digestive system essay in english

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18.2: Introduction to the Digestive System

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• Suzanne Wakim & Mandeep Grewal
• Butte College

If you’re a dessert lover, then just the sight of this flan dish may make your mouth water. The “water” in your mouth is actually saliva, a fluid released by glands that are part of the digestive system. Saliva contains digestive enzymes among other substances important for digestion. When your mouth waters at the sight of a tasty treat, it’s a sign that your digestive system is preparing to digest food.

What Is the Digestive System?

The digestive system consists of organs that break down food, absorb its nutrients, and expel any remaining waste. Organs of the digestive system are shown in Figure \(\PageIndex{2}\). Most of these organs make up the gastrointestinal (GI) tract. Food actually passes through these organs. The rest of the organs of the digestive system are called accessory organs. These organs secrete enzymes and other substances into the GI tract, but food does not actually pass through them.

Functions of the Digestive System

The digestive system has three main functions relating to food: digestion of food, absorption of nutrients from food, and elimination of solid food waste. Digestion is the process of breaking down food into components the body can absorb. It consists of two types of processes: mechanical digestion and chemical digestion. Mechanical digestion is the physical breakdown of chunks of food into smaller pieces. This type of digestion takes place mainly in the mouth and stomach. Chemical digestion is the chemical breakdown (bonds are broken) of large, complex food molecules into smaller, simpler nutrient molecules that can be absorbed by body fluids (blood or lymph). This type of digestion begins in the mouth and continues in the stomach but occurs mainly in the small intestine.

After food is digested, the resulting nutrients are absorbed. Absorption is the process in which substances pass into the bloodstream or lymph system to circulate throughout the body. The absorption of nutrients occurs mainly in the small intestine. Any remaining matter from food that is not digested and absorbed passes out of the body through the anus in the process of elimination.

Gastrointestinal Tract

The gastrointestinal (GI) tract is basically a long, continuous tube that connects the mouth with the anus. If it were fully extended, it would be about 9 meters (30 feet) long in adults. It includes the mouth, pharynx, esophagus, stomach, and small and large intestines. Food enters the mouth and then passes through the other organs of the GI tract where it is digested and/or absorbed. Finally, any remaining food waste leaves the body through the anus at the end of the large intestine. It takes up to 50 hours for food or food waste to make the complete trip through the GI tract.

Tissues of the GI Tract

The walls of the organs of the GI tract consist of four different tissue layers, which are illustrated in Figure \(\PageIndex{3}\): mucosa, submucosa, muscularis externa, and serosa.

• The mucosa is the innermost layer surrounding the lumen, or open space within the organs of the GI tract. This layer consists mainly of the epithelium with the capacity to secrete and absorb substances. For example, the epithelium can secrete digestive enzymes and mucus, and it can absorb nutrients and water.
• The submucosa layer consists of connective tissue that contains blood and lymph vessels and also nerves. The vessels are needed to absorb and carry away nutrients after food is digested, and nerves help control the muscles of the GI tract organs.
• The muscularis externa layer contains two types of smooth muscle: longitudinal muscle and circular muscle. The longitudinal muscle runs the length of the GI tract organs and circular muscle encircles the organs. Both types of muscles contract to keep food moving through the track by the process of peristalsis (Figure \(\PageIndex{4}\).
• The serosa layer is the outermost layer of the walls of GI tract organs. This is a thin layer that consists of connective tissue and separates the organs from surrounding cavities and tissues.

Peristalsis in the GI Tract

The muscles in the walls of GI tract organs enable peristalsis, which is illustrated in Figure \(\PageIndex{4}\). Peristalsis is a continuous sequence of involuntary muscle contraction and relaxation that moves rapidly along an organ like a wave, similar to the way a wave moves through a spring toy. Peristalsis in organs of the GI tract propels food through the tract.

Divisions of the GI Tract

The GI tract is often divided into an upper GI tract and a lower GI tract. For medical purposes, the upper GI tract is typically considered to include all the organs from the mouth through the first part of the small intestine, called the duodenum. For instructional purposes, it makes more sense to include the mouth through the stomach in the upper GI tract and all of the small intestine as well as the large intestine in the lower GI tract. The latter approach is followed here. All organs of GI which are discussed in the text are illustrated in Figure \(\PageIndex{2}\).

Upper GI Tract

The mouth is the first digestive organ that food enters. The sight, smell, or taste of food stimulates the release of digestive enzymes and other secretions by salivary glands inside the mouth. The major salivary gland enzyme is amylase. It begins the chemical digestion of carbohydrates by breaking down starches into sugar. The mouth also begins the mechanical digestion of food. When you chew, your teeth break, crush, and grind food into increasingly smaller pieces. Your tongue helps to mix the food with saliva and also helps you swallow.

A lump of swallowed food is called a bolus. The bolus passes from the mouth into the pharynx and from the pharynx into the esophagus. The esophagus is a long, narrow tube that carries food from the pharynx to the stomach. It has no other digestive functions. Peristalsis starts at the top of the esophagus when food is swallowed and continues down the esophagus in a single wave, pushing the bolus of food ahead of it.

