kaksikmembraan (kaks bilipiidset kihti), mis ümbritseb tuuma, A nuclear membrane, also known as the nucleolemma or karyotheca, is the lipid bilayer membrane which surrounds the genetic material and nucleolus in eukaryotic cells. The nuclear membrane consists of two lipid bilayers—the inner nuclear membrane, and the outer nuclear membrane. The space between the membranes is called the perinuclear space, a region contiguous with the lumen (inside) of the endoplasmic reticulum. It is usually about 20–40 nm wide. The nuclear membrane also has many small holes called nuclear pores that allow material to move in and out of the nucleus.