The heart has four chambers – an auricle and a ventricle on each side. The atria are both provided by large blood vessels that bring blood to the heart (see below for details). The atria have special valves that open in the ventricles. The ventricles also have valves, but in this case they open into the blood vessels. The walls of the heart chambers consist mainly of special heart muscle. The different sections of the heart must tighten (contract) in the right order so that the heart can pump blood efficiently with each heartbeat. A sinusoidal capillary (or sinus capillary) is the least common type of capillary. The sinus capillaries are flattened and have extensive intercellular gaps and incomplete basement membranes, in addition to cracks and intercellular windows. This gives them a look a bit like Swiss cheese. These very large openings allow the passage of the largest molecules, including plasma proteins and even cells. Blood flow through the sinusoids is very slow, leaving more time for the exchange of gases, nutrients and waste. Sinusoids are found in the liver and spleen, bone marrow, lymph nodes (where they carry lymph, not blood), and many endocrine glands, including the pituitary gland and adrenal glands.
Without these specialized capillaries, these organs would not be able to perform their myriad functions. For example, when the bone marrow forms new blood cells, the cells must enter the blood supply and can only do so through the large openings of a sinusoidal capillary; they cannot pass through the small openings of the continuous or fenestrated capillaries. The liver also needs specialized sinusoidal capillaries to process the materials brought by the hepatic portal vein of the digestive tract and spleen and circulate plasma proteins. Lumens: Inside a tubular structure, such as a blood vessel or part of the digestive canal, through which blood, porridge or other substances travel When the amounts of cholesterol in the blood are excessive, cholesterol can accumulate in the arteries, which can lead to coronary heart disease and many other serious conditions. Acute coronary syndrome (ACS) is an umbrella term used to describe any situation in which the blood supply to the heart is suddenly obstructed, including unstable angina and acute myocardial infarction. The main cause is atherosclerosis, a condition in which plaque accumulates and thickens the walls of the arteries. The main vein in your body is the hollow vein. The superior vena cava is located in the upper right part of your chest. It carries blood from your head, neck, arms and chest to your heart. The inferior vena cava is located near the right side of your diaphragm. It brings blood from your legs, feet, abdomen and pelvis back to your heart. All blood vessels are essentially hollow tubes with an internal space called a light through which blood flows.
The light of an artery is shown in cross-section in the microphotograph below. The width of blood vessels varies, but they all have a light. The walls of blood vessels differ depending on the type of vessel. In general, arteries and veins are more similar to each other than capillaries in the structure of their walls. The right side of the heart receives oxygen-depleted blood (oxygen-poor blood) from the body. After passing through the right atrium and right ventricle, this blood is pumped into the lungs. Here, the blood absorbs oxygen and loses another gas called carbon dioxide. Once in the lungs, the blood returns to the left atrium. It then passes into the left ventricle and is pumped into the main artery (aorta) that supplies the body. The oxygen-rich blood is then transported through the blood vessels to all tissues of the body. Here, oxygen and other nutrients enter the cells, where they are used to perform the essential functions of the body. White blood cells are part of the immune system.
They detect and fight infections or foreign substances that enter the body. The function of blood vessels is to deliver blood to the organs and tissues of your body. The blood provides them with the oxygen and nutrients they need to function. Blood vessels also carry waste and carbon dioxide away from your organs and tissues. Surgeons and vascular technicians Vascular surgery is a specialty in which the doctor mainly treats diseases of the vascular part of the cardiovascular system. These include repair and replacement of diseased or damaged vessels, removal of plaque from vessels, minimally invasive procedures, including insertion of venous catheters, and traditional surgeries. After completing medical school, the doctor usually undergoes 5 years of surgical specialist training, followed by additional 1-2 year vascular specialist training. In the United States, most vascular surgeons are members of the Society of Vascular Surgery. An arteriole is a very small artery that leads to a capillary.
The arterioles have the same three tunics as the larger vessels, but the thickness of each is significantly reduced. The critical endothelial mucosa of the intima tunic is intact. The middle of the tunic is limited to one or two layers of smooth muscle cells in thickness. The outer tunic is preserved, but is very thin (see (figure)). The walls of arteries and veins are largely made up of living cells and their products (including collagen and elastic fibers); cells need food and produce waste. Since blood flows relatively quickly through the larger vessels, there is only a limited possibility for blood in the light of the vessel to nourish the cells of the vessel or eliminate waste from them. In addition, the walls of the larger vessels are too thick for nutrients to penetrate into all cells. Large arteries and veins contain small blood vessels in their walls known as vasa vasorum – literally «vessels of the vessel» – to provide them with this critical exchange. Since the pressure in the arteries is relatively high, the vasa vasorum must work in the outer layers of the vessel (see (figure)) or the pressure exerted by the blood circulating in the vessel would cause it to collapse and prevent it from being replaced. The lower pressure in the veins allows the vasa vasorum to be closer to light.
It is believed that the restriction of vasa vasorum to the outer layers of the arteries is one of the reasons why arterial diseases are more common than venous diseases, since their location makes it more difficult to nourish the cells of the arteries and eliminate waste. There are also tiny nerves in the walls of both types of vessels that control the contraction and expansion of smooth muscles. These tiny nerves are known as the vasorum nerve. The intima tunic (also called the inner tunic) consists of epithelial layers and connective tissue. The lining of the intima tunic is the specialized single squamous cell called the endothelium, which is continuous throughout the vascular system, including the lining of the heart chambers. Damage to this endothelial mucosa and exposure of the blood to the underlying collagen fibers are one of the main causes of clot formation. Until recently, the endothelium was simply seen as the boundary between blood in light and the walls of vessels. However, recent studies have shown that it is physiologically crucial for activities such as regulating capillary exchanges and altering blood flow. The endothelium releases local chemicals called endothelials, which can tighten smooth muscles in the vessel walls to increase blood pressure. An uncompensated overproduction of endothelins can contribute to high blood pressure (high blood pressure) and cardiovascular disease.
Venous reserve: The volume of blood contained in the systemic veins of the integument, bone marrow and liver, which can be sent back to the heart for blood circulation if necessary, and your blood can provide useful information about how your body works and help doctors test for certain diseases and conditions. Some common blood tests are: When blood flow needs to be distributed to other parts of the body, the vasomotor center in the oblong marrow sends sympathetic stimulation to the smooth muscles in the walls of the veins, resulting in narrowing — or in this case, venoconstriction. Less dramatically than vasoconstriction observed in small arteries and arterioles, venoconstriction can be compared to a «stiffening» of the vascular wall. This increases the pressure on the blood in the veins and accelerates its return to the heart. As you will notice in (figure), about 21% of venous blood is located in the venous networks of the liver, bone marrow and integument. This volume of blood is called a venous reserve. Venostriction allows this volume of «reserve» blood to return more quickly to the heart to redistribute it to other parts of the circulation. Figure 1. Pulmonary circulation moves blood from the right side of the heart to the lungs and to the heart. Systemic circulation moves blood from the left side of the heart to the head and body and returns it to the right side of the heart to repeat the cycle. .
