oxygen makes it red
I would think it has to do with the amount of oxygen in the blood stream.
from the lungs
It is bright red.
Fresh blood is brilliant red, but as it clots it will turn brown.
Blood coming from the lungs has lower pressure while that from the heart has higher pressure. Blood coming from the lungs also has higher oxygen content and lower carbon dioxide content compared to that coming from the heart.
Blood coming from the lungs has lower pressure while that from the heart has higher pressure. Blood coming from the lungs also has higher oxygen content and lower carbon dioxide content compared to that coming from the heart.
The blood coming from the lungs
Blood is pumped by the heart. Blood leaves the heart via the arteries and returns to the heart via the veins. Blood returning to the heart goes to the lungs where it is oxygenated then pumped around the arteries
In humans, the heart has four openings (or chambers). There is an opening for the oxygen-poor blood going in, one for the oxygen-poor blood going to the lungs, an opening for the oxygen-rich blood coming back from the lungs, and one for the oxygen-rich blood circulating through the rest of the body.
deoxygenated blood
Blood is de-oxygenated when it it pumped into the lungs, and after going through the lungs, is now oxygenated.
Blood that flows from the lungs to the heart is oxygenated, so it's bright red. In contrast, blood that flows from the heart to the lungs is deoxygenated, and so is dark red.
its bright red because it passes by the lungs wich oxygenates it
Different amounts of oxygen alter its color due to the high levels of iron in the hemoglobin. Coming from the lung region, blood is extremely oxygen-rich, making it a brighter red. When the oxygen is stripped away the blood turns blue.