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For this reason, the blood flow velocity is the fastest in the middle of the vessel and slowest at the vessel wall. In most cases, the mean velocity is used. [18] There are many ways to measure blood flow velocity, like videocapillary microscoping with frame-to-frame analysis, or laser Doppler anemometry. [19]
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).
Vascular resistance occurs when the vessels away from the heart oppose the flow of blood. Resistance is an accumulation of three different factors: blood viscosity, blood vessel length and vessel radius. [30] Blood viscosity is the thickness of the blood and its resistance to flow as a result of the different components of the blood.
A breakthrough in understanding the flow of blood through the heart and body came with the publication of De Motu Cordis (1628) by the English physician William Harvey. Harvey's book completely describes the systemic circulation and the mechanical force of the heart, leading to an overhaul of the Galenic doctrines. [ 93 ]
Turbulent flow is present in circumstances under which Re > 4000. The range of 2000 < Re < 4000 is known as the transition range. Most blood flow in humans is laminar, having a Re of 300 or less, it is possible for turbulence to occur at very high flow rates in the descending aorta, for example, in highly conditioned athletes.
Normal blood pressure when at rest is within the range of 100–140 millimeters mercury (mmHg) systolic and 60–90 mmHg diastolic. [69] High blood pressure is present if the resting blood pressure is persistently at or above 140/90 mmHg for most adults. [67] Different numbers apply to children. [70]
Perfusion is measured as the rate at which blood is delivered to tissue, [2] or volume of blood per unit time (blood flow) per unit tissue mass. The SI unit is m 3 /(s·kg) [ citation needed ] , although for human organs perfusion is typically reported in ml/min/g. [ 3 ]
The anatomy of arteries can be separated into gross anatomy, at the macroscopic level, and microanatomy, which must be studied with a microscope.The arterial system of the human body is divided into systemic arteries, carrying blood from the heart to the whole body, and pulmonary arteries, carrying deoxygenated blood from the heart to the lungs.