The Lacrimal Sac is a small hole in your eyelids that drains tears to your nose. It's the reason why you get a runny nose after crying.
The lacrimal glands are serous type exocrine glands that secrete lacrimal fluid onto the surfaces of the conjunctiva and cornea of the eye. The Lacrimal fluid acts to clean, nourish and lubricate the eyes. It forms tears when produced in excess.
The lacrimal apparatus is the system responsible for the drainage of lacrimal fluid from the orbit. After secretion, lacrimal fluid circulates across the eye and accumulates in the lacrimal lake located in the medial canthus of the eye. From here, it drains into the lacrimal sac via a series of canals.
The lacrimal sac is the dilated end of the nasolacrimal duct and is located in a groove formed by the lacrimal bone and frontal process of the maxilla. Lacrimal fluid drains down the nasolacrimal duct and empties into the inferior meatus of the nasal cavity.