The endomembrane system inside the eukaryotic cells functions in a coordinated manner.
The endomembrane system include endoplasmic reticulum (ER), Golgi complex (GB or Golgi bodies), lysosomes and vacuoles.
Since the functions of the mitochondria, chloroplast and peroxisomes are not coordinated with the above components, these are not considered as part of the endomembrane system.