Chewing muscles: temporal, lateral, medial pterygoid: function, anatomy

Skeletal muscles take part in the formation of the walls of the oral cavity, abdominal cavity, pelvis, esophagus, and larynx. They activate the auditory bones, the eyeball, they are involved in the function of breathing, chewing and swallowing. The muscles of the skull are divided into 2 groups: mimic and chewing.

The chewing muscles of the face (musculus masseter) are formed from the mesoderm of the first jaw arch. A characteristic feature is that they are one part attached to the mandibular bone, ensuring its movement, thereby participating in the processing of food. In addition, together with mimic, they provide swallowing, yawning, speech.

There are 4 pairs of masticatory muscles:

• lateral pterygoid (m. pterygoideus lat.);
• medial pterygoid (m. pterygoideus med.);
• actually chewing (m. masseter);
• temporal (m. temporalis).

The anatomy of the masticatory muscles is simple, but its functions are very important.

Muscles of the chewing apparatus and their functions

Chewing muscles include 4 muscles.

Lateral (external) pterygoid

Runs horizontally. It has the shape of a triangle.

Start

The lateral pterygoid muscle is divided into 2 segments - the lower and upper heads.

They come from the outer plate of the pterygoid process and the large wing of the sphenoid bone.

Attachment

The upper head of the muscle is attached to the articular capsule, the lower one - to the neck of the condylar process of the mandibular branch, uniting with the upper one.

Blood supply

It is carried out by the posterior and anterior pterygoid arteries. They belong to the section of the maxillary artery, being its branches.

Innervation

The lateral pterygoid nerve innervates this muscle. It belongs to the motor branch of the 3rd pair trigeminal nerve. Passes along with the deep temporal nerves and often together with the buccal nerve.

Functions

Pushes the mandibular bone forward with the movement of both muscles, moves to the side with a unilateral contraction.

Functional muscle tests

Kinesiology is the science of the muscular functions of living organisms, which studies various aspects of movement.

Kinesiological test (functional muscle test) is a diagnostic direction both for assessing the work of one muscle and muscle groups connected into a single block, for example, performing similar functions.

The traditional functional test is the Herbst muscle test. They are necessary when trying on and correcting individual spoons in the manufacture of full removable dentures. You need to do the following:

• swallow saliva;
• open your mouth as wide as possible;
• run your tongue along the borders of both lips;
• touch the tip of the tongue to the cheek, during this the mouth should be partially open (halfway);
• try to touch your nose with your tongue;
• stretch your lips forward with a tube.

The muscular-functional consequence of these tests was the kinesiological testing of A.A. Davydov, bearing the name "Smiling Dentist". The patient is asked to do the following:

• smile as broadly as possible;
• say the letter "U", stretching out your lips;
• push the mandibular bone downward and anteriorly to assess the state of tension of the chin muscle;
• stick out your tongue as much as possible;
• yawn without opening your mouth wide;
• swallow saliva.

The opening level is set using a triangle or an occlusal gauge. If they are not available, use a ruler. Another way is to place the patient's fingers between the front teeth of the upper and lower jaws. The criterion for the normal state is the volume of the greatest opening of the mouth 4 cm (3-4 fingers folded across). There are 3 types of opening restrictions: light - 20-30 cm, medium - 10-20 mm, heavy - up to 10 mm.

Method for determining the functional efficiency of the lateral pterygoid fascia - opening the mouth:

• the patient is relaxed, looks straight ahead;
• the doctor looks at the patient, asks to push the mandibular bone forward, tightly closing his teeth.

Painful sensations and a small amplitude indicate muscle pathology.

Medial (internal) pterygoid

It looks like a quadrangle.

Start

Comes from the inner plate of the pterygoid process.

Attachment

Attaches to the pterygoid tuberosity on the mandibular bone.

Blood supply

Like the external pterygoid muscle.

Innervation

The medial pterygoid muscle is innervated by the medial pterygoid nerve.

It is the motor branch of the 3rd pair of the trigeminal nerve.

Functions

Raises the bone up.

Functional muscle tests

Closing the mouth:

• the patient is relaxed, looks in front of him;
• the dentist looks at the patient, asks to show tightly closed teeth;
• then palpates the fascia, asks to show tightly clenched teeth.

With functional impairment, pain occurs during lateral movements of the jawbone. For example, when yawning and chewing.

Chewing proper

The masseter muscle itself is subdivided into 3 segments: deep, middle and superficial.

Start

Comes from the cheekbone and arch.

Attachment

Attaches to the chewing tuberosity of the mandibular bone.

Blood supply

It is carried out at the expense of the chewing artery. It also belongs to the section of the maxillary artery.

Innervation

Carries out the nerve of the same name. Moreover, it gives off a sensitive branch to the capsule of the temporomandibular joint.

Functions

Raises the mandibular bone up. The superficial part of the fascia takes part in its forward movement.

Functional tests

Similar to tests for the medial pterygoid muscle.

Overvoltage m. masseter can cause bruxism (teeth grinding in sleep). It is a symptom of a head injury.

In this case, the functions of the chewing muscle proper begin to be performed by the temporal and internal pterygoid apparatuses.

Temporal

The temporalis muscle, which also belongs to the chewing apparatus, has a fan-like configuration, represented by 3 layers: outer, middle and inner.

Start

Occupies the entire temporal fossa. It starts from the frontal, parietal, temporal bones and the greater wing of the sphenoid bone. The fascia bundles, converging downward, go beyond the zygomatic arch to the attachment point.

Attachment

It joins the coronoid process of the mandibular bone.

Blood supply

It is carried out from the deep temporal artery, which belongs to the pterygoid section of the maxillary artery.

Innervation

It is carried out at the expense of the anterior and posterior deep temporal nerves, which have motor and sensory fibers. They move away from the mandibular nerve in the area of ​​the oval opening of the skull.

Functions

Raises the mandibular bone and pulls it posteriorly.

Functional muscle tests

The technique is the same. Muscle damage occurs with TMJ dysfunction (temporomandibular joint) and tension headaches. Functional ability should be assessed together with m. masseter and m. pterygoideus med. Stress test for a group of these 3 fasciae:

• the dentist passively opens the patient's mouth to the maximum level;
• if the action cannot be performed in the required volume and elastic resistance is felt, this is evidence of muscle shortening;
• the patient feels muscle tension.

Muscle-function tests in the maxillofacial area help determine:

• balance or imbalance in functionally related muscle groups;
• participation in compensation or decompensation of functional and muscular disorders of the maxillofacial region;
• the level of progress or regression (wilting) of the muscles.

The patient can do these jaw muscle tests independently every day. It is necessary to adhere to a certain regimen after agreement with the doctor. Such exercises can significantly reduce the level of muscle-functional disorders of the maxillofacial region, as well as accelerate recovery.