Innervation of the lacrimal gland

[TexasTriathlete]

Can someone explain this to me in plain English please?

Every source I look in makes it look simple.

My professor who taught this lecture makes it a little more complex, and he also speaks his own language that he made up, and I am not fully-fluent yet. He also does not typically check his e-mail on the weekends, or I'd just ask him directly. And my exam is tomorrow.

So I've got fibers from V2, VII/greater petrosal n., pterygopalatine ganglion, and that's about it. How does it all fit together?

Perhaps I'm making this more complicated than it actually is.

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[turkeyjerky]

The lacrimal nerve (branch of V1) does sensory to the lacrimal gland and surrounding area.

For parasympathetic innervation: Facial-> Greater Petrosal -> Nerve of pterygoid canal (aka vidian nerve, combination of greater petrosal and deep petrosal, which is sympathetics from the carotid plexus) -> Synapse in pterygopalatine ganglion. Then the parasympathetics hitch a ride on the infraorbital nerve (continuation of V2), then the zygomatic nerve, then jump (via a communicating branch) to the lacrimal nerve, and from there to the gland to synapse.

It's pretty complicated and confusing when you look at all the hitchiking going on. What you had is pretty much the basic info you had to know.

You could probably ask your professor to explain it to you quickly right before the exam. And if you want to impress him with a bit of trivia, ask him to show you where the tympanic canaliculis is (where tympanic nerve (IX) enters the cranium en route to the middle ear).

 

[badasshairday]

Ok.

The cell bodies that are sending the signals reside in the pons and called the superior salvitory nucleus. They send signals through VII fibers starting off with the intermediate nerve and passes the geniculate ganglia (do not synapse here! just passes it). Then the signal runs into the greater petrosal nerve and follows that along until right before the pterygoid canal. Right before that canal, the deeper petrosal nerve and greater petrosal nerve run into each other and form the nerve of the pterygoid canal. This nerve then connects to the pterygopalantine ganglion (attached to V2) and synapses here. The post synaptic fibers run along the zygomaticotemporal nerve (V2 fiber) which runs into the lacrimal nerve (V1 fiber) and causes the lacrimation.

 

[TexasTriathlete]

Got it. Thanks.

I knew all those pathways. Somehow I just never put it all together.

 

[DonkeyD]

The two explanations above are correct, just keep in mind that the sympathetic axons in the deep petrosal nerve don't actually synapse in the pterygopalantine ganglion. They've already synapsed in the superior cervical ganglion. Remember sympathetic innervation of the body comes from the thoracic spinal cord, in the head the sympathetic innervation is going to come from the cervical sympathetic trunk.