Final answer:
The submandibular (digastric) triangle contains the submandibular gland, submandibular ducts, submandibular lymph nodes, facial artery and vein, hypoglossal nerve, and branches of the lingual and glossopharyngeal nerves.
Step-by-step explanation:
The contents of the submandibular (digastric) triangle, an anatomical area located beneath the jaw, include several important structures. Notably, this triangle contains the submandibular gland, which is responsible for secreting saliva that aids digestion and oral hygiene. The submandibular ducts transport this saliva from the gland into the oral cavity. Additionally, other structures within this triangle are the submandibular nodes (part of the lymphatic system), the facial artery and vein, as well as nerves such as the hypoglossal nerve (CN XII) which innervates the tongue muscles, and branches of the lingual and glossopharyngeal nerves. The saliva produced by the submandibular gland is a mixed secretion containing both serous fluid, which includes salivary amylase, and mucous which helps in lubrication.