Question

What are typical pressures in arteries and in veins? Where veins rich in oxygen come
from? Where the ones rich in CO2 come from?

Answer 1

The pressures experienced by these vascular structures are the blood pressure that acts on the walls of these vessels. The pressure inside arteries are 120/80 mmHg. The arteries receive high pressure blood from the heart. But the pressure in veins are in the range of 5-8 mmHg. As the blood reaches a long way along the body the pressure drops. Veins bring blood back to the body. As no such pump acting like the heart blood pressure in veins become much less.

The oxygen rich blood which is carried in the veins comes from the lungs. Pulmonary veins are the veins that carry oxygen rich blood. The deoxygenated blood get oxygenated in the lungs and it's carried to the left atrium by pulmonary veins. The CO2 rich blood is carried in veins comes from the body tissues. The body tissues consume oxygen and gives out CO2. This CO2 rich blood is taken to the left atrium by the veins.