In: Anatomy and Physiology
Heart:The heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone. The heart pumps blood through the network of arteries and veins called the cardiovascular system.
Blood : Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed of blood cells suspended in blood plasma.
Blood vessels : There are five types of blood vessels: the arteries, which carry the blood away from the heart; the arterioles; the capillaries, where the exchange of water and chemicals between the blood and the tissues occurs; the venules; and the veins, which carry blood from the capillaries back towards the heart.
Cardiovascular physiology :
Cardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular").
These subjects are sometimes addressed separately, under the names cardiac physiology and circulatory physiology.
Regulation of blood pressure
Hemodynamics
Under most circumstances, the body attempts to maintain a steady mean arterial pressure.[2]
When there is a major and immediate decrease (such as that due to hemorrhage or standing up), the body can increase the following:
In turn, this can have a significant impact upon several other variables:
Name of circulation | % of cardiac output | Autoregulation | Perfusion | Comments |
pulmonary circulation | 100% (deoxygenated) | Vasoconstriction in response to hypoxia | ||
cerebral circulation | 15% | high | under-perfused | Fixed volume means intolerance of high pressure. Minimal ability to use anaerobic respiration |
coronary circulation | 5% | high | under-perfused | Minimal ability to use anaerobic respiration. Blood flow through the left coronary artery is at a maximum during diastole (in contrast to the rest of systemic circulation, which has a maximum blood flow during systole.) |
splanchnic circulation | 15% | low | Flow increases during digestion. | |
hepatic circulation | 15% | Part of portal venous system, so oncotic pressure is very low | ||
renal circulation | 25% | high | over-perfused | Maintains glomerular filtration rate |
skeletal muscular circulation | 17% | Perfusion increases dramatically during exercise. | ||
cutaneous circulation | 2% | over-perfused | Crucial in thermoregulation. Significant ability to use anaerobic respiration |