Digestive System: Ingestion to Egestion Explained in Simple Words

Summary

Highlights

• On average, we consume about 550 kilograms of food per year, more than two adult black bears' weight! 🐻
• The digestive system is like a biological factory turning food into basic nutrients 🌿.
• Seven main organs and three digestive glands power up the digestive system. 🏭
• The stomach's acid is so strong it can dissolve metal, while mucus protects the stomach lining! 🧪
• Our intestines are like a farm for helpful gut bacteria that assist in digestion and nutrient synthesis ⚗️

Key Takeaways

• Our digestive system breaks down what we eat into essential nutrients that fuel our body 🚀.
• Digestion involves both mechanical and chemical processes working in harmony ⚙️.
• The gut plays a surprising role in affecting our mood and immune system 😄.
• Gut bacteria are our microscopic helpers, synthesizing vitamins and breaking down tough molecules 🔬.
• Always look after your digestive system, it's doing a lot of heavy lifting for your body 🍴.

Overview

Digestive System: Ingestion to Egestion Explained in Simple Words Transcription

• 00:00 - 00:30 The average amount that a person eats every  day is 1.5 kilograms, which translates to   roughly 550 kilograms of food each year! That’s  more than the weight of two adult black bears!  All of this food we eat goes to the hungry  cells of our body. However, your cells can’t   eat a whole salad, so the body must convert it  into smaller molecules that the cells can use.   This is the primary function of our digestive  system. Along with the circulatory system,
• 00:30 - 01:00 the digestive system is a “meals on  wheels” program for the cells of your body.  If it weren’t for digestion, we wouldn’t have  the energy to work and play. Not only that, but   digestion enables the body to use the nutrients  present in food to grow and renew itself.  What is the digestive system? The digestive system is like a   biological factory with many organs, glands and  tissues that manage the task of nourishing us.   It deconstructs the food we eat into  its basic nutrients--carbohydrates,
• 01:00 - 01:30 proteins, fats, and nucleic acids, from molecules  like DNA and RNA--that the body can absorb.  There are 7 main organs in the digestive  system--the mouth, esophagus, stomach,   small intestine, large intestine, rectum  and anus. From the mouth to the anus,   all these organs are linked together by a twisting  and tangled tube made of soft tissue and muscle.   This tube is called the alimentary canal or the  gastrointestinal tract (the GI tract for short),
• 01:30 - 02:00 but it is most commonly known as the gut. These 7 organs get some help from 3 additional   glands--the liver, pancreas, gallbladder--each  of which contains glands that secrete chemicals   and help digestion occur. The Mouth - Making a bolus  The process of digestion begins before you’ve  even put the food in your mouth. Upon seeing,
• 02:00 - 02:30 smelling or even thinking about lunchtime, your  brain will begin preparing your gut for the food.   Your mouth will become flooded by saliva in  anticipation of the meal, and your stomach   will prepare its arsenal of digestive juices. However, once you take a bite of your food,   that’s when the action really begins.  The teeth work hard to tear and grind,   breaking down food into smaller pieces. This is referred to as mechanical   digestion—physically crushing  food into smaller chunks.
• 02:30 - 03:00 At the same time, salivary glands present in our  mouth secrete saliva—a watery liquid containing   various enzymes. Enzymes are proteins that speed  up a given reaction. The saliva contains amylase,   which breaks down carbohydrates, as well as  lingual lipase, which goes to work on fats.  The combination of chewing and saliva turn  the food in our mouths into a pasty ball   called the bolus. We swallow the bolus,  which travels down our food pipe,
• 03:00 - 03:30 or esophagus, to the pouch of  acid we know as our stomach.  The esophagus pushes the bolus via involuntary  smooth muscle movements. The muscles contract and   relax, similar to how a slug or caterpillar  moves by contracting its whole body,   pushing the bolus down into the stomach.  This muscle movement happens throughout   the gut and is formally called peristalsis. This muscle movement ensures that the food   only travels to the stomach and not the other way  around, which is why even if we’re upside down,
• 03:30 - 04:00 our stomach’s contents stay right where they are. The Stomach - The gastric phase of digestion  After its journey through the esophagus,  the bolus has now reached the stomach.  Remember how we said the alimentary canal is  a continuous tube of muscle? Well, here at   the stomach, that tube takes the form of a muscle  sack. The stomach has several jobs—it takes food   from the esophagus, breaks it down with gastric  juice (stomach acid + enzymes), and then passes
