The endoplasmic reticulum is shortly abbreviated as ER. It is a type of organelle in eukaryotic cells.
The structure of ER is composed of the interconnected network of flattened and membrane-enclosed sacs or tube-like structures. These structures are known as cisternae.
There are two regions of the ER. Smooth ER and rough ER are classified on the basis of absence and presence of ribosomes on the surface of the ER respectively.