From the esophagus, food passes into the stomach, where both mechanical and chemical digestion continue. The muscular walls of the stomach churn and mix the food, thus completing mechanical digestion as well as mixing the food with digestive fluids secreted by the stomach. One of these fluids is hydrochloric acid. As well as killing pathogens in food, it gives the stomach the low pH needed by digestive enzymes that work in the stomach. One of these enzymes is pepsin, which chemically digests proteins. The stomach stores the partially digested food until the small intestine is ready to receive it. Food that enters the small intestine from the stomach is in the form of a thick slurry (semi-liquid) called chyme.

Lower GI Tract

The small intestine is a narrow but very long tubular organ. It may be almost 7 meters (23 feet) long in adults. It is the site of most chemical digestion and virtually all absorption of nutrients. Many digestive enzymes are active in the small intestine, some of which are produced by the small intestine itself, and some of which are produced by the pancreas, an accessory organ of the digestive system. Much of the inner lining of the small intestine is covered by tiny finger-like projections called villi, each of which in turn is covered by even tinier projections called microvilli. These projections, shown in Figure \(\PageIndex{5}\), greatly increase the surface area through which nutrients can be absorbed from the small intestine.

The small intestine is made up of three parts:

• The duodenum is the first part of the small intestine. It is also the shortest part. This is where most chemical digestion takes place.
• The jejunum is the second part of the small intestine. This is where most nutrients are absorbed into the blood.
• The ileum is the last part of the small intestine. A few remaining nutrients are absorbed in the ileum. From the ileum, any remaining food waste passes into the large intestine.

From the small intestine, any remaining nutrients and food waste pass into the large intestine. The large intestine is another tubular organ like the small intestine, but it is wider and shorter than the small intestine. It connects the small intestine and the anus. Waste that enters the large intestine is in a liquid state. As it passes through the large intestine, excess water is absorbed from it. The remaining solid waste, called feces, is eventually eliminated from the body through the anus.

Accessory Organs of the Digestive System

Accessory organs of the digestive system are not part of the GI tract, so they are not sites where digestion or absorption take place. Instead, these organs secrete or store substances that are needed for the chemical digestion of food. The accessory organs include the liver, gallbladder, and pancreas. They are shown in Figure \(\PageIndex{6}\) and described in the text:

• The liver is an organ that has a multitude of functions. Its main digestive function is producing and secreting a fluid called bile, which reaches the small intestine through a duct. Bile breaks down large globules of lipids into smaller ones that are easier for enzymes to chemically digest. Bile is also needed to reduce the acidity of food entering the small intestine from the highly acidic stomach because enzymes in the small intestine require a less acidic environment in order to work.
• The gallbladder is a small sac below the liver that stores some of the bile from the liver. The gallbladder also concentrates the bile by removing some of the water from it. It then secretes the concentrated bile into the small intestine as needed for fat digestion following a meal.
• The pancreas secretes many digestive enzymes and releases them into the small intestine for the chemical digestion of carbohydrates, proteins, and lipids. The pancreas also helps to lessen the acidity of the small intestine by secreting bicarbonate, a basic substance that neutralizes the acid.

• What is the digestive system?
• What are the three main functions of the digestive system? Define each function.
• Describe the GI tract.
• Distinguish between the upper and lower GI tracts.
• Relate the tissues in the walls of GI tract organs to the functions the organs perform.
• Identify accessory organs of digestion and their general function in digestion.
• Identify the points in the GI tract where food becomes a bolus, chyme, and feces, respectively.
• Does food pass through the pancreas? Why or why not?
• True or False. Absorption mainly occurs in the stomach.
• True or False. Some chemical digestion occurs in the mouth.

A. Gall bladder

C. Small intestine

D. Large intestine

b. Describe one way in which carbohydrates are at least partially chemically digested in the digestive system.

• If the villi in your small intestine were damaged and could not function normally, what effect might this have on your body? Explain your reasoning.

A. An accessory organ of the digestive system

B. Part of the upper GI tract

C. Part of the lower GI tract

D. The longitudinal muscle

Explore More

Check out this 3D animation video to see peristalsis in the Large Intestine:

Why do we feel hungry? Check out this video to learn more:

Attributions

• Caramel cream flan by RitaE via Pixabay license
• Digestive system diagram by Mariana Ruiz, Public Domain via Wikimedia Commons
• Mucosa by National Institute of Health, Public Domain via Wikimedia Commons
• Peristalsis by Zachary Wilson , CC BY NC 3.0 via CK12.org
• Small Intestines from Microbiology by Open Stax CC BY 3.0
• Gallbladder-Liver-Pancreas Location by Blausen.com staff (2014). " Medical gallery of Blausen Medical 2014 ". WikiJournal of Medicine 1 (2). DOI : 10.15347/wjm/2014.010 . ISSN 2002-4436 . licensed CC BY 3.0 via Wikimedia Commons
• Text adapted from Human Biology by CK-12 licensed CC BY-NC 3.0

Essay on Human Digestive System

Students are often asked to write an essay on Human Digestive System in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

Let’s take a look…

100 Words Essay on Human Digestive System

The human digestive system.

