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Cut through the superior belly of the omohyoid muscle near its attachment to the hyoid bone and reflect it inferiorly. Next, cut the sternohyoid muscle and reflect it inferiorly. Identify the thyrohyoid muscle and sternothyroid muscle. Cut the thyrohyoid muscle and reflect it inferiorly. You may need to cut the inferior portion of the submandibular gland and remove it in order to have adequate exposure of this region. Be careful not to cut the facial artery that passes in a groove on the surface of the submandibular.

Links and References:
Grant's: 8.23
Netter: 27
Rohen/Yokochi: 176, 177, 178