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nuclear envelope

noun

The double-layered membrane surrounding the nucleus of a eukaryotic cell, separating the contents of the nucleus from the cytosol (cytoplasm).

It is made up of two layers, each composed of a lipid bilayer. It is perforated with holes, called nuclear pores, to facilitate and regulate the exchange of materials (for example, proteins and RNA) between the nucleus and the cytoplasm. In between these two membranes is a space called perinuclear space. The outer membrane is continuous with the endoplasmic reticulum. The inner membrane is associated with a network of intermediate filaments called nuclear lamina, which is made of lamin. The lamina acts as a site of attachment for chromosomes. It also acts like a shield for the nucleus.

Also known as the perinuclear envelope, nuclear membrane, nucleolemma or karyotheca.