The cardiovascular system plays a crucial role in the body by providing oxygen and nutrients to the cells of the body and removing waste from them. The system is a pump with a circle of tubing running away from the pump toward the tissues and then back to the pump. These components include the heart, arteries and veins.
The Heart
According to Dr. Costanzo, author of the book "Physiology," the right side of the heart receives deoxygenated blood from the body and pumps it to the lungs. The left side receives the newly oxygenated blood from the lungs and pumps it out to the body. The heart is composed of four chambers, two on the right to pump the blood to the lungs and two on the left to pump the blood to the body. The chambers are called atria and ventricles, and there is one of each on the left and right. The two atria receive the blood, and ventricles and pump it out. Four one-way valves at the exit of each chamber ensure the proper direction of flow.
Arteries
Arteries transfer blood away from the heart. The left ventricle delivers the blood to a the largest artery in the body, the aorta. The aorta divides into smaller arteries, then into smaller arterioles. Arteries have three layers, as noted in the book "Wheater's Functional Histology" by Barbara Young. The outer most layer is composed of connective tissue. The middle layer is a relatively thick layer composed of muscle. The innermost layer lining the vessels has smooth cells that facilitate the flow of blood.
Capillaries
Capillaries connect arteries to veins. They form a large network of tiny blood vessels in the tissues. Their diameter is so small that cells flow through them in single-file lines. In addition the walls have many perforations. Their small diameter and multiple pores ensure maximum exposure of the blood cells to the tissues for efficient exchange of oxygen, nutrients and waste products.
Veins
Veins return blood to the heart. They start after the capillaries as venules, which become larger veins until becoming the largest veins in the body, the vena cavae, which connect to the right atrium of the heart. The walls of veins are flexible and distend to act as a reservoir for blood. The walls have three layers like arteries do, but arteries have a large middle muscular layer while veins have a larger outer connective tissue layer, making them more flexible. In addition, veins also have one-way valves to ensure the proper direction of blood flow.
References
- "Physiology"; Linda Costanzo; 2009
- "Wheater's Functional Histology"; Barbara Young; 2006
