Overview nuclear membrane (Nucleolemma,
Pages with explanations are linked to the
text below the images if available! (Labelling is in German)
The nuclear membrane (Nucleolemma; Terminologia histologica: Membrana
nuclearis) is the border between the nucleus
and the cytoplasm. It has an outer
unit membrane (thickness ~ 7 nm; phospholipid double layer)
attached ribosomes followed by the
space wich is 20 - 100 nm in width and an inner elementary
membrane lacking ribosomes. The nuclear
lamina is directly attached to the inner nuclear membrane and responsible
for nuclear stability. It consists of the interconnected intermediate filaments
A and C, which are attached to a Lamin-B receptor protein belonging
to the inner nuclear membrane.
|nuclear lamina & mem-
brane skin (human)
|nuclear membrane during
|bleb: dilated nuclear membrane
fibroblast of human placenta
|bleb of a myoepithelial
cell parotid gland (rat)
|nuclear membrane of a
pneumocte type 2, lung (rat)
|nuclear membrane + pores of
an ovum, ovary (rat)
The nuclear membrane originates from rough
endoplasmic reticulum (RER) which can be seen in the telophase
of a mitosis when it is newly synthetised.
The nuclear membrane decays with the transition of the prophase to the
metaphase in mitosis forming small membrane
tubes or vesicles that correspond to RER.
Under normal conditions (in interphase) sometimes a direct transition
from RER to the nuclear membrane is visible
whereby the perinuclear space is directly continuing into the interior
of the RER and the outer nuclear membrane,
which has attached ribosomes, is in continuity with RER
membranes. In some cases considerable widenings of the outer
nuclear membrane appear which are called blebs
(see image above).
Ring-like connections between the inner and the outer nuclear membrane
exist only at the disk-like nuclear pores.
or exit of substances to the nucleus can only occur at these locations.
Very electron-dense material is directly attached to the outer nuclear
membrane which later is involved in formation of the acrosome during spermiogenesis
--> nucleus, nuclear
pore, karyoplasm, euchromatine,
--> Electron microscopic atlas Overview
--> Homepage of the workshop
Images, page & copyright H. Jastrow.