أسئلة المحاضرة الـ 18 فسيولوجي (قبل التعديل)
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Questions and Answers

What is the primary factor that influences fluid movement from blood to interstitial fluid?

  • Capillary hydrostatic pressure (correct)
  • Plasma osmotic pressure
  • Interstitial fluid hydrostatic pressure
  • Interstitial fluid colloid pressure

How much fluid is typically drained by the lymphatic system daily?

  • 2 liters (correct)
  • 20 liters
  • 4 liters
  • 18 liters

Which principle describes the passage of fluid across the capillary membrane?

  • Bernoulli's equation
  • Fick's law
  • Ohm's law
  • Starling's principle (correct)

What is the total amount of fluid filtered at the arterial ends of capillaries each day?

<p>20 liters (C)</p> Signup and view all the answers

Which of the following factors does NOT influence fluid movement across capillaries?

<p>Oxygen diffusion rate (C)</p> Signup and view all the answers

What is the average capillary pressure at the arterial end?

<p>30 mmHg (C)</p> Signup and view all the answers

Which pressure is considered the main absorbing force in the capillary membrane?

<p>Capillary colloid osmotic pressure (D)</p> Signup and view all the answers

What is the total outward force at the venous end?

<p>21 mmHg (B)</p> Signup and view all the answers

What is the effect of interstitial fluid pressure at the venous end?

<p>It remains unchanged at 3 mmHg (C)</p> Signup and view all the answers

What is the average functional mean capillary pressure?

<p>17.3 mmHg (A)</p> Signup and view all the answers

Which factor contributes positively to interstitial fluid pressure?

<p>Donnan effect (D)</p> Signup and view all the answers

How does the interstitial fluid hydrostatic pressure affect fluid movement?

<p>It counteracts fluid movement to the interstitium (B)</p> Signup and view all the answers

In which tissue does the interstitial fluid pressure indicate a positive value?

<p>Kidney (C)</p> Signup and view all the answers

What is the net filtration pressure at the arterial end of capillaries?

<p>13 mmHg (D)</p> Signup and view all the answers

At the venous end of capillaries, what is the total force acting inward?

<p>28 mmHg (A)</p> Signup and view all the answers

Which value represents the mean effective capillary pressure?

<p>17.3 mmHg (C)</p> Signup and view all the answers

What happens to the majority of fluid at the venous end of capillaries?

<p>It flows into lymph vessels. (D)</p> Signup and view all the answers

Among the forces moving fluid, what is the value of plasma colloid osmotic pressure?

<p>28 mmHg (D)</p> Signup and view all the answers

What is the significance of interstitial fluid pressure in this context?

<p>It is negative and contributes to fluid movement. (D)</p> Signup and view all the answers

Which of the following represents the mean outward force calculated?

<p>28 mmHg (D)</p> Signup and view all the answers

What does a net outward force of 0.3 mmHg indicate?

<p>A state of equilibrium. (C)</p> Signup and view all the answers

Which of the following factors would increase the movement of fluid from blood to interstitial fluid?

<p>Decreased interstitial fluid hydrostatic pressure (A), Increased capillary hydrostatic pressure (D)</p> Signup and view all the answers

What is the total volume of fluid that remains in the bloodstream after filtration and reabsorption at the venous ends of capillaries?

<p>18 liters (C)</p> Signup and view all the answers

Which fluid dynamics principle states that the rate and direction of fluid movement is related to the sum of hydrostatic and osmotic forces?

<p>Starling's principle (D)</p> Signup and view all the answers

Which of the following factors would likely hinder the movement of fluid into the bloodstream from the interstitial fluid?

<p>Increased interstitial fluid hydrostatic pressure (C)</p> Signup and view all the answers

What role does the lymphatic system play in relation to interstitial fluid?

<p>It drains excess interstitial fluid to prevent swelling. (D)</p> Signup and view all the answers

What is the total outward force at the arterial end of capillaries?

<p>41 mmHg (D)</p> Signup and view all the answers

How much is the negative interstitial fluid pressure at the arterial end?

<p>3 mmHg (B)</p> Signup and view all the answers

Which of the following pressures is responsible for causing fluid to move inward through the capillary membrane?

<p>Plasma colloid osmotic pressure (C)</p> Signup and view all the answers

What is the average plasma colloid osmotic pressure at the venous end?

<p>28 mmHg (C)</p> Signup and view all the answers

Which of the following tissues is associated with a positive interstitial fluid pressure?