The human digestive system is a complex mechanism that helps us process food. It starts at the mouth, where food is chewed and mixed with saliva.

Swallowing and Stomach Digestion

Swallowed food travels down the esophagus to the stomach. Here, it’s broken down into a liquid mixture.

Small Intestine and Absorption

This mixture enters the small intestine, where nutrients are absorbed into the bloodstream.

Large Intestine and Waste Removal

Undigested food moves to the large intestine. Water is absorbed, and the rest is expelled as waste. This system keeps us healthy and energetic.

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• 10 Lines on Human Digestive System

250 Words Essay on Human Digestive System

Introduction.

The human digestive system, a complex network of organs and structures, is responsible for breaking down food into nutrients, which the body uses for energy, growth, and cell repair. It operates through a series of interconnected stages involving both mechanical and chemical processes.

The Digestive Process

Digestion begins in the mouth, where food is broken down by chewing and mixed with saliva. Saliva contains an enzyme called amylase that starts the process of carbohydrate digestion. The food then travels down the esophagus into the stomach through a process called peristalsis.

In the stomach, food is further broken down by powerful stomach acids. Proteins are denatured by the acidic environment and an enzyme, pepsin, initiates protein digestion. The stomach churns the food into a liquid mixture called chyme, which then enters the small intestine.

The small intestine is where most digestion and absorption of nutrients occur. Bile from the liver aids in fat digestion, while pancreatic enzymes and intestinal enzymes further break down carbohydrates, proteins, and fats. The inner walls of the small intestine, covered with finger-like projections called villi, absorb the nutrients into the bloodstream.

Finally, the undigested food material moves into the large intestine, where water is absorbed, and the remaining waste material is expelled from the body. The human digestive system, thus, plays a critical role in maintaining overall health, highlighting the importance of a balanced diet and good nutrition. Understanding its intricacies can provide insights into many health issues, from food intolerances to more serious digestive diseases.

500 Words Essay on Human Digestive System

The human digestive system is a complex series of organs and glands that process food, breaking it down into usable energy and nutrients. The system plays a crucial role in maintaining overall health by providing the body with essential elements needed for cellular function.

Anatomy of the Digestive System

The digestive system is divided into two main parts: the alimentary canal (or gastrointestinal tract) and the accessory digestive organs. The alimentary canal is a continuous, coiled, hollow muscular tube that winds through the body, extending from the mouth to the anus. It includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

The accessory organs, which include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas, play essential roles in digestion but are not part of the alimentary canal.

Digestion begins in the mouth, where food is mechanically broken down by the teeth and chemically by salivary enzymes. The food is then swallowed and transported down the esophagus to the stomach through a process called peristalsis.

In the stomach, gastric juices further break down the food. Enzymes like pepsin begin protein digestion, and the churning action of the stomach mixes everything into a semi-liquid substance known as chyme.

The chyme then enters the small intestine, the primary site for nutrient absorption. Here, pancreatic enzymes and bile from the liver further break down proteins, fats, and carbohydrates. The nutrients are then absorbed into the bloodstream through the intestinal wall.

Finally, the undigested food residue enters the large intestine, where water and electrolytes are absorbed, and the remaining waste is compacted into feces and expelled from the body.

Regulation of Digestive System

The digestive system is regulated by both hormonal and nervous mechanisms. Hormones such as gastrin, secretin, and cholecystokinin are released in response to the presence of food, stimulating the secretion of digestive juices.

The nervous system also plays a crucial role. The enteric nervous system, a semi-independent part of the nervous system, directly controls the gastrointestinal system. Additionally, the central nervous system regulates digestion through the autonomic nervous system, particularly the parasympathetic division, which stimulates digestive activities.

The human digestive system is a marvel of nature, efficiently processing food into the nutrients necessary for life. Its complexity and precision underscore the importance of maintaining digestive health. Understanding the intricate workings of this system can provide insights into a wide range of health issues and can guide dietary and lifestyle choices that promote overall well-being. In essence, the digestive system is much more than a food processing plant; it is a crucial component of our health and vitality.

