List of abbreviations |
Vocabulary
of micros- copic anatomy specialist terms explained in English + German |
Every attempt was made to provide correct information and labelling, however any liability for eventual errors or incompleteness is rejected! |
dieser Seite Editor:
|
Conditions of use |
|
|
|
|
|
|
heart mucle: intercaltaed
disc overview (monkey) |
detail: nexus and fascia
adhaerens (monkey) |
Nexus in intercalated disc
of heart muscle (rat) |
gap-junction heart
muscle cell (rat) |
gap-junction detail from
intercalated disk (rat) |
Gap-Junction, eye
lens epithelial cells (rat) |
A nexus or gap junction is an electrical synapse (nonvesicular synapse; Terminologia histologica: Macula communicans, Nexus, Synapsis non vesicularis, Synapsis electrica). It consists of spot- or stripe-like communicating junctions (Terminologia histologica: Junctiones communicantes) between two neighbouring cells. Nexus are well formed in the intercalated discs of heart muscle cells and here are arragned as round to irregular cell-cell contact areas with a contact surface of up to 1 µm². Otherwise this kind of cell-cell contact shows diameters of 0,1 – 1 µm whereby the distance between the cell membranes involved is only 2 - 3, maximal 5 nm. In the nexus tunnel proteins (connexons) of the cell membranes of adjacent cells directly continue into each other.
molecular composition:
The connecting tunnels are formed by an exact
aggregation of two open pores of the cell
membrane of neighbouring cells (1 per cell) which as hlaf-channels
are called connexons (Terminologia histologica: Connexonae). One
connexon consists of 6 subunits
of the protein connexin (Terminologia
histologica: Connexina) in hexagonal arrangement in each cell
membrane. Thus a complete tunnel consists of 2 x 6 = 12 connexin molecules.
Seventeen different genes are known to code for connexins. In some cases
even different kinds of connexins are present in the same nexus. Connexin
43
(molecular weight: 43.000 Da) is typical for the nexus of heart
mucles cells, vascular endothelial cells
and astrocytes. The nexus of basal
cells of the skin consist of connexin 43,
the epithelial cells of the above stratum
spinosum of connexin 31 (molecular weight: 31.000 Da). Connexin
32
(32.000 Da) and connexin
26 (26.000 Da) are present in nexus between
epithelial
cells of pancreas,
liver
and gut. The cell membranes of
Schmidt-Lanterman's incisures of peripheral nerves
contain gap junctions with connexin 32. Under normal conditions
small molecules and ions can penetrate the myelin sheath here easily.
Function is is only available in the professional version of this atlas.
--> cell-to-cell contacts, tight-junction,
desmosome,
fascia
adhaerens, synapse
--> Electron microscopic atlas Overview
--> Homepage of the workshop
Three images were kindly provided by Prof. H. Wartenberg;
other images, page & copyright H. Jastrow.