There are many places where one can find the terminology on the process of the human digestive system. One can find this information on the human digestive system Wikipedia page. One may also find this information through many different medical related websites.
In reality, it would become readily apparent if someone in a medical setting didn't understand medical abbreviations or terminology. The reason for this is abbreviations and specific medical terms are used on such a large scale that if someone didn't understand them, they wouldn't be able to hide it very long. In a medical setting people use medical terminology and/or abbreviations every few seconds.
Someone writing "for 24 hours" in medical abbreviations would typically write "x24h"
Hetero- is the medical terminology combining form meaning unlike or different. For instance, heterosexual refers to someone sexually attracted to the opposite sex. Heterochromia means different colors.
-penic means deficient. For instance, osteopenic is an adjective for someone with low bone density.
If someone wants to be a medical transcriptionist then they need to have excellent hearing and writing skills. They will also need some experience of medical terminology and so science experience will be useful.
nonagenarian
Possibly, although there would be significant medical challenges for the rest of the person's life. The duodenum is where a lot of initial digestion takes place, and is where the exocrine pancreas and the liver secrete digestive enzymes into the digestive tract.
There is a danger if good medical and correct medical terminology is not used by physicians, nurses and medical transcriptionists. Imagine if someone put hypoglycemia instead of hyperglycemia on a chart. A patient could be given too much insulin and be killed or put into a coma. Any incorrect understanding of the sugar levels and the disease can cause severe and possibly permanent problems. And if a person entered a disease the patient did not have then that patient could be subjected to severe problems from incorrect treatment too.
When the digestive process is completed, the guano emerges. No decision is involved.
It is not necessarily unhealthy if it takes someone 24 hours to fully process a meal. This is about average. If you think that you are having digestive problems, see a doctor as soon as possible.
It is a parasite that absorbs predigested food. Why need a digestive system when someone else does it for you?
After someone has disease, what is the medical treatment?