Physiology Week 5

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Questions and Answers

What is the primary consequence when interstitial fluid pressure exceeds approximately 2 mmHg?

Decreased lymphatic flow

Edema formation (correct)

Increased blood pressure

Enhanced reabsorption in capillaries

Which of the following is NOT a factor responsible for lymphatic pumping?

External compression

Skeletal muscle contraction

Contraction of lymph vessel walls

Increased interstitial fluid pressure (correct)

Which condition is primarily associated with increased fluid filtration leading to edema?

Blood clot formation

Heart failure

Histamine release (correct)

Mastectomy

What is the mechanism by which pitting edema differs from non-pitting edema?

Pitting edema is related to tissue compliance and fluid accumulation. Signup and view all the answers

What physiological event occurs when the smooth muscle in lymphatic vessels is stretched?

Automatic contraction of the vessel walls Signup and view all the answers

Which of the following clinical examples does NOT represent decreased fluid reabsorption?

Increased arterial pulsation Signup and view all the answers

Which situation could contribute to the development of edema due to decreased lymphatic flow?

Tumors obstructing lymphatic pathways Signup and view all the answers

In which scenario does increased vascular permeability most likely lead to edema?

Allergic reactions Signup and view all the answers

What is the primary characteristic that defines pitting edema?

The area remains indented after pressure is applied and released. Signup and view all the answers

How does the distensibility of veins compare to that of arteries?

Veins expand more for a given change in blood pressure than arteries. Signup and view all the answers

What effect do small changes in blood volume have on arterial pressure?

They cause a significant increase in arterial pressure. Signup and view all the answers

During diastole, what is the primary function of aortic recoil?

To apply inward pressure against the blood to facilitate circulation. Signup and view all the answers

What anatomical feature of veins contributes to their higher distensibility compared to arteries?

Thinner and more flexible walls. Signup and view all the answers

Which of the following accurately describes the distribution of blood volume in the body?

Veins contain a larger volume of blood compared to arteries. Signup and view all the answers

When there is an increase in blood volume, how does this impact venous pressure?

There is little effect on venous pressure. Signup and view all the answers

What occurs in the arterial system when the volume of blood is significantly increased?

Arterial pressure experiences a considerable rise. Signup and view all the answers

What role does the elastic recoil of the aorta play in the cardiovascular system?

It maintains blood flow even when the heart is relaxing. Signup and view all the answers

How is pulse pressure defined?

The difference between systolic arterial blood pressure and diastolic arterial blood pressure. Signup and view all the answers

Which condition is indicated by a high pulse pressure?

A bounding pulse. Signup and view all the answers

Which factor is MOST likely to lead to a low pulse pressure?

A reduction in stroke volume. Signup and view all the answers

What is the effect of increased stroke volume on pulse pressure?

It increases pulse pressure. Signup and view all the answers

If a person's blood pressure is 140/80 mmHg, what is their pulse pressure?

60 mmHg Signup and view all the answers

How does noncompliance of the arterial tree influence pulse pressure?

It increases arterial pressure. Signup and view all the answers

What could a thready pulse indicate in a clinical scenario?

Low systolic pressure. Signup and view all the answers

What percentage of the fluid filtered from capillaries is typically reabsorbed back into capillaries?

90% Signup and view all the answers

Which substance has the most significant effect on oncotic pressure in blood?

Albumin Signup and view all the answers

How does fluid move from the interstitial compartment into the intracellular compartment?

Via direct osmosis related to ion concentration Signup and view all the answers

Which of the following best describes the role of plasma proteins in fluid movement?

They create osmotic pressure that pulls fluid back to the plasma. Signup and view all the answers

What is the fate of the remaining 10% of the fluid that is filtered out of capillaries?

It is returned to circulation via lymphatic vessels. Signup and view all the answers

Which statement is true regarding the influence of electrolytes on fluid movement?

Electrolyte concentration gradients significantly affect fluid movement. Signup and view all the answers

What happens to fluid movement when there is liver dysfunction affecting albumin levels?

Colloid osmotic pressure decreases, influencing fluid movement. Signup and view all the answers

Which of the following statements about Starling's forces is incorrect?

Plasma proteins do not play a role in these forces. Signup and view all the answers

What is the reason for the higher plasma colloid osmotic pressure at the venous end of the capillary?

Proteins are more concentrated due to fluid being pushed out. Signup and view all the answers

What effect does increased arterial pressure have on net filtration?

Increases capillary hydrostatic pressure, leading to greater net filtration. Signup and view all the answers

How does increased venous pressure affect fluid movement in the capillaries?

Reduces the ability for fluid to return from the interstitium into capillaries. Signup and view all the answers

What percentage of fluid filtered out at the arterial end of the capillaries is typically reabsorbed at the venous end?

Typically 90% Signup and view all the answers

What happens to interstitial fluid pressure when fluid is pushed out of the capillaries?

