- Most of the food we eat is in the solid form. How is its form changed, so that it can pass into the bloodstream and circulate throughout the body?
Any kind of food we eat is ultimately changed into tiny liquid particles. This is what happens in digestion.This process actually starts even before we put food into the mouth.The sight and smell of the food starts the salivary glands working. Inside the mouth, the saliva mixes with the food to soften it,the teeth chew and grind the food,and the tongue helps to push the soft mass down the throat.
Food travels down to the stomach via the oesophagus, a kind of pipe that lies in the chest.
The stomach is a sac that lies quite high up underneath the ribs (not underneath the navel, as most people think).The stomach contains digestive juices that, further soften the food.The muscular churning of the stomach wall helps this activity. After some time(depending on the kind of food), the food passes into the small intestine as a liquid.
Here the liquid is worked on by more juices. All the digestive juices, beginning with saliva,work to separate the various elements of which food is composed:- carbohydrates,fat, protein, vitamins, minerals, glycerides. When the food is completely liquid, it is absorbed by the walls of the small intestine and seeps into the bloodstream.
Waste material that cannot be digested (such as the fiber that makes up the cell walls of fruits and vegetables) passes into the large intestine. Here it is formed into more solid material. It passes out of the body through the rectum and anus. Waste liquid is filtered through the kidneys, goes down to the bladder, and passes out as urine.
