GROSS ANATOMY

Detailed explanation-1: -Red blood cells get their bright red color from a protein that allows them to carry oxygen from your lungs and deliver it to other tissues in your body (hemoglobin). Red blood cells are microscopic and have the shape of a flat disk or doughnut, which is round with an indentation in the center, but it isn’t hollow.

Detailed explanation-2: -Each hemoglobin protein is made up subunits called hemes, which are what give blood its red color. More specifically, the hemes can bind iron molecules, and these iron molecules bind oxygen. The blood cells are red because of the interaction between iron and oxygen.

Detailed explanation-3: -Human blood is red because hemoglobin, which is carried in the blood and functions to transport oxygen, is iron-rich and red in color. Octopuses and horseshoe crabs have blue blood.