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23: The Digestive System

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• 23.0: Introduction The digestive system is continually at work, yet people seldom appreciate the complex tasks it performs in a choreographed biologic symphony.
• 23.1: Overview of the Digestive System The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process.
• 23.2: Digestive System Processes and Regulation The digestive system uses mechanical and chemical activities to break food down into absorbable substances during its journey through the digestive system. The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation.
• 23.3: The Mouth, Pharynx, and Esophagus In this section, you will examine the anatomy and functions of the three main organs of the upper alimentary canal—the mouth, pharynx, and esophagus—as well as three associated accessory organs—the tongue, salivary glands, and teeth.
• 23.4: The Stomach Although a minimal amount of carbohydrate digestion occurs in the mouth, chemical digestion really gets underway in the stomach. An expansion of the alimentary canal that lies immediately inferior to the esophagus, the stomach links the esophagus to the first part of the small intestine (the duodenum) and is relatively fixed in place at its esophageal and duodenal ends. In between, however, it can be a highly active structure, contracting and continually changing position and size.
• 23.5: The Small and Large Intestines The word intestine is derived from a Latin root meaning “internal,” and indeed, the two organs together nearly fill the interior of the abdominal cavity. In addition, called the small and large bowel, or colloquially the “guts,” they constitute the greatest mass and length of the alimentary canal and, with the exception of ingestion, perform all digestive system functions.
• 23.6: Accessory Organs in Digestion- The Liver, Pancreas, and Gallbladder Chemical digestion in the small intestine relies on the activities of three accessory digestive organs: the liver, pancreas, and gallbladder (Figure 23.6.1). The digestive role of the liver is to produce bile and export it to the duodenum. The gallbladder primarily stores, concentrates, and releases bile. The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.
• 23.7: Chemical Digestion and Absorption - A Closer Look As you have learned, the process of mechanical digestion is relatively simple. It involves the physical breakdown of food but does not alter its chemical makeup. Chemical digestion, on the other hand, is a complex process that reduces food into its chemical building blocks, which are then absorbed to nourish the cells of the body. In this section, you will look more closely at the processes of chemical digestion and absorption.

Home — Essay Samples — Nursing & Health — Digestive System — Organs of Digestive system

Organs of Digestive System

• Categories: Digestive System Human Anatomy

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Published: Dec 18, 2018

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Small intestine.

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Human Digestion Essay

Introduction.

Digestive system is one of the most important systems of any organism. It enables the organism get nutrients which are important for functioning. The most important organs of the human digestive system are mouth, salivary glands, pharynx, oesophagus, stomach, liver, pancreas, gallbladder, small intestine, large intestine and anus (Grosvenor & Smolin, 2012). Food travels through the digestive system and each organ contributes to rendering food into molecules or nutrients.

Factors Affecting the Amount of Time Necessary to Digest Food and Helpful Foods

It is necessary to note that this travel can take from 24 hours to 72 hours. A number of factors affect the amount of time necessary for digestion. Firstly, the type of food plays an important role in this process (Gropper & Smith, 2012). Such products as vegetables, fruit and grains are rich in fibre.

Thus, fibre moves quickly through the digestive tract. On the contrary, eating a lot of meat will slow down the process as this food needs more time to be digested. Notably, physical training positively affects digestion process as it helps food move through the digestive tract. Drugs containing enzymes can also reduce the amount of time necessary for digestion. Caffeine slows down digestive processes.

Digestion in Organs

Digestion starts in the mouth. Food is grinded with the help of teeth. Notably, salivary glands secrete certain enzymes which start processing food in the mouth (Gropper & Smith, 2012). Saliva also moisturises food which helps it travel to the stomach. Food moves to the stomach through the pharynx and oesophagus with the help of contractions. In the stomach, food is grinded and mixed with the help of enzymes and acid secreted by this organ.

After this, food travels to the small intestine where it is processed with the help of enzymes secreted by pancreas and bile secreted by the liver. Bile is secreted by the liver but it is first stored in gallbladder which sends it to the small intestine. The small intestine is the organ which absorbs most nutrients. When all nutrients are absorbed, the food moves to the large intestine where liquid may be absorbed. Then the food leaves the body.

Breakdown of fats, carbohydrates and proteins

There are three types of nutrients. These are fats, carbohydrates and proteins. Each type of nutrient breaks down to be used in the body. Notably, the process of breakdown is different for all three types of nutrients (Gropper & Smith, 2012). With the help of enzymes, proteins are broken down into amino acids.

These acids are used to build other types of proteins necessary for transporting molecules and catalysing numerous chemical reactions which take place in the body. Fats are transformed into fatty acids travel to blood which transports them to cells which need these acids.

Acids which are not necessary are stored in fat cells. Fats are necessary for energy. Carbohydrates are also important for energy. These nutrients are broken down into glucose which is stored in liver for a short period of time until the needs of the body are met. Then glucose which is not needed is transformed into fats which are used for energy.

On balance, it is necessary to note that digestive system consists of several organs which perform certain roles. Remarkably, people need different types of nutrients which can be acquired from different foods, e.g. vegetables, fruit, meat, fish, grains, cereals, nuts, etc. Hence, people need a balanced diet consisting of proteins, carbohydrates and fats.

Reference List

Gropper, S., & Smith, J. (2012). Advanced nutrition and human metabolism . Belmont, CA: Cengage Learning.

Grosvenor, M.B., & Smolin, L.A. (2012). Visualizing nutrition: Everyday choices . Hoboken, NJ: John Wiley & Sons.

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Human Digestive System

Digestive system of humans.

The digestive tract of humans starts with the mouth and ends with the anus. It includes different structures such as the mouth, oesophagus, pancreas, stomach, small intestine, large intestine, liver, gall bladder, and anus.

