These are very interesting questions; not a lot of people know about the spleen and try to learn so much about it.

The spleen is located to the left of the stomach in the upper abdomen. It's an organ mostly found in vertebrates, like humans. Two of its most important functions are to filter and store blood. Healthy red blood cells pass through the spleen, but unhealthy red blood cells are broken down by macrophages, large white blood cells, in the spleen. Any useful components of old cells, especially iron, are stored in the spleen. The iron is then transferred to the bone marrow to help with hemoglobin production; hemoglobin is a protein in the blood that helps transport oxygen from the lungs to the rest of your body. The spleen also stores extra blood, so if the body is ever in need of extra blood the spleen suppled it. The spleen is like a large lymph node so if it ever has to be surgically removed, other lymph nodes and the liver replace its job functions. In other words, you can live without your spleen. In terms of your immune system, though, loss of spleen function does make a person more vulnerable to infections because it does so much for your body. If someone does get his or her spleen removed, doctors prescribe some injections and antibiotics to protect the patient.

When there is an increase in abnormal erythrocytes, the spleen has to work harder than usual which causes it to enlarge. Enlarged spleen, or splenomegaly, can cause hypersplenism (Banti syndrome) where the spleen starts to prematurely destroy blood cells. Also, as the spleen enlarges it starts to filter both abnormal and healthy blood cells causing less healthy blood cells in the bloodstream. Since there are more blood cells being filtered than normal function, the spleen can get clogged. There are many reasons the spleen can become enlarged. Sometimes treatments are offered, and the first suggestion is to not get it surgically removed.

Pathology is the study and diagnosis of disease, so no, it does not cause spleen "pathology". I'm afraid I don't understand this particular question. But an increase in abnormal red blood cells does caused an enlarged spleen, as mentioned earlier.

Good luck with the rest of your research!