Autonomic plexuses can contain both sympathetic and parasympathetic neurons. CSF is secreted by choroid plexuses located on the roofs of the ventricles. The lumbar and sacral plexuses innervate the pelvic girdle and lower limbs. Choroid plexuses appear in the ventricles which produce cerebrospinal fluid. Major plexuses include the cervical, brachial, lumbar, and sacral plexuses. Together, these plexuses innervate the intestines. They are sometimes found in connection with the ganglia of other sympathetic plexuses. It is from these ganglia that many of the gastric plexuses arise. The sympathetic nervous system consists of nerve plexuses in the epidermis and alimentary canal. The blood supply of these plexuses is from the posterior inferior cerebellar artery. The trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa. From these plexuses numerous branches are distributed to the viscera of the pelvis. It communicates with the pudendal and vesical plexuses. It communicates with the external vertebral venous plexuses. It communicates with the vertebral venous plexuses.