How Does the Stomach Digest Food?
We eat various types of food from fruits and vegetables to highly processed junk food. All of this food is eventually broken down into smaller and simpler substances by the cells of our body. This breakdown of food into simpler substances is known as digestion. This process involves various organs of our body working together in a coordinated manner. It includes the mouth, the teeth, the tongue, the food pipe, the intestine etc. The stomach plays a very crucial role in this process. In this article, we will discuss about the stomach in detail.
What is a Stomach?
The stomach of a human is located on the upper left side of the abdomen. An adult's stomach is about 10 inches (25 centimetres) long. It can hold up to 1 quart (0.9 litres) of food. Gastric juices are produced by the stomach glands which contain HCl (Hydrochloric acid). Food is partially broken down by these juices. The inside of the stomach is protected from gastric juices by a mucus lining. Stomach muscles perform churning movement when food enters the stomach and therefore, it combines food and gastric juices. Here, food is converted into semi-liquid form and protein digestion begins in the stomach. The stomach also transports food to the small intestine.
The Stomach
Functions of Stomach
The purpose of the stomach is to digest food and send it to the small intestine for further digestion. It has three major functions:
It stores the food temporarily for about four to five hours.
It helps in grinding the food particles with the help of its wall.
Produce enzymes and other specialised cells to aid in food digestion.
Stomach: Other Animals
Other animals' stomachs differ significantly from humans; many have multiple-chambered organs or special adaptations. Cows' and most cud-chewing (ruminant) animals' stomachs are divided into four sections. The rumen receives food first, where mucus is added and cellulose is broken down. It then returns to the mouth to be thoroughly rechewed. When it is swallowed again, it travels to the reticulum and omasum, the second and third chambers, where water is extracted and absorbed. The food is then transported to a final chamber, the abomasum, to be digested by enzymes. Birds have three chambers whereas rodents have only one stomach area. Starfish can turn its stomach upside down and crayfish produce stones of calcium in their stomach.
Facts About Stomach
It is a muscular bag in our body that churns the food.
Even after having their stomach removed, a person can survive by changing their diet and eating more frequently and in smaller portions.
The maximum time required to digest a normal meal is five to seven hours or more. Protein- and fat-rich foods take longer to digest than high-fibre foods.
There is no relationship between a person's weight and stomach size. Both the thin and the obsessed have the same stomach size.
Our immune system's first line of defence is the stomach. The acid in our stomach sterilises and kills the bacteria and other toxins found in the food we eat.
The stomach is the only organ in the digestive system with three muscle layers.
Animals like seahorses and lungfish have no stomachs.
Solved Questions
1. How many chambers does a cow's stomach have?
Ans: A stomach has four chambers.
2. Write a short note on the human stomach.
Ans: The stomach is the organ that receives food through the oesophagus. It acts as the storage organ. It is round, hollow, muscular and expendable. It is internally located in the body and is J-shaped.
3. How many hours does a human stomach store food?
Ans: It stores food for about four to five hours.
Learning by Doing
Write true/false for the following.
Stomach is a C-shaped organ________
Animals like seahorse has no stomach_________
The stomach is the only organ in the digestive system with four muscle layers______.
Summary
The stomach is the digestive system's largest, hollowest, most muscular, expendable and most important organ. It is a bean-shaped, sack-like structure found behind the lower ribs and between the oesophagus and small intestine. The stomach's primary function is to secrete gastric juices, digest food molecules and store them. The stomach can hold more than a quarter-gallon or half-pound of food on average.
FAQs on Essential Facts About the Human Stomach
1. What is the stomach and what is its main job in our body?
The stomach is a J-shaped, hollow muscular bag located in the upper abdomen. Its main job is to act as the body's food churner. After we swallow, food travels down the food pipe (esophagus) and enters the stomach. Here, it is mixed with strong digestive juices and churned by muscular contractions into a thick, soupy liquid called chyme, preparing it for the next stage of digestion in the small intestine.
2. How does the stomach's muscular wall help in churning food?
The wall of the stomach has three strong layers of muscle. These muscles contract and relax in a coordinated wave-like motion. This powerful squeezing and mixing action, known as peristalsis, physically breaks down large food particles and thoroughly mixes them with the stomach's digestive juices, much like a mixer-grinder turns solid ingredients into a fine paste.
3. What are the digestive juices in the stomach made of and what do they do?
The digestive juices in the stomach are a powerful mix of substances, primarily:
- Hydrochloric Acid: A very strong acid that kills most of the harmful bacteria and germs that may have entered the body with our food.
- Enzymes (like Pepsin): These are special proteins that start the chemical digestion of complex proteins (found in foods like milk, eggs, and dal) into simpler forms.
4. If the stomach's acid is so strong, why doesn't it damage the stomach itself?
The stomach has a clever self-protection mechanism. Its inner wall is coated with a thick, sticky layer of mucus. This mucus lining acts as a protective barrier, preventing the strong hydrochloric acid and digestive enzymes from coming into direct contact with and damaging the stomach wall. It's like having a special shield on the inside.
5. Why does my stomach 'growl' or make rumbling noises when I'm hungry?
That rumbling sound, scientifically called borborygmi, is caused by the muscles of the stomach and intestines contracting. When your stomach has been empty for a while, your brain sends signals to the digestive system to prepare for food. These signals trigger the muscles to move, and as they push around the air and leftover fluids inside your empty stomach, it creates the familiar 'growling' noise.
6. Do all types of food take the same amount of time to be churned in the stomach?
No, the time food spends in the stomach varies.
- Simple carbohydrates, like those in fruits and juices, are digested and passed into the small intestine relatively quickly, often within 1-2 hours.
- Proteins, found in dal, paneer, or eggs, take longer, typically 3-4 hours.
- Fats, found in oily or fried foods, take the longest to break down, sometimes staying in the stomach for up to 6 hours.
7. What happens to the food after it is churned by the stomach?
Once the food is turned into the thick, soupy liquid called chyme, a muscular valve at the bottom of the stomach (the pyloric sphincter) opens and closes. It squirts small amounts of the chyme from the stomach into the small intestine. This is where the next and most important phase of digestion and nutrient absorption takes place.
