Anatomy, Head and Neck: Inferior Alveolar Arteries

Structure and Function

As the external carotid artery ascends the face, it will branch into six arteries: the superior thyroid artery, lingual artery, ascending pharyngeal artery, facial artery, occipital artery, and posterior auricular artery. The external carotid artery will terminate and become the superficial temporal artery and the maxillary artery. The maxillary artery is what branches into the inferior alveolar artery. The inferior alveolar artery is a small muscular artery that branches from the first portion of the maxillary artery.[1]

The course of the inferior alveolar artery is similar to the inferior alveolar nerve. Before the inferior alveolar artery enters the mandibular foramen, it will branch into the mylohyoid and lingual branch of the inferior alveolar artery. While the inferior alveolar artery traverses the mandibular foramen, it branches into the incisor arteries. Once the inferior alveolar artery reaches the mental foramen and exits, it becomes the mental artery; this makes the inferior alveolar artery the main blood supply to the mandible bone.[2][3]

The mylohyoid branch of the inferior alveolar artery will descend toward the mylohyoid muscle and perfuse the mylohyoid muscle and the anterior muscle belly of the digastric muscle. The lingual branch of the inferior alveolar artery perfuses the genioglossus muscle in the tongue. The incisor arteries that branch from the inferior alveolar artery is responsible for perfusing the teeth, dental sockets, and the gingivae of the lower jaw. The mental artery is responsible for the perfusion of the anterior chin. These arterial branches of the inferior alveolar will also perfuse their corresponding nerves.[4]

The inferior alveolar artery also forms anastomoses with the inferior labial artery and the submental artery. The anastomosis with the inferior labial artery will provide collateral blood to the lower lip, anterior chin, skin, and the muscles in that region. The connection made with the submental artery will provide collateral blood to the skin and muscles on the inferior aspect of the chin.[3][5]

Embryology

During embryology, the structures in the face and neck derive from the brachial apparatus, while the arteries in the face and neck derive from the aortic arches. Mesenchymal tissue is the embryonic tissue that will differentiate into blood vessels. The first aortic arch will form the maxillary artery. The maxillary artery will continue to elongate and form branches such as the inferior alveolar artery; this makes the inferior alveolar artery a derivative of the mesenchymal tissue from the first aortic arch.

Blood Supply and Lymphatics

The inferior alveolar arteries are responsible for the direct perfusion of the lower jaw and the lower jaw's structures. The branches that arise from the inferior alveolar artery will travel with the corresponding nerve to perfuse the same structure as the nerve innervation. The inferior alveolar artery is the main blood supply to the mandible bone. The perfusion territory of the inferior alveolar artery includes the lower jaw gingivae and teeth. The branches of the inferior alveolar artery perfuse regions, including the chin, neck, and lower lip.

The lymphatic drainage of the inferior alveolar artery and its perfusion territory will drain toward the submental and submandibular lymph nodes. The lymph fluid in these lymph nodes will eventually drain into the central circulation via the right lymphatic duct and the thoracic duct. The thoracic duct will drain lymph from the left side of the face and neck while the right lymphatic duct will drain the lymph from the right side of the face and neck.

Nerves

There are three primary nerves that the inferior alveolar provides perfusion. These three arteries are:

• Inferior alveolar nerve
• Mental nerve
• Mylohyoid nerve

As the inferior alveolar artery descends toward the mandibular foramen, it gives off a branch called the mylohyoid artery. The mylohyoid artery descends into the mylohyoid fossa and joins the mylohyoid nerve. Both the mylohyoid artery and nerve travels toward the mylohyoid muscle and the anterior belly of the digastric muscle. While the inferior alveolar artery course through the mandibular foramen, it follows closely with the inferior alveolar nerve. As the inferior alveolar artery and nerve approach the mental foramen. Both the inferior alveolar artery and nerve will become the mental artery and nerve as they exit the mental foramen. These are the primary nerves that mainly receive blood from the inferior alveolar nerve, but the collateral circulation in the face is so vast. That these nerves will also be perfused from other arteries in the face, neck, and head via collateral blood flow.

Muscles

The inferior alveolar artery mainly perfuses the lower jaw, including the teeth and gingivae. Also, the inferior alveolar branches will perfuse some of the muscle nearby. The mylohyoid branch of the inferior alveolar artery perfuses the mylohyoid muscle and the anterior muscle belly of the digastric muscle.[4] The mental branch of the inferior alveolar artery perfuses the muscles in the chin such as the mentalis muscle and the depressor anguli oris muscle. The lingual branch of the inferior alveolar artery perfuses the genioglossus muscle of the tongue.

The anastomoses that the inferior alveolar artery and its branches form will perfuse other muscles in the face indirectly.[3] 

Physiologic Variants

As the maxillary artery starts to branch, the inferior alveolar artery usually arises from the first portion. The location of the origin of the inferior alveolar artery is highly dependent on the maxillary artery.[6][7] In some rare instances, the inferior alveolar artery is found to arise from the external carotid artery instead of the maxillary artery.[8] The inferior alveolar artery has been found in duplication form also. The duplication of the inferior alveolar artery can arise as two inferior alveolar arteries branching from the maxillary artery. Also, there can be a bifurcation into two inferior alveolar arteries after branching from the maxillary artery.[9]

Surgical Considerations

In surgery, the knowledge of the anatomy of the mandible is valuable when it comes to the jaw or even oral surgeries. The inferior alveolar artery is the predominant blood supply to the mandible. If there is a compromise of the inferior alveolar artery, this could lead to necrosis of the mandible and structures perfused by the branches of the inferior alveolar artery.

In some situations, if there is uncontrolled hemorrhaging from the dental sockets on the lower jaw. The inferior alveolar artery can be embolized to achieve hemostasis and save the patient's life.[10]

Clinical Significance

Arterial bleeding that comes from gingivae and dental damage to the lower jaw is usually originating from the inferior alveolar artery or the inferior alveolar artery's branches. Bleeding that occurs from the dental sockets are from the incisor branches of the inferior alveolar artery.

During dental procedures, the gingivae can easily suffer damage. Gingival damage may lead to bleeding. Bleeding from dental sockets is common during teeth extractions. Clinicians can control dental socket bleeding with packing and pressure. If conservative measures are ineffective, then cauterization can be done. The cauterization of the incisor branches will resolve the dental socket bleeding and achieve hemostasis. If the arterial bleeding is coming from the gingivae that do not involve the dental socket. It usually suggests damage to the inferior alveolar artery. If the inferior alveolar artery bleeding is uncontrollable, embolization of the artery may be warranted.

Other Issues

Since the inferior alveolar artery arises from the maxillary artery and the maxillary artery is one of the terminal arteries formed by the external carotid artery. Any damage or compromise to the arteries proximal to the inferior alveolar artery will manifest as possible ischemia. The ischemia may manifest in the regions perfused by the inferior alveolar artery if coupled with poor collateral blood supply. The injury may present as weakness in the mandible. This weakness may be due to nerve, tissue, or muscle ischemia from lack of perfusion.