HN12 - The Styloid process, infratemporal fossa and mandible

This is a long, slender, bony process projecting downwards from the undersurface of the petrous temporal bone.

It's easily located between the mastoid process and the ramus of the mandible, but at a much deeper level.

It actually lies between the internal and the external carotid arteries.

Its main interest lies in the fact that there are several muscles arising from it, and they all have both different functions and different nerve supplies.

Let's look at each of these muscles in turn.

Arising from the lower anterior third, and passing into the posterior aspect of the tongue is the styloglossus.

Styloglossus, being one of the main tongue muscles, is supplied by the hyperglossal nerve.

As the muscle reaches the tongue, it interdigitates with both the hyoglossus and the palatoglossus.

Probably one of its main functions is to pull the tongue backwards and particularly aids in moving a bolus towards the back of the mouth.

Next, let's look at stylohyoid.

That arises from the upper posterolateral third and inserts onto the hyoid bone just around or posterior to the lesser corneum.

Characteristically, it splits into two small bits of muscle which actually pass on either side of the tendinous part of the digastric.

You'll remember from our guide as to how to remember all the muscles in the head that this was one of the four odd men out that are supplied by the facial nerve and yet are not truly muscles of facial expression.

Its main function is to lift the hyoid bone slightly posteriorly but essentially to elevate it.

In terms of elevating the hyoid bone and the larynx generally, one can associate this muscle working in association with the myelohyoid and the digastric.

All three of these muscles will cause considerable elevation of the larynx and hyoid and are essential during swallowing.

The third muscle to look at is stylopharyngeus.

That's in fact coming from the upper posteromedial third.

It passes downwards and attaches to the thyroid lamina posteriorly.

It is supplied by the glossopharyngeal nerve and represents the single muscle that is associated with the third pharyngeal arch.

Its function is yet again to lift the whole hyoid and larynx and is again important during swallowing.

Other muscles which act with it for this specific function are salpingopharyngeus and palatopharyngeus.

These latter muscles have a joint tendon which attaches to the upper part of the thyroid cartilage.

So there, in summary, we have muscles which are attached to the styloid process.

One to the tongue, one to the hyoid bone and one to the pharynx.