The artery is ... Structure, function and features
The organism lives up to the moment when oxygenated blood moves through its blood system, which provides nourishment for body parts. As soon as the heart stops working and the blood supply becomes impossible, the body dies. And the artery is a blood vessel through which the so-called life force moves to the body tissues. So in the 16th-18th centuries naturalists spoke, trying to explain the essence of the blood circulation process and demonstrate their understanding of gas exchange. Today, almost everything is known about him, which makes it possible, on the basis of this knowledge, to improve the comfort of a patient with arterial diseases, to save many lives and to increase its duration.
In humans, the circulatory system consists of a heart and two closed circles. This closure - ensuring the integrity of the entire circulatory system, which is achieved through two types of vessels - arteries and veins.They vary greatly in the structure of the wall and blood flow velocity. Artery is the area of the circulatory system through which blood is delivered to organs. Vienna is the vessel through which blood is returned from the body’s tissues to the heart. Capillaries are the smallest vessels through which direct gas exchange with tissues and interstitial fluid is carried out.
Arterial vessels depart from the heart and end in a capillary bed at a great distance from it. They originate from the ventricles, where their diameter is maximum. One pulmonary artery departs from the right ventricle, which later divides into two branches of a smaller diameter, heading for the right and left lung. Further, from each of the branches, there are lobar pulmonary arteries of even smaller diameter, which branch further, reaching the areas of direct gas exchange, where they end with arterioles and sinusoidal capillaries.
From the left ventricle of the heart leaves the largest artery. This is the aorta, the diameter of which in an adult is about 3 cm at its mouth and about 2.5-2 cm in the descending and abdominal region.Many regional arteries are separated from it, each of which goes to a specific organ or group of organs. In particular, the right and left arteries of the heart are separated from the aortic orifice, forming two circles of myocardial blood supply that are connected to each other.
In the area of the aortic arch, three large branches separate from the aorta. This is the right artery (brachiocephalic trunk) with the left carotid and left subclavian arteries. The first directs blood to the right upper limb, neck, right half of the head. On the left side, the carotid artery is responsible for the blood supply to the corresponding half of the face and brain. The left upper limb is supplied with blood by the left subclavian artery. Small branches depart from each of them, along which blood will be delivered to muscle areas, to the brain and other smallest structures of the body.
Abdominal and pelvic arteries
At the level of the thoracic aorta, quite small regional branches depart from it, and after passing through the diaphragm, the celiac trunk and mesenteric arteries branch off to feed the stomach, intestines, spleen and fatty tissue.Below, large right and left renal arteries and several smaller regional branches will branch out. In the pelvic region, the aorta ends with a place of bifurcation in the iliac arteries. From them will take their beginning branches to the genitals and lower extremities. The uterine artery departs directly from the pelvic basin, whereas the arteries of the testicles branch off much higher from the renal vessels. They will gradually decrease in diameter as a result of division and will supply blood to the structure of the body at a smaller level. And with a decrease in the diameter of the vessels, the structure of their walls will also change.
Arterial tract diagram
The general plan of the structure of the arterial bed can be expressed in the following sequence, starting from the heart: aorta, elastic arteries, transitional and muscular arteries, arterioles, capillaries. From capillaries after the implementation of gas exchange and the distribution of oxygen in the tissues of the body, blood should be redirected to the place of oxygen saturation. For this, it should be collected in larger vessels, first venules, then regional veins.
The venous bed of the inferior and inferior vena cava ends, which discharge blood directly into the right atrium. From him, through the right ventricle, she will travel through the arterial system to the lungs for oxygenation.At the same time, an artery is a vessel through which blood flows from the heart, while it is delivered through the veins to the heart. For example, oxygenated blood, collected from the lungs, flows into the left atrium through the pulmonary veins, despite the fact that it is saturated with oxygen.
General plan of anatomy
An artery is an elastic tube through which blood flows under a pressure of 120 mmHg. It has its own cavity and wall, and is capable of transmitting a pulse wave from the heart to the transitional arteries, which is what makes it unique. At the same time, the aorta and large vessels that branch off from it are capable of withstanding great pressure and have mainly elastic properties. This allows pushing blood through them at a speed of 0.6 m / s, and also partially extinguish it when approaching less durable arteries of the muscular-elastic type. These include arteries of the limbs, internal brain and others. As the blood flow rate decreases, they pass into the vessels of the muscular type.
