Microcirculation Quiz: Capillary Fluid Exchange G. 16 - 1.5

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Questions and Answers

What is the primary factor that determines osmotic pressure?

  • The size of the dissolved molecules
  • The mass of the dissolved molecules
  • The type of dissolved molecules
  • The number of dissolved molecules (correct)

Which protein contributes the most to the total plasma colloid osmotic pressure?

  • Globulins
  • All contribute equally
  • Fibrinogen
  • Albumin (correct)

What is the approximate total plasma colloid osmotic pressure (Πp)?

  • 8 mm Hg
  • 28 mm Hg (correct)
  • 41 mm Hg
  • 30 mm Hg

What is the approximate contribution of globulins to the total plasma colloid osmotic pressure?

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

What is the approximate contribution of fibrinogen to the total plasma colloid osmotic pressure?

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

Which force is responsible for moving fluid outward from the arterial end of the capillary?

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

What is the approximate total outward force at the arterial end of the capillary?

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

What is the typical range of interstitial fluid pressure in the arterial ends of capillaries?

<p>30 to 40 mm Hg (D)</p> Signup and view all the answers

In which tissue does the glomerular capillary have the highest hydrostatic pressure?

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

What is the general rule regarding interstitial fluid pressure compared to the pressure surrounding the tissue?

<p>Interstitial pressure is usually a few millimeters of mercury lower than surrounding pressure. (D)</p> Signup and view all the answers

What is the average cerebrospinal fluid pressure in an animal lying on its side?

<p>10 mm Hg (C)</p> Signup and view all the answers

What is the average hydrostatic pressure in the peritubular capillaries of the kidneys?

<p>13 mm Hg (B)</p> Signup and view all the answers

How does the pressure in the interstitial fluid of most tissues compare to the pressure exerted by their encasements?

<p>It is always lower. (C)</p> Signup and view all the answers

What is the primary function of caveolins?

<p>Transport small molecules across the cell membrane (A)</p> Signup and view all the answers

Why are there discrepancies in interstitial fluid pressure measurements?

<p>All of the above. (D)</p> Signup and view all the answers

What are the small, oval windows present in the endothelial cells of the glomerular capillaries called?

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

Which of the following processes is NOT directly associated with the function of caveolae?

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

Which of the following is NOT a method for measuring interstitial fluid hydrostatic pressure?

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

What is the significance of caveolae in the transport of macromolecules?

<p>Caveolae facilitate the movement of macromolecules across the cell membrane through a process called transcytosis. (D)</p> Signup and view all the answers

According to the passage, what is the role of caveolae in the transport of plasma proteins?

<p>Caveolae engulf packets of plasma containing plasma proteins and move them through the endothelial cell. (B)</p> Signup and view all the answers

How does the intermittent flow of blood through capillaries differ from continuous flow?

<p>Intermittent flow is characterized by short bursts of blood flow, while continuous flow is a steady and constant flow. (D)</p> Signup and view all the answers

What is the key difference in the composition of the fluid that can pass through the glomerular capillaries compared to the fluid that passes through other capillaries?

<p>Glomerular capillaries allow the passage of only small molecules, while other capillaries allow larger molecules as well. (D)</p> Signup and view all the answers

What can we conclude about the role of the caveolae in the overall transport of substances through the endothelial cell?

<p>Caveolae work together with other transport mechanisms to facilitate the movement of substances through the endothelial cell. (B)</p> Signup and view all the answers

What is the primary mechanism that prevents backflow of lymph through the lymphatic capillaries?

<p>Overlapping edges of endothelial cells acting as valves (D)</p> Signup and view all the answers

How does fluid pressure within a lymphatic capillary affect the flow of lymph?

<p>Increased pressure causes the lymphatic capillary endothelial cells to contract, pushing lymph forward. (D)</p> Signup and view all the answers

What is the role of the lymphatic pump in the movement of lymph?

<p>The lymphatic pump is the primary driver of lymph flow, pushing lymph towards the venous circulation. (A)</p> Signup and view all the answers

Which of the following is NOT a factor that contributes to lymph flow?

<p>Blood pressure in the capillary network. (A)</p> Signup and view all the answers

What evidence suggests that contraction of the lymphatic capillary endothelial cells contributes to lymph pumping?

<p>The observation of rhythmic contraction in lymphatic capillaries in certain animal tissues. (A), The presence of actomyosin filaments within the lymphatic capillary endothelial cells. (B)</p> Signup and view all the answers

What is the primary function of the lymphatic capillaries?

