Pterygoideus Proprius

Origin, Insertion, Action & Nerve

Attachments explained

The Pterygoideus Proprius is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Action & function

When the Pterygoideus Proprius contracts, it produces the following movement: Inconstant accessory slip of the lateral pterygoid (variant muscle).

As part of the Mastication group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Pterygoideus Proprius receives its nerve supply from the Mandibular nerve (CN V3).

Because a muscle can only contract when its nerve is intact, injury to the Mandibular nerve can weaken or paralyse the Pterygoideus Proprius, impairing the movements it normally produces (inconstant accessory slip of the lateral pterygoid (variant muscle)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Pterygoideus Proprius (the OIANS method)

Approach the pterygoideus proprius as an accessory of the lateral pterygoid rather than as a muscle to memorise in isolation. Anchor it to the same bony neighbourhood, the lateral pterygoid plate and greater wing of the sphenoid, then remember that it simply reinforces lateral pterygoid function. If you already know how the lateral pterygoid opens and protracts the jaw, you know most of what this slip does.

Use its variant status as the memory hook. The point to retain for exams is that this is an inconstant muscle supplied by CN V3, so it shares the innervation of every muscle of mastication. Grouping it mentally with the lateral pterygoid under one nerve keeps the fact from becoming an isolated detail you are likely to forget.

Frequently asked questions

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