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η(δ) = viscosity of blood in the wall plasma release-cell layering; r = radius of the blood vessel; δ = distance in the plasma release-cell layer; Blood resistance varies depending on blood viscosity and its plugged flow (or sheath flow since they are complementary across the vessel section) size as well, and on the size of the vessels.
Blood vessels also circulate blood throughout the circulatory system. Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95–100%) with oxygen.
To summarize, vasoconstriction is a physiological process that involves the narrowing of blood vessels, particularly arteries and arterioles, resulting in a reduction of blood flow to specific tissues or organs. This phenomenon is primarily regulated by the contraction of smooth muscle cells within the vessel walls.
The dissolved gas in the alveolar blood is transported to the body tissues by the blood circulation. There it diffuses through the cell membranes and into the tissues, where it may eventually reach equilibrium. The greater the blood supply to a tissue, the faster it will reach equilibrium with gas at the new partial pressure. [3] [18]
The cardiomyocytes make up the bulk (99%) of cells in the atria and ventricles. These contractile cells respond to impulses of action potential from the pacemaker cells and are responsible for the contractions that pump blood through the body. The pacemaker cells make up just (1% of cells) and form the conduction system of the heart.
Blood viscosity is a measure of the resistance of blood to flow. It can also be described as the thickness and stickiness of blood. This biophysical property makes it a critical determinant of friction against the vessel walls, the rate of venous return, the work required for the heart to pump blood, and how much oxygen is transported to tissues and organs.
Though veins might make it appear as such, human blood is never naturally blue. [3] The blue appearance of surface veins is caused mostly by the scattering of blue light away from the outside of venous tissue if the vein is at 0.5 mm deep or more. Veins and arteries appear similar when skin is removed and are seen directly. [4] [5]
In a healthy vascular system, the endothelium lines all blood-contacting surfaces, including arteries, arterioles, veins, venules, capillaries, and heart chambers. This healthy condition is promoted by the ample production of nitric oxide by the endothelium, which requires a biochemical reaction regulated by a complex balance of polyphenols, various nitric oxide synthase enzymes and L-arginine.