Large intestine
Absorbtion of salt
After the food has passed through the small intestine, the sticky mass of food that remains is transferred to the large intestine, which is about 1,5 metres long. This is where all excess water, salts and certain vitamins are absorbed.
There are different types of good bacteria that make the large intestine so compact that it prevents harmful bacteria from reaching the bloodstream. The 1-2 kilos of bacteria inside our intestines, mainly in our large intestine, help us absorb the last nutrients in the food, before the remains are pushed forward into the rectum where they finally become stool. It’s not until the last metres of the entire digestive system that our food start to resemble stool – before that, they are practically odourless!
Fermentation of fiber and decomposition of lactose
When food is broken down by bacteria in the large intestine, the leftover food particles begin to ferment to enable the body to absorb even more nutrients from the food. This process creates gas – about 1-2 litres per day. This is perfectly normal, and most of the gas escapes the body without you even noticing it, through farting, burping, or via the blood and out through the lungs. The passing of gas can result in quite different smells, depending on what you have eaten. Some foods, for instance beans, peas and onions, generate more gas than other types of food.
In some people, certain types of food can create extra amounts of gas, such as lactose found in dairy products. Most adults have a hard time breaking down lactose. In fact, only a small part of the world population is able to decompose lactose as adults, thanks to a mutation in their DNA. The mutation that allows the lactase enzyme to retain its ability to break down lactose is especially found in people in the Nordic countries.
Cecum
The small, narrow appendage connected to the first part of the large intestine is called the cecum (appendix). Appendicitis is when the appendix gets inflamed. This is a somewhat rare but serious condition, in which the appendix must often be immediately removed through surgery. Appendicitis is most common in children and adolescents between the ages of 10-20 years old, and happens to about 1 in 10 Swedes.
So what good does the appendix actually do? Although it has not been firmly established, some researchers speculate that it contains a reserve of “friendly” bacteria that can replenish the bacterial storage in the large intestine if needed.
Rectum
There are those who have calculated that we spend a total of more than a year of our lives on the toilet. So you better appreciate this time! So think about the long journey that the food has completed in order to get here. It usually takes 0,5-2 two days for the food to travel from the mouth to the rectum.
Once it reaches the rectum, there is not much left of the food we have eaten. Most of what remains consists of water and plant fibres that we are unable to break down, as well as mucus, dead cells and bacteria from the intestines. The leftover food particles, squeezed out through the rectum, are no longer a formula-like mass, but have a texture that is more similar to toothpaste (unless you have eaten something that did not sit well with your stomach or intestines - in which case the consistency could be either harder or looser).
Sphincter
The next time you eat, and the food makes its journey down into your stomach, a signal is automatically sent to the large intestine that now it’s time to push the “food mass” further along. A third of the contents of the large intestine are then emptied into the rectum for a final squeeze to extract water.
Around the rectal opening, there are two ring-shaped muscles, one of which we can control – which is a good thing as we wouldn’t want our stool to automatically come out as soon as new food particles reach the rectum. But remember to be kind to your intestines, and don’t wait too long to use the lavatory when you feel it’s time. Most people need to empty their bowels at least once a day, although for some people it may take a few days. The more often the better, as long as the consistency is good. Meanwhile, we urinate several times a day.
Out of all the food we eat, there is not a lot left to be passed through the rectum - only about 150 grams. Sometimes it’s hard; sometimes it’s loose. If what you are defecating is in the form of small hard balls, it might be the result of not enough fibre or water. If the stool is excessively loose, it might be because you need more good bacteria that can help process your leftover food particles a little better. The bacteria actually perform a lot of the work of breaking down food in our large intestine.
The stool may also vary in colour, depending on what you have eaten – and if it has taken a longer time to process and has become a little harder, the stool is often darker. Meanwhile, light-coloured stool has usually passed through the body somewhat faster, and contains more liquid. If you have a bacterial or viral infection in the stomach, your stool might practically come gushing out of you (diarrhoea).
Did you know that:
- The intestinal cells need salt (sodium) to be able to absorb sugar.
- The smell of your farts depends on what you have eaten and which bacteria have been active.
- Only the last metre of the large intestine has anything to do with stool. Before that, the intestines are largely clean and odourless.
- It usually takes a 0.5–2 days for food to travel from the mouth to the rectum.