It increases due to higher fluid volume. Signup and view all the answers

Which of the following best describes the fluid dynamics at the venous end of a capillary?

High plasma colloid osmotic pressure, along with increased interstitial pressure, drives fluid into the capillaries. Signup and view all the answers

What is the main consequence of filtration exceeding reabsorption in the capillary system?

Potential edema due to excess interstitial fluid. Signup and view all the answers

What role do proteins play in plasma colloid osmotic pressure at the venous end of the capillary?

They create a pull factor to reabsorb fluid into the capillaries. Signup and view all the answers

Study Notes

Pulse Pressure

Pulse pressure is the difference between systolic and diastolic blood pressure (SBP - DBP)
A high pulse pressure (bounding pulse) can indicate a large difference between systolic and diastolic pressure, but doesn't specify the reason.
- Examples include a healthy exercise blood pressure, hypertension, or a normal systolic pressure with a low diastolic pressure.
A low pulse pressure (thready pulse) is often due to a low systolic pressure. It also doesn't indicate the reason, similar to a bounding pulse.

Factors Affecting Arterial Pulse Pressure

Stroke volume: Higher stroke volume leads to greater pressure fluctuations.
- Stroke volume is influenced by cardiac contractility and afterload.
Compliance of the arterial tree: Low compliance (stiffness) increases arterial pressure.

Fluid Movement Between Compartments

Vascular and Interstitial: Fluid (water and electrolytes) is filtered from capillaries into the interstitial fluid and reabsorbed back into the capillaries.
- About 90% of the filtered fluid is reabsorbed, with the remaining 10% returning via lymphatic vessels.
- Starling's forces govern this movement. Electrolytes don't significantly influence fluid movement between these compartments.
Interstitial and Intracellular: Fluid and electrolytes move across interstitial fluid and cell membranes via channels and transporters.
- Electrolyte concentration gradient influences the direction of movement.
- Water movement is dependent on cell osmolarity.

Fluid Filtration

Plasma Proteins: Plasma proteins contribute to osmotic (oncotic) pressure.
- They don't diffuse through capillaries, creating a "pulling" force that draws fluid from the interstitium back into the plasma.
- Albumin accounts for 80% of colloid osmotic pressure.
Starling Forces: Four forces govern fluid movement:
- Capillary hydrostatic pressure (pushes fluid out)
- Interstitial hydrostatic pressure (pushes fluid in)
- Capillary osmotic pressure (pulls fluid in)
- Interstitial osmotic pressure (pulls fluid out)
Capillary Hydrostatic Pressure and Filtration: Increased arterial pressure leads to increased capillary hydrostatic pressure and greater filtration.
Venous Pressure and Reabsorption: Increased venous pressure reduces fluid reabsorption and increases net filtration.
Lymphatic Circulation: Under normal conditions, approximately 90% of filtered fluid is reabsorbed at the venous end of the capillaries, with the remaining 10% entering the lymphatic system for circulation.

Lymphatic System

Lymph Flow: Increased interstitial fluid volume raises interstitial pressure, leading to higher lymph flow until the lymphatic system reaches its maximum capacity.
- Excess fluid accumulation results in edema.
Lymphatic Pumping: Lymphatic pumping mechanisms include:
- Contraction of lymph vessel walls (smooth muscle)
- Rhythmic compression of lymphatic vessels (skeletal muscle contraction, movement, arterial pulsation, external compression)

Edema

Causes: Extracellular edema can be caused by:
- Increased fluid filtration: Increased vascular permeability due to factors like histamine release, inflammation, or capillary damage.
- Decreased fluid reabsorption: Increased venous resistance (blood clots, heart failure, external compression) or slowed/stopped lymphatic flow (tumor blockage, surgery, parasitic infections).
Pitting vs Non-pitting Edema:
- Pitting edema: Excess interstitial fluid accumulates, causing the gel-like structure of the interstitium to transform into free fluid.
- Non-pitting edema: Fluid remains bound to the interstitial matrix, resulting in a solid-like consistency.

Vascular Function

Distensibility Differences: Arteries/arterioles have thicker smooth muscle layers than veins/venules.
- This makes veins more distensible than arteries, allowing them to expand more for a given pressure.
- Veins serve as blood reservoirs.
Volume and Pressure Relationship:
- Arterial system: Small changes in volume significantly affect pressure.
- Venous system: Large changes in volume have a minimal effect on pressure.
Aortic Distensibility and Circulation: The aorta stretches during systole to accommodate blood.
- During diastole, the aorta recoils, creating an inward pressure that drives blood forward throughout the systemic circulation.
- The aortic valve prevents blood from backflow into the heart.

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Description

This quiz explores the concept of pulse pressure and its implications in cardiovascular health. Understand the factors affecting arterial pulse pressure, including stroke volume and arterial compliance, as well as the significance of fluid movement between vascular and interstitial compartments. Test your knowledge of these critical physiological concepts.