---
title: "Medial Pterygoid | Anatomy and Physiology I"
description: "Medial pterygoid is a chewing muscle that elevates and moves the mandible side to side, working with the masseter and temporalis in Anatomy and Physiology I."
canonical: "https://fiveable.me/anatomy-physiology/key-terms/medial-pterygoid"
type: "key-term"
subject: "Anatomy and Physiology I"
unit: "Unit 11"
---

# Medial Pterygoid | Anatomy and Physiology I

## Definition

The medial pterygoid is a deep muscle of mastication in Anatomy and Physiology I. It helps close the jaw and move the mandible side to side during chewing.

## What It Is

The medial pterygoid is a deep chewing muscle in Anatomy and Physiology I that works on the mandible, or lower jaw. It is one of the main muscles of mastication, so its job is to help you bite down and grind food.

Anatomically, it is a thick, quadrilateral muscle tucked on the inside of the jaw. It originates from the medial surface of the lateral pterygoid plate and inserts on the inner surface of the mandibular angle and ramus. That deep location is why you do not see it from the outside the way you might see a facial expression muscle.

Its action is simple but very useful: it elevates the mandible, which closes the jaw, and it also helps with side-to-side movements. That sideways motion matters when you chew tough food because your teeth do not just move straight up and down. They also shift a little to grind food before swallowing.

The medial pterygoid often works with the masseter and temporalis. Think of it as part of a chewing team. The masseter gives a strong vertical bite, the temporalis helps elevate and retract the jaw, and the medial pterygoid adds more elevation plus the grinding motion that makes chewing efficient.

You can also connect it to the condylar process of the mandible, because jaw movement happens at the temporomandibular joint. When the mandible is pulled upward or shifted side to side, the condylar process moves at that joint while the muscle contracts. In lab diagrams, the medial pterygoid is usually shown as a deep internal muscle on the medial side of the ramus, not as a surface landmark.

## Why It Matters

The medial pterygoid matters because it shows how anatomy and function line up in the jaw. A muscle is not just a name to memorize here, it is part of the mechanics of chewing, biting, and grinding food into a form you can swallow.

This term also helps you separate the deep muscles of mastication from the superficial ones. If you are looking at a skull model, cadaver image, or muscle chart, the medial pterygoid is easy to mix up with the lateral pterygoid or the masseter unless you know where it sits and what direction it pulls.

In class, this muscle often comes up when you trace mandibular movement at the temporomandibular joint. If the jaw is closing forcefully or moving in a grinding pattern, the medial pterygoid is part of that action. That makes it useful for understanding chewing, bite mechanics, and why jaw muscles are arranged in different layers and directions.

It also gives you practice reading origin, insertion, and action together instead of memorizing them separately. That is a major skill in Anatomy and Physiology I, because many muscles only make sense when you connect their attachment points to the movement they produce.

## Connections

### Masseter

The masseter is another major muscle of mastication, and it is the one most people think of when they picture clenching the jaw. It works with the medial pterygoid to elevate the mandible, but it sits more superficially on the outside of the jaw. If you are comparing chewing muscles, the masseter is the strong outer jaw closer, while the medial pterygoid is the deep inner helper.

### Temporalis

The temporalis helps elevate the mandible too, but it also assists with retraction. That makes it a good comparison point when you are sorting out which jaw muscle does what. In diagrams, temporalis is easy to spot on the side of the skull, while the medial pterygoid is hidden deeper near the mandible. Together they show that jaw closure is not done by one muscle alone.

### [Lateral Pterygoid](/anatomy-physiology/key-terms/lateral-pterygoid)

The lateral pterygoid is the pterygoid muscle most often confused with the medial pterygoid. Both are deep muscles involved in mandibular movement, but they do different jobs. The lateral pterygoid helps open and protrude the jaw, while the medial pterygoid helps elevate and move it side to side. Their names sound similar, but their actions point in opposite directions during chewing.

### [condylar process of the mandible](/anatomy-physiology/key-terms/condylar-process-of-the-mandible)

The condylar process is the part of the mandible that meets the temporal bone at the temporomandibular joint. The medial pterygoid affects how that process moves when you close your jaw or grind food. If you are tracing motion in a model, this is the bony landmark that makes the muscle action easier to visualize.

## On the AP Exam

A label question or muscle ID item often asks you to point out the medial pterygoid on a diagram and state its action. The fastest way to handle it is to link three things: deep location, inner surface of the mandible, and jaw elevation with side-to-side chewing.

If a quiz shows several muscles of mastication, use the action to sort them out. Medial pterygoid closes the jaw and helps grinding, which is different from the lateral pterygoid, and different from the outer, more obvious masseter. When you can pair origin, insertion, and function, you usually have enough to answer both naming and function questions.

You may also see it in a case about painful chewing, jaw motion, or temporomandibular joint movement. In that situation, the skill is not just memorizing the name, but explaining how this muscle contributes to mandibular mechanics.

## medial pterygoid vs Lateral Pterygoid

These two are easy to mix up because they both sit deep in the jaw and both belong to the pterygoid group. The medial pterygoid elevates the mandible and helps with side-to-side grinding, while the lateral pterygoid helps open the jaw and protrude it. If the question asks about closing the mouth, think medial pterygoid; if it asks about opening or pushing the jaw forward, think lateral pterygoid.

## Key Takeaways

- The medial pterygoid is a deep muscle of mastication that helps close the jaw.
- It also helps move the mandible side to side, which matters during grinding food.
- Its deep position on the inner side of the mandible makes it harder to spot on surface diagrams.
- It works with the masseter and temporalis, but it is not the same as the lateral pterygoid.
- Knowing its origin, insertion, and action helps you read muscle charts and anatomy lab images faster.

## FAQs

### What is the medial pterygoid in Anatomy and Physiology I?

The medial pterygoid is a deep chewing muscle that helps elevate the mandible and move it side to side. In Anatomy and Physiology I, it is one of the main muscles of mastication and is usually studied with the masseter, temporalis, and lateral pterygoid.

### What does the medial pterygoid do?

It closes the jaw and helps grind food by shifting the mandible side to side. That makes it part of the chewing motion, not a facial expression muscle. Its action is easiest to remember if you connect it to biting and mastication.

### Is the medial pterygoid the same as the lateral pterygoid?

No. They are related muscles, but their actions differ. The medial pterygoid helps elevate the jaw, while the lateral pterygoid helps open and protrude it. They are commonly confused because they are both deep jaw muscles with similar names.

### How do you identify the medial pterygoid on a diagram?

Look for a deep muscle on the inside of the mandible, near the ramus and angle. If a figure shows the chewing muscles from a medial view, the medial pterygoid is usually the one attached to the inner surface of the jaw rather than the outer cheek side.

## Related Study Guides

- [11.3 Axial Muscles of the Head, Neck, and Back ](/anatomy-physiology/unit-11/3-axial-muscles-head-neck/study-guide/T18iHjO6luAZ0pd7)

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