Final answer:
The correct answer to the amount of fluid secreted daily into the lumen of the digestive tract is (a) 7 liters.
Step-by-step explanation:
The amount of fluid secreted daily into the lumen of the digestive tract is quite significant. Each day, there is a continuous excretion of water in the form of digestive juices that enter the small intestine. This includes both the water from ingested foods and beverages, as well as gastrointestinal (GI) secretions. The total amount of this internal secretion is between 7 to 10 liters per day, which is critical for the digestive processes.
While the majority of this water, approximately 90%, is absorbed in the small intestine, the rest continues through the digestive tract. Intestinal glands, known as crypts of Lieberkühn, contribute to the secretion by producing intestinal juice, with volumes ranging from about 0.95 to 1.9 liters daily.
This secretion occurs in response to the distention of the small intestine and the presence of chyme.