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Fourth ventricle location shown in red (E), pons (B); the floor of the ventricle is to the right, the roof to the left. The fourth ventricle has a roof at its upper (posterior) surface and a floor at its lower (anterior) surface, and side walls formed by the cerebellar peduncles (nerve bundles joining the structure on the posterior side of the ventricle to the structures on the anterior side).
The superior cerebellar peduncles (bracchia conjunctiva) emerge from the cerebellum and ascend to form the lateral portion of the roof of the fourth ventricle, where they enter the brainstem below the inferior colliculi. They are bridged by the superior medullary velum.
Ventricular system anatomy showing the cerebral aqueduct, labelled centre right. The cerebral aqueduct is the part of the ventricular system which links the third ventricle (rostrally) with the fourth ventricle (caudally); as such it is responsible for continuing the circulation of cerebrospinal fluid.
The middle cerebellar peduncle is the largest of the three cerebellar peduncles. It connects the pons and cerebellum.It consists almost entirely of fibers passing from the pons to the cerebellum (fibrocerebellar fibers); the fibers arise from the pontine nuclei and decussate within the pons before entering the peduncle [1] to end in the contralateral cerebellar hemisphere.
The ventricles contained within the rhombencephalon become the fourth ventricle, and the ventricles contained within the mesencephalon become the aqueduct of Sylvius. Separating the anterior horns of the lateral ventricles is the septum pellucidum : a thin, triangular, vertical membrane which runs as a sheet from the corpus callosum down to the ...
The upper portion of the roof is formed by the cerebellum. The roof of ventricle is diamond shaped and can be divided into superior and inferior parts. The superior part or cranial part is formed by superior cerebellar peduncles and superior medullary velum. The inferior or caudal part is formed by ventricular ependyma and double fold of pia mater.
The metencephalon is composed of the pons and the cerebellum; it contains: a portion of the fourth (IV) ventricle, the trigeminal nerve (CN V), abducens nerve (CN VI), facial nerve (CN VII), and a portion of the vestibulocochlear nerve (CN VIII).
Thanks to the number of different nuclei located within the pontine tegmentum, it is a region associated with a range of functions including sensory and motor functions (due to the cranial nuclei and fiber tracts), control of stages of sleep and levels of arousal and vigilance (due to the ascending cholinergic systems), and some aspects of respiratory control.