Pterygoideus internus

Medial pterygoid
The Pterygoidei; the zygomatic arch and a portion of the ramus of the mandible have been removed. (Internus is visible at center bottom.)
The otic ganglion and its branches. (Pterygoideus internus labeled at bottom right.)
Details
Origin	deep head: medial side of lateral pterygoid plate behind the upper teeth superficial head: pyramidal process of palatine bone and maxillary tuberosity
Insertion	medial angle of the mandible
Artery	pterygoid branches of maxillary artery
Nerve	mandibular nerve via nerve to medial pterygoid
Actions	elevates mandible, closes jaw, helps lateral pterygoids in moving the jaw from side to side
Identifiers
Latin	musculus pterygoideus medialis, musculus pterygoideus internus
MeSH	A02.633.567.600.700
Dorlands /Elsevier	m_22/12550302
TA	A04.1.04.009
FMA	49011
Anatomical terms of muscle []

The medial pterygoid (or internal pterygoid muscle), is a thick, quadrilateral muscle of mastication.

The mandibular branch of the fifth cranial nerve, the trigeminal nerve, innervates the medial pterygoid muscle.

It consists of two heads.

Its fibers pass downward, lateral, and posterior, and are inserted, by a strong tendinous lamina, into the lower and back part of the medial surface of the ramus and angle of the mandible, as high as the mandibular foramen. The insertion joins the masseter muscle to form a common tendinous sling which allows the medial pterygoid and masseter to be powerful elevators of the jaw.

Medial pterygoid is innervated by nerve to medial pterygoid (a branch of the mandibular nerve), which also innervates tensor tympani and tensor veli palatini.

Unlike the lateral pterygoid and all other muscles of mastication which are innervated by the anterior division of the mandibular branch of the trigeminal nerve, the medial pterygoid is innervated by the main trunk of the mandibular branch of the trigeminal nerve (V), before the division.

Given that the origin is on the medial side of the lateral pterygoid plate and the insertion is from the internal surface of the ramus of the mandible down to the angle of the mandible, its functions include:

Position of medial pterygoid muscle (red).

Left palatine bone. Posterior aspect. Enlarged.

Mandible. Inner surface. Side view.

Plan of branches of internal maxillary artery.

Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion.

Mandibular division of trifacial nerve, seen from the middle line.