explain the circulatory system

The Circulatory System refers to the flow and control of
the blood around the body.In humans the system runs like this:
Heart>Artery>Arteriole>Capillary>Venule>Vein>Heart.
As blood begins to circulate, it leaves the heart from the left ventricle and goes into
the aorta, the largest artery in the body. The oxygenated blood leaving the aorta
travels throughout the body in its system of arteries into the smallest arterioles. On
its way back to heart, the blood travels through a system of veins. As it reaches the
lungs, the carbon dioxide which is a waste product is removed from the blood and
replaced with fresh oxygen that we have inhaled through the lungs. Blood that comes from
the left side of the heart is full of oxygen and nutirients like protein, fat,
carbohydrates, vitamins, and minerals.This blood in systemic
arteries, full of oxygen and nutrients, is systemic arterial
blood.

The biggest systemic artery in the body
is the aorta, the large blood vessel that comes out of the heart. Smaller arteries
branch off from the aorta. These arteries have further smaller arteries that branch off
from them. The smallest arteries turn into arterioles.

The
smallest blood vessels are capillaries. Systemic arterioles turn into capillaries. The
blood from arterioles goes into the capillaries. There oxygen and nutrients go out of
the blood into the tissue around the capillaries. The blood also picks up carbon
dioxide and waste from the tissue. Venules are the smallest veins that drain
deoxygenated blood from the capillary bed to the veins.Veins take blood back to the
heart. As veins go back to the heart, they get bigger. The biggest systemic veins in the
body are the vena cava. There are two vena cava:
the inferior vena cavatakes blood from the lower part of the body
to the right side of the heart, and the superior vena cava takes
blood from the upper part of the body to the heart.