Introduction
The gastrointestinal tract of the human body is one of the most unique systems to exist. Since evolution, the system has adapted to humans’ different and varied changing lifestyles, from hunter-gatherers to the sedentary lifestyle we have come to welcome. The digestive system is made up of the alimentary canal and other important organs, such as the oesophagus, stomach, and intestines. The tube starts at the mouth and continues to the rectum and the anus. It is also called the digestive tract or the alimentary canal.
Digestive System
The digestive system comprises the gastrointestinal tract, liver, pancreas and gallbladder. The track is a series of organs connected from your mouth to your anus.
Body
Here are the most important organs and their functions in the digestive system:
Mouth
The process commences in the mouth, much before food reaches the stomach. When our senses contact food or even imagine a delicious meal, our salivary glands present in front of the ear, under the tongue, and near the lower jaw generate saliva.
The teeth break down the food and saliva, moistening it to swallow the substance easily. An enzyme in the saliva called amylase starts to break down some carbohydrates present in the food even before it leaves the mouth.
Pharynx
Swallowing is done by movement of muscles in the tongue and mouth, which transports the food into the pharynx. This is a tube-like passageway maintained for food and air. A soft flap of tissue called the epiglottis is present, which closes over when we swallow, to prevent us from choking on it, and it is integral to perform the following functions.
Oesophagus
Then food travels down a muscular tube called the oesophagus. Waves of muscle extensions and contractions transport the food down to the stomach.
At the end of the oesophagus, a muscular valve called a sphincter allows food to enter the stomach and then presses/ squeezes itself shut, to prevent food or fluid from flowing back up into the oesophagus. The stomach muscles churn the food with digestive juices with acids and enzymes, turning it into smaller, digestible pieces.
Small intestine
When it is ready to leave the stomach, it is processed into a thick liquid called chyme which is then pushed into the small intestine, where digestion continues and the body absorbs the nutrients into the bloodstream.
The small intestine consists of three parts:
- the duodenum,
- the jejunum,
- the ileum
The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi which are vesicles through which nutrients can be absorbed into the blood. The blood then transfers these absorbed nutrients to the rest of the body.
Associated organs in the digestive system are the liver, gallbladder, and pancreas, but they are not part of the alimentary canal. However, these organs are required for digestion.
Large intestine
From the small intestine, undigested food (and some water) travels to the large intestine through a muscular valve that prevents food from returning to the small intestine. By the time food reaches the large intestine, absorbing nutrients is almost done.
The large intestine’s main role is to remove water from the undigested matter and form solid waste to be excreted.
The abdomen then connects to the rectum.
The alimentary tract has accessory organs including salivary glands, liver, gallbladder, and pancreas.
Rectum
Rectum is a straight, 8-inch chamber that connects the colon to the anus. The rectum’s job is to receive stool from the colon, let you know that there is stool to be evacuated (pooped out) and hold the stool until evacuation happens. When anything (gas or stool) comes into the rectum, sensors send a message to the brain. The brain then decides if the rectal contents can be released or not.
If they can, the sphincters relax and the rectum contracts, disposing of its contents. If the contents cannot be disposed of, the sphincter contracts, and the rectum accommodates so that the sensation temporarily goes away.
Anus
The lining of the upper anus can detect rectal contents. It lets you know whether the contents are liquids, gas or solids.
The anus is surrounded by sphincter muscles that allow control and passing of stool. The internal sphincter is always tight, except when stool enters the rectum. This keeps us continents (prevents us from pooping involuntarily) when we are asleep or otherwise unaware of the presence of stool.
When we urge to go to the bathroom, we rely on our external sphincter to hold the stool until reaching a toilet, where it then relaxes to release the contents.
Conclusion:
This entire process of digestion takes a couple of hours from commencement and differs from gender, age and lifestyle. A fascinating system naturally present in our bodies is something to dive deep into. We still have not been able to replicate and study the system completely, and research has been in progress to study the alimentary canal in animals. Lot of similarities have been found in mammals and birds. Our bodies are a mystery, and another interesting topic to read up on would be the nervous system to see how it controls the complete functioning of our bodies.