Table of Contents

Introduction Structure Parts

• Small Intestine

Large Intestine

Accessory organs, digestion process.

• Mixing and Movement

Disorders Functions  Notes

The Human Digestive System

The digestive system of the human body comprises a group of organs working together to convert food into energy for the body. Anatomically, the digestive system is made up of the gastrointestinal tract, along with accessory organs such as the liver, pancreas and gallbladder. The hollow organs that make up the gastrointestinal tract (GI tract) include the mouth, stomach, oesophagus, small intestine and large intestine that contains the rectum and anus.

Human Digestive System and Nutrition involve the intake of food by an organism and its utilization for energy. This is a vital process which helps living beings to obtain their energy from various sources. The food which we eat undergoes much processing before the nutrients present in them are utilized to generate energy. This processing is known as digestion. Humans and other animals have specialized organs and systems for this process.

The digestion process involves the alimentary canal along with various accessory organs and organ systems. In humans, the process is quite simple due to our monogastric nature. This means that we have a one-chambered stomach, unlike other animals such as cows, which have four chambers.

Some parts of nervous and circulatory systems also play a significant role in the digestion process. A combination of nerves, bacteria, hormones, blood and other organs of the digestive system completes the task of digestion.

Let us have a detailed look at the human digestive system, its parts and functions. Also provided at the end of the chapter are digestive system notes.

Also Read:  Alimentary Canal

Diagram Of The Human Digestive System

The diagram given below represents different parts of the human digestive system that convert food into essential nutrients absorbed by the body.

Parts of the Human Digestive System

The digestive system of the human body comprises a group of organs that work together in converting food into energy and other basic nutrients to power the body. The food we take in is digested and utilized by our body, and the unused parts of the food are defecated.

The digestive system of the human body is the sum of the gastrointestinal tract (GIT; also called alimentary canal) and accessory organs (tongue, liver, pancreas, etc.). These two parts together help in the digestion process.

The alimentary canal is the long tube through which the food that we eat is passed. It begins at the mouth (buccal or oral cavity), passes through the pharynx, oesophagus or food pipe, stomach, small intestines, large intestines, rectum and finally ends at the anus. The food particles gradually get digested as they travel through various compartments of the alimentary canal.

Accessory organs are organs which participate in the digestion process but are not actually a part of GIT. They stimulate the digestion by releasing certain enzymes that help in breaking down the food.

Let us have a detailed look at the digestive system of the human body, along with its parts and functions:

Food starts its journey from the mouth or the oral cavity. There are many other organs that contribute to the digestion process, including teeth, salivary glands, and tongue. Teeth are designed for grinding food particles into small pieces and are moistened with saliva before the tongue pushes the food into the pharynx.

A fibromuscular y-shaped tube attached to the terminal end of the mouth. It is mainly involved in the passage of chewed/crushed food from the mouth through the oesophagus. It also has a major part in the respiratory system, as air travels through the pharynx from the nasal cavity on its way to the lungs.

This is a muscular tube that connects the pharynx, which is a part of an upper section of the gastrointestinal tract. It supplies swallowed food along with its length.

Also Read:  Food Pipe

It serves as a muscular bag which is situated towards the left side of the abdominal cavity, beneath the diaphragm. This vital organ acts as a storage for the food and provides enough time to digest meals. The stomach also produces digestive enzymes and hydrochloric acid that maintains the process of digestion.

Mucous : It is an aqueous secretion produced by the mucous membranes. It functions by protecting the stomach lining and gastric pits from the acid, which is produced by the glands to destroy the bacteria that entered along with the food particles.

Digestive enzymes : They are the group of enzymes which functions by breaking down polymeric macromolecules like biopolymers into their smaller and simpler substances.

Hydrochloric acid : It is the digestive fluid formed by the stomach during the process of digestion. It functions by destroying harmful microorganisms present in the food particles.

The small intestine is a thin, long tube of about 10 feet long and a part of the lower gastrointestinal tract. It is present just behind the stomach and acquires a maximum area of the abdominal cavity. The complete small intestine is coiled and the inner surface consists of folds and ridges.

This is a thick, long tube measuring around 5 feet in length. It is present just beneath the stomach and wraps over the superior and lateral edges of the small intestine. It absorbs water and consists of bacteria (symbiotic) that support the breakdown of wastes to fetch small nutrients.

Also Read:  Large Intestine

Waste products are passed into the end of the large intestine called the rectum and eliminated out of the body as a solid matter called stool. It is stored in the rectum as semi-solid faeces which later exits from the body through the anal canal through the process of defecation.

It is a large gland present just behind the stomach. It is short with its anterior connected to the duodenum and posterior pointing towards the left part of the abdominal cavity. The pancreas releases digestive enzymes to complete the process of chemical digestion.

Read More:  Pancreas

The liver is a roughly triangular, reddish-brown accessory organ of the digestive system located to the right of the stomach. It produces bile , which helps in the digestion of fat in the small intestine. The bile is stored and recycled in the gallbladder. It is a small, pear-shaped organ which is located just next to the liver.

