What is Spleen? Structure, Functions

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.

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Spleen

Organ associated with Spleen

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.