Which two muscles have fibers that cross throughout their course?

• A. Lateral Rectus and Superior Rectus
• B. Superior Rectus and Superior Oblique
• C. Superior Oblique and Inferior Rectus
• D. Inferior Rectus and Medial Rectus

Answer: (B)

Think about how each extraocular muscle travels from its origin to its insertion. Some muscles follow a straightforward, parallel path, while others have a path that twists or crosses as they course toward the eye. The pair that shows a crossing of fibers throughout its course are the superior rectus and the superior oblique. The superior rectus travels upward from the common tendinous ring, and its fibers approach the globe in a way that involves crossing relative to the vertical plane. The superior oblique has a unique route: it runs toward the trochlea, passes through it, and then inserts on the superior and posterior aspect of the globe, with its fibers wrapping and crossing as they go. This combination gives both vertical (elevation/depression) and torsional actions and reflects a crossing pattern along the entire length of each muscle.

The other muscle pairs don’t share this same continuous crossing arrangement. Their fibers tend to run in more parallel, direct paths to their insertions, without the same decussating pattern throughout the course.