Our bodies were first thought to be hollow vessels in which our souls reside. The reality proved to be the complete opposite but nevertheless fascinating. Our body is formed by billions of cells working in perfect harmony that initially started from a single one. Our organs need oxygen to survive to produce energy, and the delivery of oxygen along with countless other nutrients and chemicals is carried out by blood. The blood is formed of a fluid component called plasma and a cellular component. Cells of the blood are unique and differ from each other in most of their properties and functions, and all of them originate from the bone marrow.
What is the bone marrow?
During fetal life, the blood is created in many organs including the liver, bones, lymph nodes and a vestigial structure called the yolk sac. When the baby is born, his or her blood is only formed in a group of stem cells in the cavities of bones called the bone marrow. Bones -especially long bones like the thigh- are composed of a hard shell called the cortex and a soft cavity within called the medulla. The medulla is filled with a soft tissue called the marrow. It is formed of cells that divide adequately to form all blood components. The main types of cells are the common myeloid progenitors, which give rise to red blood cells, platelets, and all white blood cells except for lymphocytes. The common lymphoid progenitor gives rise to lymphocytes. Other cells found in the bone marrow are fat cells, bone cells, and fibroblasts, which form the connective tissue framework that supports these cells.
The bone marrow is “red’ at birth, which means that it is very active that most of its cells are stem cells actively producing blood elements. As we age, most of these cells are replaced by fat cells “adipocytes,” and by adulthood, the red marrow is only found at the ends of long bones, the sternum, and the hip bone.