TO THE SOUL OF MY FRIEND DR ABDWAHAB BARSHA

2. Dr. MAGDI AWAD SASI, MB ChB,LMB
Consultant Cardiologist
Faculty of Medicine
Benghazi University
LIMU

15. Blood pressure
What drives blood along the blood
vessels after it has left the heart?

16. The peripheral resistance
As the blood flows from the arterial to the venous
side of the circulation, it meets resistance
because of the smaller caliber of the vessels and
the viscous nature of the blood. This is called the
peripheral resistance. It is an important factor in
generating and maintaining the arterial blood
pressure. Vasoconstriction of the small vessels
increases the peripheral resistance, which in turn
elevates the arterial blood pressure. Whilst
vasodilatation decreases the resistance and
lowers the pressure.
The main factor is a gradient of blood pressure.

17. RESISTANCES IN SERIES
RT = RA + RC + RV
RESISTANCES IN PARALLEL
R1
R2
R3
PA
PV
1
RT
1
R1
1
R2
1
R3
= + +
1
R1
1
R2
1
R3
RT
1
+ +
=

18. Pressure Drop in the Vascular System
LARGE ARTERIES
SMALL ARTERIES
ARTERIOLES
CAPILLARIES
VENULES &VEINS
INSIDE DIAMETER
SMALL LARGE
LARGE
ELASTIC TISSUE
MUSCLE

19. Pressure Drop in the Vascular System

20. THE SYSTEMIC CIRCULATION

21. NORMAL

22. NORMAL

24. * The wall of the left ventricle is much thicker
(15 mm) than the wall of the right ventricle (5
mm), yet the capacities and outputs of both
ventricles are equal.
* The thickness of the ventricular wall reflects
the pressure load on the ventricle. The
pressure load on the left ventricle (the aortic
pressure) is much higher than the pressure
load on the right ventricle (the pulmonary
arterial pressure).

25. Ventricles occupy the bulk of the
heart. Why?
Left ventricle wall is thicker than that
of the right. Why?
Blood flows unidirectionally. How?

26. The continuous adequate blood flow to various tissues
depends directly on the ability of the heart to pump
blood into the arteries and to maintain sufficient
pressure within the circulatory system.