The cardiovascular system consists of the heart and circulating blood vessels dispersed throughout the body. Cardiac tissue includes external and internal structures that are designed to work in unison as a pump. The heart's main job is to pump freshly oxygenated blood through the blood vessels to all parts of the body so that individual cells receive oxygen and nutrients to keep the body running. Blood vessels form a transport system via hollow interconnected tubes.
Layers of the Outer Heart
The heart is housed in a thin fibrous sac-like tissue called pericardium. According to the "Mayo Clinic Family Health Book," three layers of the heart unite in design and function to expand and contract for a pumping mechanism. The outermost layer of the heart consists of a shiny membrane called epicardium. The thick layer of heart muscle itself is the middle layer, called myocardium. Finally, the innermost layer, endocardium, consists of a smooth, shiny membrane that is in contact with the blood being pumped through the heart. Endocardium also covers the inside chambers and valves.
Interior of the Heart
According to the American Heart Association, there are four separate chambers in the heart. The right side of the heart consists of the right atrium, which receives oxygen-poor blood from the body and sends it down to the right ventricle to pump it toward the lungs to be oxygenated. The left side of the heart, similarly, consists of an atrium and ventricle. The left atrium receives oxygen-rich blood from the lungs and sends it down to the left ventricle, which pumps the blood towards the rest of the body. The septum, a muscular wall, divides the right and left sides of the heart. Four flexible structures, called valves, keep the flow of the blood in proper direction through the heart.
Blood Vessels
Blood vessels make up the circulatory system and consist of arteries, veins and capillaries. According to the Texas Heart Institute, if all the blood vessels of the circulatory system were laid out in a horizontal line, they would extend for over 60,000 miles. Arteries, the vessels leading away from the heart, carry oxygenated blood towards the rest of the body. Veins, the vessels going towards the heart, carry back deoxygenated blood to be "recycled" by the heart. Capillaries are networks of tiny vessels that simultaneously deliver oxygen and nutrients to cells while picking up carbon dioxide and waste products. Arteries and veins connect to capillaries by their smaller counterparts, arterioles and venules, respectively.
References
- "Mayo Clinic Family Health Book;" Scott Litin, M.D.; 2009
- American Heart Association: Your heart and how it works
- Texas Heart Institute: Anatomy of the cardiovascular system
- American Heart Association: Circulatory system