<p>Kidney (B)</p> Signup and view all the answers

What is the effective mean capillary pressure?

<p>17.3 mmHg (D)</p> Signup and view all the answers

At the venous end of capillaries, what is the total inward force calculated?

<p>21 mmHg (D)</p> Signup and view all the answers

Which factor contributes least to the outward movement of fluid through the capillary membrane?

<p>Plasma colloid osmotic pressure (C)</p> Signup and view all the answers

What pressure represents the primary inward force at both arterial and venous ends of the capillaries?

<p>Plasma colloid osmotic pressure (A)</p> Signup and view all the answers

What is the net filtration pressure at the venous end of the capillaries?

<p>7 mmHg (C)</p> Signup and view all the answers

How much fluid is reabsorbed by the venous capillaries relative to the amount filtered?

<p>9/10 of the filtered fluid (B)</p> Signup and view all the answers

What contributes to the mean effective capillary pressure within the circulation?

<p>Outward and inward forces averaged (D)</p> Signup and view all the answers

What is the contribution of negative interstitial fluid pressure to the total outward force calculation?

<p>It adds 3 mmHg. (B)</p> Signup and view all the answers

What is the implication of having a net outward force of 0.3 mmHg?

<p>Fluid movement favors outward flow. (C)</p> Signup and view all the answers

What is the role of lymphatics in the context of fluid movement in capillaries?

<p>They return excess interstitial fluid to circulation. (C)</p> Signup and view all the answers

Flashcards

Interstitium

The space between cells in the body, making up about 1/6 of tissues.

Interstitial fluid

Gel-like fluid found in the interstitium, constantly moving between blood and tissues.

Filtration

The movement of fluid across capillary membranes, driven by hydrostatic and osmotic pressure differences.

Starling's principle

The principle explaining fluid movement across capillaries, based on hydrostatic and osmotic forces, determining the direction and rate.

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Factors determining filtration

The main factors influencing fluid movement across capillaries, including pressure inside and outside the blood vessel, and the ability of blood to attract water.

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Capillary Hydrostatic Pressure (Pc)

The pressure within a capillary that pushes fluid outward, tending to filter fluid out of the capillary and into the interstitial space.

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Interstitial Fluid Hydrostatic Pressure (Pi)

The pressure of the fluid surrounding the capillary that pushes fluid inward, tending to draw fluid from the interstitial space back into the capillary.

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Plasma Colloid Osmotic Pressure (πc)

The pressure exerted by proteins dissolved in the blood plasma, drawing water into the capillary due to osmosis.

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Interstitial Fluid Colloid Osmotic Pressure (πi)

The pressure exerted by proteins dissolved in the interstitial fluid, drawing water out of the capillary due to osmosis.

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Net Filtration Pressure (Arterial End)

The overall force that drives fluid outward from the capillary at the arterial end.

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Net Filtration Pressure (Venous End)

The overall force that drives fluid inward toward the capillary at the venous end.

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Net Hydrostatic Pressure

The pressure difference between the hydrostatic pressure inside the capillary and the interstitial fluid hydrostatic pressure.

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Capillary Hydrostatic Pressure

The pressure exerted by the fluid within a capillary, pushing fluid outwards.

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Plasma Colloid Osmotic Pressure

The pressure exerted by the proteins in the blood, pulling fluid inwards.

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Net Filtration Pressure

The difference between the forces pushing fluid out and the forces pulling fluid in.

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Interstitial Fluid Pressure

The pressure exerted by the fluid in the spaces between cells, pushing fluid inwards.

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Interstitial Colloid Osmotic Pressure

The pressure exerted by the proteins in the interstitial fluid, pulling fluid outwards.

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Mean Effective Capillary Pressure

The average pressure within capillaries, combining arterial and venous pressures.

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Slight Disequilibrium

The condition where the net filtration pressure at the arterial end is slightly higher than the reabsorption pressure at the venous end, leading to a small amount of fluid leak into the interstitial space.

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Lymphatics

The lymphatic system collects excess fluid that was filtered out of the capillaries and returns it to the bloodstream.

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What is filtration in terms of fluid movement?

The movement of fluid across a capillary membrane, driven by differences in hydrostatic and osmotic pressures.

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What is Starling's principle?

The principle that explains how filtration occurs, stating that the rate and direction of fluid movement across a capillary is determined by the combined forces of hydrostatic and osmotic pressures.

