This document discusses the general principles of circulation, including: 1. It describes the functional organization and structures of the vascular system, including the different types of blood vessels like windkessel vessels, resistance vessels, and exchange vessels. 2. It discusses pressure and blood flow in different segments of the circulatory system, providing tables of typical pressure values in structures of the systemic and pulmonary circulations. 3. It covers hemodynamics, explaining concepts like blood flow, cardiac output, laminar versus turbulent flow, and how blood flow is determined by factors like pressure difference and vascular resistance according to Poiseuille's law.

1. General principals ofGeneral principals of
circulationcirculation
Dr. Kamla Choudhary
Assistant Professor

2. Dynamics of Circulation will be discussed
under following heading:-
1.Functional organization and structure of
Vascular System
2. Pressure and Blood Flow in different segments
of circulatory system
3.Hemodynamic
4. Blood pressure

4. 12/21/16 4
Characteristics of various types of blood
vessels

5.  Windkessel vessels: large arteries
 Resistance vessels: small arteries
 Exchange vessels: formed by a single
layer of endothelial cells
 Capacitance vessels: veins
 Shunt vessels: Meta-arterioles
12/21/16 5

6. VSM – vascular smooth muscles
Key structure in vascular system
Types – VSM
single unit – response to stretching
Multiunit- absent of response
Arrangement of VSM
Spiral in arteries
Circular in arterioles

8. 2- Pressure and Blood volume in different
segments of circulatory system

9. 12/21/16 9

10. SYSTEMIC CIRCULATIONSYSTEMIC CIRCULATION
Structure Pressure in mmHg
Left Atrium 7-8/0
Left Ventricle 120/0
Aorta & large arteries 120/80
Arterioles 60
Capillaries 25
Venules & large veins 10
Vena cava (SVC&IVC) 2

12/21/16 10

11. PULMONARY CIRCULATIONPULMONARY CIRCULATION
Structure Pressure in mmHg
Right Atrium 4-6/0
Right Ventricle 25/0
Pulmonary arteries 25/8
Arterioles 10
Capillaries 6-8
Venules & larger branches 5
Pulmonary veins 2
12/21/16 11

12. 12/21/16 12
Pressures in Vascular System

13. Vessel % of blood volume
Systemic 84 %
Arteries 13 %
Arteriole 1-2 %
Capillary 5 %
Veins 64 %
Pulmonary/Heart 16 %
Lungs 9 %
Heart 7 %
12/21/16 13
BLOOD DISTRIBUTION

14. 14

15. 3-HEMODYNAMICS
Physics which deals with blood
flow through circulatory
system
Blood flow
Amount of blood that flows through any
tissue in a given period of time
 mL/min
Over all blood that flows in the
circulation at rest in adult is about
5000ml/ min.

16. •Distribution of CO into different body tissues:
1.Pressure difference of different parts of the
body
Pressure ↑ → Blood Flow ↑
2.Resistance of specific blood vessels to
blood flow
Resistance ↑ → Blood Flow ↓
Total blood flow: Volume of blood that circulates
through the systemic and pulmonary blood vessels
each minute → •Cardiac Output (CO)
•Cardiac output (CO) = heart rate (HR) x stroke
volume (SV)

17. Blood flow patterns - two
types
Laminar blood flow
 Turbulent blood flow

19. Parabolic velocity profile during
laminar flow

21. Probability Of TurbulenceChance of
turbulent are determine by the probability of
turbulence which is denoted as
Re (Reynolds number) = vρD/η
The tendency for turbulent flow are
Directly proportion to
Velocity of blood flow (v in cm/sec.)
Density of the blood (ρ in kg/m3)
Diameter of the blood vessel (D)
Inversely proportion to
Viscosity of blood (η in poise)

22. Predicts Laminar flow versus Turbulent flow
Low Number means Laminar Flow
High Number means Turbulent Flow
When Reynolds no. exceed 2000 turbulence flow
chance increase.

23. Blood flow is determined by following factors
Pressure difference b/w two ends of vessels
Vascular resistance
F= ∆P/R

25. INTERRELATIONSHIP B/W FLOW, PRESSURE
AND RESISTANCE
Studied by French Physiologist
Poiseuille’s in 1842 in rigid tube in Newtonian
fluid
Known as Poiseuille’s - Hagen law or
Poiseuille-Hagen equation

26. According mathematical calculation in
Principles of physics, Resistance is
represented as -
R = 8ηl/∏r4
After replacing these values in Poiseuille’s law
by R
Blood flow Q will be
Q = ∆P/R

31. Blood Flow Examples
Suppose you have an emergency requirement for a five-fold
increase in blood volume flow rate (like being chased by a big
dog)? How does your body supply it?
According to Poiseuille's law, a five-fold increase in blood pressure
would be required if the increase were supplied by blood pressure
alone!
But the body has a much more potent method for increasing volume
flow rate in the vasodilatation of the small vessels called arterioles
Since the smaller vessels provide most of the resistance to flow, the
arterioles in their position just prior to the capillaries can provide a major
controlling influence on the volume flow rate. This system of small
vessels can constrict flow to one part of the body while enhancing the
flow to another to meet changing demands for oxygen and nutrient.

32. 12/21/16 32

33. Blood Flow Examples
12/21/16 33