General plan of the arterial wall structure
The arterial wall is multi-layered, which accounts for its unique qualities, which are not easy to describe by the laws of mechanics and hydrodynamics.Because of this, due to its qualities, it is more reminiscent of composite materials, combining elastic properties and at the same time characterized by high tensile strength, ability to deform and the ability to self-repair non-critical damage.
There are 3 layers in the artery wall, which are more convenient to study from the inside to the outside. The inner layer is a single layer of the epithelium, the intima of the artery. It is located on the loose layer of connective tissue containing collagen fibers. On top of it is the inner elastic membrane, a semi-permeable membrane that separates the inner mostly epithelial membrane from the middle one - elastic or smooth muscle. And depending on the structure of the middle shell, the arteries are divided into elastic, transitional and muscular.
On top of the middle shell is the outer connective tissue. It represents an environment in which the smallest vessels and nerves pass to the middle shell. This is surprising, but the blood vessels themselves have a blood supply and innervation system, since only endothelium can feed directly from oxygenated blood in their cavity.
Differences in the structure of the arteries
Elastic fibers are strongly pronounced in the middle shell of the aorta and large arteries, but muscle cells are absent or poorly represented. Such arteries are phenomenal strength. Their main task is to conduct a pulse wave at high speed. As their diameter decreases and blood flow slows down among the elastic fibers, muscle cells appear that give the arteries the ability to contract and maintain the strength of the pulse wave, which gradually dies away as they approach it.
At greater distances from the heart are the arteries of the muscular type. In their middle shell there are many smooth muscle cells responsible for the contraction of the arterial wall. There are practically no elastic fibers, and the connective tissue sheath is less durable. As a rule, these are internal arteries feeding the parenchyma of organs or skeletal muscle.
Not all arteries are equally prone to damage. For example, the aorta over the age of 50-60 years is almost 100% of cases affected by atherosclerosis and calcified, whereas in small vessels cholesterol plaques are never formed.In large arteries, congenital anomalies are less common, whereas in small arteries they are very frequent. It is anomalies and malformations of large vessels that deserve more attention and require correction. This is because the consequences of the rupture of small arteries, if they are not in the brain, are easily tolerated.
Acquired stenosis, congenital anomalies and defects should be distinguished from all groups of arterial pathologies. Anomalies should be attributed to underdevelopment of an artery, in which its lumen is much less than normal in a healthy person. This condition is called artery syndrome when there is less blood flowing through the vessel than in most other patients. Interestingly, such an underdevelopment of the vessel may not manifest symptomatically, which is often observed. This is due to a compensatory increase in blood flow on the opposite side or by increasing the number of anastomoses, as is observed in the case of the vertebral artery.
Atherosclerosis and hyalinosis
Another group of arterial lesions is acquired pathologies. These include atherosclerosis, hyalinosis and aneurysm.Under atherosclerosis refers to the gradual postponement of cholesterol with the development of chronic inflammation under the inner arterial membrane. The result of this is arterial stenosis, which leads to ischemic diseases. Atherosclerosis can develop in all elastic and muscular-elastic arteries.
Under hyalinosis is meant such a defeat of the wall, in which the oxidation products of metabolites are deposited in its wall and also cause chronic inflammation. Unlike atherosclerosis, it does not lead to a narrowing of the lumen, but it complicates the ability to contract. Observed in all types of arteries in diabetes, significantly enhances the damage caused by atherosclerosis. It is believed that the aorta does not affect the hyalinosis, but this process in the large arteries has not been sufficiently studied.
Aneurysm - a separation of the artery wall, which is caused by a variety of factors. The most important of these are atherosclerosis and hyalinosis in diabetes and metabolic syndrome. It is these conditions that lead to the separation of the artery wall, the loss of its elastic and contractile properties, which also threatens to rupture the artery. Aneurysms develop in both small arteries and large ones.They are most dangerous in aortic or cerebral. Their rupture often leads to severe brain damage.