Also Read:  Cellulose in Digestion

The process of digestion begins from the mouth and ends in the small intestine – the large intestines’ main function is to absorb the remaining water from the undigested food and enable bacterial fermentation of materials that can no longer be digested.

The alimentary canal or the gastrointestinal tract is a series of hollow organs and tubes that begins from the mouth cavity and continues into the pharynx, through the stomach, small intestines, large intestines, and finally ending at the anus. Food particles gradually get digested as they travel through various compartments of the gastrointestinal tract.

The digestion process takes place in the following steps.

The very first step involves mastication (chewing). The salivary glands, along with the tongue, helps to moisten and lubricate food, before being pushed down into the food pipe.

It involves the process of lubricating and manipulating food and pushing it down the food through the food pipe (using peristalsis ), and into the stomach.

The stomach, small intestine, liver, and pancreas secrete enzymes and acids to aid the process of digestion. It functions by breaking down food particles into simple components and easily absorbable components.

Also Read:  What is Liver

The process of converting complex food particles into simpler substances in the presence of enzymes and acids secreted by different digestive organs.

Read more: What are digestive juices?

This process begins in the small intestine where most of the nutrients and minerals are absorbed. The excess water in the indigestible matter is absorbed by the large intestines.

The process of removing indigestible substances and waste by-products from the body through the process of defecation.

In a nutshell, the digestion process consists of the six following steps:

Ingestion  ⇒ Mixing and Movement  ⇒  Secretion  ⇒  Digestion  ⇒ Absorption  ⇒ Excretion

Also Read:  Gastrointestinal Tract

Disorders of the Human Digestive System

Vomiting : It is the ejection of stomach contents through the mouth.

Diarrhoea : It is the abnormal watery bowel movement. Prolonged diarrhoea eventually leads to dehydration.

Constipation : A condition in which the faeces are clutched within the rectum due to an irregular bowel movement.

Indigestion : A pain or discomfort in the stomach which is caused when food is not digested properly, resulting in the feeling of fullness.  Indigestion is mainly caused due to inadequate enzyme secretion, food poisoning, anxiety, overeating and eating spicy foods.

Also Read:  Difference between trachea and oesophagus

Functions of the Human Digestive System

Digestion and absorption are the two main functions of the digestive system.

Digestion is necessary for breaking down food particles into nutrients that are used by the body as an energy source, cell repair and growth.

Food and drink need to be converted into smaller molecules of nutrients before it is absorbed by the blood and carried to the cells throughout the body. The body breaks the nutrients present in the drinks and food into carbohydrates, vitamins, fats and proteins.

Human Digestive System Notes

• The human digestive system breaks down food to release energy essential for the body to carry out its activities.
• The process of digestion takes place in 6 major steps.
• The food is ingested by the alimentary canal and is propelled through the body for further processing.
• The autonomous nervous system controls the peristalsis, contraction and relaxation of muscles within the alimentary canal wall.
• The food is passed to the small intestine where it is digested, and the nutrients are absorbed.
• Water, electrolytes and vitamins are absorbed by the large intestine and the waste is defecated.

Also Read:  Mouth and Buccal Cavity

To learn more about the human digestive system parts and functions, as well as related topics such as the digestion process and disorders of the digestive system, keep visiting  BYJU’S Biology or download the BYJU’S app, for further reference.

Frequently Asked Questions

Deduce the function of the human digestive system..

The digestive system consists of the alimentary canal and the accessory organs. Their main function is to break down the ingested food into its components and produce vital nutrients and energy required to sustain life.

What are accessory organs?

Accessory organs are organs which are not part of the digestive system; however, they aid in the digestion process by performing many secondary functions. The main accessory organs of the digestive system are the tongue, liver, pancreas and gall bladder.

Outline the process of digestion, step by step.

The process of digestion involves the following steps, namely:

List out the parts of the digestive system.

• Mouth & Buccal Cavity

Explain the role of the tongue as an accessory organ.

The tongue is not a part of the digestive system, but it provides support functions such as moving and manipulating the food within the buccal cavity. Furthermore, moistening food also helps to swallow and pass through the oesophagus without much resistance.

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Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

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Human Digestive System | Essay for Children & Students

December 16, 2017 by Study Mentor Leave a Comment

The digestive system is a system of organs working together for the uptake of food, its digestion and to eliminate the indigestible waste products out of the body. It is also known as the Alimentary canal.   

Table of Contents

What is digestion? 

Digestion is defined as the breakdown of complex organic food materials into simpler compounds and thus process, releasing energy required by the body.

The complex food substances are carbohydrates, fats, proteins, vitamins, minerals etc.  Digestion involves two processes: Mechanical digestion in which food is broken down by the peristaltic movement of the organs involved in digestion and chemical digestion in which digestive juices act on the complex food materials to convert it into simpler compounds.   

