Why absorption is important

They also contain blood capillaries to carry away the absorbed food molecules. Excess water is absorbed back into the body in the large intestine. What is left then is undigested food. This is stored in the rectum, the lower part of the large intestine, until we are ready to go to the toilet. It then comes out of the rectum through the anus as faeces. This process is called egestion. Take care not to confuse egestion with excretion.

The digestive system contains many bacteria and about half of the dry weight of faeces consists of bacteria. Serious electrolyte disturbances, such as dehydration and over-hydration, may lead to cardiac and neurological complications that, unless they are rapidly resolved, will result in a medical emergency.

Water and minerals are reabsorbed back into the blood in the colon large intestine where the pH is slightly acidic—about 5.

Privacy Policy. Skip to main content. Digestive System. Search for:. Absorption in the Small Intestine The absorption of nutrients occurs partially by diffusion through the wall of the small intestine.

Learning Objectives Describe the role played by the small intestine in the absorption of nutrients. Key Takeaways Key Points Digested food is able to pass into the blood vessels in the wall of the small intestine through the process of diffusion. The inner wall, or mucosa, of the small intestine is covered in wrinkles or folds called plicae circulares that project microscopic finger-like pieces of tissue called villi, which in turn have finger-like projections known as microvilli.

Each villus transports nutrients to a network of capillaries and fine lymphatic vessels called lacteals close to its surface. Key Terms villi : Tiny, finger-like projections that protrude from the epithelial lining of the intestinal wall. Examples Examples of nutrients absorbed by the small intestine include carbohydrates, lipids, proteins, iron, vitamins, and water.

Absorption of Monosaccharides, Amino Acids, Dipeptides, Tripeptides, Lipids, Electrolytes, Vitamins, and Water Glucose, amino acids, fats, and vitamins are absorbed in the small intestine via the action of hormones and electrolytes. Learning Objectives Describe the process of absorption of nutrients in the small intestine. Key Takeaways Key Points Proteins are degraded into small peptides and amino acids di- and tripeptides before their absorption by proteolytic and digestive enzymes such as trypsin.

Lipids fats are degraded into fatty acids and glycerol by pancreatic lipase. Carbohydrates are degraded into monosaccharide or oligosaccharide sugars by the action of amylase. Carbohydrates, such as cellulose, pass through the human intestinal tract undigested.

Water and some water-soluble vitamins are absorbed by diffusion. Some electrolytes and water non-soluble vitamins require an active uptake mechanism. Key Terms trypsin : A digestive enzyme that cleaves peptide bonds a serine protease. Carbohydrates are the sugars, starches, and fiber found in many foods. Carbohydrates are called simple or complex, depending on their chemical structure. Simple carbohydrates include sugars found naturally in foods such as fruits, vegetables, milk, and milk products, as well as sugars added during food processing.

Complex carbohydrates are starches and fiber found in whole-grain breads and cereals, starchy vegetables, and legumes. Foods such as meat, eggs, and beans consist of large molecules of protein that the body digests into smaller molecules called amino acids.

The body absorbs amino acids through the small intestine into the blood, which then carries them throughout the body. Fat molecules are a rich source of energy for the body and help the body absorb vitamins. Oils, such as corn, canola, olive, safflower, soybean, and sunflower, are examples of healthy fats. Butter, shortening, and snack foods are examples of less healthy fats.