Human blood in veins is blueish in color, what's the reason behind it- The wavelength of light or oxygenated blood

The color of your blood is red... No doubt. 

But the blood in your veins is bluish. Isn't it a strange thing?

 let's talk about this. 

Blood is the fluid that our hearts pump through our circulatory systems to reach oxygen and other materials to all the cells in our body. The average amount of blood in a human body is 4.5 liter and the fluid is made up of clearish liquid plasma.

 There are three types of blood cells such as red, white, and platelets, and they are floating into it. R.B.C bears Oxygen W.B.C fights against the antigen. Platelets help to clot blood,

 RBC has hemoglobin which is an iron-rich protein that binds to oxygen (HbO2) and gives our blood a red hue. Hemoglobin is a kind of Hemochrome, a protein that is the red coloring matter of the blood. 

Not all animals use hemoglobin, so that's why not all animals' blood is red. That indicates that, our blood color depends on what we are, and how our blood moves oxygen around our body.

 For example,

 Some genus of skinks bleeds green blood because there is a greenish pigment called biliverdin(C₃₃H₃₄N₄O₆), a byproduct of the breakdown of hemoglobin. , Most mollusks such as Octopus, squid, and some arthropods bleed blue blood Because their blood contains Hemocyanin

. A copper-containing protein that turns from basically colorless to dark blue when exposed to oxygen!

Now back to human blood.

There is a misconception that human blood is blue until it comes to the open air and gets oxygenated to its red colour.. well, it's not true. 

It only appears blue in our veins from the outside because of the way different light wavelengths entered in our skin, but the blood in our arteries and capillaries are indeed a brighter red in the deep red blood in our veins, which has to do with how recently that blood picked up new oxygen.

 On our way back to our heart it's just like darker because it has delivered that oxygen. A last noticeable thing is, if we cut a little bit in our finger, then the blood seemed lighter and brighter than the darker blood you saw coming from your forearm at a blood drive. 

After all, that was capillary blood and was full of oxygen, and blood drive blood was venous blood that had just delivered its oxygen... it's because of different oxygenation processes but they are not blue. !
Nadeem Abdullah 
dept. of Chemistry
University of Rajshahi