In the histology of skeletal muscle, a triad is the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side. Each skeletal muscle fiber has many thousands of triads, visible in muscle fibers that have been sectioned longitudinally.
In the microscopic examination of skeletal muscle tissue, a triad is a distinctive structure consisting of a T tubule and two sarcoplasmic reticulum cisternae on either side. Thousands of these triads can be seen within each skeletal muscle fiber when it is cut in a specific direction.