Description

Figure 1 illustrates the subdivision of the nervous system with particular reference to the sympathetic nervous system and the structures related to the eye which are innervated by it.

A diagram of the sympathetic nervous system is shown in Figure 2. Its outflow emerges from the central nervous system in the ventral roots of the spinal nerves of the first thoracic to third lumbar segments of the spinal cord. The sympathetic nervous system distribution is to effector organs throughout the body, whereas the parasympathetic nervous system distribution is more limited. As far as sympathetic innervation of the structures in the eye is concerned, the nervous supply leaves the spinal cord at T1 and ascends to the superior cervical ganglion. Long postganglionic fibres (c.f. the parasympathetic nervous system where the postganglionic fibres are short) then leave the superior cervical ganglion to innervate the dilator pupillae muscle, the smooth muscle in the eyelid (Mllers muscle), conjunctival blood vessels and the ciliary body.