The correct answer is: Two of the statements above are correct.
A cardiac muscle cell contracts spontaneously and is joined to other cardiac muscle cells by structures called intercalated discs.
Explanation:
Cardiomyocytes, the only ones responsible for the contractile function of the myocardium, are terminally differentiated cells that cease to proliferate almost immediately after birth. Cardiomyocytes are mononucleated cells, with the nucleus in a central position. These are linked together by the so-called intercalary discs, which appear as dark bands in histological preparations, and which are a set of junction complexes where desmosomes and adherent junctions can be found (here called fascia adherens). The intercalary discs are therefore the boundaries between cells.
Substance abuse can spread STIs because when a user shares needles with an infected person, it can spread through the blood. Any high-risk behavior like this spreads STIs.
