Your body must injest and absorb nutrients such as proteins, fats, carbohydrates, vitamins, minerals, and water to survive.
Your digestive system includes processes like chewing (mouth), swallowing (peristalsis) enzymes and digestive juices (Stomach and small intestine) to break down the nutrients into parts small enough for your body to convert into energy, growth, and cellular repair.
- Proteins broken into amino acids (More information in Amino Acids Types and Uses)
- Fats broken into fatty acids and glycerol
- Carbohydrates broken down to simple sugars
Mouth: The digestive process begins as soon as you chew food in your mouth. Saliva is released and moistens food so it moves more easily through your esophagus into your stomach. Saliva also has an enzyme that begins to break down starches in the food.
Stomach: When food enters your stomach, the stomach muscles begin the digestive process by mixing food and liquid with digestive juices. This process produces chyme, a semi-fluid mass (bolus) of partly digested food that is pushed from your stomach, through the pyloric valve, into the duodenum – the beginning of the small intestine. Chyme results from the mechanical and chemical breakdown of a bolus and consists of partially digested food, water, hydrochloric acid, and various digestive enzymes. Muscles of your stomach mix the food with these digestive juices.
Small intestine: Most of the digestive enzymes and juices are made in your small intestine. These juices are mixed with bile and pancreatic juice to complete the breakdown of proteins, carbohydrates, and fats. Small Intestinal Bacteria make some of the enzymes you need to digest carbohydrates. Recently, the health of your Small Intestine Bacteria has become of interest, as imbalances in healthy and unhealthy bacteria may occur affecting your general health. (More information in Probiotics and Prebiotics). Finally, your small intestine moves water from your bloodstream into your Gastrointestinal Tract to help break down food. Your small intestine also absorbs water with other nutrients. Your small intestine mixes chyme with digestive juices from the pancreas, liver, and intestine. The contents of your small intestine absorbs water and the digested nutrients, secreting its contents into your bloodstream. Waste products are pushed along the small intestine via peristalsis and into the large intestine.
Large intestine: In your large intestine, more water moves from your Gastrointestinal Tract into your bloodstream. Bacteria in your large intestine help break down remaining nutrients and make vitamin K. Remaining waste products including parts of food that are still too large become stool, consisting of undigested parts of food, fluid, and older cells from the lining of your GI tract.
Pancreas: Your pancreas makes a digestive juice that has enzymes that break down carbohydrates, fats, and proteins. The pancreas delivers the digestive juice to the small intestine through small tubes called ducts.
Liver: Your liver produces bile that helps digest fats and some vitamins. Bile ducts carry bile from your liver to your gallbladder for storage, or to the small intestine for use.
Gallbladder: Your gallbladder stores bile between meals. When you eat, your gallbladder squeezes bile through the bile ducts into your small intestine.
How does my body control the digestive process?
Your hormones and nervous system work together to help control the digestive process.
Specific cells lining your stomach and small intestine make and release hormones. These hormones control how your digestive system works by telling your body when to make digestive juices by sending signals to your brain that you are hungry or full. Your pancreas also produces hormones important to digestion.
Nerves in your central nervous system connect to your digestive system and control some digestive functions. For example, your brain can react to the smell of food and produce a release of saliva from your salivary glands.
You also have an enteric nervous system (nerves within the walls of your Gastrointestinal Tract). As food stretches the walls of your GI tract, the nerves of your enteric nervous system release a variety of substances that speed up or delay the movement of food and production of digestive juices.