The digestive system contains numerous organs that contribute to the secretion of digestive juices
- These organs include the salivary glands, stomach, liver, pancreas and small intestine
Organs Involved in Digestive Juice Production
Salivary Glands
- Initiate chemical digestion while food is still being physically chewed within the mouth
- Secretes salivary amylase, which assists in the breakdown of glucose polymers (e.g. starch)
Stomach
- Produces stomach acids which aid in the chemical breakdown of food materials
- Secretes proteases to function as the initial site of protein digestion
- Stomach proteases typically require acid conditions for activation (e.g. pepsinogen → pepsin)
Liver
- Produces bile which is responsible for the emulsification of fats (separates fats globules to enhance lipase activity)
- Bile produced in the liver is commonly stored in the gall bladder until a release
Pancreas
- Secretes bicarbonate ions into the duodenum to neutralize stomach acids (intestine pH is usually ~ 7 – 8)
- Also secretes lipase (for fat digestion), amylase (for carbohydrate digestion) and protease (for protein digestion)
- Pancreatic proteases are activated by enzymes and not by acid conditions (enterokinase converts trypsinogen to trypsin)
Small Intestine
- Intestinal juices are secreted from pits called crypts of Leiberkuhn, located between intestinal villi
- Digestive enzymes in the small intestine are typically immobilized on the epithelial membrane (e.g. maltase)
- This prevents the enzymes from being removed from the body as part of the normal digestive cycle
- It also concentrates the digestive products at sites where membrane proteins are present (to optimize absorption)
