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The circulatory system is an organ system that passes nutrients (such as amino acids, electrolytes and lymph), gases, hormones, blood cells, etc. to and from cells in the body to help fight diseases, stabilize body temperature and pH, and to maintain homeostasis.
The main components of the human cardiovascular system are the heart, blood, and blood vessels. It includes: the pulmonary circulation, a "loop" through the lungs where blood is oxygenated; and the systemic circulation, a "loop" through the rest of the body to provide oxygenated blood. An average adult contains five to six quarts (roughly 4.7 to 5.7 liters) of blood, which consists of plasma, red blood cells, white blood cells, and platelets. Also, the digestive system works with the circulatory system to provide the nutrients the system needs to keep the heart pumping.
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Pulmonary circulation scheme
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The pulmonary circulatory system is the portion of the cardiovascular system in which oxygen-depleted blood is pumped away from the heart, via the pulmonary artery, to the lungs and returned, oxygenated, to the heart via the pulmonary vein.
Oxygen deprived blood from the vena cava, enters the right atrium of the heart and flows through the tricuspid valve into the right ventricle, from which it is then pumped through the pulmonary valve into the pulmonary artery to the lungs. Gas exchange occurs in the lungs, whereby CO2 is released from the blood, and oxygen is absorbed. The pulmonary vein returns the now oxygen-rich blood to the heart.
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The systemic circulation is the portion of the cardiovascular system which transports oxygenated blood away from the heart, to the rest of the body, and returns oxygen-depleted blood back to the heart. Systemic circulation is, distance-wise, much longer than pulmonary circulation, transporting blood to every part of the body.
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The normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the sinoatrial node through both atria and forward to the atrioventricular node. The Purkinje fibers and the His bundle allow further propagation from the atrioventricular node to the ventricle. Both the sinoatrial and atrioventricular nodes stimulate the myocardium. Time ordered stimulation of the myocardium allows efficient contraction of all four chambers of the heart, thereby allowing selective blood perfusion through both the lungs and systemic circulation.
Cardiac neurons innervating the myocardium bear limited similarities to those of skeletal muscle as well as other important differences. Cardiac neurons are uniquely subject to influence by the sympathetic and parasympathetic influence of the autonomic nervous system unlike skeletal muscle.
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Videos and evaluation
Video 1: Atrium, Ventricles and Arteries