hydrostatic pressure

Examples of hydrostatic pressure in the following topics:

• Capillary Dynamics

  • Hydrostatic and osmotic pressure are opposing factors that drive capillary dynamics.
  • 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.
  • 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.
  • Describe hydrostatic pressure and osmotic pressure, the factors of capillary dynamics

• Regulation of Glomerular Filtration Rate

  • GFR=Filtration Constant X (Hydrostatic Glomerulus Pressure–Hydrostatic Bowman's Capsule Pressure)–(Osmotic Glomerulus Pressure+Osmotic Bowman's Capsule Pressure)
  • Changes in either the hydrostatic or osmotic pressure in the glomerulus or Bowman's capsule will change GFR.
  • GFR is most sensitive to hydrostatic pressure changes within the glomerulus.
  • The Bowman's capsule space exerts hydrostatic pressure of its own that pushes against the glomerulus.
  • Increased Bowman's capsule hydrostatic pressure will decrease GFR, while decreased Bowman's capsule hydrostatic pressure will increase GFR.

• Movement of Fluid Among Compartments

  • 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.

• Bulk Flow: Filtration and Reabsorption

  • 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.

• High Pressure

  • Under very high hydrostatic pressure(HHP) of up to 700 MPa, water inactivates pathogens such as E. coli and Salmonella.
  • Under very high hydrostatic pressure of up to 700 MPa (100,000 psi), water inactivates pathogens such as Listeria, E. coli and Salmonella.
  • Around 1970, researchers renewed their efforts in studying bacterial spores after it was discovered that using moderate pressures was more effective than using higher pressures.
  • When subjected to moderate pressures, bacterial spores germinate, and the resulting spores are easily killed using pressure, heat, or ionizing radiation.
  • The pumps may apply pressure constantly or intermittently.

• Blood Pressure

  • Blood pressure is the pressure of the fluid (blood) against the walls of the blood vessels.
  • Fluid will move from areas of high to low hydrostatic pressures.
  • In the arteries, the hydrostatic pressure near the heart is very high.
  • The systolic pressure is defined as the peak pressure in the arteries during the cardiac cycle; the diastolic pressure is the lowest pressure at the resting phase of the cardiac cycle.
  • The blood pressure of the systole phase and the diastole phase gives the two readings for blood pressure .

• Measurements: Gauge Pressure and the Barometer

  • Barometers are devices used for measuring atmospheric and gauge pressure indirectly through the use of hydrostatic fluids.
  • Early barometers were used to measure atmospheric pressure through the use of hydrostatic fluids.
  • In theory, a hydrostatic barometer can be placed in a closed system to measure the absolute pressure and the gauge pressure of the system by subtracting the atmospheric pressure.
  • Such pressure measuring devices are more practical than hydrostatic barometers for measuring system pressures.
  • The concept of determining pressure using the fluid height in a hydrostatic column barometer

• Types of Skeletal Systems

  • A hydrostatic skeleton is one formed by a fluid-filled compartment within the body: the coelom.
  • This compartment is under hydrostatic pressure because of the fluid and supports the other organs of the organism.
  • Movement in a hydrostatic skeleton is provided by muscles that surround the coelom.
  • The muscles in a hydrostatic skeleton contract to change the shape of the coelom; the pressure of the fluid in the coelom produces movement.
  • The skeleton of the red-knobbed sea star (Protoreaster linckii) is an example of a hydrostatic skeleton.

• Gauge Pressure and Atmospheric Pressure

  • Pressure is often measured as gauge pressure, which is defined as the absolute pressure minus the atmospheric pressure.
  • Atmospheric pressure is due to the force of the molecules in the atmosphere and is a case of hydrostatic 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.

• Introduction to Blood Pressure

  • 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.
  • Gravity affects blood pressure via hydrostatic forces (for example, during standing) Valves in veins, breathing, and pumping from contraction of skeletal muscles also influence venous blood pressure.