Rahman Masum, Tadi Prasanna
Boston Medical Center
Asram Medical College, Eluru, India
The pons is the portion of the brainstem between the midbrain above and the medulla oblongata below. The transverse section of pons is subdivided into 2 areas: the ventral and the dorsal. The ventral portion of pons contains pontine nuclei, vertically traversing corticopontine and corticospinal tracts, and transversely crossing fibers arising from pontine nuclei that project to the opposite cerebellum through the middle cerebellar peduncle. The ventral segment of the pons is bulky due to the pontine nuclei and their connection to the corticopontocerebellar. The dorsal part of the pons, also known as the tegmentum, is occupied mainly by the reticular formation. The tegmentum is bounded laterally and superiorly by the inferior cerebellar peduncle in the superior cerebellar peduncle. Internal structures of the pons are usually described along with anatomical landmarks; structures at upper pons are mainly superior cerebellar peduncles, medial longitudinal fasciculus, locus coeruleus, pedunculopontine tegmental nucleus, and parabrachial nucleus. The transverse section at the middle cerebellar peduncle shows the trapezoid body, medial lemniscus, lateral lemniscus, and trigeminal nucleus (sensory and main motor). Pontine structures at the level of the facial nucleus are the abducens nerve nucleus, facial nerve nucleus, and vestibular nuclei.
脑桥是脑干位于上方中脑和下方延髓之间的部分。脑桥的横切面可分为两个区域：腹侧和背侧。脑桥腹侧部分包含脑桥核、垂直走行的皮质脑桥束和皮质脊髓束，以及起源于脑桥核并通过小脑中脚投射至对侧小脑的横向交叉纤维。由于脑桥核及其与皮质脑桥小脑的连接，脑桥腹侧段较为粗大。脑桥背侧部分，也称为被盖，主要由网状结构占据。被盖在上方由小脑下脚和小脑上脚在外侧和上方界定。脑桥的内部结构通常与解剖标志一起描述；脑桥上段的结构主要是小脑上脚、内侧纵束、蓝斑、脚桥被盖核和臂旁核。在小脑中脚水平的横切面显示斜方体、内侧丘系、外侧丘系和三叉神经核（感觉核和主要运动核）。面神经核水平的脑桥结构是展神经核、面神经核和前庭核。
