The endomembrane system contains all of the following structures except the

Organelles include the endoplasmic reticulum, the Golgi body, various vesicles, lysosomes, and the plasma membrane. Ribosomes can also be counted, if they are attached to a member of the endomembrane system (think rough ER). Some people also include the nuclear envelope because it is involved in the early steps of protein production, and is continuous with much of the ER system.