What kind of blood is carried in a vein

When blood enters the small capillaries of the lung called the pulmonary capillaries , fresh oxygen enters the blood and carbon dioxide is removed.

This is called " gas exchange " or " respiration ". Because this is the exchange of gases between the atmosphere and the bloodstream, it is also called " external respiration ". When freshly oxygenated blood reaches the capillaries of the tissues, oxygen moves from the blood toward the tissues, and carbon dioxide moves from the tissues toward the blood. This gas exchange that occur between the blood and the cells of the tissues and organs is called " internal respiration ".

Blood vessels have a muscle layer that is able to relax or contract. When we need to increase our blood pressure, the muscle layer contracts and makes the blood vessel diameter smaller. This is called "vasoconstriction".

When the muscle layer of a blood vessel relaxes, the blood vessel diameter becomes larger. This is called "vasodilation". Vasodilation lowers the blood pressure. Drugs that cause the diameter of the blood vessels to change are called vasoactive drugs. Drugs that make blood vessels constrict are used to treat low blood pressure and are called vasocontrictors.

Drugs that relax the blood vessels and make them relax are used to treat high blood pressure. They are called vasodilators. In fact, there are valves within the lumen of veins to prevent the backflow of blood. Capillaries are tiny vessels that branch out from arterioles to form networks around body cells. In the lungs, capillaries absorb oxygen from inhaled air into the bloodstream and release carbon dioxide for exhalation.

Elsewhere in the body, oxygen and other nutrients diffuse from blood in the capillaries to the tissues they supply. The capillaries absorb carbon dioxide and other waste products from the tissues and then flow the deoxygenated blood into the veins. The blood moving through the circulatory system puts pressure on the walls of the blood vessels.

Blood pressure results from the blood flow force generated by the pumping heart and the resistance of the blood vessel walls. When the heart contracts, it pumps blood out through the arteries. The blood pushes against the vessel walls and flows faster under this high pressure. When the ventricles relax, the vessel walls push back against the decreased force. Blood flow slows down under this low pressure. Download Blood Vessels Lab Manuals. See more from our free eBook library.

Functions of the Blood. Anatomy of the Heart. Doctors can detect varicose veins by examining the Merck and Co. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world.

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Venules and veins. Biology of the Heart and Blood Vessels. Test your knowledge. Swelling is a condition caused by excess fluid in the tissues. The fluid involved in swelling is primarily water. Swelling may occur in one or several parts of the body, often the feet and lower legs.

Swelling that occurs throughout the body has different causes than swelling in a single limb or part of a limb. Which of the following is a frequent cause of swelling in a single limb or part of a limb?