Paraympathetic supply originates as preganglionic fibres from the superior
salivatory nucleus. They travel in the nervus intermedius and leave the
middle ear as the greater petrosal nerve to enter the middle cranial fossa.
The fibres enter the pterygoid canal and travel to pterygopalatine fossa.
Synapses occur in the pterygopalatine ganglion. The post-ganglionic fibres
travel along the zygomaticotemporal and lacrimal nerves to innervate the
lacrimal gland.
The first order fibres of sympathetic nerve originate in hypothalamus
and travel down the spinal cord to synapse at the intermiodlateral grey
horn. The second order fibres exist the spinal cord to enter the sympathetic
chain and synapse at the superior cervical ganglion. The third order fibres
ascend in the internal carotid plexus and enter the deep petrosal nerve.
The fibres then join the greater petrosal nerve and innervate the lacrimal
gland viat the zygomaticotemporal and lacrimal nerves.
The parasympathetic nerve mediates the reflex lacrimation and the sympathetic
nerve the basal secretion.
