Red blood cells are formed in the red bone marrow of bones. Stem cells in the red bone marrow called hemocytoblasts give rise to all of the formed elements in blood. If a hemocytoblast commits to becoming a cell called a proerythroblast, it will develop into a new red blood cell.

What is bone marrow?

Bone marrow is the spongy tissue inside some of your bones, such as your hip and thigh bones. It contains stem cells. The stem cells can develop into the red blood cells that carry oxygen through your body, the white blood cells that fight infections, and the platelets that help with blood clotting.

Researchers have known for a long time that bones have an efficient system of blood vessels to enable immune cells made here, in the bone marrow, to move quickly into general circulation.

But they’ve only just managed to see the many microscopic vessels that play a key role in that process. As we zoom out, you can see lots of small holes marking the entrance and exit points of these teeny capillaries. Without knowing it, trauma surgeons have been making use of this fast and direct transport system for years.

When they can’t get quick access to a patient’s veins, instead they inject drugs or fluid directly into the patient’s leg bone. This technique, first developed by the military and used on battlefields is called intra-osseous infusion.

To figure out how intra-osseous infusions work, scientists turned to a technique called “clearing”. This involves washing away the fatty membrances that surround cells to make whole organs see- trough. Its been applied to many structures, including hearts.

Our bone marrow produces blood cells, called red blood cells, platelets, and white blood cells. 

Red blood cells

These cells are red because they are filled with a protein called haemoglobin. Oxygen and carbon dioxide attach to the iron that is in haemoglobin, allowing the red blood cell to transport oxygen to the body. The red blood cells also get rid of carbon dioxide which leaves your body through the lungs when you breathe out.

White blood cells

The bone marrow produces many types of white blood cells. These are necessary for a healthy immune system. They prevent and fight infections.

How does the immune system fight against infection?

These cells originate in the bone marrow. They make proteins called antibodies which attach onto the surface of infection-causing microbes. Generally, these are Y or T shaped. Each type of antibody reacts to different microbes by sticking to molecules, called antigens, which sit on the surface of the microbe.