tailieunhanh - Chapter 060. Enlargement of Lymph Nodes and Spleen (Part 4)

Splenomegaly Structure and Function of the Spleen The spleen is a reticuloendothelial organ that has its embryologic origin in the dorsal mesogastrium at about 5 weeks' gestation. It arises in a series of hillocks, migrates to its normal adult location in the left upper quadrant (LUQ), and is attached to the stomach via the gastrolienal ligament and to the kidney via the lienorenal ligament. When the hillocks fail to unify into a single tissue mass, accessory spleens may develop in around 20% of persons. The function of the spleen has been elusive. Galen believed it was the source of "black. | Chapter 060. Enlargement of Lymph Nodes and Spleen Part 4 Splenomegaly Structure and Function of the Spleen The spleen is a reticuloendothelial organ that has its embryologic origin in the dorsal mesogastrium at about 5 weeks gestation. It arises in a series of hillocks migrates to its normal adult location in the left upper quadrant LUQ and is attached to the stomach via the gastrolienal ligament and to the kidney via the lienorenal ligament. When the hillocks fail to unify into a single tissue mass accessory spleens may develop in around 20 of persons. The function of the spleen has been elusive. Galen believed it was the source of black bile or melancholia and the word hypochondria literally beneath the ribs and the idiom to vent one s spleen attest to the beliefs that the spleen had an important influence on the psyche and emotions. In humans its normal physiologic roles seem to be the following 1. Maintenance of quality control over erythrocytes in the red pulp by removal of senescent and defective red blood cells. The spleen accomplishes this function through a unique organization of its parenchyma and vasculature Fig. 60-1 . 2. Synthesis of antibodies in the white pulp. 3. The removal of antibody-coated bacteria and antibody-coated blood cells from the circulation. Figure 60-1 Schematic spleen structure. The spleen comprises many units of red and white pulp centered around small branches of the splenic artery called central arteries. White pulp is lymphoid in nature and contains B cell follicles a marginal zone around the follicles and T cell-rich areas sheathing arterioles. The red pulp areas include pulp sinuses and pulp cords. The cords are dead ends. In order to regain access to the circulation red blood cells must traverse tiny openings in the sinusoidal lining. Stiff damaged or old red cells cannot enter the sinuses. .