Which human blood cells are primarily responsible for carrying oxygen?

Red blood cells are the human blood cells primarily responsible for carrying oxygen.

Also called erythrocytes, red blood cells pick up oxygen in the lungs and deliver it to tissues throughout the body. They transport most of that oxygen using hemoglobin, an iron-containing protein that gives blood its red color. They also carry some carbon dioxide back toward the lungs.

Mature human red blood cells normally lack a nucleus and most other internal organelles. This leaves more room for hemoglobin and gives the cells flexibility as they pass through narrow capillaries. Their biconcave disc shape increases surface area for gas exchange and helps them bend without tearing.

Red blood cells are different from white blood cells, which mainly support immune defense, and platelets, which help blood clot. New red blood cells are produced in red bone marrow. A typical cell circulates for about 120 days before being removed, especially by the spleen and liver.