• 04:00 - 04:30 it on to the small intestine. In fact, the stomach  makes around 4 liters of gastric juice per day!  After the bolus enters the stomach, the organ  secretes copious amounts of hydrochloric acid,   released by parietal cells lining  the inner wall of the stomach.   This stomach acid is so strong  that it can even dissolve metal!   Additionally, the stomach produces a thick  layer of mucus to protect itself from acid.
• 04:30 - 05:00 The hydrochloric acid chemically burns the  food and kills any pathogens that are present.  The low pH from the acid also activates pepsin,  an enzyme secreted by the stomach cells. This   enzyme helps break down proteins  into smaller pieces called peptides.  Along with hydrochloric acid, parietal  cells also secrete “intrinsic factor”,   which helps cells absorb vitamin B12. Without  that, our body wouldn’t be able to make DNA!
• 05:00 - 05:30 The stomach senses the food,  and begins tossing the mixture.   Peristalsis tosses and squeezes the food even  further. It works like a churner, where the   food is crushed and mixed with stomach acid,  ensuring that everything gets equally digested.  It takes the stomach anywhere  from 1 to 4 hours to digest food,   after which the bolus that entered the stomach  has turned into chyme. The stomach now opens   a sphincter valve, called the pyloric valve, and  gradually releases chyme into the small intestine.
• 05:30 - 06:00 The Small Intestine - The  Intestinal phase of digestion  Here, a biological cocktail  composed of all our various enzymes,   digestive juices and other biomolecules forms  and breaks down the food. The now smaller food   molecules are absorbed as they move down the small  intestine, which stretches for almost 20 feet!  The small intestine has three anatomically  different parts--the duodenum, jejunum and ileum.
• 06:00 - 06:30 Once the stomach begins emptying its  contents into the duodenum, the duodenum   will signal via hormones to stop digesting. The duodenum will also signal the liver,   pancreas and gallbladder to give the  food chemicals one final breakdown.  Into the duodenum, via the pancreatic  duct, the pancreas secretes digestive   enzymes to break down proteins into their  smallest unit, amino acids, along with fats.  The gallbladder secretes bile,  which is made in the liver.
• 06:30 - 07:00 Bile has certain salts that emulsify fat, so it  gets dissolved in the watery digestive juices.   This makes it easier for the pancreatic  enzymes to digest the fat more rapidly.  As peristalsis pushes the chyme further, the small  intestine continues to absorb nutrients and water.  For example, the duodenum absorbs most of  the iron, the jejunum absorbs the majority   of the vitamin folic acid, while  the ileum reabsorbs the bile salts.
• 07:00 - 07:30 Lining the inner surface of the intestine  are very tiny projections called villi.   They are finger-like structures that grow out  of the inner lining of the intestine. Think of   it as your own hairy carpet, inside your body,  that traps all the food traveling along the gut.  The villi increase the surface area of the small  intestine, which allows for even more nutrients   to be absorbed into the bloodstream. The Large Intestine - Making Poop
• 07:30 - 08:00 Through a muscular opening  called the ileocecal valve,   whatever nutrients that couldn’t be absorbed by  the small intestine pass into the large intestine.  The large intestine’s job is primarily to absorb  water, but it also gets a little help from our   microscopic intestinal friends – gut bacteria.  Gut bacteria present in the large intestine help   break down tough-to-digest food molecules, such  as fiber, and synthesize vitamins while doing so.  It takes about 36 hours for food to  fully pass through the large intestine.
• 08:00 - 08:30 Finally, after passing through the  large intestine, the remaining leftover,   indigestible food or waste settles in the rectum.  Once it passes through, the waste (yes, we  mean poop) leaves our body from the anus.  Digestion is critical for our body because it  breaks down all the complex biomolecules present   in the food to the simple materials that our  body’s cells are best equipped to work with.   As this video explains, this process is  done both mechanically and chemically.
• 08:30 - 09:00 Your gut also plays a key role in your mood due to  its connection with the nervous system. Believe it   or not, gut bacteria help your immune system  in ways that we don’t yet fully understand!  So, next time you’re tearing  through a bag of Doritos,   be confident in the fact that your  digestive system is already working   hard to break down those Cool Ranch chips  and pull as much energy from them as it can!