spleen

spleen The spleen was linked in past centuries to a variety of emotions, characteristics, or behaviours — usually spitefulness, bad temper, or melancholy, but also sometimes to general liveliness and explosive wit. In the seventeenth century Shakespeare provided many a quote, including the tag ‘spleeny Lutheran’. In the eighteenth century we have Addison's ‘touchy testy pleasant fellow’ with ‘so much Wit and Mirth and Spleen’, whilst less positively a ‘touch of the spleen’ was what we would now call psychosomatic illness. In the late nineteenth century the concept still survived in such whimsies as Gilbert's in Patience: ‘… a sentimental passion of a vegetable fashion must excite your languid spleen’. And ‘venting one's spleen’ has traditionally described a vituperative outburst.

There seems no good reason why the spleen should have deserved these associations — unlike, say, the heart which manifests its link with love by an increase in beating rate with excitement. The spleen is physiologically and anatomically unobtrusive. It is in fact — unusually in the body for an unpaired organ — dispensible. We can live without it because its functions can be taken over elsewhere. It is a small spongy purple mass in a fibrous capsule, tucked under the left side of the diaphragm (smaller than the liver which is tucked under the right side).

The spleen is in a way a poor relation among organs in that it is rarely in the public eye — not even on the butcher's counter. It is not susceptible to dramatic televisual imaging and it does not invite transplantation. It does however sometimes need to be removed: it can suffer hidden injury, for example in crushing or road traffic accidents, when its rupture can cause internal bleeding; other causes for splenectomy include some blood diseases.

Although we can do without it if necessary, the spleen does normally have important functions. In fetal life it is the site of red blood cell formation, until this is taken over by the bone marrow. It contributes to the immune system, forming antibodies and producing and storing masses of lymphocytes. It contains extensive channels and spaces (sinuses) where the blood flows slowly and where senescent red blood cells break down and are removed from the circulation. It therefore becomes enlarged in some infective, parasitic, and blood diseases.

The spleen acts to some extent as a blood reservoir, although this mechanism for increasing circulating blood volume is relatively minor and unimportant in humans compared with some other animals. The smooth muscle in its capsule is activated by the autonomic nervous system in conditions of ‘fight or flight’ or after blood loss, squirting a little extra blood into the circulation — which is perhaps the nearest physiological equivalent to the metaphoric ‘venting’.

Sheila Jennett

See lymphatic system.See also blood; humours; immune system.