Blood is primarily made in the bone marrow. This spongy tissue, located within the center of many bones, is responsible for producing approximately 95% of the body's blood cells.
The Role of Bone Marrow in Blood Cell Production
The bone marrow's crucial function is hematopoiesis, the process of blood cell formation. Within the bone marrow reside hematopoietic stem cells, which are capable of differentiating into all types of blood cells:
- Red blood cells (erythrocytes): Carry oxygen throughout the body. Millions are produced and die every second, constantly replenishing the supply. (Source: NHS Blood Donation)
- White blood cells (leukocytes): Part of the immune system, fighting infection and disease.
- Platelets (thrombocytes): Essential for blood clotting.
The bone marrow’s production is continuous; nearly a pint of fresh blood is generated weekly. (Source: OneBlood Blog) Red bone marrow, specifically, contains these blood stem cells. Yellow bone marrow, primarily composed of fat, plays a less significant role in blood cell production. (Source: NCI Dictionary of Cancer Terms)
Beyond Bone Marrow: Minor Contributions
While the bone marrow is the main site of blood cell production, other areas may contribute to a lesser extent during specific circumstances, such as the spleen and liver in fetal development. However, for adults, bone marrow is the primary and most significant contributor.
(Sources: Johns Hopkins Medicine, MedlinePlus, Leukaemia Foundation, Numerous other provided links confirm this consistent finding.)
