carbon dioxide
Blood entering the kidneys has more water; the water is extracted by the kidneys and sent through the ureter to the bladder.
Technically, blood is always oxygenated to some degree. The capillaries are where the blood exchanges oxygen with the tissues so the blood entering the capillaries has more oxygen than the blood leaving the capillaries but under resting conditions venous blood is still 75% oxygenated.
if blood entering the heart gets mixed with blood leaving the heart the the blood leaving the heart will get poluted. the blood entering the heart is poluted when it enters the heart, the heart cleans it up; so when the blood leaves the heart it is clean so if it gets polluted the person may get sick and this leads to his/her death.
The blood coming from the lungs
It's not so much that the lungs need alot of blood, but more that the blood depends on the lungs. The nature of the lungs allows the blood to pick up and carry oxogen to the rest of the body and the very thin membranes of the lungs allow the exchange of gasses, oxygen into the blood and carbon dioxide out of the blood.
Ossomosis. The blood travels near the lungs then Oxygen travels from the lungs to the blood. More->Less And the previous blood, does the same with CO2 More->Less.
The oxygen poor blood (not enough oxygen) goes to the lungs to get more oxygen to turn into oxygen rich blood (has plenty of oxygen)
The energy broken down from the oxygen is transported into throughout the body by blood vessels. That energy is dropped of at what ever part of the body needs it, and the blood vessel goes back to the lungs for more.
Blood coming from the lungs enters the left side of the heart.
heart is hypertensive, and lungs are working increasingly hard to supplement more oxygen to the rest of your organs.
Seeing as the lungs act as a filter for your body, they remove toxins from the blood and add new blood back to the old dirty blood. The lungs are a wonderful invention! Actually, the lungs remove carbon dioxide from the blood and add oxygen. The liver is more the "filter".
It helps to filter out foreign particles, such as things that can cause disease. Cold air lowers your lungs temperature, but the mucus helps regulate your lungs temperatue by warming the air entering your lungs.