Hypoglossus

Hypoglossus, commonly referred to as the hyoglossus muscle, is a paired extrinsic muscle of the tongue located in the floor of the mouth. It originates from the body and greater horn of the hyoid bone and inserts into the lateral aspect of the tongue. The muscle fibers run upward to a position between the tongue’s deep surface and its lateral border.

The primary action of the hyoglossus is to depress the tongue; it can also assist in retracting the tongue’s sides during swallowing and speech. It functions as part of the coordinated action of the tongue’s extrinsic muscles, which position the tongue within the oral cavity.

Innervation is provided by the hypoglossal nerve (cranial nerve XII), which supplies most intrinsic and extrinsic tongue muscles. The palatoglossus is a notable exception, being innervated by the pharyngeal plexus via the vagus nerve (CN X). Blood supply to the hyoglossus comes from branches of the lingual artery.

Clinically, weakness or paralysis of the hypoglossus portion of the tongue can result from hypoglossal nerve injury, leading to impaired tongue movements, dysarthria, and dysphagia. The hyoglossus can be affected by floor-of-mouth pathology or during surgical approaches to the tongue and oropharyngeal region, where its relationships to surrounding structures are considered.

In summary, the hyoglossus is a key muscle for depressing the tongue, innervated by CN XII, and supplied by branches of the lingual artery, with important implications in normal speech and swallowing as well as clinical contexts involving the tongue and floor of the mouth.