A 9-year-old girl comes to the dentist with her

mother. A large swelling, even a cyst, is forming under her tongue. It is a

so-called ranula, which is a retention cyst of the sublingual gland, formed by

obliteration (closure) of the duct, probably as a result of a previous

infection. The outflow of the saliva produced is impossible. The stagnant

saliva dilates the ducts, forming a secretion-filled cyst. The treatment here

is extirpation (surgical removal). Which characteristic describes the closed

main duct of the salivary gland here?