The human digestive system consists of a group of organs that work together to convert food into energy for the body. The organs of the digestive system include the gastrointestinal tract, along with accessory organs, such as the liver, pancreas, and gallbladder.
The hollow organs constituting the gastrointestinal tract (GI tract) include the mouth, stomach, esophagus, small intestine, and large intestine, which houses the rectum and anus.
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Functions of the Human Digestive System
Digestion and absorption are the 2 main functions of the digestive system. Digestion helps to break down complex food particles into nutrients that are used by the body as an energy source, cell repair, and growth. The food particles are broken down into carbohydrates, vitamins, fats, and proteins.
The digestion process takes place in the alimentary canal, along with various accessory organs and organ systems. The process of digestion is quite simple in nature due to its monogastric nature. In other words, the one-chambered human stomach, unlike in other animals such as cows, makes digestion easier.
The human digestive system is responsible for the process of nutrition. Nutrition is the intake of food by an organism and its utilization for energy. Nutrition is a vital process that helps living organisms obtain energy from various sources.
The food we eat is processed in the digestive system to extract the nutrients that are utilized to produce energy. This processing is known as digestion. Humans and other animals have specialized organs and systems for digestion.
Some parts of the nervous and circulatory systems also play a role in the digestion process. A combination of nerves, bacteria, hormones, blood, and other organs of the digestive system completes the task of digestion.
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Parts of the Human Digestive System
The human digestive system works to convert food into energy and other basic nutrients that act as fuels for our body. Besides the intake and processing of foods inside the body, the digestive system is also partly responsible for the excretion of undigested and unutilized food particles.
The human digestive system is made up of the gastrointestinal tract or alimentary canal, along with the accessory organs such as the tongue, liver, pancreas, and gall bladder. These 2 parts work together to process digestion.
- 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, esophagus or food pipe, stomach, small intestines, large intestines, rectum, and ends at the anus. The food particles gradually get digested as they travel through the various compartments of the alimentary canal.
- Accessory organs participate in the digestion process but are not actually a part of the GI tract. They stimulate digestion by releasing certain enzymes that help in breaking down the food.
The journey of food starts its journey from the mouth or the buccal cavity. There are many other organs within the buccal cavity that contribute to the digestion process, including teeth, salivary glands, and the tongue. The teeth are designed for grinding food particles into small pieces and are moistened with saliva before the tongue pushes the food into the pharynx.
The pharynx is 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 esophagus. The pharynx, in fact, plays a crucial role in the respiratory system as well, as air travels through it from the nasal cavity en route to the lungs.
The esophagus is a muscular tube that connects the pharynx to the rest of the gastrointestinal tract. It supplies swallowed food along its length.
The stomach is a muscular bag that is situated towards the left side of the abdominal cavity, beneath the diaphragm. It acts as a storage for the food and provides enough time to digest meals. The stomach also produces digestive enzymes and hydrochloric acid that maintain the process of digestion.
- Mucous is an aqueous secretion released by the mucous membranes. It protects the stomach lining and gastric pits from the acids produced by the glands to destroy the bacteria that entered along with the food particles.
- Digestive enzymes help to break down polymeric macromolecules like biopolymers into smaller and simpler substances.
- Hydrochloric acid 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, forming a part of the lower GI tract. It is present just behind the stomach and occupies the maximum area of the abdominal cavity. The entire small intestine is coiled and the inner surface consists of folds and ridges.
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The large intestine is a thick, long tube measuring around 5 feet in length. It is present just beneath the stomach, wrapping itself over the superior and lateral edges of the small intestine. The large intestine absorbs water and consists of bacteria (symbiotic) that support the breakdown of waste products.
Waste products are passed onto the end of the large intestine, a portion that is called the rectum. The rectum is the site for the elimination of solid, waste matter, known as stool. The stool is stored in the rectum as semi-solid feces which later exits the body through the anal canal through the process of defecation.
- The pancreas 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.
- 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. The latter is a small, pear-shaped organ which is located just next to the liver.
Process of Digestion
The process of digestion begins from the mouth and ends in the small intestine. This digestive system diagram should help you understand the process better. We will also discuss each step in detail.
Ingestion is the first step. It involves mastication (chewing). The salivary glands, along with the tongue, helps to moisten and lubricate food, before it is pushed down into the food pipe.
Mixing and Movement
This stage involves the process of lubricating and manipulating food and pushing it down through the food pipe (using peristalsis), and into the stomach.
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The stomach, small intestine, liver, and pancreas secrete enzymes and acids to aid the process of digestion. During this process, food particles are broken down into simple and easily absorbable components.
Digestion is the process of converting complex food particles into simpler substances in the presence of enzymes and acids secreted by different digestive organs.
The process of absorption starts in the small intestine, which is the site for absorption of most of the nutrients and minerals. The excess water in the indigestible matter is absorbed by the large intestines.
Excretion is the process of removing indigestible substances and waste by-products from the body through defecation.
Disorders of the Human Digestive System
Vomiting is the ejection of stomach contents through the mouth.
Diarrhea is an abnormal and watery bowel movement. Prolonged diarrhea can result in dehydration.
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Constipation is a condition in which feces are stuck within the rectum due to an irregular bowel movement.
Indigestion is a pain or discomfort felt in the stomach. Improper digestion of food, which results in the feeling of fullness, causes indigestion. Indigestion is mainly caused due to inadequate enzyme secretion, food poisoning, anxiety, overeating, and eating spicy foods.