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What is capillary hydrostatic pressure?

The pressure exerted by the fluid within a capillary, pushing fluid outwards.

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What is plasma colloid osmotic pressure?

The pressure exerted by proteins dissolved in the blood plasma, pulling water into the capillary due to osmosis.

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What is net filtration pressure?

The difference between the forces pushing fluid out of a capillary and the forces pulling fluid into the capillary; determines the direction and rate of fluid movement.

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Filtration Predominates (Arterial End)

Forces pushing fluid out of the capillary are stronger than the forces pulling it back in.

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Reabsorption Predominates (Venous End)

Forces pulling fluid back into the capillary are stronger than the forces pushing it out.

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Interstitial Fluid Hydrostatic Pressure

The pressure exerted by the fluid surrounding the capillary, pushing fluid INTO the capillary.

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Interstitial Fluid Colloid Osmotic Pressure

The pressure exerted by proteins dissolved in the interstitial fluid, pulling fluid OUT of the capillary.

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Study Notes

Physiology Lecture (18) - Interstitial Fluid and Filtration

  • Interstitial Fluid:

    • The space between cells, comprising about 1/6 of body tissue.
    • Gel-like fluid entrapped in the interstitium.
    • Body fluids continually move out of blood into it, and back.

  • Filtration:

    • Movement of body fluids across capillary membranes, driven by hydrostatic and osmotic pressure differences.

  • Starling's Principle:

    • The rate and direction of fluid movement are proportional to the algebraic sum of hydrostatic and osmotic forces.

  • Starling Equation:

    • Describes the net fluid flux across a capillary membrane.
      • Net fluid flux = Kf [(Pc - Pi) - σ(πc - πi)]
        • Kf = Filtration coefficient
        • Pc = Capillary hydrostatic pressure
        • Pi = Interstitial fluid hydrostatic pressure
        • σ = Reflection coefficient
        • πc = Capillary colloid osmotic pressure
        • πi = Interstitial fluid colloid osmotic pressure

  • Forces in Filtration:

    • Outward (Filtration) Forces:
      • Capillary hydrostatic pressure (30 mmHg at arterial end, 10 mmHg at venous end)
      • Net interstitial fluid pressure (-3 mmHg)
      • Negative interstitial fluid colloid osmotic pressure (8 mmHg)
    • Inward (Reabsorption) Forces:
      • Plasma colloid osmotic pressure (28 mmHg)

  • Capillary Hydrostatic Pressure (PC):

    • Pushes fluid out of capillaries, stronger at arterial end (30 mmHg).
    • Pushes fluid back into capillaries, weaker at venous end (10 mmHg)
    • Average effective capillary pressure is 17.3 mmHg

  • Interstitial Fluid Hydrostatic Pressure (Pi):

    • Fluid pressure in interstitial spaces.
    • Tends to draw fluid into the capillary, generally negative (-3 mmHg)

  • Plasma Colloid Osmotic Pressure (πc):

    • Osmotic pressure exerted by plasma proteins, strong and inward drawing force (28 mmHg).
    • 9 mmHg generated by plasma proteins, with added ionic contributions (Donnan effect)

  • Interstitial Fluid Colloid Osmotic Pressure (πi):

    • Osmotic pressure exerted by proteins in the interstitial fluid, pulling fluid into the interstitial space (8 mmHg).
    • Lower protein concentration in interstitial fluid
    • Average protein concentration is approximately 3 gm/100 ml interstitial fluid, generating an osmotic pressure of 8 mmHg for reabsorption.

  • Formation and Drainage of Interstitial Fluid:

    • 20 liters of fluid are filtered daily.
    • 18 liters are reabsorbed.
    • 2 liters are drained by the lymphatic system.

  • Dynamic of Flow Across Capillary Membrane:

    • The balance of forces determine the net filtration pressure.
    • At the arterial end, outward forces (41 mmHg) are greater than inward forces (28 mmHg), creating 13 mmHg of net filtration.
    • At the venous end, outward forces (21 mmHg) are less than inward forces (28 mmHg), creating 7 mmHg net reabsorption.

  • Starling's Equilibrium:

    • A state of near equilibrium where slight imbalances are handled by the lymphatic system.
    • Mean functional capillary pressure is about 17.3 mmHg.
    • The small imbalance (0.3 mmHg) leads to net filtration, essential for fluid return to the circulatory system.

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