All the food we eat goes into our stomach. Here, it is broken into smaller and simpler substances and get absorbed into the blood. Then, the blood carries these food particles to the different cells of the body, where they are used to provide energy to our body.
How is food broken into smaller particles?
When we eat, the glands lining the walls of the stomach secrete a thin, strongly acidic, almost colorless liquid, called gastric juice. It contains two kinds of enzymes called pepsin and rennin that break down the food to simpler substances. These enzymes can function only in a highly acidic environment.
That is why the gastric juices contain a very strong acid called hydrochloric acid. It is a colourless, or, faintly yellow, corrosive, and fuming liquid. The acid is so strong that it can corrode metal and burn almost anything that touches it.
Though all humans carry this strong acid in their stomachs, surprisingly it does not harm them. This is because of the presence of a slimy, white liquid that flows out our noses. It is called mucus.
It is a viscous mixture of mucins, water, electrolytes, epithelial cells, that form the inner lining of the skin, and leukocytes, which are white blood cells that fight disease. It is secreted by glands present on the surface of our nose and stomach.
Mucins are glycoproteins which make any substance viscous and act as a lubricant.
The mucus secreted by different parts of our bodies have special functions. In our nose, it serves as a lubricator and stops dirt and dust from going deep into the nose and also aids breathing. In our stomach, it forms a layer between the deadly gastric juices and the lining of the stomach walls. This mucus lining prevents the acid present in the gastric juices from damaging the stomach.
This wall created by the mucus layer is called the mucus membrane. It behaves like an acid-proof glove that the stomach uses to save itself from getting burnt while using harmful acids.