Final answer:
Both heart muscle and unitary smooth muscle share gap junctions that allow synchronized contraction as a functional group.
Step-by-step explanation:
The structure that both heart muscle and unitary smooth muscle share, allowing them to contract as a functional group, is c. gap junctions.
Unitary or single-unit smooth muscle cells are connected by gap junctions, which allow the cells to communicate with each other, synchronizing the contraction of the muscle as a whole. This ensures that the muscle tissues in the walls of hollow organs, like the intestines, bladder, and uterus, contract together uniformly. Similarly, cardiac muscle cells are also connected by gap junctions located in the intercalated discs. These junctions are essential for the synchronized contraction of the heart muscle, enabling it to function effectively as a pump.
Both heart muscle and unitary smooth muscle share gap junctions that allow them to contract as a functional group. Gap junctions are specialized protein channels that connect adjacent cells, allowing for the rapid transmission of electrical signals between cells. In the case of smooth muscle, the gap junctions enable synchronized contractions of multiple smooth muscle cells, resulting in a coordinated and efficient contraction.