Arteries are a type of blood vessels. Vessels in the body are divided into arteries, veins, and lymphatic vessels. Arteries transport blood pumped by the heart to the whole body. This blood is oxygenated and contains substances necessary for proper function of tissues and cells. Because blood flowing through the arteries is under high pressure, they need to be sufficiently robust and flexible. The structure of vascular walls generally consists of 3 layers, which may differ slightly according to the type of vessels. Arteries, in comparison to other vessels, have a much stronger layer composed of muscle tissues. This layer can withstand the high pressure of blood pumped from the heart and because they are elastic, blood can quickly flow through the arteries.
Properties of Arteries
Some arteries help pump blood by being able to contract regularly, thereby distributing blood all over the body. The muscles in arteries are always under the control of the nervous system. If the blood flow needs to be decreased under certain circumstances, vessels constrict (vasoconstriction) and a reduced amount of blood is able to flow through. This is the way arteries in the skin function with exposure to cold. They react in this way in order to reduce heat loss. If, on the other hand, blood flow needs to be increased, the vessels dilate (vasodilation), helping the body cool itself.
Function of the Arteries
The main artery in the human body is the aorta. The aorta is connected to the left ventricle, is very flexible and measures about 2.5 cm (1 inch) in diameter. It continues through the chest and abdominal cavity, splitting into two smaller iliac arteries at the lumbar (pelvic) region. Along this artery, major arteries branch off of it as well, supplying oxygenated blood to the organs, the most important being the brain and organs of the abdomen and pelvis. Similar to these organs, the heart also needs a continuous supply of oxygenated blood in order to function properly. The heart is unable to use the blood that it pumps into the body. It needs its own supply of blood, therefore it is surrounded by its own network of blood vessels. The most important are the coronary arteries, which branch from the aorta, penetrate the heart muscle and nourish it with oxygen. The arteries branching off of the aorta further branch into smaller arterioles, and then into capillaries. Capillaries are one of the most important parts of the circulator system, because it is at their level that the exchange of oxygen and other substances occurs. Capillaries combine among themselves to from venules, which further form smaller veins, finally forming the superior and inferior venae cavae through which blood is able to return back to the heart.
The most Common Arterial Illnesses
The most common illnesses affecting the arteries include atherosclerosis, i.e. hardening of the arteries, aortic dissection, aortic aneurysm and Raynaud's disease.
Atherosclerosis includes changes in the walls of the blood vessels, changing its lumen. It is therefore considered the cause of a number of other illnesses. Atherosclerosis develops in virtually every individual from birth; therefore it is questionable whether it can in fact be classified as a disease. If so, then it is most definitely a chronic disease where fat is collected on arterial walls. This causes narrowing of the vessel leading to impaired blood circulation into the affected organ and in the most serious of cases, complete blockage of the artery. In this case, ischemia develops, i.e. local deprivation of blood in the surrounding tissue, causing myocardial infarction (heart attack) or stroke. Atherosclerosis is diagnosed with the help of the Doppler ultrasound or x-rays. It is treated with the help of a balloon angioplasty, a surgical procedure where a catheter containing a balloon is introduced into the affected artery and blown up in order to expand the vessel. It is also possible to subsequently reinforce the vessel with metal mesh (a stein).
An aortic aneurysm is bulging that occurs most frequently in the abdominal aorta. It is caused by weakening of the walls of this strained artery. An aneurysm usually develops form atherosclerosis and appears a lot more often in men. Bulging usually does not have any symptoms but it can be discovered by simple palpation, where pulsing can be felt in the abdomen. In the event that the aneurysm bursts, sever pain follows and can lead to major bleeding, which is usually fatal. An aneurysm can be found with a CT or ultrasound of the abdomen. The only treatment option of an aortic aneurysm is surgery.
Aortic dissection is a tear, usually in the ascending part of the aorta, creating a pocket where blood accumulates. The tear can progress along the aorta all the way to the area of its branching. The blood tends to flow back into the blood vessel, which is favourable, but in the event that the blood flows out, the patient can die. It is not completely certain what causes aortic dissection, but it has been discovered that most patients with aortic dissection suffer from hypertension (high blood pressure). Dissection is manifested by severe pain behind the sternum and may resemble myocardial infarction. It is therefore necessary that the two different conditions are distinguished from each other during diagnosis. Treatment is based on medication to lower blood pressure, and surgical reparation of the blood vessel.
Raynaud's disease is a vascular disease typically manifested by attacks of pallor and pain in the finger tips. It is caused by constriction of the muscular layer of the blood vessels, narrowing the vessels and therefore decreasing blood flow. The cold and mental illnesses can trigger these symptoms, but the true cause of the vascular spasms themselves is not known. Young women are affected more often.