Capillaries are tiny blood vessels where the smallest arteries meet the smallest veins and where the blood exchanges food and oxygen for waste products. Veins, which are also blood vessels, return depleted blood to the heart.Continue Reading
Some capillaries are so small that they can only be seen under a microscope, and tiny blood cells can only pass through them one at a time. Because capillaries are so small, their walls are correspondingly thin. Nutrients carried by the blood are able to pass through these walls to the cells of the body. Waste materials from the cells and tissues can also pass through the walls and be carried away. In the lungs, the capillaries exchange oxygen and carbon dioxide.
Capillary-sized veins are called venules. The small veins join together to form larger ones. Eventually, the veins all flow into the superior and inferior vena cava. The superior vena cava carries blood to the heart via the head and arms. The inferior vena cava carries blood from the legs and the trunk.
The walls of veins have three layers, though they're thinner and more rigid than the walls of the arteries. Many of the larger veins have valves that make sure the blood flows toward the heart and doesn't flow backward.Learn more about Blood
Capillary density is a physiological measure that takes a cross section of muscle and counts the number of capillaries, or blood vessels, contained within. This measurement can be an indicator of overall health and is also related to the ability to engage in strenuous physical activity.Full Answer >
A blood reservoir is an organ or vessel that holds large proportions of blood, and veins are vessels termed as the blood reservoirs of the body. This is because they hold the largest amount of blood, which is about 50 to 60 percent of the entire body’s blood volume.Full Answer >
There are a variety of diagrammatic representations of the human cardiovascular system depicting major and minor arteries and veins that are available in human anatomy textbooks. On the Internet, Healthline and InnerBody offer interactive diagrams of the arterial and venous systems, available as 2-D or 3-D diagrams.Full Answer >
When blood is too thick, it clots more easily, and the potential exists for blockage of the blood flow through the arteries and veins, according to the National Heart, Lung and Blood Institute. This may trigger a heart attack or stroke. Polycythemia vera is a condition in which the body produces too many red blood cells, causing thickening of the blood and increasing the possibility that clotting occurs.Full Answer >