Are red blood cells alive

German Red Cross

Red blood cells - the most numerous cells in the blood
The red blood cells - also called erythrocytes - are small, round discs that do not have a nucleus.
As a result, they are compressed in the middle on both sides. They have a diameter of about 7.5 thousandths of a millimeter, are very flexible and can squeeze into the smallest blood vessels. In people up to the age of 20, the red blood cells are formed from the bone marrow of all bones - in older people only in those parts of the body that have bone marrow, namely the ribs, spine and pelvis.
In total, there are an average of 35 trillion erythrocytes in the human body. Around three million of the small round disks are produced in one second, but just as many die in that second. That means a wear and tear of 260 billion red blood cells per day. On average, the erythrocytes live for 120 days and are broken down in the spleen.

Hemoglobin is what gives red blood cells their color
The erythrocytes get their characteristic red color from hemoglobin, which is also essential for the function of oxygen transport. To build up hemoglobin, iron, vitamin B 12 and folic acid must be available in sufficient quantities.

A constant cycle in the human body

Erythrocytes swim with the bloodstream through the human body. The hemoglobin within the blood cells is built up in such a way that it can take up the oxygen in the lungs and bind it to itself.
From the lungs, it goes through the heart and from there into the body's circulation to the individual cells, where the oxygen is ultimately necessary for the cells to function properly.

In those parts of the body where oxygen levels are low and carbon dioxide levels high, the red blood cells begin to work:
They exchange the oxygen bound to the hemoglobin for the carbon dioxide - released during cell respiration - and transport this via the veins back to the heart and into the pulmonary circulation, through which the carbon dioxide can be exhaled again.
This process begins and ends in the lungs and takes place in a constant cycle.

Little helpers for the protective mechanism
The formation of red blood cells is controlled by hormones. If the human body does not receive sufficient oxygen, e.g. in the case of shortness of breath, this is signaled by the hormone "erythropoietin", which is increasingly produced in the kidney in an acute emergency and stimulates the formation of red blood cells in the bone marrow. These can quickly transport the necessary oxygen to the appropriate places in the body. After normalization of the oxygen content, the increased hormone production is reduced or stopped again. The human body protects itself with this mechanism.