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A precapillary sphincter is a band of contractile mural cells either classified as smooth muscle or pericytes that adjusts blood flow into capillaries. They were originally described in the mesenteric microcirculation, and were thought to only reside there.
The sphincter regulates the secretion of pancreatic juice and bile into the duodenum. [3] It also prevents reflux of duodenal contents into the ampulla of Vater. [4] By preventing reflux of the contents of the duodenum, the sphincter of Oddi prevents the accumulation of particulate matter and sludge in the bile ducts, reducing the risk of cholangitis.
Red represents a higher value (e.g. of temperature or the partial pressure of a gas) than blue so the property being transported in the channels flows from red to blue. In fish a countercurrent flow (lower diagram) of blood and water in the gills is used to extract oxygen from the environment. [6] [7] [8] All basal vertebrates breathe with gills.
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 endothelium provides a smooth surface for the flow of blood and regulates the movement of water and dissolved materials in the interstitial plasma between the blood and the tissues. The microcirculation contrasts with macrocirculation , which is the circulation of blood to and from the organs.
The smooth muscle of the blood vessels reacts to the stretching of the muscle by opening ion channels, which cause the muscle to depolarize, leading to muscle contraction. This significantly reduces the volume of blood able to pass through the lumen, which reduces blood flow through the blood vessel
Learn how muscle memory works, how long it takes to develop, and why it’s crucial for fitness. Plus, tips to train smarter and build strength and muscle faster.
T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.