Final answer:
Intercalated discs connect individual heart muscle cells and are vital for synchronized contractions, containing gap junctions for electrical coupling and desmosomes for structural support.
Step-by-step explanation:
The structures that connect individual heart muscle cells are called intercalated discs. These discs are critical for the synchronized contraction of cardiac muscle cells, as they contain gap junctions and desmosomes.
Gap junctions facilitate the flow of depolarizing current between cardiac muscle cells, promoting electric coupling and allowing action potentials to be quickly transmitted across the cells.
This creates a functional unit of contraction known as a syncytium. Meanwhile, desmosomes anchor the cells together, ensuring they do not pull apart during contraction. The intercalated discs form a part of the cardiac muscle sarcolemma and are integral to the function of the heart.