It is an organ derived from mesenchyme and lying in the mesentery.
The organ consists of masses of lymphoid tissue of granular appearance located around fine terminal branches of veins and
arteries. These vessels are connected through the splenic pulp by modified capillaries called splenic sinuses. Cross sections
of the spleen reveal a red soft surface which is divided into red and white pulp. Red pulp corresponds to the sinuses which
are usually filled with blood. The white pulp shows white nodules, called Malpighian corpuscles. Under the microscope, these
areas correspond to lymphoid follicles, rich in B-lymphocytes, and the periarteriolar lymphoid sheaths, rich in T-lymphocytes.
The human spleen is located in the upper left part of the abdomen,
behind the stomach and just below the diaphragm. In a normal individual this organ measures about 125 × 75 × 50
mm (5 × 3 × 2 in) in size.
In certain animals such as dogs and horses, the spleen sequesters
a large number of erythrocytes (red blood cells), which can be dumped into the bloodstream during periods of physical exertion.
These animals also have large hearts in relation to their body size to accommodate the higher-viscosity blood that results.
Some athletes have tried doping themselves with their own stored red blood cells to try to achieve the same effect, but the
human heart is not equipped to handle the higher-viscosity blood.
Approximately 10% of people have one or more accessory spleens.
They may form near the hilum of the main spleen, the junction at which the splenic vessels enter and leave the organ.
Enlargement of the spleen is known as splenomegaly. It may be caused
by malaria, bacterial endocarditis, leukaemia, pernicious anaemia, leishmaniasis, Hodgkin's disease, Banti's disease, hereditary
spherocytosis, cysts, glandular fever (mononucleosis), and tumours. Primary tumours of the spleen include hemangiomas and
hemangiosarcomas. Marked splenomegaly may result in the spleen occupying a large portion of the left side of the abdomen.
The spleen is the largest collection of lymphoid tissue in the body.
It is normally palpable in preterm infants, in 30% of normal, full-term neonates, and in 5% to 10% of infants and toddlers.
A spleen easily palpable below the costal margin in any child over the age of 3-4 years should be considered abnormal until
Splenomegaly can result from antigenic stimulation (eg, infection),
obstruction of blood flow (eg, portal vein obstruction), underlying functional abnormality (eg, hemolytic anemia), or infiltration
(eg, leukemia or storage disease, such as Gaucher's disease). The most common cause of acute splenomegaly in children is viral
infection, which is transient and usually moderate. Basic work-up for acute splenomegaly includes a complete blood count with
differential, platelet count, and reticulocyte and atypical lymphocyte counts to exclude hemolytic anemia and leukemia. Assessment
of IgM antibodies to viral capsid antigen (a rising titer) is indicated to confirm Epstein-Barr virus or cytomegalovirus.
Other infections should be excluded if these tests are negative.
the operation to remove the spleen is i slpeemecomy
after surgery patients are suseptable to mant diseases and require a ttrple
vaccine for pneumococcal polysacharide (pneumovac), meningococcal (ACWY vax) and haemophilus influenzae(Hib)