Not everyone is aware of the certain luminal space found between the inner and outer bilayers of the nuclear envelope, which is known as perinuclear space. This small gap is actually the one that separates the nucleus from the cytoplasm, with a width of space that is approximately around 100 A and 500 A. The perinuclear space is a continuous joint with the endoplasmic reticulum’s lumen, due to the fact that its outer nuclear membrane is continuous with the endoplasmic reticulum. This space is also termed as PNS in some major medical and scientific publishing, and can also called as the nuclear envelope lumen or the perinuclear cisterna.
Since the nuclear envelope has two membranes, with each having a typical unit membrane structure, both of these encloses a flattened PNS sac that are in connection with the nuclear pore sites. The gap between the inner and outer membranes is also incessant with the space of the rough endoplasmic reticulum, and the outermost membrane has ribosomes attached on it as it is in continuous with the rough endoplasmic reticulum. The inner nuclear membrane serves as the chief residence of various inner nuclear membrane proteins. The inner and outer nuclear membranes are bonded at the spot of nuclear pore complex insertion. The perinuclear cisterna is the space or gap between the two membranes that mark up the nuclear envelope.