The<unk>  is an organ located in the abdomen of the human body, where it functions in the destruction of old red blood cells and holding a small reservoir of blood.  It is regarded as one of the centers of activity of the reticuloendothelial system (part of the immune system). Until recently, the purpose of the<unk>  was not known. It is increasingly recognized that its absence leads to a predisposition to certain infections.
Spleen
Thymus
Bone marrow
Pancreas
Lymphatic tissues
Thyroid gland
Breast
Gallbladder