Question

multiple choice question

how would you classify this muscle based on its fascicle orientation?

• bipennate
• parallel
• triangular
• fusiform

Explanation:

Analyze the muscle illustration

Using the Skeletal Muscle Shapes knowledge point, we examine the visual characteristics of the muscle shown on the left. The muscle has a thick middle region (the belly) and tapers at both ends where it connects to tendons. Additionally, it features transverse tendinous intersections that divide it into segments, but the overall structural shape remains thick in the middle and tapered at the ends.

Evaluate the classification options

Using the Fusiform Muscle and Pennate Muscle Structure knowledge points:

• Bipennate: Fascicles approach a central tendon from both sides, resembling a feather. This does not match the image.
• Parallel: Fascicles run parallel to the long axis of the muscle, forming a uniform width (such as the rectus abdominis or sartorius). While this muscle has parallel-running fibers within its segments, its overall shape is distinctly tapered.
• Triangular: Fascicles converge from a broad origin to a single, narrow insertion (like the pectoralis major). This does not match.
• Fusiform: Muscles that are thick in the middle (belly) and tapered at each end (such as the biceps brachii). The illustrated muscle exhibits this characteristic spindle-like, tapered shape.

Answer:

• (A) Bipennate
• (B) Parallel
• (C) Triangular
• (D) Fusiform (Correct answer)