What is digestion?
Large intestine, last chance

The large intestine is the last
chance for nutrient absorption.

Most of the food particles, including 90 percent of the water in the digested food, have been absorbed by the small intestine. So what else is left for the large intestine to do? Actually, the large intestine will still perform three tasks.

Simple explanation:
It comes as no surprise that although the small intestine has done the bulk of water and nutrient absorption, the large intestine still needs to absorb a few more stuff that the small intestine has failed to take advantage of. This includes the further absorption of water and electrolytes.

The next task of the large intestine is to push undigested organic matter and fiber deeper into the colon, which absorbs the nutrients that are recovered further from the ingesta. From here, the remaining material is pushed further into the anus until bacteria turn it into feces, which is stored in the rectum until one is ready to eject it from the body.

During this process, the bacteria is able to ferment the fecal matter which produces the B vitamins as well as vitamin K. These vitamins are further absorbed by the large intestine.

Once one is ready to expel feces, the various muscles in the anal canal contract and relax consecutively in order to push the solid excrement out through the anal opening, finally ridding the body of the waste produced from digesting food.

Advanced explanation:
After the small intestine has absorbed most of the nutrients from the food, the undigested particles will now be pushed onward through peristaltic movement to the large intestine, passing through the ileocecal valve which regulates the flow of material into the cecum and prevents it from returning into the small intestine. In this pouch-like structure, more water and electrolytes, like sodium and chloride which are needed by the small intestine in order to transport the nutrients into the bloodstream, are absorbed. The remaining material is further churned and kneaded by the muscles in the cecum.

From the cecum, the fecal material is pushed towards the colon. Here, further absorption of the remaining water and electrolytes takes place. Aside from this, the colon also secretes mucus in order to lubricate the waste products and prevent damage to the tissue by the solid waste. It also releases bicarbonates into the waste which would neutralize the acidity later in the rectum during waste fermentation.

Once the waste reaches the rectum, it is stored there until the person is ready to excrete the waste. In this region of the large intestine, fermentation of the waste is done by the bacteria, which produces the B vitamins such as thiamine, riboflavin, and cyanocobalamin, as well as vitamin K, and absorbed by the large intestine. The undigested fibers from the food facilitate waste excretion by maintaining regular bowel movement.

Once the rectum is full of fecal waste, it exerts pressure on the waste and forces the walls of the anal canal apart. This will, in turn, push out the fecal waste from the rectum into the anal canal, where two valves known as the internal and external sphincters control the excretion of the waste through the anal opening, allowing you to control your bowel movement until you are ready to release it.

And once you start to defecate, a variety of events take place in your body to aid you in releasing the waste from your body. First, respiration temporarily stops as the filled lungs exert pressure on the digestive tract. Along with this, various muscles in the chest, diaphragm and abdominals also do the same thing. Your blood pressure also rises. And because of the various pressures exerted, urination is stimulated. And once the waste is finally released from the body, these events return to their normal state until the whole process takes place again.

Normally, a person would feel the need to excrete feces once or twice a day, so length of stay in the large intestine varies with each person.

With that, you have finally digested the cheeseburger that you had for lunch. And the next time you take a bite out of any food, you will know exactly what is going on inside your body. This not only makes eating pleasurable, but a personal experience of enjoying a systematic process in life.

Go back to the start.


The large intestine is the last chance for nutrient absorption.		Most of the food particles, including 90 percent of the water in the digested food, have been absorbed by the small intestine. So what else is left for the large intestine to do? Actually, the large intestine will still perform three tasks. Simple explanation: It comes as no surprise that although the small intestine has done the bulk of water and nutrient absorption, the large intestine still needs to absorb a few more stuff that the small intestine has failed to take advantage of. This includes the further absorption of water and electrolytes. The next task of the large intestine is to push undigested organic matter and fiber deeper into the colon, which absorbs the nutrients that are recovered further from the ingesta. From here, the remaining material is pushed further into the anus until bacteria turn it into feces, which is stored in the rectum until one is ready to eject it from the body. During this process, the bacteria is able to ferment the fecal matter which produces the B vitamins as well as vitamin K. These vitamins are further absorbed by the large intestine. Once one is ready to expel feces, the various muscles in the anal canal contract and relax consecutively in order to push the solid excrement out through the anal opening, finally ridding the body of the waste produced from digesting food. Advanced explanation: After the small intestine has absorbed most of the nutrients from the food, the undigested particles will now be pushed onward through peristaltic movement to the large intestine, passing through the ileocecal valve which regulates the flow of material into the cecum and prevents it from returning into the small intestine. In this pouch-like structure, more water and electrolytes, like sodium and chloride which are needed by the small intestine in order to transport the nutrients into the bloodstream, are absorbed. The remaining material is further churned and kneaded by the muscles in the cecum. From the cecum, the fecal material is pushed towards the colon. Here, further absorption of the remaining water and electrolytes takes place. Aside from this, the colon also secretes mucus in order to lubricate the waste products and prevent damage to the tissue by the solid waste. It also releases bicarbonates into the waste which would neutralize the acidity later in the rectum during waste fermentation. Once the waste reaches the rectum, it is stored there until the person is ready to excrete the waste. In this region of the large intestine, fermentation of the waste is done by the bacteria, which produces the B vitamins such as thiamine, riboflavin, and cyanocobalamin, as well as vitamin K, and absorbed by the large intestine. The undigested fibers from the food facilitate waste excretion by maintaining regular bowel movement. Once the rectum is full of fecal waste, it exerts pressure on the waste and forces the walls of the anal canal apart. This will, in turn, push out the fecal waste from the rectum into the anal canal, where two valves known as the internal and external sphincters control the excretion of the waste through the anal opening, allowing you to control your bowel movement until you are ready to release it. And once you start to defecate, a variety of events take place in your body to aid you in releasing the waste from your body. First, respiration temporarily stops as the filled lungs exert pressure on the digestive tract. Along with this, various muscles in the chest, diaphragm and abdominals also do the same thing. Your blood pressure also rises. And because of the various pressures exerted, urination is stimulated. And once the waste is finally released from the body, these events return to their normal state until the whole process takes place again. Normally, a person would feel the need to excrete feces once or twice a day, so length of stay in the large intestine varies with each person. With that, you have finally digested the cheeseburger that you had for lunch. And the next time you take a bite out of any food, you will know exactly what is going on inside your body. This not only makes eating pleasurable, but a personal experience of enjoying a systematic process in life. Go back to the start.