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The pons (from Latin pons, "bridge") is part of the brainstem that in humans and other mammals, lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Varolius"), after the Italian anatomist and surgeon Costanzo Varolio (1543–75). [ 1 ]
The pons lies between the midbrain and the medulla oblongata. It is separated from the midbrain by the superior pontine sulcus, and from the medulla by the inferior pontine sulcus. [9] It contains tracts that carry signals from the cerebrum to the medulla and to the cerebellum and also tracts that carry sensory signals to the thalamus.
It is important in mediating saccadic eye movements. [2] It is probably not involved in smooth pursuit. [2] The PPRF generates excitatory bursts that are delivered to the ipsilateral abduecens nucleus to drive ipsilateral saccades (inhibitory saccadic stimuli are meanwhile delivered to the abducens nucleus from the contralateral medulla oblongata).
The pontine tegmentum, or dorsal pons, is the dorsal part of the pons located within the brainstem. The ventral part or ventral pons is known as the basilar part of the pons, or basilar pons. Along with the dorsal surface of the medulla oblongata, it forms part of the rhomboid fossa – the floor of the fourth ventricle.
medulla (floor of fourth ventricle) corresponding to the lower part of the area acustica in the rhomboid fossa; [citation needed] the caudal end of this nucleus is sometimes termed the descending or spinal vestibular nucleus. This nucleus is sometimes termed the nucleus of Schwalbe. lateral vestibular nucleus or nucleus of Deiters medulla (upper)
The modulatory functions are primarily found in the rostral sector of the reticular formation and the premotor functions are localized in the neurons in more caudal regions. The reticular formation is divided into three columns: raphe nuclei (median), gigantocellular reticular nuclei (medial zone), and parvocellular reticular nuclei (lateral zone).
The ventral portion of the medulla oblongata contains the medullary pyramids. These two ridge-like structures travel along the length of the medulla oblongata and are bordered medially by the anterior median fissure. They each have an anterolateral sulcus along their lateral borders, where the hypoglossal nerve emerges from.
Pontocerebellar fibers are the sole efferent pathway of the pontine nuclei. The fibers mostly decussate within the pons to pass through the (contralateral) middle cerebellar peduncle to terminate in the contralateral cerebellum as mossy fibers; they form terminal synapses in the cerebellar cortex, but also issue collaterals to the cerebellar nuclei.