Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system Figure 1, blue fibers). Most are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. The exceptions are the four paired parasympathetic ganglia of the head and neck (shown in Figure 2). These paired ganglia supply all parasympathetic innervation to the head and neck: ciliary ganglion (spincter pupillae, ciliary muscle), pterygopalatine ganglion (lacrimal gland, glands of nasal cavity), submandibular ganglion (submandibular and sublingual glands), and otic ganglion (parotid gland).
Each has three roots entering the ganglion (motor, sympathetic, and sensory roots) and a variable number of exiting branches. The motor root carries presynaptic parasympathetic nerve fibers (general visceral efferent fibers) that terminate in the ganglion by synapsing the postsynaptic fibers traveling to target organs. The sympathetic root carries postsynaptic sympathetic fibers (general visceral efferent fibers) that traverse the ganglion without synapsing. The sensory root carries general sensory fibers (general somatic afferent fibers) that also do not synapse in the ganglion. Some ganglia also carry special sensory fibers (special visceral afferent) for taste sensation.
Nerves supplying parasympathetic fibers to the parasympathetic ganglia of the head include the oculomotor nerve (ciliary ganglion), the facial nerve (pterygopalatine ganglion, submandibular ganglion), the glossopharyngeal nerve (otic ganglion), the vagus nerve, and the pelvic splanchnic nerves Figure 2.
Because of its location, the parasympathetic system is commonly referred to as having "craniosacral outflow," which stands in contrast to the sympathetic nervous system, which is said to have "thoracolumbar outflow."