Final answer:
Intercalated discs in cardiac muscle contain gap junctions and desmosomes, which facilitate coordinated contraction.
Step-by-step explanation:
Intercalated discs are part of the cardiac muscle sarcolemma and contain two important structures for cardiac muscle contraction: gap junctions and desmosomes. Gap junctions form channels between adjacent cardiac muscle fibers, allowing the depolarizing current to flow from one cell to the next, enabling quick transmission of action potentials and coordinated contraction of the heart. Desmosomes anchor the ends of cardiac muscle fibers together, ensuring the cells do not pull apart during contraction.