What is Spleen?
The spleen is formed by reticular and lymphatic tissues and is the largest lymph organ. The spleen lies in the left hypochondriac region of the abdominal cavity between the fundus of the stomach and the diaphragm. It is purplish in color and varies in size in different individuals but is usually about 12cm long, 7cm wide and 2.5 cm thick. It weighs about 200g.
Spleen
Organ associated with Spleen
| Superiorly and posteriorly | Diaphragm |
| Inferiorly | Left colic flexure of the large intestine |
| Anteriorly | Fundus of the stomach |
| Medially | Pancreas and the left kidney |
| Laterally | Separated from the 9th and 11th ribs and the intercostal muscle by the diaphragm |
Structure
The spleen is slightly oval in shape with the hilum on the lower medial border. The anterior surface is covered with peritoneum. It enclosed in a fibroelastic capsule that dips into the organ forming trabeculae. The cellular material , consisting of lymphocytes and macrophages, is called splenic pulp z, ans it lies between the trabeculae. Red pulp is the part suffused with blood and white pulp consist of areas of lymphatic tissue where there are sleeves of lymphocytes amd macrophages around blood vessels. The structure entering and leaving the spleen at the hilum are:
- Splenic artery, a branch of the celiac artery
- Splenic vein, a branch of the portal vein
- Lymph Vessels (efferent only)
- Nerves.
Blood passing through the spleen flows in sinuses which have distinct pores between the endothelial cells, allow ingit to come into close association with splenic pulp.
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Functions
Phagocytosis — As described previously ood and abnormal erythrocyte are destroyed in the spleen and the breakdown products , bilirubin and iron are passed to the liver via splenic and portal vein . other cellular materials e g leukocytes platelets, and microbes are phagocytosed in the spleen . unlike lymph nodes the spleen has no afferent lymphatics entering it sout not exposed to disease speed by lymph.
Storage of Blood — The spleen contains upto 350 ml of blood and in response sympathetic stimulation can rapidly return a large part of this volume to the circulation e.g. haemorrhage.
Immune response — The spleen contains T amd B lymphocytes, which are activated by the presence of antigen eg. In infection . Lymphocytes proliferation during serious infection can cause enlargement of spleen (splenomegaly)
Erythropoiesis — The spleen and liver are important sites of fetal blood cell production and the spleen can also fulfill this function in adults in times of great need.