The structure and significance of the EPS.

The endoplasmic reticulum (EPS) is a large organelle of membrane sheets and tubules that begin near the nucleus and pass through the cell. The entire structure can make up a significant part of the endodemembrane system of the cell. For example, in cells such as hepatocytes of the liver, which specialize in protein secretion and detoxification, EPS can account for more than 50% of the total cell lipid bilayer. Likewise, the EPS membrane system is especially prominent in the beta cells of the pancreas, which secrete insulin, or in activated B lymphocytes, which produce antibodies.