Fig. 5. Scanning electron micrograph of human trochlea, left orbit from the front. The tendon has been sectioned (arrowheads). The tendon is surrounded by fibrovascular tissue and supported by a crescent-shaped plate of cartilage underneath. The tendon is about 3 mm in diameter, and the plate of cartilage is about 6 mm broad and 4 mm long. The cartilage is attached to the fovea trochlearis of the frontal bone by fibrous tissue to form a tube through which the tendon slides. The tendon from here to its insertion is about 20 mm in length. (Courtesy of Dr. Eugene Helveston.)