Note: For background on this series, please read the Introduction to the 32-Parts Project.
Bones form the structure of the human body. They are comprised mostly of calcium and phosphorus, minerals that remain in place long after death and the breakdown of other tissues. Bones also protect sensitive organs and serve other functions as well. One of those very necessary functions is to provide the environment for marrow, without which human life would be impossible.
Bone marrow is a gelatinous substance that resides within the hollow core of a bone. There are two types of marrow, red and yellow. Each type is predominate in certain kinds of bones and in specific areas of them. In the newborn, all marrow is red. As the person ages, some red marrow converts to yellow until, in an adult, there is about 50 percent of each.
The cells of each kind of marrow have the capacity to do what cells of other mature tissues do not. Throughout one’s life, cells divide according to the genetic code in their DNA. A single skin cell will divide in two to become exact, specialized duplicates of the original. Liver cells do this, as do bone cells, stomach cells, and so forth. Specialization begins in the developing fetus with a process called differentiation.
At conception, the first cell is undifferentiated. It is unspecialized with no purpose other than to divide again and again. It’s a cell with lots of potential. It’s a cell from which all specialized cells will derive, eventually. It’s a stem cell. During gestation, as cells divide, they gradually differentiate and become fixed as a specific kind.
Bone marrow cells are undifferentiated. They, too, are stem cells. However, unlike embryonic stem cells, which can become any other kind of cell needed by the body, marrow stem cells have limited destinies. The cells of red marrow will differentiate into red blood cells, platelets, or one of several kinds of white blood cells. The cells of yellow marrow can become bone cells, cartilage cells, muscle cells, or fat cells.
A number of diseases can be treated with a bone marrow transplants. Marrow can be harvested from a healthy individual – usually from the hip bones – and transplanted into the circulatory system of someone who has undergone chemotherapy (which kills rapidly dividing cells – cancer cells as well as healthy cells). Once in the blood stream, it will find its way into the bone where it can begin making new, healthy cells. Bone marrow also can be harvested from and reintroduced into the system of the same individual.
Stem cells also are used in research to find cures for irreversible diseases like Parkinson’s disease. Controversy surrounds the use of embryonic stem cells.
The four-minute video below compares a new way of harvesting marrow with the way it’s been done for many years.
For background on this series, please read the Introduction to the 32-Parts Project.
