Hemodynamics of Blood Flow in Circulatory System

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Questions and Answers

What describes laminar blood flow?

Flow is always turbulent regardless of velocity.

Velocity changes gradually from outer to inner layers. (correct)

Laminar flow is characterized by loud sounds and eddies.

It occurs only in larger blood vessels.

Which factors influence the Reynolds number?

Sound frequency, pressure exerted, temperature of blood.

Density of blood, velocity of blood flow, diameter of the vessel. (correct)

Length of the blood vessel, blood color, electrical conduction.

Viscosity of blood, surface tension, elasticity of blood vessel.

What is indicated by a Reynolds number greater than 3000?

Turbulence is almost always present. (correct)

Endothelial damage is unlikely.

Flow is laminar and silent.

Blood flow is smooth and regular.

Which characteristic is typical of turbulent blood flow?

Formation of eddies in various directions. Signup and view all the answers

At what Reynolds number is flow usually not turbulent?

Re < 2000 Signup and view all the answers

Which scenario is likely to produce turbulent blood flow?

Blood ejecting from the heart during systole at high velocity. Signup and view all the answers

What is the significance of Laplace's law in the circulatory system?

It relates wall tension to radius and pressure in blood vessels. Signup and view all the answers

Which of the following is a consequence of turbulent blood flow?

Endothelial damage leading to atherosclerosis. Signup and view all the answers

What is the primary purpose of the slow velocity of blood flow in capillaries?

To allow for nutrient and waste exchange Signup and view all the answers

According to the law of Laplace, what happens when the radius of a cardiac chamber increases?

More tension must be developed for a given pressure Signup and view all the answers

How does narrowing of a vessel due to atherosclerosis affect blood flow velocity?

Velocity increases as potential energy decreases Signup and view all the answers

Which statement about the aorta compared to capillaries is true regarding blood velocity?

Aorta has a higher velocity than capillaries Signup and view all the answers

What does the total energy in a blood vessel consist of according to the Bernoulli principle?

Kinetic and potential energy Signup and view all the answers

What effect does the small radius of capillaries have on wall tension?

It decreases wall tension, allowing withstanding high pressures Signup and view all the answers

What is the primary reason for the increased velocity of blood flow as it re-enters the heart through veins?

Total cross-sectional area is reduced Signup and view all the answers

Which of the following best describes the effect of resistance in the arterial system according to Bernoulli's principle?

It leads to energy dissipation as heat Signup and view all the answers

What is the primary role of aortic compliance during systole?

To stretch the wall of the aorta and absorb excess energy Signup and view all the answers

What function does the elastic recoil of the aorta have during diastole?

It acts as a second pump to maintain blood flow Signup and view all the answers

Which of the following is a direct consequence of decreased aortic elasticity?

Increased pulse pressure Signup and view all the answers

How is velocity defined in the context of blood flow?

The speed at which blood flows per unit of time Signup and view all the answers

What happens to blood flow velocity when total cross-sectional area decreases?

Velocity increases Signup and view all the answers

Which statement accurately describes the relationship between flow and total cross-sectional area?

Flow is inversely proportional to total cross-sectional area Signup and view all the answers

What is the typical cardiac output in liters per minute through the circulatory system?

5 L/min Signup and view all the answers

Which of the following correctly describes the distinction between flow and velocity?

Flow is volume per unit time; velocity is displacement per unit time Signup and view all the answers

What happens to a blood vessel when the transmural pressure is negative?

The vessel collapses and flow stops. Signup and view all the answers

How is vascular compliance defined?

The amount by which a vessel increases in volume for a given increase in distending pressure. Signup and view all the answers

What is the relationship between vascular compliance and elasticity?

Higher elasticity means lower compliance. Signup and view all the answers

What would be the effect of severe anemia on blood vessel dynamics?

Increased blood velocity despite decreased viscosity. Signup and view all the answers

What does critical closing pressure refer to?

The pressure at which blood flow stops and a vessel collapses. Signup and view all the answers

What physiological feature allows the aorta and large arteries to accommodate the blood ejected from the left ventricle?

High amounts of elastin in their walls. Signup and view all the answers

Which statement is correct regarding the systemic venous system's compliance?

It accommodates a large volume of blood with minimal pressure change. Signup and view all the answers

What is the equation for vascular compliance?

