How Your Blood Gets Around
Moving the blood from heart to lungs and from heart to body and returning it back to the heart is a monumental task that requires miles of vessels throughout the body. In this section is a list of some of the major arteries and veins that should be familiar to anyone looking for a better understanding of the vascular system of the human body.
Major Arteries
As blood leaves the ventricles of the heart, it will pass into one of the so-called “great vessels.” From the right ventricle, the blood moves into a single large pulmonary trunk (the aorta) that soon divides into right and left pulmonary arteries on the way to the lungs. From the left ventricle the blood enters into the aorta that arches up over the superior portion of the heart where large vessels leave to service the superior part of the body and the arms.
Anatomy of a Word
brachiocephalic
Brachio means “arm” and cephalic refers to the head; hence the name of the artery that first branches off the aorta, the brachiocephalic, indicates that it goes to the head and arm.
The first branch from the aortic arch is known as the brachiocephalic artery, which sends blood to the right side of the body including head and neck. It branches into two arteries, the right common carotid artery and the right subclavian artery, which extends through the body wall and into the arm as the brachial artery.
Just beyond the brachiocephalic artery, two additional arteries extend directly from the aortic arch, the left common carotid and the left subclavian artery. The aorta continues to arch 180° and descends into the body as the systemic or descending aorta, from which other arteries branch to the remainder. The largest branch off the aorta is the celiac artery, which supplies most organs of the upper digestive tract. From the celiac, many arteries branch out:
· The artery that goes to the liver is the hepatic artery.
· The artery that goes to the stomach is the gastric artery.
· The artery that goes to the spleen is the splenic artery.
· The artery that goes to the right and left kidneys are the renal arteries.
Moving farther down, the superior and inferior mesenteric arteries sprout from the aorta and supply portions of the small and large intestines, respectively.
At the most inferior end, the aorta divides into the right and left common iliac arteries that descend into each leg, becoming the external iliac arteries in the pelvic region. The vessels continue down each leg as the femoral arteries, which branch to the muscles of the leg and the foot.
Major Veins
Many of the major veins in the body mirror those of their counterparts of the arterial circulation. Blood from the feet and legs are drained from tissue via the femoral vein into the common iliac. This moves blood into the inferior vena cava (also called the posterior vena cava), the large vein that transports deoxygenated blood back to the right atrium. The inferior vena cava supplies the major venous drainage for the abdominal and inferior part of the body.
While many of the abdominal veins are named as their arterial counterparts (superior and inferior mesenteric, gastric, splenic), the majority of the veins from organs of the digestive tract drain into a large vein called the hepatic portal vein, which transports the blood to the liver.
In the liver, blood passes through the sinusoidal capillaries to the liver cells where it is metabolized. Here materials can be processed, excreted, or stored. From these sinusoids, blood is moved out of the liver by the hepatic vein into the inferior vena cava.
Blood from the head and neck is drained by large veins called the internal and external jugular veins, which empty their blood into the arching right or left brachiocephalic vein. These join together in the midline of the body to form the superior vena cava, which returns blood to the right atrium. From the arms, blood moves upward into the brachial vein, which becomes the subclavian vein and joins onto the brachiocephalic to return to the heart.
What is blood pressure?
Hydrostatic pressure (blood pressure) is the pressure the blood exerts on the vessel walls due to the contraction of the ventricles of the heart. With each ventricular contraction (systole), high-pressure blood is ejected into vessels of the body. For the average person, the pressure in the brachial artery during this contraction will be approximately 120 mmHg, and is termed the systolic pressure. During a ventricular relaxation (diastole), when the ventricle is expanding and creating a lower-pressure area to pull blood from the atria, the pressure will fall to near 0 mmHg inside the ventricles. However, because of the similar valves in the great vessels and the elastic nature of these arteries, the blood pressure will not fall below 80 mmHg on average and represents the person’s diastolic pressure.
Cardiovascular System Diseases and Disorders
Any problem that causes the pumping action of the heart to be diminished or restricts blood flow into specific areas of the body can lead to reduced life expectancy or imminent danger of death.
Ischemia
Because of diet or heredity, many people have high cholesterol levels in their blood streams. Over the long term, if left untreated, this material can accumulate in the walls of blood vessels and obstruct the flow of blood, a condition called ischemia. If the narrowed vessel is in the heart, lungs, or brain, the danger may be grave. Some lipoproteins in the blood help to remove these cholesterol accumulations in the blood vessel, while others actually make the situation worse. Often referred to as “good” or “bad” cholesterol, these lipoproteins can be tested for and adjustments made to lifestyle and diet to help improve ischemia.
Myocardial Infarct
If an ischemic event occurs in the vessels supplying the heart itself, the cardiac muscle, which is not designed to function under hypoxic (low-oxygen) conditions, can be destroyed, causing a heart attack. A heart attack is actually muscular death and degeneration of the heart muscle. It does not regenerate, but is replaced with connective tissue.
As one can imagine, if enough muscle dies, the heart either functions poorly or doesn’t function at all. One vessel that is critical to heart function and must remain open is the left anterior descending (LAD) coronary artery. It supplies two-thirds of the left ventricular muscle and if it becomes blocked, a person will suffer a massive heart attack, from which survival is unlikely.