Final answer:
7 to 10 liters of fluid are secreted into the digestive tract daily, with 90 percent reabsorbed in the small intestine. About 2.3 liters of fluid come from ingested food and beverages, while the rest is from gastrointestinal secretions.
Step-by-step explanation:
Every day, the body secretes a substantial amount of fluid into the lumen of the digestive tract. This internal secretion accounts for a total of 7 to 10 liters daily, including water from digestive juices, ingested foods, and beverages. Specifically, about nine liters of fluid make their way to the small intestine, which includes around 2.3 liters from what we eat and drink and the remainder from gastrointestinal secretions.
Approximately 90 percent of this water is reabsorbed in the small intestine, driven by a concentration gradient. The large intestine absorbs most of the remaining water, further concentrating the undigested material into feces. It's fascinating to note that even the small intestine itself secretes about 0.95 to 1.9 liters of intestinal juice each day in response to the presence of chyme.