Digestion and Absorption MCQ

The chemical breakdown of ingested food into absorbable molecules is known as digestion. Absorption is the process of nutrients, water and electrolytes passing from the small intestinal lumen into the cell and then into the blood. The digestive system is where digestion and absorption take place. After nutrients are absorbed, they become available to all cells in the body and are used in metabolism by those cells. 

Digestion

Large insoluble food molecules are broken down into little water-soluble food molecules during digestion, allowing them to be absorbed into the watery blood plasma. Certain creatures ingest these tiny chemicals into their bloodstream via the small intestine. Digestion is a type of catabolism that is frequently separated into two processes: mechanical and chemical digestion, depending on how food is broken down. The physical breakdown of large chunks of food into smaller fragments that digestive enzymes can access is referred to as mechanical digestion. Mastication takes place in the mouth, while segmentation contractions take place in the small intestine. Enzymes break down food into little molecules that the body can utilise in chemical digestion. 

Human Digestion Process

Saliva and its digestive enzymes start the digestion process in the mouth. By mechanical mastication, food is shaped into a bolus and ingested into the oesophagus, from whence it enters the stomach by peristalsis. Gastric juice contains hydrochloric acid and pepsin, which can harm the stomach’s walls, thus mucus and bicarbonates are released to protect them. More enzymes are released in the stomach, breaking down the meal even more, and this is combined with the stomach’s churning movement. Proteins are primarily digested in the stomach. Partially digested food reaches the duodenum as a thick semi-liquid chyme. The majority of digestion takes place in the small intestine, which is aided by bile, pancreatic juice, and intestinal juice secretions. The intestinal walls are lined with villi, and their epithelial cells are coated with many microvilli to increase the surface area of the intestine and promote nutritional absorption. Bile aids in the emulsification of lipids and also acts as a lipase activator. 

Absorption

The transfer of digested food molecules through the intestinal wall into the blood or lymph is known as absorption. 

The small intestine is the site of absorption of digested food. Majority of absorption occurs in the ileum. This section of the small intestine is the longest, measuring between 2-4 metres in length. The small intestine contains a vast interior surface area, which allows for rapid and effective absorption.

Mechanism

When digestion is complete, many simple nutrient molecules are produced, which must be absorbed from the GI tract by blood or lymph before being utilised by cells throughout the body. In the stomach and large intestine, only a few chemicals are absorbed. Water, for example, is absorbed in both of these organs, and the large intestine also absorbs several minerals and vitamins. The small intestine, on the other hand, absorbs around 95% of nutritional molecules. The majority of these molecules are absorbed in the jejunum, which is the second section of the small intestine. There are, however, a few exceptions. Iron, for example, is absorbed in the duodenum, and vitamin B12 is absorbed in the ileum, the last region of the small intestine. Nutrient molecules are transferred to different areas of the body for storage or chemical alteration after being absorbed in the small intestine. Amino acids, for example, are delivered to the liver and utilised in protein synthesis. 

The small intestine’s epithelial epithelium is tailored to absorb specific nutrients. It has a lot of wrinkles and is coated in villi and microvilli, which gives it a lot of surface area for absorption. Each villus also possesses a network of blood capillaries and fine lymphatic tubes termed lacteals near to its surface. 

Conclusion

For the body to utilise food for energy, development, and cell repair, it must be broken down into nutrients. Food and drink must be broken down into smaller nutrition molecules before the circulation absorbs and delivers nutrients to cells throughout the body. The body breaks down food and drink ingredients into carbohydrates, protein, lipids, and vitamins.