The sphenomandibular ligament (internal lateral ligament) is one of the three ligaments of the

temporomandibular joint In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral Synovial joint, synovial articulation between the temporal bone of the skull above and the condylar process of mandible be ...

. It is situated medially to - and generally separate from - the articular capsule of the joint. Superiorly, it is attached to the spine of the sphenoid bone; inferiorly, it is attached to the lingula of mandible. The SML acts to limit inferior-ward movement of the mandible. The SML is derived from

Meckel's cartilage In humans, the cartilaginous bar of the mandibular arch is formed by what are known as Meckel's cartilages (right and left; also known as Meckelian cartilages), above which the incus and malleus are located. Meckel's cartilage arises from the fir ...

Anatomy

The SML is a tough,'flat, thin band. It broadens inferiorly, measuring about 12 mm in width on average at the point of its inferior attachment. It is derived from the perichondrium of

Attachments

Superiorly, the SML is attached to the spine of the

sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of occipital bone, basilar part of the occipital bone. The sphenoid bone is one of the seven bon ...

(spina angularis by a narrow attachment. Inferiorly, it is attached at to lingula of mandible and the inferior margin of the mandibular foramen.

Anatomical relations

The

lateral pterygoid muscle The lateral pterygoid muscle (or external pterygoid muscle) is a muscle of mastication. It has two heads. It lies superior to the medial pterygoid muscle. It is supplied by pterygoid branches of the maxillary artery, and the lateral pterygoid n ...

auriculotemporal nerve The auriculotemporal nerve is a sensory branch of the mandibular nerve (CN V3) that runs with the superficial temporal artery and vein, and provides sensory innervation to parts of the external ear, scalp, and temporomandibular joint. The nerve a ...

, and the

maxillary artery The maxillary artery (eg, internal maxillary artery) supplies deep structures of the face. It branches from the external carotid artery just deep to the neck of the mandible. Structure The maxillary artery, the larger of the two terminal branches ...

and maxillary vein are situated laterally to the SML (the vessels and nerve coursing betwixt the SML, and the neck of the mandibular condyle). The

chorda tympani nerve Chorda tympani is a branch of the facial nerve that carries gustatory (taste) sensory innervation from the front of the tongue and parasympathetic ( secretomotor) innervation to the submandibular and sublingual salivary glands. Chorda tympani ...

is situated medially to the SML near its upper end. The medial pterygoid muscle is situated inferolaterally to the SML. The

inferior alveolar nerve The inferior alveolar nerve (IAN) (also the inferior dental nerve) is a sensory branch of the mandibular nerve (CN V3) (which is itself the third branch of the trigeminal nerve (CN V)). The nerve provides sensory innervation to the lower/mandibu ...

artery An artery () is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in ...

and vein, and a parotid lobule are situated anteroinferiorly to the SML (all being interposed between the SML and the

ramus of mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

). The SML is pierced by the mylohyoid nerve (a branch of the inferior alveolvar nerve) and the accompanying mylohyoid artery and vein. Any remaining space between the SML and mandible is taken up by the parotid gland. Between the SML and the pharynx are situated adipose tissue, and a pharyngeal vein.

Function

The function of the sphenomandibular ligament is to limit distension of the mandible in an inferior direction. It is slack when the

(TMJ) is in closed position; it is taut when the condyle of the mandible is situated anterior to the temporomandibular ligament. The SML has about 5 mm of slack when the jaw is closed; it becomes taut when the jaw is open roughly half-way.

References

External links

* * http://ect.downstate.edu/courseware/haonline/labs/l27/070105.htm {{Authority control Ligaments of the head and neck