Learn Russian: Если пищеварение работает хорошо, еда продолжает усваиваться. - If digestion works well, food continues to be absorbed.

After verbs that denote the start, continuation, or end of an action, like продолжать (to continue), Russian strictly requires the following infinitive to be in the imperfective aspect. Even if you are talking about an eventual result, you must use the imperfective усваиваться rather than the perfective усвоиться.

How does the -ся ending function on усваиваться in this context?

The base verb усваивать means to absorb or digest something, which is an active process. Adding the reflexive particle -ся here creates a passive meaning, showing that the food is being absorbed. Using the reflexive suffix is the standard way to form the passive voice for ongoing, imperfective actions in Russian.

Is there a trick to remembering the word пищеварение?

Yes, it is a compound noun made from two words you likely already know: пища (food) and варить (to boil or cook). Literally translating to the boiling of food, this compound is how Russian expresses the concept of digestion.