The hypoglossal nerve's primary function is to enable tongue movement, which is essential for speaking, swallowing, and manipulating substances in the mouth.
Detailed Functionality of the Hypoglossal Nerve
The hypoglossal nerve (cranial nerve XII) is a motor nerve that controls several muscles of the tongue. Specifically, it innervates the following muscles:
- Hyoglossus: Depresses and retracts the tongue.
- Intrinsic Muscles: These muscles (superior longitudinal, inferior longitudinal, transverse, and vertical) alter the shape of the tongue.
- Genioglossus: Protrudes the tongue and depresses the center.
- Styloglossus: Retracts and elevates the tongue.
These muscles work together to allow for a wide range of tongue movements necessary for:
- Speech: Forming words and articulating sounds.
- Swallowing: Moving food and liquids from the mouth to the pharynx.
- Oral Manipulation: Moving food around in the mouth, mixing it with saliva, and positioning it for chewing.
Breakdown of the Muscles Controlled by the Hypoglossal Nerve
The following table provides a summary of the tongue muscles controlled by the hypoglossal nerve and their respective functions:
| Muscle | Function |
|---|---|
| Hyoglossus | Depresses and retracts the tongue |
| Genioglossus | Protrudes the tongue and depresses the center |
| Styloglossus | Retracts and elevates the tongue |
| Intrinsic Muscles | Alters the shape of the tongue |
Clinical Significance
Damage to the hypoglossal nerve can result in:
- Dysarthria: Difficulty speaking due to impaired tongue movement.
- Dysphagia: Difficulty swallowing.
- Tongue Fasciculations: Involuntary twitching of the tongue muscles.
- Tongue Atrophy: Wasting away of tongue muscles.
- Deviation of the Tongue: When protruding the tongue, it deviates towards the side of the lesion due to weakness of the genioglossus muscle on the affected side.
