The Mandible (Lower Jaw): Anatomy, Structures, and Function

The Mandible (Lower Jaw): Anatomy, Structures, and Function
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Table of Contents

  1. What Is the Mandible?
  2. Anatomy & Structure
  3. Functions
  4. Problems That Affect the Mandible
  5. Frequently Asked Questions

The mandible is the lower jawbone, the largest bone in the human skull. It carries the responsibility of breaking down food through chewing. It also allows humans to speak, and it gives us a big part of our facial definition.

The jawbone has joints on each side, which can be a source of headaches and other medical issues.

Among the disorders that involve the mandible are:

  • Temporomandibular Joint and Muscle Disorder (TMJD)
  • Cluster Headaches
  • Trigeminal Neuralgia 
  • Sinusitis

What Is the Mandible (Lower Jaw)?

The mandible, the lower jawbone, is the largest bone in the human skull and houses the lower teeth.

This bone facilitates jaw movement for chewing and speaking and works in conjunction with several muscles. 

It comprises two major parts — the body and ramus. Health problems associated with the mandible include TMJD, cluster headaches, sinus problems and trigeminal neuralgia. 

The lower jaw is the largest and strongest bone in the human skull. It is the only moving bone on your face. Attached to it are major muscles for chewing (mastication).

It houses all the lower teeth in your mouth.

Anatomy and Structure

Horseshoe-shaped, the mandible defines the lower part of the face, making up a key component of one’s appearance. The lower jaw is made up of two major sections, the body and the ramus.

The Body

The mandibular body has two borders and two defined surfaces: 

  • Alveolar border (superior), which holds the lower teeth
  • Base (inferior), which is where the digastric muscle medially attaches
  • External surface
  • Internal surface

The mandibular symphysis — the area in the top-middle of the chin — acts as a midline in the body and shows where the right and left sides of the lower jaw fuse together during early age development. In later years, it also serves as a place where surgeons can harvest healthy bone material for grafting in other areas of the body.

Ramus

The ramus features a quadrilateral shape. It has four borders, two surfaces and two processes. 

Borders

  • The superior border gives rise to the condyloid and coronoid processes, located on each side of the top front of the lower jaw.
  • The Inferior border contributes to the jawline and is attached to the inferior border of the mandibular body.
  • The posterior border is attached to the inferior border of the ramus. This border determines the gonial angle. 
  • Anterior border is attached to the oblique line found on the external body’s surface. 

Surfaces

  • The lateral surface has oblique ridges and is flat in shape. It offers attachment to the whole of the masseter. 
  • The medial surface has an irregular opening and has a prominent ridge with a sharp spine. This surface also enables the entrance of the inferior alveolar nerve and vessels.
Foramina

The foramen refers to openings through which neurovascular structures travel. The mandible has two foramina. 

  • The mandibular foramen is found on the ramus of the mandible. This foramen serves as the opening for the inferior alveolar artery and the inferior alveolar nerve. These two neurovascular structures travel through the mandibular foramen, the canal, and exit through the mental foramen. 
  • The mental foramen’s location is on the outer part of the mandible body. It serves as the exit point for the inferior alveolar artery and nerve.

Functions of the Mandible

Movement of the mandible controls the opening and closing of the mouth, enabling chewing and speaking. The four muscles connecting to the mandible help facilitate up and down and side to side movements, enabling acts such as speech, yawning, and laughing. 

Since the mandible is the strongest and largest bone in the skull, it helps provide facial definition and protects facial organs.

Problems That Affect the Mandible 

Several conditions can affect the mandible and the jaw as a whole. The most common are:

  • Temporomandibular Joint and Muscle Disorder (TMJD)
  • Cluster Headaches
  • Trigeminal Neuralgia 
  • Sinusitis

Temporomandibular Joint and Muscle Disorder (TMJD)

TMD has a prevalence rate of between 5 percent and 12 percent of Americans each year (about 10 million people), making it the most common jaw condition.

It affects the temporomandibular joints, which are the hinge joints located on either side of the jaw. Causes of this condition include injury to the jaw or teeth, clenching, teeth grinding, and poor posture. 

