What is the stomach?
The stomach is a J-shaped organ in the upper left side of your belly that stores food, mixes it and starts breaking it down for digestion.
It receives food from the oesophagus and, after breaking it down, empties it into the small intestine to continue the digestion process.
What is it made of?
The wall of the stomach has four main layers, each with a special role:
- Mucosa (innermost layer)
Lines the inside of the stomach.
Contains glands that produce gastric acid, digestive enzymes and mucus. - Submucosa
Supportive layer of connective tissue – keeps everything together. and provides strength to the wall.
Contains blood and lymphatic vessels, nerves and glands.
Supplies the mucosa with nutrients and helps control stomach secretions. - Muscularis
Made up of three layers of muscle (longitudinal, circular and oblique).
The muscles contract in waves (peristalsis), to mix food with the digestive juices and move it toward the small intestine.
These muscles move in different directions, helping to thoroughly mix food with stomach acid and digestive enzymes – much like the way kneading blends dough evenly. - Serosa (outermost layer)
Thin and smooth membrane that covers and protects the stomach.
Helps reduce friction with nearby organs.
What does the stomach do?
The stomach is your body’s blender. When food reaches it, it’s mixed with gastric acid and digestive enzymes, which help break the food down, so your body can digest and absorb it properly.
The stomach has two main roles:
- Food reservoir – it stores the food you eat.
- Blender – it mixes the food with digestive juices and breaks it into smaller pieces.
Proteins, fats, and sugars need to be broken into smaller pieces before your body can use them. The stomach produces several substances to help with part of this process:
- Gastric acid (hydrochloric acid)
Breaks down proteins
Protects against bacterias and microbes present in the food
Activates digestive enzymes
Creates right environment for nutrients like iron to be absorbed - Mucus
Keeps the stomach lining moist, so food can move easily
Protects the stomach wall from the acid and enzymes - Intrinsic factor
A protein that binds to vitamin B12, helping your body absorb it later in the intestine - Pepsinogen
An enzyme that helps break down proteins into smaller pieces - Gastric lipase
Starts the digestion of fats – though most fat digestion happens later in the intestine - Hormones
Control the release of digestive substances and regulate stomach movements. Key ones include gastrin, histamine, serotonin and somatostatin
How does digestion work in the stomach?
When food enters, the stomach muscles relax to stretch and make room. This sends signals to get the digestion started.
Your stomach adjusts to the type and quality of food you eat, how much you eat and how fast you eat it, all these affects how well your body can digest the food.
The stomach muscles move in waves, called peristalsis, similar to the movements in the oesophagus.
These waves break the food into smaller pieces and mix it with digestive juices, so the stomach can both, mash the food (mechanical digestion) and start breaking down proteins and a little bit of fat (chemical digestion).
In short, the stomach stores and mixes the food you eat and starts breaking it down, using movement and digestive juices to prepare nutrients for your body to absorb later.
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