Mechanical digestion begins in the mouth, where teeth break down food into smaller pieces. This process is aided by saliva, which contains enzymes that begin to break down carbohydrates. The food is then swallowed and travels down the esophagus to the stomach.
The stomach is a muscular organ that churns the food and mixes it with stomach acid. Stomach acid is hydrochloric acid, which helps to break down proteins. The food is churned for several hours until it becomes a semi-liquid substance called chyme.
Chemical digestion continues in the small intestine. The small intestine is a long, coiled tube that is lined with villi. Villi are small, finger-like projections that increase the surface area of the small intestine and help to absorb nutrients.
The small intestine produces enzymes that break down carbohydrates, proteins, and fats. These enzymes are produced by the pancreas and the liver. The pancreas is a small, pear-shaped organ that is located behind the stomach. The liver is a large, glandular organ that is located on the right side of the abdomen.
Carbohydrates are broken down into simple sugars by the enzymes amylase and maltase. Proteins are broken down into amino acids by the enzymes pepsin, trypsin, and chymotrypsin. Fats are broken down into fatty acids and glycerol by the enzymes lipase and phospholipase.
The products of digestion are absorbed through the villi and into the bloodstream. The undigested material travels to the large intestine, where it is eventually excreted.
Digestion is an essential process that allows the body to absorb the nutrients it needs to function properly. Without digestion, the body would not be able to convert food into energy and would eventually starve.