Symptoms of TMJD

  • Pain in the jaw
  • Difficulty chewing 
  • Headaches
  • Pain in and around the ear
  • Pain around one or both TMJ joints
  • Difficulty in opening or closing of the mouth

Treatment

  • Ice packs
  • Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs)
  • Massages and stretches
  • Botox injections
  • Prescription medication
  • Physical therapy
  • Surgery

Cluster Headaches

Cluster headaches are debilitating and painful headaches that occur in patterns or with many in a short period of time. Cluster headaches occur in a cyclical pattern every day and can affect a patient for weeks or months at a time.

It is possible to get up to eight headaches a day. Mainly impacting the eye region, pain from this condition can radiate to the jaw, causing mandible issues.

Symptoms

  • Piercing pain on one side of the head, affecting the temples, eyes, nose and jaw, that lasts anywhere between 15 minutes and three hours at a time 
  • Runny nose or congestion
  • Drooping eyelid or watery eye
  • Flushed face

Treatment

Unfortunately, there is no known cure for cluster headaches. People who endure them have only the option of painkillers to ease their discomfort. Other treatments:

  • Some doctors suggest abortive treatments, such as injected medications or nasal sprays, including zolmitriptan, sumatriptan, and dihydroergotamine.
  • Prescription medication to shorten the cycles and reduce headache severity. Patients can take medicines like topiramate, verapamil, calcium channel blockers, divalproex sodium, and lithium carbonate to improve their quality of life. 

Trigeminal Neuralgia 

This is a condition characterized by chronic pain in the face. The trigeminal nerve is responsible for sensation in the face. 

Symptoms

  • Mild or severe episodes of stabbing facial pain that last a few minutes
  • Tingling or burning sensation on your face
  • Muscle spasms

Treatment 

Surgery is rarely an option for patients suffering from trigeminal neuralgia because surgery carries risks like permanent facial sensory loss. 

The best treatment options available are medications that block pain signals sent to the brain. The most common medication doctors prescribe for this condition are anticonvulsants like carbamazepine

Sinusitis

Sinuses are air-filled cavities found near jaw joints. They are responsible for forming mucus that drains out of channels and helps clean the nose. Sometimes, the sinuses become blocked and fill with fluids. Sinus infections cause excess mucus, placing pressure on the jaw and causing pain. 

Symptoms

  • Nasal inflammation
  • Blocked or stuffy nose
  • Drainage down the back of the throat
  • Pain around the nose, eye, forehead, and jaw
  • Headaches
  • Toothaches unrelated to cavities

Treatment

  • Nasal decongestants
  • Antibiotics in case of bacterial infection 
  • Steroids to reduce inflammation
  • Saline rinses (neti pots)
  • Over-the-counter pain medication

Frequently Asked Questions

What is the mandible and maxilla?

The mandible is the strongest and largest bone in the human skull. It forms the lower jaw, holds the lower teeth and aids with mastication (chewing).

Maxillae are a pair of bones that provide critical bone structure to the face and skull. The maxilla forms a portion of the jaw, houses the upper teeth, and helps with mastication.

What type of bone is the mandible?
The mandible is an irregular bone. Other bone types fall into categories such as flat, short, long, and sesamoid. The mandible is an irregular bone since it does not fit into the classification of the other bone types because of its somewhat complex shape. Irregular bones serve a specific purpose, hence their unique shapes.
How does the mandible work?
Four muscles control how the mandible moves, including the masseter, lateral pterygoid, medial pterygoid, and temporalis. These muscles work separately to move the mandible in different directions. The contraction of the lateral pterygoid opens the mouth while the other three muscles close the mouth.

References

Anatomy, Head and Neck, Mandible. (June 2021). National Center for Biotechnology Information. 

Carbamazepine. (February 2019). National Health Service. 

Cluster Headaches. (February 2021). Cleveland Clinic.

Prevalence of TMJD and its Signs and Symptoms. (July 2018). National Institute of Dental and Craniofacial Research.

Disclaimer: This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to serve as dental or other professional health advice and is not intended to be used for diagnosis or treatment of any condition or symptom. You should consult a dentist or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.

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