Hemodynamics Flashcards
Hemodynamics
The study of blood moving through the circulatory system
Flow
- Also called volume flow rate
- Indicates the volume of blood moving during a particular time
- units: L/min
Arteries
Tubes that carry blood away from the heart
Veins
Tubes that return blood to the heart
Capillaries
Connect arteries and veins. Tiny to sell exchange food oxygen and weighs between blood and body cells
Circulatory System
Consist of the heart, arteries, arterioles, capillaries, venules, and veins
Heart
The pump that produces flow through the circulatory system
Layers of blood vessel walls
- Tunica intima-inner layer
- Tunica Media-middle
- Tunica adventitia
- Arteries typically have a much thicker Tunica media compare with veins
The three basic forms of blood flow
- Pulsatile flow
- Phasic flow
- Steady flow
Pulsatile flow
-Occurs when blood moves with the variable velocity
-Cardiac contraction
Commonly appears in the arterial circulation
Phasic flow
Occurs when blood moves with the variable velocity. Respiration. Often appears in the Venous circulation
Steady flow
Occurs when the fluid moves at a constant speed of velocity. Present in the venous circulation one individual stop breathing for a brief moment.
Laminar flow
A flow condition in which streamlines are aligned and parallel. Characterized by layers of blood that travel individual speeds. The highest velocity’s are in the center of the vessel.
Plug flow
Occurs in all of the layers and blood cells travel at the same velocity. Also known as blunted flow.
Parabolic flow
Bullet shaped profile. Velocity is highest in the center of the lumen and is gradually decreases to it’s minimum at the vessel wall.
Stenosis
A narrowing in the lumen of a vessel
Pre-stenosis
-Velocity decreases
Pressure increases
Dampened blood flow/ slows down
At stenosis
Velocity increases
Pressure decreases
Post-stenosis
Velocity decreases
Because of turbulent blood flow
Pressure increases
Reynolds number
Predicts whether flow is laminar or turbulent.
Greater than 2000 is true turbulence
Less than 1500 is laminar flow
How is energy imparted to blood?
By the contraction of the heart during Systole
Forms of energy associated with blood
- Pressure energy
- Kinetic energy
- Gravitational energy
The continuity equation
Ties together the relationship between the vessel area, the velocity of blood, in the volume of blood flow
Q=VA
Diameter and velocity are inverse
Bernoulli effect
Describes the relationship between velocity and pressure in a moving fluid
Derive from the principle of conservation of energy, which states that with steady flow the sum of all forms of energy is the same everywhere
P1-P2(change in P)=4V^2
Poiseuille’s Law
Describes the relationship between volume flow, pressure, and resistance.
-The radius of a vessel is directly proportional to the volume flow. Slow resistance most strongly depend on the vessel radius because the radius in the equation is with power 4(r^4).So that a small changes in radius may result in large changes in flow.
Venous hemodynamics
-Veins are thin walled and collapsible
During normal function, veins have a low pressure, or only partially filled with blood and therefore, only partially expand
The cross-sectional shape of a vein during normal function is flattened or hourglass shaped
The greatest portion of circulating blood is located in the venous system
