spleen can be called as the graveyard of the RBC because the RBC undergo disintegration in the spleen

Neither. The spleen is part of the immune system

The spleen of a frog carries the same role as the spleen in a human. The spleen destroys white blood cells and develops antibody's to defend the frogs immune system. This helps protect the immune system from viruses, such as the common cold.

Most splenic tumors don't begin in the spleen, and those that do are quite often lymphomas. Lymphoma is a kind of blood growth that creates in the lymphatic framework. It is more regular for a lymphoma to begin in another piece of the lymphatic framework and attack the spleen than it is for lymphoma to begin in the spleen itself.

That is called as Spleen.