The Heart and It’s Working - 2

The veins walls are considerably thinner in comparison to arterial walls. The larger veins have a system of internal one-way valves which do not allow the blood from flowing downward under the pull of gravity when person stands up. When a human being makes movement, the veins get squeezed by the surrounding muscle that helps in moving more blood towards the heart. Without valves in the veins, blood would move in the legs, which would then be continuing to grow.

The Pulmonary Circulation

The most important function of the pulmonary circulation is to transfer oxygen to the blood and free it from carbon dioxide. This task is completed when the blood flows through the lungs. The pressure at this part of the system is only about one-sixth as great as in the systemic circulation, and the pulmonary arteries walls and veins are thinner in comparison to the walls of other vessels in the rest of the body. In the pulmonary circulation, the role of arteries and veins are the opposite of what they do in the systemic circulation. Blood in the arteries has lesser oxygen, while blood in the veins has higher oxygen. The circuit starts with the pulmonary artery, which extends from the right ventricle and brings blood with low level oxygen content to the lungs. In the lungs, it branches off into the two different arteries, one for each lung, and then into arterioles and capillaries. The gas exchange between the air we breathe in and the blood takes place in the pulmonary capillaries. Pulmonary Capillaries walls work like filters by permitting molecules of gas to pass through but not to molecules of fluid. The total surface area of the capillaries in the lungs ranges from around 500 to 1,000 square feet.

Blood Vascular function

Blood is a life-saving fluid which helps to maintain an optimum environment in the body by providing a regular supply of nutrients from the outer world and removing waste products from the tissues present in body. Its cells are produced in the bones marrow, primarily in the flat bones like the ribs and the breastbone. The volume of blood in an average adult human being amounts to around 10.5 pints.