Does higher water potential always mean hydrostatic pressure? and blood plasma q

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jazz_xox_
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Just checking that a high water potential means higher hydrostatic pressure?
I did a question asking why less proteins in the blood plasma means more tissue fluid formed- the answer was higher water potential in blood plasma means that more tissue fluid formed- is this because of a high hydrostatic pressure and a larger overall outward pressure?

Also, how would you differentiate between blood and blood plasma on a picture, and what are the different roles of blood and blood plasma in the formation of tissue fluid?

Thanks
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Jpw1097
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(Original post by jazz_xox_)
Just checking that a high water potential means higher hydrostatic pressure?
I did a question asking why less proteins in the blood plasma means more tissue fluid formed- the answer was higher water potential in blood plasma means that more tissue fluid formed- is this because of a high hydrostatic pressure and a larger overall outward pressure?

Also, how would you differentiate between blood and blood plasma on a picture, and what are the different roles of blood and blood plasma in the formation of tissue fluid?

Thanks
Water potential refers to the solute concentration, or how 'salty' the solution is, with water having the highest water potential of 0 kPa, everything else has a negative water potential. Hydrostatic pressure is the force exerted on the walls of the vessel/container, per unit area.
Tissue fluid (or interstitial fluid) is formed when plasma (minus large plasma proteins) moves out of the blood in the capillary. The amount of fluid that moves out of the capillary into the tissue depends on the hydrostatic pressure of the blood and the interstitial space, as well as the water potential of the blood plasma and the interstitial fluid. A higher hydrostatic pressure in the blood (or simply, blood pressure) causes more fluid to move out of the capillary into the tissue, and so more tissue fluid is formed. A higher hydrostatic pressure in the tissue decreases the pressure gradient across the capillary, and so less tissue fluid is formed. A higher water potential in the blood plasma (e.g. less protein) causes more fluid to leave the capillary by osmosis (fluid moves down its 'water potential gradient', and so more tissue fluid is formed - it has nothing to do with hydrostatic pressure. In fact, low protein in the blood would cause the hydrostatic pressure to decrease because more fluid is leaving the circulation and forming tissue fluid, so less fluid is in the circulation. Blood has 3 compontents: red blood cells (45%), plasma (which contains dissolved carbon dioxide and oxygen, antibodies, nutrients, ions, plasma proteins, amino acids, clotting factors, hormones, etc.) (55%), and the 'buffy coat' (~1%) which is made up of platelets and white blood cells.
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jazz_xox_
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(Original post by Jpw1097)
Water potential refers to the solute concentration, or how 'salty' the solution is, with water having the highest water potential of 0 kPa, everything else has a negative water potential. Hydrostatic pressure is the force exerted on the walls of the vessel/container, per unit area.
Tissue fluid (or interstitial fluid) is formed when plasma (minus large plasma proteins) moves out of the blood in the capillary. The amount of fluid that moves out of the capillary into the tissue depends on the hydrostatic pressure of the blood and the interstitial space, as well as the water potential of the blood plasma and the interstitial fluid. A higher hydrostatic pressure in the blood (or simply, blood pressure) causes more fluid to move out of the capillary into the tissue, and so more tissue fluid is formed. A higher hydrostatic pressure in the tissue decreases the pressure gradient across the capillary, and so less tissue fluid is formed. A higher water potential in the blood plasma (e.g. less protein) causes more fluid to leave the capillary by osmosis (fluid moves down its 'water potential gradient', and so more tissue fluid is formed - it has nothing to do with hydrostatic pressure. In fact, low protein in the blood would cause the hydrostatic pressure to decrease because more fluid is leaving the circulation and forming tissue fluid, so less fluid is in the circulation. Blood has 3 compontents: red blood cells (45%), plasma (which contains dissolved carbon dioxide and oxygen, antibodies, nutrients, ions, plasma proteins, amino acids, clotting factors, hormones, etc.) (55%), and the 'buffy coat' (~1%) which is made up of platelets and white blood cells.
Thank you so much! So in the case of having a high water potential in the blood plasma, tissue fluid forms because of this water potential? Would it only be water moving out of the capillaries in this case, or the small proteins too (although these wouldn't move down the WP gradient?)

Also, is it the movement of fluid into the spaces around cells that forms tissue fluid? And is there tissue fluid already there (so tissue fluid moving into already present tissue fluid?)

Thanks again and sorry for using 'tissue fluid' so many times in the last paragraph
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Jpw1097
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(Original post by jazz_xox_)
Thank you so much! So in the case of having a high water potential in the blood plasma, tissue fluid forms because of this water potential? Would it only be water moving out of the capillaries in this case, or the small proteins too (although these wouldn't move down the WP gradient?)

Also, is it the movement of fluid into the spaces around cells that forms tissue fluid? And is there tissue fluid already there (so tissue fluid moving into already present tissue fluid?)

Thanks again and sorry for using 'tissue fluid' so many times in the last paragraph
Yes, the amount of tissue fluid formed depends on the hydrostatic pressure gradient and the water potential gradient. No, essentially all components of the plasma except large plasma proteins (such as albumin) form the tissue fluid. Tissue fluid bathes the cells/tissues and provides them with oxygen and nutrients including glucose, lipids, amino acids, small proteins, and also removes waste products such as carbon dioxide. Yes, the tissues are constantly bathed with tissue fluid. Tissue fluid is always being formed, and at the same time, tissue fluid is also being removed from the tissues via the lymphatic system, so although tissue fluid is always being formed and removed, the overall amount of tissue fluid remains relatively constant (unless there is some blockage in the lymphatic vessels, causing lymphoedema).
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