Digestive System: Absorption, Egestion, and Common Disorders

The Absorption and Egestion

As a result of nutrient digestion, small molecules are obtained, allowing them to pass through the walls of the digestive tract and enter the blood. This process is called absorption.

Most substances are absorbed in the jejunum and ileum. In these sections, the inner walls of the small intestine are highly folded to form villi. Inside the villi, blood vessels collect and distribute digested substances to all body cells.

Egestion

Substances that have not been absorbed pass into the large intestine through peristaltic movements of its walls. In this part, almost all the water and mineral salts are absorbed, so the residues of digestion grow stronger until they become stool.

The large intestine also contains a large number of symbiotic bacteria, which ferment and decompose the unabsorbed remains. In the process, the bacteria synthesize some vitamins, like B or K, which are also absorbed, and produce intestinal gas, causing the bad smell of feces. Stools accumulate for a time in the last section of the intestine, the rectum. Once there, they are periodically removed and expelled outside through the anus via egestion.

Digestive Disorders

Causes of digestive diseases are very diverse. Some seem to have a hereditary component, although a large number of them are due to diverse factors such as stress, inadequate diets, tobacco, or alcohol. The vast majority of these diseases can be prevented by adopting certain preventive measures, such as food and care to maintain proper living habits.

Some of the diseases of the digestive system are:

• Cavities: An infectious disease caused by bacteria that affects the tooth's hard tissues (enamel, dentin, and cement). Bacteria in your mouth feed on ingested carbohydrates and produce acids that create cavities in teeth. Reducing consumption of candy, brushing your teeth after each meal and before bed, and going to the dentist regularly are the best ways to prevent cavities.
• Constipation: A disorder that hinders the evacuation of stool. It is due to excessive water absorption by the intestine, causing dry, hard stools. Its causes are varied, the most common being stress, certain drugs, and diets low in vegetable fiber.
• Ulcers: Open wounds on the inner walls of the digestive tract. They occur mainly in the stomach and duodenum. Their causes are varied, and among them include stress and infection by the bacterium Helicobacter pylori.
• Gastroenteritis: An inflammation of the inner membranes lining the stomach and intestine. This is mainly due to infection with viruses or bacteria. It causes vomiting, diarrhea, and abdominal discomfort. This inflammation prevents much of the water and salts from being absorbed in the intestine, so the feces are very liquid.
• Liver Cirrhosis: A chronic disease involving a progressive death of liver tissue, leading to malfunctioning of the liver. Many cases of cirrhosis are due to excessive consumption of alcohol.