Nuclear membrane and Endoplasmic Reticulum

Cell nucleus is surrounded by the double nuclear membrane (two layers of the elementary cell membrane). There are pores in the nuclear membrane through which for example mRNA travels in its way to code for proteins in the cell cytoplasm.

Nuclear membrane is connected to the endoplasmic reticulum (ER). ER is called rough ER where it is covered with ribosomes and smooth ER where no ribosomes adhere to it. Rough ER is more common in the central part of the cell, more peripherally we encounter the smooth ER. Proteins manufactured in the rough ER are further modified in the smooth ER and the transported in membrane vesicles to the Golgi complex, where they are finalized. Golgi complex produces vesicles which travel to the inner side of the cell membrane, fuse with it and so excrete the vesicle content out of the cell. This is the common procedure in gland cells.