Blood is one of the vital forces in keeping our bodies alive. Blood moves through our bodies, carrying with it oxygen and nutrients, but also carbon dioxide and other waste materials to the lungs, kidneys, and digestive system to be expelled and processed out.
But what exactly is blood? And how are we able to donate blood, or survive blood loss if it’s so essential to life? Let’s take a look at how our body produces and replaces blood, so next time you accidentally cut yourself, you understand what your body has to do to repair itself.
What is Blood?
Blood makes up roughly 7 – 8% of our body’s weight, or around 10 pints. Blood, just like its functions, has multiple components, including red blood cells (approximately 45% of blood), plasma (45% of blood), and white blood cells and platelets making up the remaining 10%.
Plasma is one of the “majority shareholders” in blood’s composition, so it’s helpful to understand what exactly it is. Plasma is mostly composed of water and salts from the digestive tract, and it creates the highway that blood cells are carried around the body through. It is a clear, straw-colored liquid portion of blood, the liquid that remains when everything else ( red blood cells, white blood cells, platelets, and other cellular components) are removed. Plasma makes up 55% of the human body.
The second majority stakeholder, red blood cells, are the largest travelers on this system. Red blood cells, which are produced in bone marrow, contain and transport oxygen throughout the body, and also includes the protein hemoglobin, which makes blood look red. Red blood cells can live up to 120 days before they die off.
The other 10% of blood is made up of white blood cells and platelets. The white blood cells are the infection-fighting cells, rejecting germs, allowing blood to clot when needed, and eliminating invasive bacteria. Like red blood cells, white blood cells are also (mainly) produced in bone marrow, but can be formed elsewhere in the body too. Platelets, generally made in bone marrow as well, work to help regulate the flow of bleeding and contribute to the healing of the injury or cut.
How is blood made, though?
So now that we know what blood consists of, and we know that bone marrow plays a crucial role in the production of blood, how is it actually produced? What tells our bodies to make more?
The process itself is called hematopoiesis. When the kidney detects a need for red blood cells, which occurs on a daily basis, it begins producing a specific hormone to facilitate red blood cell production. Stem cells, which start in the spongy tissue called bone marrow, replicate themselves, producing red blood cells, white blood cells, and platelets. The cells release into the bloodstream and begin their work fighting viruses, carrying oxygen, or sealing off leaks. As mentioned above, red blood cells survive for around four months; white blood cells can survive for hours to years; platelets’ life span is about nine days.
Aren’t our bodies amazing?