MICROANATOMY

Detailed explanation-1: -Deoxygenated blood is darker due to the difference in colour between deoxyhaemoglobin and oxyhaemoglobin. Here, oxygenated blood is represented in red and deoxygenated in blue colour.

Detailed explanation-2: -When it is attached to oxygen (O2), it is called oxyhemoglobin and its color is an intense light red (arterial blood). In contrast, deoxyhemoglobin is the name given to reduced hemoglobin, that is, when it has lost oxygen and has a darker color (venous blood).

Detailed explanation-3: -Hemoglobin forms an unstable, reversible bond with oxygen. In its oxygenated state it is called oxyhemoglobin and is bright red. In the reduced state it is called deoxyhemoglobin and is purple-blue.

Detailed explanation-4: -Oxygenated (arterial) blood is bright red, while dexoygenated (venous) blood is dark reddish-purple.

Detailed explanation-5: -Deoxygenated blood is darker due to the difference in shape of the red blood cell when oxygen binds to haemoglobin in the blood cell (oxygenated) versus does not bind to it (deoxygenated). Though veins might make it appear as such, Human blood is never naturally blue.