Slide 27: Lower Pons

Identify:

• Basilar Pons and Pontine Gray (PG)
• Middle Cerebellar Peduncle (MCP)
• Corticospinal Tract fibers (CST)
• Medial Lemniscus (ML)
• Tectospinal Tract (TST)
• Medial Longitudinal Fasciculus (MLF)
• Central Tegmental Tract (CTT)
• Superior Olivary Nucleus (SO)
• Lateral Lemniscus (LL)
• Trapezoid Body (TB)
• Spinothalamic Tract (STT)
• (Rubrospinal Tract (RST)
• Ventral Spinocerebellar Tract (VSCT)
• Hypothalamo-Autonomic Tract (HAT)
• Facial Motor Nucleus (7) and Genu of the Facial Nerve
• Abducens Nucleus (6) and Abducens Nerve Fibers
• Facial Colliculus
• Spinal Trigeminal Tract and Nucleus (SpT)
• Mesencephalic Trigeminal Tract and Nucleus (MesT)
• Superior Vestibular Nucleus (SVN)

Note:

• The Corticospinal Tract fibers which form the Pyramidal Tracts in the medulla can be seen surrounded by the Pontine Gray. In addition, Corticopontine Fibers which terminate in the Pontine Gray are present, as well as Pontocerebellar Fibers that cross and form the Middle Cerebellar Peduncle (MCP).
• The Medial Lemniscus has now assumed a "horizontal" position and forms part of the border between the Basilar Pons and Pontine Tegmentum.
• The Superior Olivary Nucleus (SO)gives rise to the efferent olivocochlear projection to the inner ear.
• Secondary auditory pathway fibers originating from the Cochlear Nuclei and crossing to the other side are known as the Trapezoid Body; these fibers pass beneath and through the Medial Lemniscus. Upon reaching their destination lateral to the Medial Lemniscus these fibers turn rostrally and are termed the Lateral Lemniscus; some of the fibers synapse in the Superior Olive.