Morphine has a mild vasodilator effect. This will most likely affect arteries, but there will still be some effect on veins, albeit a smaller one
The Portal Venous System
Yes, 65-70% of the blood volume is in the venous system.
The venous system is responsible for returning deoxygenated blood from the tissues back to the heart. It transports this blood through a network of veins, which have valves to prevent the backflow of blood. The venous system also plays a role in regulating blood volume and pressure in the body.
brachiocephalic
subclavian vein
lymphatic system
lymphatic system
Very simply put the venous system, the arterial system and your heart. The venous system bring blood from your organs and extremities to your heart, which pumps it and the arterial system takes it from your heart to your organs and extremities.
blood vessel bloodstream heart liver lymph lymph gland lymph node vein vena venation venous blood system venous blood vessel
In the left subclavian vein.
testicular vein and artery
Contraction of veins would increase venous return to the right atrium. It would increase the efficiency of the heart pumping.