$Compliance = rac{ΔP}{ΔV}$ Signup and view all the answers

Study Notes

Hemodynamics of Blood Flow in the Circulatory System

Hemodynamics is the study of blood flow.
Blood flow is categorized as laminar or turbulent.
Laminar flow is smooth and silent, like liquid in narrow tubes.
In laminar flow, the outer layer of blood is stationary, velocity increases towards the center of the stream until it reaches maximum velocity.
Laminar blood flow occurs if velocity is below a critical velocity.
Turbulent flow is disturbed, forming eddies in various directions.
Turbulent flow produces sounds (bruits/murmurs) detectable by a stethoscope.
Turbulent flow can lead to endothelial damage and atherosclerosis.
The probability of turbulence, also known as the Reynolds number, is directly related to blood density, velocity and vessel diameter, and inversely proportional to blood viscosity.
The Reynolds number formula is Re = pDV/η, where Re is the number, p is the density of blood, D is the diameter of the tube, V is the velocity of flow, and η is the viscosity of the fluid.
Flow is usually not turbulent if Reynolds number Re is less than 2000.
Turbulent flow may occur(transitional flow) if Re is greater than 2000.
Turbulence is almost always present if Re is greater than 3000.

Intended Learning Outcomes

Differentiate laminar and turbulent blood flow.
Identify transmural (distending) pressure and critical closing pressure of blood vessels.
Recognize pressure-volume relationships in blood vessels.
Explain velocity of blood flow in different blood vessels.
Discuss Bernoulli's principle.
Identify and explain Laplace law and its significance in heart, lungs, and capillaries.

Clinical Notes

Examples of turbulent flow:
Normally in artery branching and when blood is ejected from the aorta.
Auscultation (listening to sounds with a stethoscope) causes blood flow sounds.
Pathologically due to constrictions (e.g., atherosclerotic plaques), increased blood velocity (e.g., anemia) or cardiac valve abnormalities (stenosis or regurgitation)
Transmural (distending) pressure of blood vessels and critical closing pressure*
Blood vessels remain open because internal pressure (Pi) is greater than external pressure (Pt).
Transmural pressure (ΔP) is the difference between internal and external pressures (Pi-Pt).
A positive transmural pressure causes vessel expansion.
A negative transmural pressure causes vessel collapse.
Critical closing pressure is the pressure at which flow stops and vessel collapse occurs.

Pressure-Volume Relationship in Blood Vessels

Vascular elasticity is the ability of a vessel to return to its normal shape after being stretched.
Vascular compliance (distensibility) is the change in volume of a vessel for a given change in pressure.
Compliance is inversely related to elasticity, with high elasticity meaning lower compliance.
Veins have higher compliance than arteries.
Arteries act as pressure reservoirs.
Veins act as blood reservoirs.

Velocity of Flow

Velocity is the distance traveled per unit of time, and flow is the volume of blood moved per unit of time.
Velocity of flow is inversely related to the cross-sectional area of blood vessels.
Capillary velocity is low to allow for nutrient and waste exchange.

Law of Laplace

States that tension (T) in a hollow vessel (e.g., a blood vessel) is the product of transmural pressure (P) and radius (r) divided by wall thickness (w). The formula is T = Pr/w
The radius of a capillary is small, reducing its wall tension so it can withstand high pressures without rupturing.
Increased chamber radius causes increased myocardial workload in dilated hearts .

Bernoulli's Principle

Total energy = kinetic energy + potential energy, is constant in a tube or blood vessel.
A pressure drop in blood vessels results from resistance (energy lost as heat) or kinetic energy conversion.
Narrowing of vessels increases kinetic energy and decreases potential energy, the reverse occurs when vessels widen.
Narrowed blood vessels, such as in atherosclerosis, lead to increased blood flow velocity and decreased lateral pressure in the narrowed portion, encouraging the narrowing to persist.

Student Activity (True/False)

Laminar flow has a sound: False
Velocity in Aorta is greater than that of capillaries: True
In atherosclerosis systolic pressure is decreased: False

References

Multiple sources provided, referencing different authoritative publications on medical physiology.

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Description

Explore the principles of hemodynamics, focusing on the dynamics of blood flow in the circulatory system. Learn about laminar and turbulent flow, their characteristics, and the Reynolds number's significance in predicting flow behavior. This quiz will test your knowledge on critical velocities and the implications of turbulent flow in vascular health.