Key Takeaways Key Points Capillary exchange refers to the exchange of material from the blood into the tissues in the capillary. There are three mechanisms that facilitate capillary exchange: diffusion, transcytosis and bulk flow. Capillary dynamics are controlled by the four Starling forces. Oncotic pressure is a form of osmotic pressure exerted by proteins either in the blood plasma or interstitial fluid. Hydrostatic pressure is a force generated by the pressure of fluid on the capillary walls either by the blood plasma or interstitial fluid.
The net filtration pressure is the balance of the four Starling forces and determines the net flow of fluid across the capillary membrane. Key Terms proteinuria : Excessive protein in the urine, a condition which can alter the net filtration pressure altering flow of fluid across the capillary wall. Due to the pressure of the blood in the capillaries, blood hydrostatic pressure is greater than interstitial fluid hydrostatic pressure, promoting a net flow of fluid from the blood vessels into the interstitium.
However, because large plasma proteins, especially albumin, cannot easily cross through the capillary walls, their effect on the osmotic pressure of the capillary interiors will to some extent balance the tendency for fluid to leak from the capillaries.
In conditions where plasma proteins are reduced e. Transcytosis Transcytosis is a process by which molecules are transported into the capillaries.
Learning Objectives Describe the process of transcytosis in capillary exchange. Key Takeaways Key Points Transcytosis is the process by which various macromolecules are transported across the endothelium of the capillaries. Due to this function, transcytosis can be a convenient mechanism for pathogens to invade a tissue. Key Terms transcytosis : The process whereby macromolecules are transported across the interior of a cell via vesicles. Bulk Flow: Filtration and Reabsorption Capillary fluid movement occurs as a result of diffusion colloid osmotic pressure , transcytosis, and filtration.
Learning Objectives Explain the process of filtration and reabsorption in capillaries. Have thick muscular and elastic walls to pump and accommodate blood. Have thin walls - have less muscular tissue than arteries.
A type of supporting tissue called connective tissue provides strength. Have less connective tissue than arteries. The channel in the blood vessel that carries blood - the lumen - is narrow. That is why arteries have thick walls.
Hence the walls of arteries are thick to enable it to withstand the blood pressure. They are elastic, so that they can retain their original shape. Arteries are blood vessels responsible for carrying oxygen-rich blood away from the heart to the body.
Veins are blood vessels that carry blood low in oxygen from the body back to the heart for reoxygenation. Where does sugar enter the blood? How can you tell where sugar enters the blood? Sugar level increases when blood goes through the intestines. One of the major differences between arteries and veins is that the arteries carry oxygenated blood to all body parts, whereas veins carry the deoxygenated blood to the heart with the exception of pulmonary arteries and veins.
Superficial veins are those closer to the surface of the body, and have no corresponding arteries. Deep veins are deeper in the body and have corresponding arteries. Arteries carry blood away from the heart to the tissues of the body. Veins carry blood from the tissues of the body back to the heart. Arteries carry oxygenated blood expect pulmonary artery. Veins carry deoxygenated blood except pulmonary vein. Arteries have thick, elastic, muscular walls whereas veins have thin walls with few elastic fibres.
Arteries need these properties to give them the strength and elasticity needed to cope with the high pressure surges of oxygenated blood coming from the heart. Arteries have a much thicker wall to withstand the high pressure of blood flowing in them, whereas veins have a thinner wall so that they can be pressed flat against adjacent muscles, helping to move the blood.
Veins have valves, contrary to arteries, to prevent back-flow of blood flowing in them. What are the major structural and functional differences between arteries and veins? Functionally, Veins carry blood towards the heart, and arteries carry it towards.
Arteries are thicker due to a higher and more fluctuating blood pressure. Veins are thinner. Peripheral veins have valves to keep blood flowing in one direction toward the heart. Do arteries carry oxygenated or deoxygenated blood? The arteries have thicker smooth muscle and connective tissue than the veins to accommodate the higher pressure and speed of freshly-pumped blood.
Key Points Capillary exchange refers to the exchange of material from the blood into the tissues in the capillary. There are three mechanisms that facilitate capillary exchange: diffusion, transcytosis and bulk flow. Capillary dynamics are controlled by the four Starling forces. Oncotic pressure is a form of osmotic pressure exerted by proteins either in the blood plasma or interstitial fluid. Hydrostatic pressure is a force generated by the pressure of fluid on the capillary walls either by the blood plasma or interstitial fluid.
The net filtration pressure is the balance of the four Starling forces and determines the net flow of fluid across the capillary membrane.
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