SPLEEN
The large organ lying to the left of, below, and behind the stomach. This
organ is partially responsible for white blood cell formation (red blood cells in childhood),
and it is lined with resident macrophages that help it filter the blood, remove and recycle
old and dead red blood cells, and send this all up to the liver in the portal blood.
The liver, in fact, does most of the recycling of splenic hemoglobin derivatives.
The spleen initiates much resistance and immunologic response, being made mostly of
lymph pulp, and it stores and concentrates a large number of red blood cells. These can
be injected into the bloodstream for immediate use under flight or fight stress, since the
spleen is covered with capsule and vascular muscles that constrict in the presence of
adrenalin or sympathetic adrenergic nerve stimulus.