<p>To collect interstitial fluid and return it to the blood circulation. (C)</p> Signup and view all the answers

Explain the mechanism of lymph flow through a lymphatic vessel.

<p>Lymph flows from the interstitial fluid into the lymphatic capillaries, is pushed forward by the lymphatic pump, and returns to the blood circulation through the veins. (C)</p> Signup and view all the answers

What is the relationship between interstitial fluid pressure and lymph flow?

<p>Higher interstitial fluid pressure promotes increased lymph flow. (D)</p> Signup and view all the answers

Which of the following structures is responsible for regulating blood flow into capillary beds?

<p>Precapillary sphincters (D)</p> Signup and view all the answers

What is the primary route for the diffusion of water-soluble substances across capillary walls?

<p>Intercellular clefts (A)</p> Signup and view all the answers

Which of the following is NOT a component of the microcirculation?

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

How does the structure of the venule differ from the arteriole?

<p>Venules have a thinner muscular coat. (A)</p> Signup and view all the answers

Which of the following substances are likely to diffuse easily through the intercellular clefts of capillaries?

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

What is the primary function of the metarteriole?

<p>To transport blood directly from arteries to veins (C)</p> Signup and view all the answers

Which of the following is NOT a factor that influences the rate of diffusion across the capillary wall?

<p>Presence of a transporter protein (D)</p> Signup and view all the answers

How do caveolae contribute to the function of capillaries?

<p>They facilitate the transport of larger molecules. (A)</p> Signup and view all the answers

What is the primary reason for the high protein concentration in thoracic duct lymph?

<p>The liver and intestines contribute a significant portion of lymph to the thoracic duct. (A)</p> Signup and view all the answers

What is the primary function of the anchoring filaments in lymphatic capillaries?

<p>They help to maintain the integrity of the capillary walls. (A)</p> Signup and view all the answers

Which of the following mechanisms allows large particles, such as bacteria, to enter the lymphatic capillaries?

<p>Passage through the flap valves between endothelial cells. (D)</p> Signup and view all the answers

How do the flap valves in lymphatic capillaries contribute to the unidirectional flow of lymph?

<p>They prevent backflow of lymph into the surrounding tissues. (C)</p> Signup and view all the answers

What is the typical protein concentration of thoracic duct lymph?

<p>3 to 5 g/dl (C)</p> Signup and view all the answers

Which of the following best describes the role of the lymphatic system in the absorption of fats?

<p>The lymphatic system is responsible for absorbing nearly all dietary fats. (A)</p> Signup and view all the answers

How does the lymphatic system contribute to the removal of bacteria from the body?

<p>As lymph flows through lymph nodes, bacteria are filtered and destroyed. (B)</p> Signup and view all the answers

What is the significance of the lymphatic system's ability to absorb high molecular weight substances?

<p>It makes it possible for proteins, which cannot be absorbed by blood capillaries, to re-enter the circulatory system. (B)</p> Signup and view all the answers

Flashcards

Caveolae

Small membrane invaginations believed to transport macromolecules across the cell membrane.

Caveolins

Proteins that interact with cholesterol and form caveolae through polymerization.

Endocytosis

Process where a cell engulfs material from outside by forming vesicles.

Transcytosis

Movement of macromolecules across a cell via vesicles.

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Fenestrae

Small oval windows in endothelial cells that allow selective passage of substances.

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Capillary Blood Flow

Blood usually flows intermittently through capillaries, turning on and off.

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Endothelial Cells

Cells that line blood vessels and have specialized functions like transport.

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Vesicular Channels

Channels formed by coalescing vesicles that allow passage through endothelial cells.

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Venules

Small blood vessels that collect blood from capillaries and lead to veins.

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Arterioles

Small blood vessels that regulate blood flow from arteries into capillaries.

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Capillaries

Tiny blood vessels where nutrient and gas exchange occurs between blood and tissues.

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Intercellular clefts

Small gaps between endothelial cells of capillaries allowing substance diffusion.

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Precapillary sphincters

Muscle fibers that control blood flow into capillaries.

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Diffusion in capillaries

The process through which solutes and water-soluble molecules pass through capillary walls.

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Arteriovenous bypass

A connection that allows blood to flow directly from arterioles to venules, bypassing capillaries.

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Interstitial fluid pressure

The pressure within the interstitial spaces of tissues, affecting fluid movement.

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Capillary hydrostatic pressure

Pressure exerted by blood within capillaries, varies by tissue type.

