Topic: Neural pathways
Question: Describe the structures forming the floor of fourth-ventricle of brain?
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The floor of the fourth ventricle is formed by the dorsal surface of the brainstem, including the pons, medulla oblongata, and parts of the midbrain. The structures that make up the floor of the fourth ventricle include:
1. Medial eminence: A midline bulge caused by the underlying facial colliculus (control center for facial movements) and abducens nucleus (control center for lateral rectus muscle).
2. Sulcus limitans: A shallow groove running longitudinally on each side of the medial eminence. It separates the medial motor nuclei from the lateral sensory nuclei.
3. Motor nuclei: Include the hypoglossal nucleus (control center for tongue movements), vagus motor nucleus (control center for vagus nerve), accessory nucleus (control center for neck muscles) and trigeminal motor nucleus (control center for jaw muscles). They are involved in motor control and located medial to the sulcus limitans.
4. Sensory nuclei: Include the nucleus of the solitary tract (visceral sensory), nucleus ambiguous (taste and swallowing), spinal trigeminal nucleus (pain/touch of face), and cochlear nuclei (hearing). They are located lateral to the sulcus limitans.
5. Striae medullares: Fiber bundles that cross the fourth ventricle floor obliquely, carrying signals between the cerebellum, medulla and higher brain centers.
6. Choroid plexus: Produces cerebrospinal fluid and lines parts of the fourth ventricle. Has a seaweed-like appearance.
7. Obex: Where the central canal of the spinal cord opens into the fourth ventricle. Located in the caudal medulla.
8.Median aperture: An opening in the pons exposing parts of the cerebellum.
9.Lateral apertures: Additional openings on each side exposing the cerebellum.
10. Vestibular areas: Swellings produced by the vestibular nuclei which coordinate balance and equilibrium. Located on the lateral walls of the rostral fourth ventricle.
In summary, the floor of the fourth ventricle is formed by the dorsal pons and medulla. It contains motor and sensory nuclei, fiber tracts, the choroid plexus and openings that expose the cerebellum. A shallow groove called the sulcus limitans separates the medial motor nuclei from the lateral sensory nuclei. The structures of the fourth ventricle floor are involved in important functions such as movement, sensation, hearing, and balance.
