• The salivary glands can produce up to 1.5 quarts (1,500 milliliters) of saliva daily.
• Food remains in the esophagus for as little as five seconds before entering the stomach.
• The human stomach can hold as much as 2.1 quarts (2 liters) of food.
• The stomach produces 2.12 quarts (2 liters) of gastric juice daily.
• Gastric juice is 100,000 times more acidic than water and has about the same acidity as battery acid.
• The small intestine in an adult can reach 3.28 yards (3 meters) in length, while the large intestine is only about 1.64 yards (1.5 meters) long.
• Every square millimeter of the small intestine can contain 40 villi and 200 million microvilli.
• Food remains in the small intestine for three to five hours on average, during which most nutrients are removed.
• The intestines receive over 10 quarts (9 liters) of water daily, of which almost 95 percent is recycled back into the body.
• As little as 10–15 percent of the iron we eat in food is absorbed into the human body.
Information Source: Encyclopedia of Human Body Systems Book