GROSS ANATOMY

Detailed explanation-1: -Blood that has been oxygenated (mostly flowing through the arteries) is bright red and blood that has lost its oxygen (mostly flowing through the veins) is dark red. Anyone who has donated blood or had their blood drawn by a nurse can attest that deoxygenated blood is dark red and not blue.

Detailed explanation-2: -Human blood is red in colour, ranging from bright red when oxygenated to a very dark, almost blackish-red when deoxygenated. It owes its colour to haemoglobin, to which oxygen binds. Deoxygenated blood is darker due to the difference in colour between deoxyhaemoglobin and oxyhaemoglobin.

Detailed explanation-3: -Red blood cells contain hemoglobin, a protein with red pigment that carries oxygen. When hemoglobin picks up an oxygen molecule, its shape changes to hold the oxygen. This conformation of the protein absorbs and reflects certain wavelengths of light to look bright red.

Detailed explanation-4: -Hemoglobin is a red-colored, iron-containing protein that functions in oxygen transport by reversibly binding to oxygen. Oxygenated hemoglobin and blood are bright red; deoxygenated hemoglobin and blood are dark red.

Detailed explanation-5: -The level or amount of oxygen in the blood determines the hue of red. As blood leaves the heart and is oxygen-rich, it is bright red. When the blood returns to the heart, it has less oxygen. It is still red but will be darker.