Function of arterial & venous system

1. Function of Arterial & Venous System
Dr. Sara Sadiq
(MBBS, M.Phil)

3. CLASSIFICATION OF BLOOD VESSELS
•Conducting Vessels
•Distributing Vessels
•Resistance Vessels
•Exchange Vessels
•Capacitance / Reservoir Vessels

4. BLOOD VESSELS
-Arteries(Distributing channel)
• Thick walled tubes
• Elastic Fibers
• Circular Smooth Muscle
•Capillaries (microscopic vessels)
• One cell thick
•Veins (draining channel)

5. Basic structure
• 3 layers or tunics
1. Tunica intima
2. Tunica media
3. Tunica externa

6. ARTERIES
 Blood vessels that
carry blood away
from the heart are
called arteries.
• Lumen is small
• No valves

7. Arteries
•Elastic (conducting) arteries
• Larger arteries
•Muscular ( distributing) arteries
• Medium arterties
•Arterioles
• Tiny , tiny arteries
•Metarteriole

8. VEINS
• Blood vessels that
carry blood back to
the heart are called
veins.
• Thin Walled
• Large irregular lumen
• Have valves

11. Recall
• Distensiblity
• Compliance
• Pulse pressure
• Mean arterial pressure

12. Venous return
• Volume of blood flowing back to heart
through systemic veins
• Occurs due to pressure generated by
constriction of left ventricle
• Increase venous return influenced by:
1. Increase blood volume
2. Increase large vessel tone  increase
peripheral venous pressure
3. Dilatation of arterioles

14. Venous Pressures
• Central venous pressure  almost zero
• Peripheral venous pressure
• Effect of high right atrial pressure on peripheral
venous pressure???
• Effect of high intra-abdominal pressure on venous
pressure of leg???
• Effect of gravitational pressure on venous pressure???

15. Effect of gravitational pressure
on venous pressure???

17. Venous Valves & Venous Pump
• Valves are arranged so that the
direction of blood flow can only
be toward the heart

18. Varicose Veins
• Bulbous protrusion of the veins
• Valves of the venous system becomes incompetent or
destroyed due to excess venous pressure for prolong
duration.
• Stretching increase cross-sectional area  valves
don’t close completely  failure of venous pump

19. Blood Reservoir
• Spleen
• Liver sinuses
• Large abdominal veins
• Venous plexus