2. HEAMODYNAMICS
DEFINITION=Blood flow
BLOOD FLOW
Velocity of blood flow=Quantity of blood/cross-sectional area of blood vessel
Method of study:
Doppler flowmeter
Plethysmograph-use to measure volumeenclosed organ
Venous occlusion plethysmograph

3. Fick pricinple : dye dilution method
Types of blood flow
Laminar flow:silent flow,occur at velocities up to a critical level
Turbulent flow:
noisy flow,
occurs when the velocity is above critical level,
increase resistance to forward flow
Both forward and backflow

4. CRITICAL VELOCITY at which blood flow become turbulent is known as REYNOLD’S NUMBER
REPRESENTED AS
NR=PDV/ɳ
NR-Reynolds number
P- density of the blood
D-Diameter of the vessel
V-velocity of the flow
ɳ-viscosity

5. Factors influencing blood flow
1.PRESSURE GRADIENT=BF directly proportional to PG
2.RESISTANCE TO BLOOD FLOW(peripheral resistance)=
inversely proportional to BF
Increases away from the heart e.g resistance in aorta<artery<arteriole

6. FACTOR AFFECTING PERIPHERAL RESISTANCE
Radius of blood vessels: PR inversely proportional radius
Pressure gradient: ∆Pressure/volume of blood flow
Viscosity

7. 3. VISCOSITY: the friction of blood against the wall of the blood vessels, the thickness of blood
inversely proportional to blood flow
Increases with Hemoconcentration from burn, polycythemia
Decreases with aneamia

8. 4.DIAMETER OF BLOOD VESSELS BV flow is directly proportional to the diameter of the blood vessel(cross sectional) Factors influencing diameter of blood vessel Physiological and pathological factors

9. PHYSIOLOGICAL FACTORS
Elasticity of blood vessel:
Integrity of endothelium(the inner lining of blood vessel)
Sympathetic innervation of blood vessels (vascular tone; vasomotor tone)

10. PATHOLOGICAL FACTORS
Damage to endothelium
Blockade of blood vessel (artheroscleroris)
Increase in vascular tone(↑sympathetic nerve)
Increase adrenaline during stress

11. 5. Velocity of blood flow
BF volume is directly proportional to velocity of blood flow

12. FACTORS MAINTAINING blood flow VELOCITY
Cardiac output
Cross-sectional area of the blood vessel
Viscosity of blood

13. Conditions decreasing flow
Hypothyrodism
Polycythemia
Cardiac failure

14. Condition increasing blood flow velocity
Exercise
Adrenaline injection
Hypethyrodism
Anemia
Decrease in peripheral resistance eg by antihypertensive drug
Nitric oxide supplement

15. Local regulation of blood flow
This is the regulation of blood flow to organs initiated by the organ
It is Intrinsic
Theories of autoregulation
Myogenic theory-stretching of blood vessel by blood, intrisically results in the contraction (constriction) of the vessel =reduced blood flow
Metabolic theory=metabolites generated in working tissues increases the cross-sectional area of the vessel (vaodilators)

16. Examples of metabolic vasodilator
↑ Temperature
↑CO2 or PCO2
↓Po2
↑Lactate
↑Hydrogen ion (↓pH)
↑ADP

17. AUTOREGULATION IS PROMINENT IN
HEART
KIDNEYS
BRAIN