Examples of oncotic pressure in the following topics:
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- Capillary fluid movement occurs as a result of diffusion (colloid osmotic pressure), transcytosis, and filtration.
- The movement of materials across the capillary wall is dependent on pressure and is bidirectional depending on the net filtration pressure derived from the four Starling forces.
- When moving from the bloodstream into the interstitium, bulk flow is termed filtration, which is favored by blood hydrostatic pressure and interstitial fluid oncotic pressure.
- When moving from the interstitium into the bloodstream, the process is termed reabsorption and is favored by blood oncotic pressure and interstitial fluid hydrostatic pressure.
- Modern evidence shows that in most cases, venular blood pressure exceeds the opposing pressure, thus maintaining a positive outward force.
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- This fluid is essentially plasma that leaks out of cardiovascular capillaries into the tissues due to the forces of hydrostatic or oncotic pressure.
- Lymph capillaries have a greater oncotic
pressure (a pulling pressure exerted by proteins in solution) than blood plasma due to the greater concentration of plasma proteins
in lymph.
- Additionally, the greater size of lymphatic capillaries compared to cardiovascular capillaries allows them to take more fluid proteins into lymph compared to plasma, which is the other reason for their greater levels of oncotic pressure.
- This also explains why lymph flows into the lymph capillaries easily, since fluid follows proteins that exert oncotic pressure.
- This moves lymph further along the system despite the fall in pressure that occurs when moving from the higher-pressure capillaries to the lower-pressure collecting vessels.
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- These proteins exert a force that pulls water towards them, which is called oncotic or osmotic pressure.
- Albumins also assist in transport of different materials, such as vitamins and certain molecules and drugs (e.g. bilirubin, fatty acids, and penicillin) due to the force exerted by their oncotic pressure.
- Plasma that is pulled into the tissues by albumin-exerted oncotic pressure becomes interstitial fluid.
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- Oncotic or colloid osmotic pressure is a form of osmotic pressure exerted by proteins in the blood plasma or interstitial fluid.
- Hydrostatic pressure is the force generated by the pressure of fluid within or outside of capillary on the capillary wall.
- Movement from the bloodstream into the interstitium is favored by blood hydrostatic pressure and interstitial fluid oncotic pressure.
- Alternatively, movement from the interstitium into the bloodstream is favored by blood oncotic pressure and interstitial fluid hydrostatic pressure.
- Describe hydrostatic pressure and osmotic pressure, the factors of capillary dynamics
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- Hydrostatic pressure is generated by the contractions of the heart during systole.
- The osmotic pressure drives water back into the vessels.
- At the arterial end of a vessel, the hydrostatic pressure is greater than the osmotic pressure, so the net movement favors water and other solutes being passed into the tissue fluid.
- At the venous end, the osmotic pressure is greater, so the net movement favors substances being passed back into the capillary.
- Oncotic pressure exerted by proteins in blood plasma tends to pull water into the circulatory system.
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- Water follows these proteins due to the force of oncotic pressure that the proteins exert.
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- Pressure is often measured as gauge pressure, which is defined as the absolute pressure minus the atmospheric pressure.
- Gauge pressure is a relative pressure measurement which measures pressure relative to atmospheric pressure and is defined as the absolute pressure minus the atmospheric pressure.
- Most pressure measuring equipment give the pressure of a system in terms of gauge pressure as opposed to absolute pressure.
- For example, tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute.
- Explain the relationship among absolute pressure, gauge pressure, and atmospheric pressure
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- Measurement of blood pressure includes systolic pressure during cardiac contraction and diastolic pressure during cardiac relaxation.
- Blood pressure is the pressure blood exerts on the arterial walls.
- These pressures, called segmental blood pressures, are used to evaluate blockage or arterial occlusion in a limb (for example, the ankle brachial pressure index).The difference between the systolic and diastolic pressure is called the pulse pressure.
- A blood pressure cuff and associated monitor used for determining systolic and diastolic pressures within an artery.
- Explain how blood pressure is measured and the ranges of blood pressure readings
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- Blood pressure is a vital sign reflecting the pressure exerted on blood vessels when blood is forced out of the heart during contraction.
- Blood pressure is the pressure that blood exerts on the wall of the blood vessels.
- Systolic pressure is thus the pressure that your heart emits when blood is forced out of the heart and diastolic pressure is the pressure exerted when the heart is relaxed.
- During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure.
- A normal blood pressure should be around 120/80, with the systolic pressure expressed first.
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- Gas pressures in the atmosphere and body determine gas exchange: both O2 and CO2 will flow from areas of high to low pressure.
- Each gas component of that mixture exerts a pressure.
- The pressure for an individual gas in the mixture is the partial pressure of that gas.
- The pressure of the water vapor in the lung does not change the pressure of the air, but it must be included in the partial pressure equation.
- For this calculation, the water pressure (47 mm Hg) is subtracted from the atmospheric pressure: 760 mm Hg 47 mm Hg = 713 mm Hg, and the partial pressure of oxygen is: (760 mm Hg 47 mm Hg) 0.21 = 150 mm Hg.