Essential compounds of diet

• Water : Water is a very important compound which can be obtained from all food and drinks and is also released in the body due to oxidation of food. The optimum requirement of water for an adult is 2,000ml.  
• Carbohydrates : Carbohydrates can be obtained from food sources like cereals, bread, fruits etc. They help in providing energy.  
• Protein : Proteins help in growth and maintenance of the body. It also helps in formation of enzymes. Proteins can be obtained from pulses, milk, meat, eggs, cheese etc.  
• Fats/Lipids : It also helps in providing energy. It can be obtained from milk, butter, ghee, oil, creams, nuts etc.  
• Vitamins : Vitamins help in prevention of deficiency diseases and regulation of metabolic activities. The vitamins required by our body are A, B, B6, B12, C, D, E and K.  
• Minerals : Different minerals have different functions in the human body. Some of the important minerals are-  
• Sodium : Helps in osmotic balance, muscle contraction and nerve impulse conduction. It can be obtained from table salt and vegetables.  
• Iron : Oxygen transport as part of haemoglobin. Can be obtained from leafy vegetables and iron supplements.  
• Iodine : It helps in metabolic control of hormone thyroxine.   
• Potassium : Helps in muscle contraction and nerve impulse conduction. Can be obtained from vegetables.  

The human digestive system consists of the alimentary canal and associated digestive glands.  

Alimentary canal  

Histology.  The alimentary canal is lined with muscular layers. It consists of four layers.  

• Serosa: It is the outermost layer. It is formed of a single layer of cells.  
• Muscularised: It is formed by two layers of cells and consists of a network of nerve cells. It controls the muscular contractions.  
• Submucosa: It consists of highly vascular connective tissue. It also has another network of nerve fibres, it controls the secretion of intestinal juice.  
• Mucosa: It is the innermost layer and consists of further 3 layers. It forms the digestive juices.   

  Parts of the alimentary canal

Buccal cavity: It is the space which is bounded to the sides by jaws, top by the palate and below by the throat. The buccal cavity consists of the tongue which is a highly muscular organ and consists of papillae. The tongue helps in mixing saliva with food and facilitates in swallowing. It also helps in telling the taste of the food.  

Teeth : Teeth are embedded in both the upper and lower jaw and helps in chewing, cutting and piercing the food. There are four types of teeth present in humans – Incisors, canines, premolars and molars. Adult human being consists of 32 teeth in the permanent set.

A tooth consists of 3 regions- Crown, neck and root. The root is embedded completely in the jaw and consists of nerve endings and blood vessels. The neck is surrounded by the gum which is soft and fleshy skin. The crown is the exposes part of the tooth and is covered by a shiny material called enamel.  

Pharynx : The food and air crosses the pharynx to reach the oesophagus. It has voluntary muscles which contract and help in swallowing.  

Oesophagus : It is the long, muscular straight tube which connects the pharynx to the stomach. The major function of the oesophagus is to pass the food from pharynx to the stomach by peristaltic movement.  

Stomach . The stomach is a J shaped muscular sac which stores the food for some time. It is also involved in mechanical churning of food, partial digestion of food by gastric juices and regulation of passage of food in the small intestine.

It has 3 parts- The cardiac, fundic and pyloric. The inner surface of the stomach consists of various folding known as gastric rugae which help in increasing the surface area for maximum storage of food. Stomach also secretes the hormone gastrin.  

Small intestine: Divided into 3 major parts- duodenum, jejunum and ileum, the major function of the small intestine is absorption of food. It also consists of microscopic finger like projections known as villi which increases surface area for effective absorption. Small intestine also secretes some hormones.  

Large intestine: The large intestine is divided into 3 major parts- Caecum, Colon and Rectum. Its major role is absorption of water, formation of faeces, and production of mucus for the lubrication of mucosa.  

Anus : The function of the anus is elimination of faeces. It consists of two anal sphincters: the internal anal sphincter and the external anal sphincter.  

Digestive glands

Human digestive glands include salivary glands, gastric glands, liver, pancreas and intestinal glands.  

• Salivary glands: The function of salivary glands is to secrete saliva which is digestive in function. Saliva is secreted by 3 pairs of salivary glands-  
•  Parotid glands which lie on the sides of the face. The saliva produced by these glands is carried by Stensen’s duct.  
• Submaxillary glands which lie at a certain angle of the lower jaw. It has submaxillary ducts which open under the tongue.  
• Submandibular glands: These glands are present under the front part of the tongue. Ducts of Rivinus which carries the saliva produced by these glands open under the tongue.  
• The Saliva secreted by the salivary glands has a pH of 7 and contains salivary amylase which is an enzyme. Saliva also contains lysozyme which is anti bacterial in function.  
• Gastric glands: gastric glands are present in the stomach and is acidic having a pH of 2. There are 3 types of gastric glands present in the stomach:  
• Mucous cells which secrete mucus that helps in protection of the internal wall of the stomach from the gastric acid.  
• Peptic or chief cells which secrete pepsinogen which is the precursor of enzyme pepsin.  
• Oxyntic cells which secrete hydrochloric acid.  

