The spleen, an organ found in virtually all vertebrate animals, satiates important roles in regards to red blood cells and the immune system[1] Located in the left upper quadrant of the abdomen, It removes old red blood cells, holds a reserve in case of hemorrhagic shock in some animals such as horses, but not humans), and recycles iron while simultaneously removing from the blood circulation antibody-coated bacteria and antibody-coated blood cells.<.[2] It synthesizes antibodies in its white pulp ref name="Mebius"/>[3] Recently, it has been found to contain, in its reserve, half the body's monocytes , which is located in its red pulp, that, upon moving to injured tissue such as the heart, turns into dendritic cells and macrophages while aiding wound healing.[4][5][6] It is one of the centers aiding to the activity of the reticuloendothelial system, and can be considered analogous to a large lymph node; the spleens absence leads to a predisposition to certain infections.
 The celiac artery and its branches. |  The celiac artery and its branches. |  Horizontal disposition of the peritoneum in the upper part of the abdomen. |  Transverse section through the middle of the first lumbar vertebra. |
 The duodenum and pancreas. |  The visceral surface of the spleen. |  Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its tributaries. |  Transverse section of the human spleen, showing the distribution of the splenic artery and its branches. |
 Section of the spleen, showing the termination of the small blood vessels. |  Back of lumbar region, showing surface markings for kidneys, ureters, and spleen. |  Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green). |  Lymphatic system |
