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Countercurrent exchange means the flow of water over the gills is in the opposite direction to the flow of blood through the capillaries in the lamellae. The effect of this is that the blood flowing in the capillaries always encounters water with a higher oxygen concentration, allowing diffusion to occur all the way along the lamellae.
Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.
The primary function of perfusion is the efficient removal of cellular waste and nutrition supply during gas exchange. Perfusion occurs during heart contraction when the oxygenated blood is pumped into the arteries. The arteries deliver the blood to the capillary bed of the tissues, where the oxygen is removed by diffusion. [7] Oxygen in the ...
The term capillary exchange refers to all exchanges at microcirculatory level, most of which occurs in the capillaries. Sites where material exchange occurs between the blood and tissues are the capillaries, which branch out to increase the swap area, minimize the diffusion distance as well as maximize the surface area and the exchange time. [4]
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 acini are the basic units of respiration, with gas exchange taking place in all the alveoli present. [6] The alveolar membrane is the gas exchange surface, surrounded by a network of capillaries. Oxygen is diffused across the membrane into the capillaries and carbon dioxide is released from the capillaries into the alveoli to be breathed ...
Lymphatic capillaries are slightly larger in diameter than blood capillaries, and have closed ends (unlike the loop structure of blood capillaries). Lymph capillaries are strategically placed among the blood-related capillaries in order to have efficient and effective uptake from the interstitial fluid during capillary exchange.
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.