Question

multiple choice question

what is the action of the occipital belly of the occipitofrontalis?

elevates eyebrows; draws scalp forward and wrinkles forehead
closes eye; aids in flow of tears across eye
retracts scalp; fixes galea aponeurotica
elevates upper eyelid; opens eye

Explanation:

Identify the muscle and its components

The question asks for the action of the occipital belly of the occipitofrontalis muscle. The occipitofrontalis is a bipartite muscle of the scalp consisting of two muscle bellies connected by a broad, fibrous tendon.

Analyze the role of the epicranial aponeurosis

Using the Epicranial Aponeurosis knowledge point

$$ \text{Occipitofrontalis} = \text{Frontal belly} + \text{Epicranial aponeurosis (galea aponeurotica)} + \text{Occipital belly} $$

Determine the action of each belly

The frontal belly lies over the forehead. When it contracts, it pulls the scalp forward, elevates the eyebrows, and wrinkles the forehead. Conversely, the occipital belly lies at the posterior aspect of the skull. When the occipital belly contracts, it pulls the scalp posteriorly (retracts the scalp) and tenses/fixes the epicranial aponeurosis (galea aponeurotica) so that the frontal belly has a stable base to pull against.

Evaluate the given options

• "Elevates eyebrows; draws scalp forward and wrinkles forehead": This is the action of the frontal belly of the occipitofrontalis.
• "Closes eye; aids in flow of tears across eye": This is the action of the orbicularis oculi muscle.
• "Retracts scalp; fixes galea aponeurotica": This matches the anatomical action of the occipital belly.
• "Elevates upper eyelid; opens eye": This is the action of the levator palpebrae superioris muscle.

Answer:

• (A) Elevates eyebrows; draws scalp forward and wrinkles forehead
• (B) Closes eye; aids in flow of tears across eye
• (C) Retracts scalp; fixes galea aponeurotica (Correct answer)
• (D) Elevates upper eyelid; opens eye