Under the electron microscope, the junction is adjacentcell membraneIt is highly parallel, the cell gap is very narrow, only 2-3 nm, and there are many observation points with approximately equal intervals.According to the electron microscope observation of freeze etching, there are many regularly arranged columnar particles on the adjacent cell membrane, called connexions.Each connectome consists of 6 rod-shapedConnexin(connexin), and the center is surrounded by hydrophilic tubules with a diameter of about 2nm, called central canaliculum. The connecting bodies on both sides of adjacent cell membranes connect with each other, and the central tubules on both sides connect with each other to form a channel for direct communication between cells[1]
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The function of gap junction: ① intercellular ions andSmall moleculeSubstances (substances with molecular weight less than 1500D, such asamino acid、glucose、nucleotide、vitamin, hormonegrowth factor、cAMPExchange and transferChemical information, coordinate the metabolic activities of cells, regulate the growth and differentiation of cells, and make the tissue cells become a functional unity (also called metabolismcoupling ）。②The resistance at the gap junction is low, and charged ions can pass through freely, which is conducive to the conduction of electric impulses. The conduction speed is fast and accurate, so as to ensure that organs and tissues perform their functionsSynchronicity(also known asElectric coupling）。Gap connection is a kind ofDynamicStructure, the number of connecting corpuscles varies from several to thousands, and each connecting corpuscle has 6Subunit(Connexin) can open or close pores in a sliding manner. The opening and closing of pores are regulated by many factors, such asMembrane potentialAnd pH value decrease or Ca2+The increase of concentration can make the pores smaller to close, so as to avoid the whole tissue being affected by the damage or death of individual cells[1]
