MBBS1 FPP: Flow and Pressure

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Questions and Answers

What primarily enables the transport of oxygen and nutrients in complex multicellular organisms?

Diffusion alone

Muscle contractions

Simple cellular transport mechanisms

A circulatory system (correct)

Which law describes the relationship between flow, pressure difference, and resistance in fluid dynamics?

Darcy's Law (correct)

Archimedes' Principle

Newton's Law of Gravitation

Bernoulli's Principle

In terms of flow properties, how do laminar and turbulent flows differ?

Turbulent flow occurs only in very small vessels

Laminar flow has higher resistance than turbulent flow

Laminar flow is more efficient in transporting fluids (correct)

Turbulent flow is characterized by smooth, parallel layers

What is the effect of tubes arranged in series on total resistance compared to tubes arranged in parallel?

Parallel arrangement reduces total resistance Signup and view all the answers

How many beats does the human heart approximately make in a lifetime?

250 million beats Signup and view all the answers

What is the primary role of the cardiovascular system beyond transportation of substances?

To regulate the delivery of substances Signup and view all the answers

What is the primary factor that influences the permeability of a substance?

Physical properties of the diffusion barrier Signup and view all the answers

According to Darcy’s Law, what happens to flow if the resistance to flow increases?

Flow decreases proportionally Signup and view all the answers

Which of the following relationships between vessel radius and flow rate is correct?

Flow is proportional to the fourth power of the radius Signup and view all the answers

In the context of Poiseuille’s Law, what does a small radius of the vessel significantly affect?

Both resistance and flow Signup and view all the answers

Which of the following correctly describes the relationship between pressure difference and flow?

Flow is directly proportional to pressure difference and inversely proportional to resistance Signup and view all the answers

What is implied when the resistance to flow is said to be proportional to the fourth power of the radius?

Resistance decreases rapidly with increasing radius Signup and view all the answers

What is the effect of a 20% reduction in radius on resistance and flow?

60% increase in resistance and 60% reduction in flow Signup and view all the answers

Which stimuli are primarily responsible for vasoconstriction?

Both B and C Signup and view all the answers

How does blood viscosity affect resistance to flow?

Higher viscosity increases flow resistance Signup and view all the answers

What accounts for the non-Newtonian behavior of blood?

Presence of various blood cells and proteins Signup and view all the answers

What occurs during vasodilation?

Increased radius and reduced resistance Signup and view all the answers

Which of the following statements about blood is true?

Blood is 3-4 times thicker than water Signup and view all the answers

Which factor does NOT directly influence the rate of diffusion according to Fick's Law?

Ambient temperature of the environment Signup and view all the answers

What role does the square root of the molecular weight play in the rate of diffusion?

It inversely affects the rate of diffusion. Signup and view all the answers

What primarily drives the diffusion process in gases according to the content?

The concentration or partial pressure difference Signup and view all the answers

How does an increase in thickness of the diffusion barrier affect the rate of diffusion?

It decreases the rate of diffusion. Signup and view all the answers

What is the role of solubility in the rate of diffusion?

Higher solubility increases the diffusion rate. Signup and view all the answers

According to Fick’s Law, which equation correctly represents the rate of diffusion?

Rate of diffusion = (P1-P2) x A x solubility x √Mol.Wt. Signup and view all the answers

What effect does increased blood flow have on the diffusion of gases?

It enhances the rate of diffusion by quickly moving gases away from the barrier. Signup and view all the answers

Which of the following best describes the effect of surface area on the diffusion of substances?

Increased surface area enhances diffusion rates. Signup and view all the answers

What phenomenon describes the alignment of cells in the fastest-moving fluid?

Axial streaming Signup and view all the answers

How does the size of red blood cells relative to capillaries affect viscosity?

It decreases viscosity as the cells slip through easily Signup and view all the answers

What is the primary consequence of turbulence in blood flow?

Significant increase in flow resistance Signup and view all the answers

What condition can result from very high viscosity due to an increased red cell count?

Increased total peripheral resistance Signup and view all the answers

What effect can high velocity blood flow due to narrowed heart valves have?

It can result in murmurs Signup and view all the answers

What is the Fåhraeus-Lindqvist effect primarily associated with?

Reducing viscosity in small vessels Signup and view all the answers

Which factor is most likely to cause turbulence in fluid flow within tubes?

Sharp edges and high flow velocity Signup and view all the answers

What is one potential consequence of turbulence in airways?

Induction of wheezes Signup and view all the answers

Study Notes

Overview of the Cardiovascular System

Circulatory systems are crucial for transporting oxygen, nutrients, and waste products in multicellular organisms.
Diffusion alone is inadequate for complex organisms; bulk flow is needed for efficient transport.
Regulation of blood flow is essential for homeostasis in response to environmental changes.

Key Principles of Flow and Pressure

Flow through tubes is influenced by:
- Pressure differences and tube calibre.
- Resistance to flow and fluid viscosity.
Darcy's Law: Flow is proportional to pressure difference (P1 - P2) and inversely proportional to resistance (R).
Poiseuille's Law defines resistance: R = (8VL) / (πr⁴).

Types of Flow

Laminar flow: Fluid moves smoothly in parallel layers; affected by viscous drag and tube diameter.
Turbulent flow: Disrupted flow due to high velocity, sharp edges, or abrupt changes; significantly increases resistance.

Factors Affecting Resistance

Vessel radius has a dramatic impact: Resistance is inversely proportional to the fourth power of radius.
A small radius change can lead to substantial changes in resistance and flow rates.
Arterioles can change radius via:
- Vasoconstriction (increases resistance) through stimuli like noradrenaline and angiotensin II.
- Vasodilation (decreases resistance) through stimuli such as adrenaline and histamine.

Diffusion and Fick’s Law

Fick's Law of diffusion states that the rate depends on:
- Area of diffusion (A), thickness of barrier (T), and concentration difference (C1 - C2).
- Solubility and molecular weight of the substance also play roles.
Diffusion is slow over large distances; hence, adequate flow is necessary to transport substances.

Characteristics of Blood Flow

Blood viscosity is significantly higher than water due to red cell mass and plasma proteins; it is a non-Newtonian fluid.
In small vessels, axial streaming reduces effective viscosity, enhancing flow.
High red cell counts can increase total peripheral resistance (TPR) leading to hypertension.

Implications of Turbulence

Turbulence arises from high velocity flow, sharp edges, and branch points.
It escalates resistance and may cause murmurs in blood flow or wheezing in airways.
Disrupted flow can result in vessel wall damage and trigger clotting processes.

Distensible vs. Rigid Tubes

Flexible and distensible vessels exhibit different flow dynamics compared to rigid tubes.
Myogenic tone in blood vessels contributes to overall regulation of flow and pressure management.

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Description

This quiz explores the fundamental concepts of flow and pressure as they relate to the cardiovascular system. It focuses on factors influencing flow through tubes, including pressure differences, tube calibre, resistance, and viscosity. Test your understanding of these critical principles.