Section through the pontine region of a human brain. The section passes through the lower end of the cerebral aqueduct (Aq) and the inferior corpora quadrigemina (IC). Note the homogeneous structure of the latter. Entering its ventro-lateral aspect (as seen specially on the left side) is a part of the lateral fillet (Lf), an auditory tract. In the floor of the aqueduct are seen the medial longitudinal bundles (Md), immediately dorsal to which are situated the nuclei of the trochlear nerves. The massive decussation of the superior cerebellar peduncles (Dec) is a very conspicuous feature in sections at this level. Below is the pons (P), in which note the transversely running ponto-cerebellar fasciculi, scattered islets of grey matter forming the pontine nuclei, and fasciculi of the pyramidal tract cut across. Dorsal to the pons is seen the medial fillet which is here passing up the brain stem on its way to the thalamus.

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