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Spleen

Structure and Function

Spleenstructure.png

Structure

Its pretty small (about 1x3x5"), and is intraperitoneal (between two peritoneal membranes). The diaphragm is above and behind it and the splenic flecture is below it. It is enclosed in a capsule of peritoneum and has ligaments made of that either side of it: the gastrosplenic ligament joins to the stomach (and carries the short gastric and left gastroepiploic vessels) and the splenicorenal ligament joins to the left kidney (carrying the splenic vessels and the tail of the pancreas).

Surface Markings

It's in the right hypochondrium, the top is level with the anterior 9th rib, and bottom with the 11th rib. The top third is above the edge of the diaphragm.

Functions

There are two parts to it:

  • The red pulp (90%), made of a massive sponge like array of sinusoids and vascular sinuses. This phagocytosises red blood cells, and chucks the broken up bits into the portal vein.
  • The white pulp (10%), made mostly of lymphoid tissue. Filters antigens, and produces loads and loads of B lymphocytes which turn into plasma cells and then antibodies.

Interestingly, the spleen actually produces red blood cells in the foetus.

Arterial and Venous supply

Spleenblood.png

Nervous Supply

The nerves go in at the hilum with the splenic artery and come from the celiac plexus

Lymph

They emerge from the hilum and pass through a few nodes along the course of the splenic artery, then drain into the celiac nodes.

Histology

Dunno really. Doesn't exactly have much tissue, its just a massive lump of blood vessels with a small amount of loose support tissue. Wouldn't lose any sleep over it if I was you.

Clinical Conditions

Splenomegaly

The spleen needs to be three times its normal size before it is palpable. It will expands downwards and medially, and you'll be able to feel it under the left hand side of the rib cage. An enlarged spleen can be caused by:

  • Malaria EBV (glandular fever)
  • Viral hepatitis
  • Portal Hypertension (caused by cirrhosis, right heart failure)
  • Haematological cancer
  • Rheumatoid Arthritis
  • Autoimmune haemolysis

Splenectomy

Have increased risks of pneumococcus(Gram positive), meningococcus(G-), h influenza(G-). This is because the spleen is really good at dealing with encapsulated organisms, so without it they become more of an issue. They are treated with penicillin and/or amoxicillin for at least two years after a splenectomy.

Trauma to the Spleen

Although it looks like it is well protected it often can get lacerations in automobile accidents of the crushing or runover type. Penetrating wounds of the lower left thorax can also damage the spleen. There will be A LOT of bleeding.