Chapter 37 Circulatory System notes

The human circulatory system consists of the heart, a series of blood vessels and the blood that flows through them.
Your heart is located hear the center of your chest. It is composed almost entirely of muscle. The hard is enclosed in protective tissue called pericaridum. In the walls of the heart there are two thin layers of epithelial and connective tissue that form a sandwich around a thick layer of muscle called the myocardium. The powerful contractions of the myocardium pump blood through the circulatory. Dividing the right side of the heart from the left side is the septum or wall. The septum prevents the mixing of oxygen-poor and oxygen rich blood. On each side of the septum are two chambers. The upper chamber which receives the blood is called the atrium. The lower chamber which pumps blood out of the heart is the ventricle.
The heart functions as two separate pumps . The right side of the heart pumps blood from the heart to the lungs. The left side pumps out of the lungs and into the left side and then out to the body. This pathway is called systemic circulation. Blood that returns to the right side of the heart is oxygen poor because cells have absorbed much of the oxygen and loaded the blood with carbon dioxide. t this point, it is ready for another trip to the lungs.
As blood flows through the circulatory system, ti moves through three types of blood vessels - arteries, capillaries, and veins.
Red blood cells transport oxygen. They get their color from Hemoglobin. It is the iron containing protein that binds to oxygen in the lungs and transports it to tissues throughout the body where oxygen is released.
White blood cells, or leukcocytes are fewer than red blood cells. For every 700 red blood cells, there is just one white blood cell. White blood cells attack foreign substances or organisms.
Blood clotting is made possible by plasma proteins and cell fragments called platelets. There are certain large cells in bone marrow that bread into thousands of small pieces. Each fragment of cytoplasms is enclosed in a piece of cell membrane and released into the bloodstream as a platelet.
A network of vessels called the lymphatic system collects the fluid that is lost by the blood and returns it to the circulatory system. The fluid is called lymph. It collects in lymphatic capillaries and slowly flows into larger and larger lymph vessels. Like large veins, lymph vessels contain valves that prevent lymph from flowing backward. Ducts collect the lymph and return it to the circulatory system through two openings in the superior vena cava. The openings are under the left and right clavicle bones just below the shoulders.