specialized component of the circulatory system is the lymphatic system, consisting of a moving fluid (lymph/interstitial fluid); vessels (lymphatics); lymph nodes, and organs (bone marrow, liver, spleen, thymus)
Through the flow of blood in and out of arteries, and into the veins, and through the lymph nodes and into the lymph, the body is able to eliminate the products of cellular breakdown and bacterial invasion
The major veins, like their companion arteries, often take the name of the organ served except superior vena cava and the inferior vena cava, which collect blood from all parts of the body (except from the lungs) and channel it back to the heart
At any given time, more than half of the total blood volume is found in veins and venules
If blood is lost due to, for example, hemorrhaging, sympathetic nervous stimulation causes the veins to constrict, providing more blood to the rest of the body. In this way, the veins act as a blood reservoir.
Myocardium is the thickest part of the heart wall and is made up of cardiac muscle
Inner endocardium includes an endothelium that not only lines the heart but also continues into and lines the blood vessels. The endotheliums' smooth nature helps prevent blood from clotting unnecessarily
Blood follows this sequence through the heart: superior and inferior vena cava -> right atrium -> tricuspid valve -> right ventricle -> pulmonary semilunar valve -> pulmonary trunk and arteries to the lungs -> pulmonary veins leaving the lungs -> left atrium -> bicuspid valve -> left ventricle -> aortic semilunar valve -> aorta -> to the body .
As the left ventricle contracts, the mitral valve closes and the aortic valve opens
The closure of the mitral valve prevents blood from backing into the left atrium and the opening of the aortic valve allows the blood to flow into the aorta and flow throughout the body
Superior Vena Cava The superior vena cava is one of the two main veins bringing de-oxygenated blood from the body to the heart. Veins from the head and upper body feed into the superior vena cava, which empties into the right atrium of the heart
Inferior Vena Cava The inferior vena cava is one of the two main veins bringing de-oxygenated blood from the body to the heart. Veins from the legs and lower torso feed into the inferior vena cava, which empties into the right atrium of the heart
Aorta The aorta is the largest single blood vessel in the body. It is approximately the diameter of your thumb. This vessel carries oxygen-rich blood from the left ventricle to the various parts of the body.
Pulmonary Artery The pulmonary artery is the vessel transporting de-oxygenated blood from the right ventricle to the lungs Pulmonary Vein The pulmonary vein is the vessel transporting oxygen-rich blood from the lungs to the left atrium .
A cardiac control center in the medulla oblongata speeds up or slows down the heart rate by way of the autonomic nervous system branches: parasympathetic system (slows heart rate) and the sympathetic system (increases heart rate).
Hormones epinephrine and norepinephrine from the adrenal medulla also stimulate faster heart rate.