The digestive system includes the digestive tract and its accessory organs, which process food into molecules that can be absorbed and utilized by the cells of the body. Food is broken down, bit by bit, until the molecules are small enough to be absorbed and the waste products are eliminated. The digestive tract, also called the alimentary canal or gastrointestinal (GI) tract, consists of a long continuous tube that extends from the mouth to the anus. It includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The tongue and teeth are accessory structures located in the mouth. The salivary glands, liver, gallbladder, and pancreas are major accessory organs that have a role in digestion. These organs secrete fluids into the digestive tract.
Food undergoes three types of processes in the body:
- Digestion
- Absorption
- Elimination
Digestion and absorption occur in the digestive tract. After the nutrients are absorbed, they are available to all cells in the body and are utilized by the body cells in metabolism.
The digestive system prepares nutrients for utilization by body cells through six activities, or functions.
Ingestion
The first activity of the digestive system is to take in food through the mouth. This process, called ingestion, has to take place before anything else can happen.
Mechanical Digestion
The large pieces of food that are ingested have to be broken into smaller particles that can be acted upon by various enzymes. This is mechanical digestion, which begins in the mouth with chewing or mastication and continues with churning and mixing actions in the stomach.
Chemical Digestion
The complex molecules of carbohydrates, proteins, and fats are transformed by chemical digestion into smaller molecules that can be absorbed and utilized by the cells. Chemical digestion, through a process called hydrolysis, uses water and digestive enzymes to break down the complex molecules. Digestive enzymes speed up the hydrolysis process, which is otherwise very slow.
Movements
After ingestion and mastication, the food particles move from the mouth into the pharynx, then into the esophagus. This movement is deglutition, or swallowing. Mixing movements occur in the stomach as a result of smooth muscle contraction. These repetitive contractions usually occur in small segments of the digestive tract and mix the food particles with enzymes and other fluids. The movements that propel the food particles through the digestive tract are called peristalsis. These are rhythmic waves of contractions that move the food particles through the various regions in which mechanical and chemical digestion takes place.
Absorption
The simple molecules that result from chemical digestion pass through cell membranes of the lining in the small intestine into the blood or lymph capillaries. This process is called absorption.
Elimination
The food molecules that cannot be digested or absorbed need to be eliminated from the body. The removal of indigestible wastes through the anus, in the form of feces, is defecation or elimination.
FAQs
The digestive system converts the foods we eat into their simplest forms, like glucose (sugars), amino acids (that make up protein) or fatty acids (that make up fats). The broken-down food is then absorbed into the bloodstream from the small intestine and the nutrients are carried to each cell in the body.
How do you introduce digestion? ›
Digestion is a process that converts nutrients in ingested food into forms that the gastrointestinal tract can absorb. Proper digestion requires mechanical and chemical digestion and occurs in the oral cavity, stomach, and small intestine.
What is digestive system in simple words? ›
(dy-JES-tiv SIS-tem) The organs that take in food and liquids and break them down into substances that the body can use for energy, growth, and tissue repair.
What are the 7 steps of digestion describe each? ›
The processes of digestion include seven activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, secretion, absorption, and defecation. The first of these processes, ingestion, refers to the entry of food into the alimentary canal through the mouth.
What is a brief introduction to the digestive system? ›
The digestive system converts the foods we eat into their simplest forms, like glucose (sugars), amino acids (that make up protein) or fatty acids (that make up fats). The broken-down food is then absorbed into the bloodstream from the small intestine and the nutrients are carried to each cell in the body.
What is the main function of the digestive system? ›
The digestive system is composed of the gastrointestinal (GI) tract, or the alimentary canal, salivary glands, the liver, and the exocrine pancreas. The principal functions of the gastrointestinal tract are to digest and absorb ingested nutrients, and to excrete waste products of digestion.
What is digestive system in simple sentence? ›
Your digestive system is the system in your body that digests the food you eat. It appeared he had a problem with his digestive system which had stopped working properly.
What is digestion in very short answer? ›
Digestion is defined as the process of breaking down large, insoluble molecules of food into smaller, water-soluble molecules which can then be readily absorbed by the body. Digestion is one among many life processes observed in nearly all living organisms.
How do you explain the digestive system to a child? ›
Food and drink must be changed into smaller molecules of nutrients to be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into smaller parts so that the body can use them to build and nourish cells and to provide energy.
What are the 5 main stages of the digestive system? ›
Figure 2. The digestive processes are ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
The digestive system carries out three primary processes: mixing food, moving food through the digestive tract (peristalsis) and using chemicals to break down food into smaller molecules.
How does the human digestive system work? ›
As food passes through the GI tract, it mixes with digestive juices, causing large molecules of food to break down into smaller molecules. The body then absorbs these smaller molecules through the walls of the small intestine into the bloodstream, which delivers them to the rest of the body.
What are the 4 main processes of the digestive system? ›
Motility, digestion, absorption and secretion are the four vital functions of the digestive system.
What are the six main activities of the digestive system describe? ›
The digestive system ingests and digests food, absorbs released nutrients, and excretes food components that are indigestible. The six activities involved in this process are ingestion, motility, mechanical digestion, chemical digestion, absorption and defaecation.
How is digestion initiated? ›
Digestion of food starts in the mouth in humans. In the mouth masticated food gets mixed with saliva secreted by salivary gland. Saliva is a mixture of water, electrolytes, ptyalin enzyme (salivary amylase). The digestion of starch is initiated in the mouth due to the action of salivary amylase.
How do you activate digestion? ›
Good foods to help your digestion
- Fill up on fibre to prevent constipation. ...
- Drink plenty of fluids to aid digestion. ...
- Cut down on fat for a healthy gut. ...
- Go easy on spice to avoid tummy troubles. ...
- Beware gut symptom triggers. ...
- Choose the right drinks to ease digestion. ...
- Probiotics.
The clear plastic bag represents the stomach which is a large muscular sac that contains hydrochloric acid, it is able to churn the food, mixing it with the acid so that it can be broken down into even smaller molecules. The food is then poured into the tights, this represents the small intestine inside the body.
What is digestion short answer? ›
Digestion is defined as the process of breaking down large, insoluble molecules of food into smaller, water-soluble molecules which can then be readily absorbed by the body. Digestion is one among many life processes observed in nearly all living organisms.
