Why is the endoplasmic reticulum considered to be the circulatory system of animal cell?

The endoplasmic reticulum (ER) is often referred to as the circulatory system of the animal cell because it serves as a vast network of membranes that facilitates the transport of proteins and lipids throughout the cell. It synthesizes and processes biomolecules, enabling their distribution to various cellular locations. The rough ER is involved in protein synthesis, while the smooth ER is responsible for lipid synthesis and detoxification. Together, they play a crucial role in maintaining cellular function and organization, similar to how a circulatory system distributes nutrients and waste.