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Normal interstitial fluid pressure

Typically a few mm Hg negative compared to surrounding tissue pressure.

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Glomerular capillary pressure

Hydrostatic pressure in glomerular capillaries, averages around 60 mm Hg.

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Peritubular capillary pressure

Hydrostatic pressure in peritubular capillaries, averages about 13 mm Hg.

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Cerebrospinal fluid pressure

Pressure that surrounds the brain, averages about +10 mm Hg.

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Variability of pressures

Capillary pressures can vary significantly between different tissues.

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Measurement methods

Different techniques yield slightly different values for interstitial fluid pressure.

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Lymphatic Capillaries

Small vessels that collect lymphatic fluid from tissues.

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Collecting Lymphatics

Larger vessels that carry lymph fluid toward lymph nodes.

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Endothelial Cell Valves

Structures that ensure one-way flow of lymph in lymphatic capillaries.

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Lymphatic Pump

Automatic contraction of lymph vessels to move lymph.

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Actomyosin Filaments

Filaments in endothelial cells that help contract lymphatic capillaries.

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Rhythmic Contraction

Repeated contraction of lymphatic segments to propel lymph.

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Thoracic Duct

Largest lymphatic vessel that drains lymph into blood circulation.

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Protein Concentration in Lymph

Typically 3 to 5 g/dl in thoracic duct lymph, essential for nutrition.

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Anchoring Filaments

Strands that connect endothelial cells of lymphatic capillaries to surrounding tissue.

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Overlapping Endothelial Cells

Structure in lymphatic capillaries allowing interstitial fluid entry through flap valves.

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Lymph Nodes

Sites where lymph is filtered and particles like bacteria are destroyed.

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Fat Absorption

The lymphatic system absorbs almost all dietary fats through the intestinal lymph.

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Valves in Lymphatic Capillaries

Flap-like structures that prevent backflow of lymph once inside.

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Osmotic Pressure

Pressure caused by solute concentration in a solution.

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Colloid Osmotic Pressure

Pressure exerted by proteins in plasma, helping to keep fluid in the blood vessels.

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Albumin

A protein in plasma that contributes the most to osmotic pressure.

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Globulins

Proteins in plasma that contribute to colloid osmotic pressure.

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Fibrinogen

A protein in plasma that plays a minor role in osmotic pressure.

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Total Outward Force

Combined forces that move fluid out of capillaries to the interstitial space.

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Plasma Colloid Osmotic Pressure

Pressure that pulls fluid back into the capillaries from interstitial spaces.

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Study Notes

Microcirculation and Lymphatic System: Capillary Fluid Exchange, Interstitial Fluid, and Lymph Flow

  • The microcirculation's primary roles are nutrient transport to tissues and waste removal
  • Arterioles regulate blood flow to each tissue based on local conditions
  • Capillary walls are thin, permeable endothelial cells enabling quick exchange of water, nutrients, and waste products
  • The human body contains approximately 10 billion capillaries with a combined surface area of 500-700 square meters
  • Cells are typically within 20-30 µm of a capillary

Structure of the Microcirculation and Capillary System

  • Organ microcirculation is tailored to its specific needs
  • Nutrient arteries branch 6-8 times into arterioles (10-15 µm) before branching again into smaller arterioles (5-9 µm) that supply blood to capillaries
  • Arterioles are highly muscular, controlling diameter
  • Metarterioles, the terminal arterioles, lack a continuous muscular coat, but smooth muscle fibers are present at intervals
  • A precapillary sphincter regulates capillary entrance
  • Venules have weaker muscular walls than arterioles—despite the lower pressure, they can still contract
  • Metarterioles and precapillary sphincters respond directly to local tissue conditions (nutrients, metabolic byproducts, and hydrogen ions) to regulate blood flow

Structure of the Capillary Wall

  • Capillary walls consist of a single layer of endothelial cells and a thin basement membrane
  • Walls are about 0.5 µm thick
  • Internal diameters range from 4-9 µm, limiting blood cell passage

Pores in the Capillary Membrane

  • Intercellular clefts are passageways between endothelial cells, allowing passage
  • Width of clefts is 6-7 nanometers, smaller than many molecules
  • The cleft occupies a small fraction of the capillary wall, but allows rapid movement of water and other substances, essential for exchange

Flow of Blood in the Capillaries-Vasomotion

  • Blood flow is intermittent, not continuous, due to vasomotion (intermittent constriction of metarterioles & precapillary sphincters, sometimes arterioles)
  • Oxygen concentration in tissues is the primary regulator of vasomotion

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