Which of the following is NOT a major type of structural cell in the heart?

The correct answer is that neurons are not a major type of structural cell in the heart. The heart is primarily composed of three main structural cell types: cardiomyocytes, vascular endothelium, and vascular smooth muscle cells.

Cardiomyocytes are the specialized muscle cells responsible for the contractile function of the heart; they enable the heart to pump blood throughout the body. Vascular endothelium lines the blood vessels, playing a critical role in maintaining the barrier between the blood and surrounding tissues, as well as in vascular health and function. Vascular smooth muscle cells, found in the walls of blood vessels, help regulate blood flow and pressure through contraction and relaxation.

Neurons, while important for transmitting signals in the body and innervating the heart, do not form the structural foundation of the heart itself. They are part of the nervous system and primarily function to send signals that can influence heart rate and contractility but are not considered a major structural cell type within the heart's anatomy.