<prompt> The posterior bellies of digastric muscle are especially active duringSwallowing and speechSwallowing and smilingSwallowing and chewingSwallowing and frowning  <response>: DigastricOrigin The posterior bellay arises from the mastoid, or digastric, notch immediately behind the mastoid process of the temporal bone.Insertion The posterior belly passes downwards and forwards towards the hyoid bone where it becomes the intermediate digastric tendon and joints with the anterior belly.Nerve supply Derived from the digastric branch of the facial nerve.Vasculature Arterial blood supply from the posterior auricular and occipital arteries.Action The muscle depresses the mandible and can elevate the hyoid bone. The posterior bellies act in unison and are particularly active during swallowing and chewing. 