Richard Garvey, age 11, of Patterson, N.J., for his question:
HOW LARGE IS A PERSON'S SPLEEN?
Your spleen is a gland like organ that helps to filter the body's blood. It lies below the diaphragm, to the left of the stomach and a little behind it. An adult's spleen is about five inches long and three to four inches wide.
The average adult spleen weighs only about seven ounces. It is soft and spongy. It has a deep violet red color.
Covering the spleen is a fold of peritoneum, the same membrane that lines the abdominal cavity. The principal cells of the organ are similar to those in the lymph glands.
The spleen helps to filter foreign substances from the blood, working much as the lumph glands work to filter foreign substances from the lymph. Cells in the spleen engulf or surround and destroy these foreign substances.
In addition, the spleen also serves as a storage location for red blood cells and also as a "graveyard" for injured blood cells. When the body needs extra blood during exercise or hemorrhage, the spleen contracts and squeezes out some of the cells it has stored.
The spleen may form red blood cells in unborn babies, but it does not do so after the baby has been born.
The spleen is thought to be only a helper of other glands and organs in the body. It is possible to remove the spleen without any noticeable ill effects. There are many times when doctors find it necessary to remove the spleen.
Sometimes a disease centers in the spleen and causes it to enlarge. In some other diseases, the spleen works so hard at destroying worn out red blood cells that it also destroys healthy red cells and causes anemia.
Sometimes the spleen destroys blood platelets, which help in the clotting of blood. When too many platelets are destroyed, the patient may bleed into the body's tissues.
The spleen also produces some of the blood cells known as lymphocytes and monocytes. Lymphocytes are also produced in the lymph nodes, the thymus and other lymphoid or lymphlike organs. Monocytes are also formed by the same organs, but most of them are produced in the marrow of bones.
In some infections, notably malaria, the spleen may become very large. Enlargement of the spleen also occurs in leukemia.
If an operation is necessary to remove the spleen, the body is able to adjust. The liver, white cells and bone marrow work overtime to replace its function, and the patient without a spleen is able to go on much as before the operation.
Injury to the spleen's supporting tissues can cause a condition called wandering spleen, in which it moves about in the abdomen. In some persons, bits of spleen called accessory spleens have been found scattered throughout the abdominal cavity.