Which muscle forms the floor of the mouth and delineates the sublingual space from the submandibular space?

The mylohyoid muscle forms the muscular floor of the oral cavity (the 'diaphragm of the mouth'). It divides the floor of the mouth into two spaces: the sublingual space (above/superior to the mylohyoid, between the tongue and the mandible) and the submandibular space (below/inferior to the mylohyoid). This anatomical division is clinically significant because odontogenic infections can spread between these spaces. Ludwig's angina involves bilateral infection of the submandibular, sublingual, and submental spaces. The mylohyoid also elevates the floor of the mouth and the hyoid bone during swallowing.