ptosis vs descensus

ptosis and descensus both are nouns.

Word	Noun	Adjective	Verb	Adverb
ptosis	Yes	No	No	No
descensus	Yes	No	No	No

As nouns, descensus is a hypernym of ptosis; that is, descensus is a word with a broader meaning than ptosis:

ptosis: drooping of the upper eyelid caused by muscle paralysis and weakness
descensus: the slipping or falling out of place of an organ (as the uterus)

Other hypernyms of ptosis include prolapse, prolapsus.

ptosis (noun)	descensus (noun)
drooping of the upper eyelid caused by muscle paralysis and weakness	the slipping or falling out of place of an organ (as the uterus)