Hypoglossal nucleus

Gray695

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Medulla oblongata - posterior - very low mag

Medulla oblongata - posterior - cn xii - high mag

Hypoglossal nucleus is a neuronal structure located in the brainstem, specifically within the medulla oblongata. It is an essential component of the nervous system, playing a crucial role in the control of tongue movements. The hypoglossal nucleus is the origin of the hypoglossal nerve (cranial nerve XII), which innervates the muscles of the tongue. This nucleus and its associated nerve are vital for various tongue movements including speech, swallowing, and food manipulation.

Structure

The hypoglossal nucleus is situated in the dorsal aspect of the medulla oblongata, near the midline, directly beneath the floor of the fourth ventricle. It is elongated in shape and lies adjacent to the central canal of the spinal cord as it transitions into the brainstem.

Function

The primary function of the hypoglossal nucleus is to generate motor commands for tongue movements. It sends motor fibers via the hypoglossal nerve to the intrinsic and extrinsic muscles of the tongue, except for the palatoglossus muscle, which is innervated by the vagus nerve (cranial nerve X). The precise control of the tongue is crucial for speech articulation, swallowing (deglutition), and the mechanical manipulation of food during chewing.

Clinical Significance

Damage to the hypoglossal nucleus or its nerve can lead to a range of motor disorders of the tongue. Such damage may result from various causes, including stroke, tumors, and infections. Symptoms of hypoglossal nerve damage include difficulty in speaking (dysarthria), swallowing (dysphagia), and a deviation of the tongue towards the injured side when protruded. Diagnosis of hypoglossal nerve dysfunction typically involves clinical examination and imaging studies, such as MRI or CT scans, to visualize the path of the nerve and identify any lesions affecting it.

See Also

• Cranial nerves
• Motor neuron
• Brainstem
• Medulla oblongata