12 MYLOHYOIDAction :If the mandible is fixed: Elevates the floor of the mouth as in deglutition.If the hyoid bone is fixed: Depresses the mandible and opens the mouth.
13 DIGASTRIC TRIANGLE It lies below the body of the mandible. Boundaries: Anteriorly:Anterior belly of Digastric.Posteriorly:Posterior belly of digastric & Stylohyoid.
14 DIGASTRIC TRIANGLE Superiorly: Lower border of the body of the mandible.Floor:Mylohyoid. Hyoglossus.
15 CONTENTS A. Anterior part : (1) Submandibular salivary gland. (2) Facial artery (deep to gland).(3) Facial vein(4) Submandibular lymph nodes.The vein and lymph nodes are superficial to the gland.
16 CONTENTS(5) Hypoglossal nerve.(6) Nerve and vessels to mylohyoid.
17 CONTENTS B. posterior part: 1. Carotid sheath and its contents. 2. parotid gland (Lower part)
18 DIGASTRIC MUSCLE It has two bellies: Anterior and Posterior. Posterior belly :Arises from the mastoid process.Inserted into the intermediate tendon.Anterior belly attached to the lower border of body of mandible.
19 DIGASTRIC MUSCLE Insertion : to the Intermediate Tendon. It pierces the insertion of stylohyoid.It binds to the hyoid bone by a loop of deep fascia.
20 NERVE SUPPLY Posterior belly: Facial Nerve Anterior belly: The nerve to Mylohyoid.
21 ACTIONDepression of the mandible.ORElevation of the hyoid bone.
22 STYLOHYOID MUSCLE Origin: The styloid process. It runs along the upper border of the posterior belly of digastric.Insertion:Hyoid bone (between body and greater horn).