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Blood flows from the heart through arteries, which branch and narrow into arterioles, and then branch further into capillaries where nutrients and wastes are exchanged. The capillaries then join and widen to become venules , which in turn widen and converge to become veins , which then return blood back to the heart through the venae cavae .
Capillary bed Diagram of capillary network joining the arterial system with the venous system. The systemic circulation is a circuit loop that delivers oxygenated blood from the left heart to the rest of the body through the aorta.
Constriction of these sphincters reduces or shuts off blood flow through their respective capillary beds. This allows the blood to be diverted to elsewhere in the body. [2] Metarterioles exist in the mesenteric microcirculation, and the name was originally conceived only to define the "thoroughfare channels" between arterioles and venules. In ...
Blood flows out of the capillaries into the venules, which have little smooth muscle and are 10-200 μm. The blood flows from the venules into the veins. Metarterioles connect arterioles and capillaries. A tributary to the venules is known as a thoroughfare channel. [citation needed]
The sphincter can open and close the entrance to the capillary, by which contraction causes blood flow in a capillary to change as vasomotion occurs. [4] [unreliable source?] In some tissues, the entire capillary bed may be bypassed by blood flow through arteriovenous anastomoses or through preferential flow through metarterioles. [2]
Blood exits the glomerular capillaries by an efferent arteriole instead of a venule, as is seen in the majority of capillary systems (Fig. 4). [3] This provides tighter control over the blood flow through the glomerulus, since arterioles dilate and constrict more readily than venules, owing to their thick circular smooth muscle layer (tunica ...
The heart is the driver of the circulatory system, pumping blood through rhythmic contraction and relaxation. The rate of blood flow out of the heart (often expressed in L/min) is known as the cardiac output (CO). Blood being pumped out of the heart first enters the aorta, the largest artery of the body.
The human hepatic portal system delivers about three-fourths of the blood going to the liver.The final common pathway for transport of venous blood from spleen, pancreas, gallbladder and the abdominal portion of the gastrointestinal tract [2] (with the exception of the inferior part of the anal canal and sigmoid colon) is through the hepatic portal vein.