The Digestive System
First published: Sunday December 6th, 2020
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Hello fellow Punkers, welcome to this (hopefully) informative blog. I was actually quite bored and had nothing to do plus I have my biology final exam tomorrow but I cba to study, so here I present you, the Digestive System! Alright, without further ado...
The digestive system is an organ system that is responsible for energy absorption and subsequent egestion of indigestible wastes. This system can be further divided into 2 main subsystems: the digestive tract and the accessory organs. The digestive tract is the path in which ingested materials follow along and get both chemically and mechanically digested. Meanwhile, accessory organs produce digestive secretions that contain enzymes, which are vital for the breakdown of certain bonds in the food.
Mouth
The tract begins with the mouth, where the food is torn and ground by the teeth in order to break food in smaller parts and thereby increase the surface area. There are 4 types of teeth, named incisors, canines, premolars, and molars. Incisors are chisel-shaped and sit at the front of the row. Canines are the sharp teeth that stand just next to the incisors. Premolars and molars remain on the sides and have a broader area. Incisors and canines are used to bite and cut food whereas the premolars and molars are responsible for crushing and grinding. Incisors, canines, and most premolars have a single root whilst molars tend to have 2 or 3. Premolars have elevated tips called cusps which aid the mechanical digestion. Premolars are not adopted early on in life and only exist as permanent teeth. Children have smaller and less teeth, otherwise known as milk teeth. This set is comprised of a total of 20 teeth: 8 incisors, 4 canines, and 8 molars. Permanent teeth, however, maintain the same amount of incisors and canines with an additional 4 molars and 8 premolars. In addition, there exists chemical digestion in the mouth. Salivary glands release saliva, which contains enzymes such as salivary amylase dissolved in the fluid. This allows the nutrients to break down gradually on the increased surface area.
Esophagus
Then comes the esophagus. The esophagus is a long tube that connects the mouth to the stomach. Food moves down the track by a movement called peristalsis, where the smooth muscles along the tube contract and relax to push the food. This process gives time to the existing salivary enzymes to work and also physically squeezes foods into smaller bits.
Stomach
After the esophagus, the food enters the stomach. In the stomach, chemical digestion reaches its climax thanks to the acidic pH level. Mechanical digestion also takes place here in the form of gastric contractions. Gastric contractions are involuntary contractions of the smooth muscle linings. The food and fluids form a thick mass called chyme. Together, these processes further digest the food to be ready for absorption.
Small Intestine
As the food leaves the stomach, it enters the duodenum. The duodenum is the first segment of the small intestine, followed by the jejunum and the ileum. Here, pancreatic juices and bile are released. Bile is a liver secretion responsible for emulsification and it is stored in the gallbladder. Emulsification is the process of breaking down lipids to increase surface area for lipase to act on. (also known as fats) Sodium hydrogen carbonate is also added to the acidic mixture to neutralize it in order to protect the duodenum. The small intestine is adapted to efficiently absorb nutrients and is often around 7 meters long. It has tiny finger-like projections built-in called villi. Each villus is made up cells that have small outward extensions called microvilli. Such adaptations ensure absorption to be at the greatest possible extent so no nutrient is to be wasted.
Large Intestine
Eventually, after its long journey in the ileum, the remaining undigested parts are to be expelled by the large intestine. The large intestine is divided into three parts: cecum, colon, and rectum. The wastes include roughages and some unwelcome biproducts of digestion. Some water is reabsorbed into the blood and the rest mix together to form feces. Upon reaching the anus, the feces are egested from the body.
Alright, that's it. If you've reached this far, thank you for reading. Hope you liked this blog or had even learnt something new from it. Anyways, let me end this blog with a shameless plug: I uploaded a quiz on biology a day prior to this and you can take it here.
Have a nice day! :D
Great Blog though.