Veins contain a series of one-way valves. As the vein is squeezed, it pushes blood through the valves, which then close to prevent backflow.
Standing or sitting for prolonged periods can cause low venous return from venous pooling. In venous pooling, the smooth muscles surrounding the veins become slack and the veins fill with the majority of the blood in the body, keeping blood away from the brain, which can cause unconsciousness. Venous valve : Venous valves prevent back flow and ensure that blood flows in one direction.
Although most veins take blood back to the heart, portal veins carry blood between capillary beds. For example, the hepatic portal vein takes blood from the capillary beds in the digestive tract and transports it to the capillary beds in the liver.
The blood is then drained in the gastrointestinal tract and spleen, where it is taken up by the hepatic veins and blood is taken back into the heart. Since this is an important function in mammals, damage to the hepatic portal vein can be dangerous. Blood clotting in the hepatic portal vein can cause portal hypertension, which results in a decrease of blood fluid to the liver.
Veins are classified in a number of ways, including superficial vs. Privacy Policy. Skip to main content. Here, oxygen and nutrients are released and carbon dioxide and other waste substances are absorbed. Deoxygenated blood then moves from the capillary beds through venules into the systemic veins.
The systemic veins feed into the inferior and superior venae cavae, the largest veins in the body. The venae cavae flow deoxygenated blood to the right atrium of the heart.
See more from our free eBook library. A description of the vascular system from the edition of Gray's Anatomy of the Human Body. Functions of the Blood. Anatomy of the Heart. Blood Vessels: The Circulatory Network. Circulatory System Pathologies. When you select "Subscribe" you will start receiving our email newsletter. Use the links at the bottom of any email to manage the type of emails you receive or to unsubscribe.
These two systems form the blood circulatory system. The systemic arteries transport oxygen-rich blood from the left ventricle to the rest of the body. Afterward, the blood that is now low in oxygen is collected in systemic veins and travels to the right atrium. Pulmonary arteries transport low oxygen blood from the right ventricle to the lungs. Pulmonary veins then transport oxygen-rich blood back to the heart through the left atrium.
Capillaries are a third type of blood vessel in the body. They carry blood between arteries and veins. There are three types of arteries:. Elastic arteries are the large vessels coming out of the heart. For example, they include the pulmonary artery and the aorta. The aorta is the main artery carrying blood away from the heart. The heart forcefully pumps blood out to keep it moving around the body. Elastic arteries must be flexible to handle surges of blood.
They expand as the heart pushes blood out. Smooth muscle fibers make up the walls of muscular arteries. The muscles allow these arteries to expand and contract. These changes in size control how much blood moves through the arteries. Arterioles are the smallest type of artery. They distribute blood from larger arteries through networks of capillaries.
The outer layer of arterioles also contains smooth muscle that allows for expansions and contractions. The same layers make up arteries and veins, but veins are thinner and have less muscle, allowing them to hold more blood. Carbon dioxide can also move into your capillaries from the tissue before entering your veins.
The venous system refers to the network of veins that work to deliver deoxygenated blood back to your heart. Your body circulates blood on two different tracks called the systemic circuit and the pulmonary circuit. These symptoms are especially common in your legs. They can perform a venography. In this procedure, your doctor injects contrast die into your veins to produce an X-ray image of a particular area. Blood clotting is a normal function that occurs when you have an injury.
Find out what happens if clot doesn't dissolve or forms in a blood vessel. Temporal arteritis occurs when the temporal arteries, which supply blood to the head and brain, become inflamed or damaged.
Everyday factors can make veins more noticeable.
0コメント