Liver : It is the largest gland of the body consisting of hepatocytes, bile canaliculi and hepatic sinusoids. The liver weighs 1.6kg. There are two lobes in the liver. Right and left lobe.

The liver forms bile which is stored in concentrated form in the gall bladder. Liver also has a function in detoxification of poison or toxic substances in the body.   

Pancreas : The pancreas is a gland which is both endocrine and exocrine in function. The endocrine part secretes hormones namely, insulin, glucagon and somatostatin.

The exocrine part secretes pancreatic juice which consists of proenzyme trypsinogen, chymotrypsinogen and procarboxypeptidase. There are other enzymes also such as pancreatic lipase, nucleases and pancreatic amylase.  

Intestinal juice : the wall of villi present in the small intestine contains small, microscopic glands, Brunner’s glands and Crypts if Lieberkühn.

The both secrete enzymes, mucus and alkaline watery fluid. The mixture of all these secretions is known as the intestinal juice or succus entericus.   

Digestion of food

The organs churn the food by mass peristaltic movement and the digestive glands pour their secretions to facilitate the process of digestion. The processes of digestion in various organs are as follows:  

Mouth and buccal cavity: Digestion of starch starts in the mouth where starch is converted into maltose by the action of enzyme, salivary amylase. The saliva also contains various electrolytes such as sodium, potassium, chlorine etc. 30% of starch is hydrolysed here and the food is converted into a bolus which is further passed down to the Oesophagus.  

Oesophagus : It does not contain any digestive gland so it does not aid in digestion. It only helps in passage of food from the buccal cavity to the stomach.  

Stomach . The stomach consists of Gastric glands which secrete gastric juice. The gastric juice gets mixed with the bolus by the churning movements of the stomach. HCl helps in conversion of proenzyme pepsinogen into active form, pepsin. Pepsin helps in hydrolysis of proteins into peptides. Digestion of casein present in milk also takes place in the stomach by the action of enzyme rennin.   

Small intestine : The small intestine plays a major role in both digestion and absorption of food. The pancreatic juice and bile from the gall bladder are released into the small intestine. Bile juice helps in emulsification of fats. It also coats each small fat droplet to avoid their merging together. The Pancreatic amylase hydrolyses starch and glycogen into maltose and dextrin’s.  

Enzyme trypsinogen gets activated into trypsin by enterokinase. Trypsin converts proteins to peptides. It also converts chymotrypsinogen to chymotrypsin. Trypsin also helps in activation of procarboxypeptidase into carboxypeptidases which further converts peptides into amino acids.   

After digestion, food is absorption of nutrition from food and its passage into the blood and the lymph. In mouth, very little absorption takes place. Absorption of few drugs takes place in the mouth into the buccal mucosa. Absorption of simple sugars, water, and alcohol takes place in the stomach.

Major absorption takes place in the small intestine. The final products after digestion such as glucose, fatty acids, amino acids etc. get absorbed into the blood lymph. The large intestine is also not much involved in absorption. It only absorbs some minerals and water.  

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Critical Thinking Questions

Explain how the enteric nervous system supports the digestive system. What might occur that could result in the autonomic nervous system having a negative impact on digestion?

What layer of the alimentary canal tissue is capable of helping to protect the body against disease, and through what mechanism?

Offer a theory to explain why segmentation occurs and peristalsis slows in the small intestine.

It has been several hours since you last ate. Walking past a bakery, you catch a whiff of freshly baked bread. What type of reflex is triggered, and what is the result?

The composition of saliva varies from gland to gland. Discuss how saliva produced by the parotid gland differs in action from saliva produced by the sublingual gland.

During a hockey game, the puck hits a player in the mouth, knocking out all eight of his most anterior teeth. Which teeth did the player lose and how does this loss affect food ingestion?

What prevents swallowed food from entering the airways?

Explain the mechanism responsible for gastroesophageal reflux.

Describe the three processes involved in the esophageal phase of deglutition.

Explain how the stomach is protected from self-digestion and why this is necessary.

Describe unique anatomical features that enable the stomach to perform digestive functions.

Explain how nutrients absorbed in the small intestine pass into the general circulation.

Why is it important that chyme from the stomach is delivered to the small intestine slowly and in small amounts?

Describe three of the differences between the walls of the large and small intestines.

Why does the pancreas secrete some enzymes in their inactive forms, and where are these enzymes activated?

Describe the location of hepatocytes in the liver and how this arrangement enhances their function.

Explain the role of bile salts and lecithin in the emulsification of lipids (fats).

How is vitamin B 12 absorbed?

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Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction

• Authors: J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix
• Publisher/website: OpenStax
• Book title: Anatomy and Physiology
• Publication date: Apr 25, 2013
• Location: Houston, Texas
• Book URL: https://openstax.org/books/anatomy-and-physiology/pages/1-introduction
• Section URL: https://openstax.org/books/anatomy-and-physiology/pages/23-critical-thinking-questions

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