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Cardiovascular system anatomy and physiology
Lymphatic system anatomy and physiology
Abnormal heart sounds
Normal heart sounds
Changes in pressure-volume loops
Cardiac and vascular function curves
Altering cardiac and vascular function curves
Law of Laplace
Measuring cardiac output (Fick principle)
Stroke volume, ejection fraction, and cardiac output
Physiological changes during exercise
Cardiovascular changes during hemorrhage
Cardiovascular changes during postural change
Cardiac conduction velocity
Electrical conduction in the heart
ECG normal sinus rhythm
ECG QRS transition
ECG rate and rhythm
ECG cardiac infarction and ischemia
ECG cardiac hypertrophy and enlargement
Control of blood flow circulation
Microcirculation and Starling forces
Blood pressure, blood flow, and resistance
Compliance of blood vessels
Laminar flow and Reynolds number
Pressures in the cardiovascular system
Resistance to blood flow
Action potentials in myocytes
Action potentials in pacemaker cells
Cardiac excitation-contraction coupling
Excitability and refractory periods
Laminar means smooth, and so laminar blood flow is blood that’s flowing smoothly through the vessels. Turbulent flow, on the other hand, is when the blood’s not flowing smoothly, and we can figure out if blood is likely to be laminar or turbulent by finding its Reynolds number or Re, which is named after Osborne Reynolds, a Victorian scientist who not only studied fluid dynamics, but is a man who knows how to rock a beard and bowtie.
If everything’s moving like it should and the blood flow is laminar, the linear velocity of the blood -- how fast it’s moving in a straight line -- is greatest in the center of the blood vessel, and lowest near the walls of the vessel, dropping to zero at the wall.
Sometimes, though, blood flow is disrupted, like if it has to pass by a crusty old atherosclerotic plaque along the wall, which reduces the diameter of the blood vessel at that point and causes turbulence. There are a number of factors help predict turbulence, they include the density of the blood, usually denoted by the greek letter rho, the viscosity denoted by the greek letter nu. You can kind of think of a fluid’s viscosity as it’s thickness, like for example the viscosity of honey is greater than that of water. Alright, then there’s velocity of blood flow (v), and the diameter of the blood vessel (d).These values can all be used to come up with a single value—the reynold’s number, often denoted Re, and the equation looks like this:
NR = pdv/
Generally speaking, if the Reynolds number is low - below 2000, then blood flow will be laminar - think “low” and “laminar”, and if the Reynolds number is above 3000 it’ll be turbulent. A Reynolds number between 2000 and 3000 is somewhere in between. As a real-life example, a person with anemia has a low red blood cell count, and in general has a lower hematocrit, the ratio of red blood cells to total blood volume. This essentially means the blood’s less thick or viscous, which means based on our equation, if viscosity decreases, reynolds number increases. Also, these individuals often have an increased cardiac output, which means increased blood velocity and therefore increased reynolds number.
Laminar flow is when a fluid flows in a smooth, continuous stream. The Reynolds number is a dimensionless parameter that helps to determine whether the flow will be laminar or turbulent. When the Reynolds number is low, the flow will be laminar. When the Reynolds number is high, the flow will be turbulent.
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