THE DIGESTIVE SYSTEM
Above is the tutor taking you for today.
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.
Diagram Of The Human Digestive System
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:
Mouth
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.
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.
Oesophagus
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.
Stomach
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.
Small Intestine
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.
Large Intestine
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.
Rectum
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.
Accessory Organs
Pancreas
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
Liver
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.
Digestion Process
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.
Ingestion
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.
Mixing and Movement
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.
Secretion
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.
Digestion
The process of converting complex food particles into simpler substances in the presence of
enzymes and acids secreted by different digestive organs.
Absorption
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.
Excretion:
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
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.
Functions of the Human Digestive System
Digestion and absorption are the two main functions of the digestive system.
To Ask Any Question click on Ask,
You will be referred to a group ask any Question you have there.
Do well to send your reviews after the class.