Digastric Triangle/ Submandibular Triangle (Animated Video)

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It is so named because it is located between the two bellies of the digastric muscle and below the base of the mandible
Boundaries
Anteroinferiorly: Anterior belly of digastric muscle.
Posteroinferiorly: Posterior belly of digastric muscle, supplemented by stylohyoid muscle.
Base: It is formed by the base of the mandible and imaginary line joining the angle of the mandible to the mastoid process.
Apex: It is formed by the intermediate tendon of the digastric muscle, being bound down to hyoid bone by a fascial sling derived from investing layer of deep cervical fascia.
Roof
It is formed by investing layer of deep cervical fascia, which splits to enclose the submandibular salivary gland. In the superficial fascia over the roof lies platysma, cervical branch of facial nerve, and ascending branch of transverse cervical nerve.
Contents
The digastric triangle is subdivided into anterior and posterior parts by the stylomandibular ligament, which extends from the tip of the styloid process to the angle of the mandible. The posterior part of the triangle is continuous above with the parotid region.
Contents in the anterior part of the triangle:
1. Submandibular salivary gland.
2. Submandibular lymph nodes.
3. Hypoglossal nerve.
4. Facial vein (lies superficial to the gland).
5. Facial artery (lies deep to the gland).
6. Submental artery.
7. Mylohyoid nerve and vessels.
Contents in the posterior part of the triangle:
1. External carotid artery.
2. Carotid sheath and its contents.
3. Structures passing between the external and internal carotid arteries-
1. Deep part of the parotid gland.
2. Styloid process.
3. Styloglossus muscle.
4. Stylopharyngeus muscle.
5. Glossopharyngeal nerve.
6. Pharyngeal branch of the vagus nerve.
Submandibular triangle is the common site of swellings due to involvement of submandibular lymph nodes as they drain lymph from widespread areas such as anterior two-third of tongue (except tip), floor of mouth, frontal, ethmoidal, and maxillary air sinuses, etc.