissue of the aorta changes with age. The extensibility of the aorta in the elderly decreases, and their ability to adjust blood pressure decreases. Therefore, the blood pressure of people in old age is higher than that in youth.