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Because blood vessels are not rigid tubes, classic hydrodynamics and fluids mechanics based on the use of classical viscometers are not capable of explaining haemodynamics. [ 2 ] The study of the blood flow is called hemodynamics, and the study of the properties of the blood flow is called hemorheology .
In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. [1] [2] It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek kardia meaning heart, and Latin vascula meaning vessels).
Anastomoses provide alternative routes for blood to flow through in case of blockages. Veins can have valves that prevent the backflow of the blood that was being pumped against gravity by the surrounding muscles. [8] In humans, arteries do not have valves except for the two 'arteries' that originate from the heart's ventricles. [9]
The circulation Γ of a vector field V around a closed curve C is the line integral: [3] [4] =. In a conservative vector field this integral evaluates to zero for every closed curve. That means that a line integral between any two points in the field is independent of the path taken.
The pulmonary circulation loop is virtually bypassed in fetal circulation. [7] The fetal lungs are collapsed, and blood passes from the right atrium directly into the left atrium through the foramen ovale (an open conduit between the paired atria) or through the ductus arteriosus (a shunt between the pulmonary artery and the aorta).
Therefore its circulation is of major importance not only to its own tissues but to the entire body and even the level of consciousness of the brain from moment to moment. Interruptions of coronary circulation quickly cause heart attacks ( myocardial infarctions ), in which the heart muscle is damaged by oxygen starvation .
In a rare congenital disorder (dextrocardia) the heart is offset to the right side and is felt to be on the left because the left heart is stronger and larger, since it pumps to all body parts. Because the heart is between the lungs, the left lung is smaller than the right lung and has a cardiac notch in its border to accommodate the heart. [8]
In the systemic circulation the return is of deoxygenated blood from the organs and tissues of the body, and in the pulmonary circulation the pulmonary veins return oxygenated blood from the lungs to the heart. Almost 70% of the blood in the body is in the veins, and almost 75% of this blood is in the small veins and venules. [7]