Spleen

Spleen. The spleen is a flattened oblong body which in the adult weighs about 7 ounces; it is situated in the left hypochondriac region adjoining the cardiac end of the stomach. It is invested in a capsule consisting of connective tissue and unstriped muscular tissue fibres from the inner surface of which processes, or trabeculae as they are called, project and ramify in the interior of the spleen, forming the supporting framework to the spleen tissue proper (the spleen pulp). This last-named substance is of a dark reddish-brown colour and consists of a mass of cells, many of them like ordinary lymph corpuscles, and many resembling degenerated red blood-corpuscles. The splenic artery enters the organ at a notch on its under surface, known as the hilum, and branches and ramifies in the spleen pulp, its smaller divisions being surrounded by aggregations of lymphoid tissue which form little masses, disseminated throughout the spleen substance, and known as the Malpighian corpuscles of the spleen. The blood conveyed to the spleen in its passage through the lymphold tissue and spleen pulp undergoes important changes; it is probable that many of the red blood-corpuscles here terminate their existence, and numbers of new white corpuscles appear to be formed. The spleen undergoes rhythmical contraction and expansion in virtue of the large amount of muscular tissue contained in its capsule and trabeculae; it manifests a notable increase in size a few hours after a meal The spleen has no duct and is hence classified with the thymus, thyroid and other bodies as one of the ductless glands. In certain forms of disease great enlargement of the spleen occurs. This is markedly the case in ague and in typhoid fever; in the malady known as leucocythaemia the spleen attains sometimes a very large size.