Mastication Muscles Overview

Study Notes

Mastication Muscles: Overview

Mastication refers to the process of chewing food.
Several muscles in the head and neck are involved in this complex process.
These muscles work in coordinated and antagonistic manners to move the mandible (jaw).
The main muscles of mastication are the masseter, temporalis, medial pterygoid, and lateral pterygoid.

Masseter Muscle

The masseter muscle is a powerful muscle that elevates the mandible.
It is located on the lateral aspect of the mandible.
It has two parts: superficial and deep.
The superficial part is larger and more superficial.
The deep part is smaller and deeper.
The masseter muscle is responsible for the majority of jaw closing force.

Temporalis Muscle

The temporalis muscle is a fan-shaped muscle located on the temporal bone.
It elevates and retracts the mandible.
It plays a crucial role in jaw closing and retraction.
The temporalis muscle is located superior (above) to the masseter muscle.
Contraction of this muscle retracts or pulls the jaw backwards.

Medial Pterygoid Muscle

The medial pterygoid muscle is located on the medial (inside) side of the mandible.
It is involved in elevating the mandible.
It also assists in lateral movement of the jaw.
It works synergistically with the masseter and temporalis muscles.
Its primary role is in jaw elevation and also assisting with side-to-side grinding actions.

Lateral Pterygoid Muscle

The lateral pterygoid muscle is located on the side of the mandible.
It has two heads: superior and inferior.
The inferior head is larger and more superficial.
The superior head is smaller and deeper.
It is responsible for protracting (moving forward) and laterally moving (shifting) the mandible.
Its action is critical for opening the jaw and for lateral jaw movement.
It is crucial for side-to-side chewing movements.

Innervation of Mastication Muscles

All the muscles of mastication are innervated by the mandibular division of the trigeminal nerve (CN V3).
This innervation is essential for coordinated muscle action in chewing.

Actions of Mastication Muscles

Elevating the mandible (raising the jaw): masseter, temporalis, medial pterygoid
Protracting the mandible (moving the jaw forward): lateral pterygoid
Retracting the mandible (moving the jaw backward): temporalis
Lateral movements (side to side): lateral pterygoid, medial pterygoid, in conjunction with other muscles

Summary of Mastication Muscle Functions

Muscle	Primary Action	Secondary Action
Masseter	Jaw elevation	Minor role in jaw retraction.
Temporalis	Jaw elevation and retraction	Important in jaw closing and backward movement.
Medial Pterygoid	Jaw elevation, assists in lateral jaw movements	Crucial in chewing, assists with upward movement
Lateral Pterygoid	Jaw protraction, jaw lateral movement	Jaw opening

Proper function of these muscles is essential for efficient mastication and proper oral health.
Disorders or damage to these muscles can lead to difficulties in chewing and potentially other oral issues.

Description

This quiz explores the muscles involved in mastication, highlighting the masseter and temporalis muscles. Understand their functions, locations, and roles in the chewing process. Test your knowledge on these critical muscles of the head and neck.