Final answer:
The distinctive histologic feature of cardiac muscle is intercalated discs, which contain desmosomes and gap junctions, allowing for synchronized contractions.
Step-by-step explanation:
These structures are found at the junction of different cardiac muscle cells, known as cardiomyocytes. Intercalated discs are part of the cardiac muscle sarcolemma and contain two main elements: desmosomes and gap junctions. Desmosomes function to anchor the ends of cardiac muscle fibers together, preventing the cells from pulling apart during the stress of contraction. Gap junctions form channels that allow the passage of ions between cells, facilitating the quick transmission of action potentials and the synchronized contraction of the heart muscle.