Digestion and Absorption: Definition and Examples

Digestion and absorption are vital processes that break down food into simpler substances and absorb nutrients for energy and growth. Digestion involves mechanical and chemical breakdown in the stomach, while absorption occurs in the small intestine. These processes make sure that the body gets essential nutrients like carbohydrates, proteins, fats, vitamins, and minerals. In this article, digestion, anatomical structures and mechanisms of digestion, and absorption are discussed. Digestion and Absorption is a topic of the chapter Digestion and Absorption in Biology.

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This Story also Contains

1. What is Digestion?
2. Anatomical Structures and Mechanisms of Digestion
3. What is Absorption?

What is Digestion?

Ever wondered how that fabulous meal you ate at lunch becomes the energy and nutrients burned by your body? These two processes take place in digestion and absorption. From the very crunch of the first bite to the eventual release of the energy many hours later, these physiologic processes are part of our day-to-day lives.

Digestion starts in the mouth the moment food enters it. Teeth crush food, and saliva initiates the chemical digestion of carbohydrates. Peristalsis continues to break down food as it moves through various sections of the alimentary canal: first the oesophagus, second, the stomach, and third, the small and large intestines, each region mixing that food with various enzymes and acids. It is a complex journey that ends in absorption, with which the nutrients will be absorbed into the blood to be utilized by cells to sustain all the vital functions of life.

Human Digestive System

Anatomical Structures and Mechanisms of Digestion

The alimentary canal or the gastrointestinal tract is a very intricate system tasked with the responsibility of food digestion and absorption of nutrients that are required for the functions of the body. An understanding of the elements and processes may give a window through which we can seek to understand how our bodies draw energy and sustain them in their healthy state.

Gastrointestinal Tract

It begins with the mouth, where chewing of food initiates digestion, along with the mixing of food with saliva, followed by the oesophagus, in which food is passed involuntarily and this is because of the contraction and the relaxation of the musculature up to the stomach.

Description of the Involvement or the Role of Each Organ

• The Mouth: Digestion in the mouth starts right from the act of chewing and partial digestion by food mixed with saliva to break the carbohydrates down with salivary amylase into simpler subunits.

• Esophagus: The rhythmic muscle contraction, known as peristalsis, moves the bolus to the stomach.

• Stomach: The cellular lining secretes gastric juices for hydrolysis of proteins to chyme.

• Small Intestine: Principal area of nutrient absorption aided by villi and microvilli. They are finger-like outgrowths still increasing the absorptive area.

• Large Intestine: This is where the absorption of water and electrolytes occurs. It is also the site where the faeces are collected and expelled.

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What is Absorption?

The process of absorbing or assimilating substances into cells, tissues, or organs by osmosis or diffusion is known as absorption.

Digestion and Absorption of Carbohydrates

One of the most important components in the human diet is carbohydrates. The human digestive system is capable of breaking down two different kinds of carbohydrates: sugar and starch. Three oral enzymes—lactase, sucrase, and maltase—as well as the small intestine, break down sugar in the digestive system.

Similarly, the stomach and mouth contain enzymes called amylase that aid in the breakdown of starch. Villi are tiny projections that resemble fingers that aid in the absorption of carbohydrates in the small intestine following digestion.

Digestion and Absorption of Proteins

Proteins are essential for the development and renewal of bodily tissues and cells. The enzymes pepsin and protease aid in the breakdown of proteins into amino acids during the stomach's digestive process. The stomach's hydrochloric acid helps to facilitate the process. The small intestine wall allows amino acids, which are little substances, to enter the bloodstream.

Digestion and Absorption of Lipids

Fatty acids, which are insoluble in water, make up the chemical molecules known as lipids. The most prevalent type of lipid is fat. Lipids' intractable nature complicates the process of digesting and absorbing them. Once in the stomach, fats cling to one another as a big glob of insoluble substance because they are hydrophobic.

Bile juice, which contains bile salts, aids in its breakdown. Pancreatic lipase, one of the body's main enzymes for absorbing fat, then acts on these broken molecules. Fats are broken down by pancreatic lipase into monoglycerides and free fatty acid molecules, which are small enough to pass through the small intestine and enter the bloodstream.

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