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Blood vessels function to transport blood to an animal's body tissues. In general, arteries and arterioles transport oxygenated blood from the lungs to the body and its organs, and veins and venules transport deoxygenated blood from the body to the lungs. Blood vessels also circulate blood throughout the circulatory system.
Approximately, seven percent of the body's blood is in the capillaries which continuously exchange substances with the liquid outside these blood vessels, called interstitial fluid. This dynamic displacement of materials between the interstitial fluid and the blood is named capillary exchange. [ 5 ]
The circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. [ 1 ] [ 2 ] It includes the cardiovascular system , or vascular system , that consists of the heart and blood vessels (from Greek kardia meaning heart , and from Latin ...
A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the innermost layer of an artery or vein), consisting of a thin wall of simple squamous endothelial cells. [2]
The majority of exchange through the peritubular capillaries occurs because of chemical gradients osmosis and hydrostatic pressure. Movement of water into the peritubular capillaries is due to the loss of water from the glomerulus during filtration, which increases the colloid osmotic pressure of the blood.
The ECF can also be seen as having two components – plasma and lymph as a delivery system, and interstitial fluid for water and solute exchange with the cells. [6] The extracellular fluid, in particular the interstitial fluid, constitutes the body's internal environment that bathes all of the cells in the body.
The post-capillary venules are exchange vessels whose ultra-thin walls allow the ready diffusion of molecules from the capillaries. [10] The return of blood to the heart is assisted by the action of the muscle pump, and by the thoracic pump action of breathing during respiration. Standing or sitting for a prolonged period of time can cause low ...
The higher supply of oxygen allows the teleost retina to be thick and have few blood vessels thereby increasing its sensitivity to light. [10] In addition to raising the P O 2 {\displaystyle {P_{\rm {O_{2}}}}} , the choroid rete has evolved to raise the temperature of the eye in some teleosts and sharks .