Digestive System Facts for Kids from the Digestive System Adventure at Wonder Rotunda

This material about the process through which you digest your food, and the organs involved, is drawn from the "Learn More" reading opportunities in the Digestive System Adventure at the Wonder Rotunda, an on-line educational theme park for ages 7-12.

Your Sense of Taste

Your ability to taste foods starts with the tiny bumps on your tongue, known as papillae. Your taste buds sit on the papillae. The buds contain cells which send messages to your brain so you know how something tastes.  Your nose also plays an important role is your sense of taste. When you chew food, chemicals are released that immediately travel to your nose. Your nose has olfactory receptors that communicate with the brain and help create the sensation of the flavors you taste.   

The four basic tastes you are familiar with are salty, sour, sweet and bitter. A fifth taste has been discovered by scientists known as umami, which recognizes certain types of proteins found in foods such as soy sauce, meat broth or aged cheese.

Your Salivary Glands

Your salivary glands work hard for you. They produce 1 to 3 pint of saliva each day! Saliva initiates digestion, moistens your mouth, and help protect your teeth from decay.  Saliva is composed mostly of water (99.5%), but also includes electrolytes, mucus, antibacterial compounds, and enzymes. When it mixes with food it helps create a soft, moist ball of food, known as a bolus, which you can then swallow.

The major salivary glands are the parotid, submandibular, and sublingual glands.  The parotid secretes saliva through ducts near your upper teeth, the submandibular glands secrete saliva from under your tongue, and the sublingual through many ducts in the floor of your mouth.

Your Esophagus

Food doesn't just fall down a pipe into your stomach--- it is pushed down by the esophagus, the tube that connects your throat to your stomach---by a process known as peristalsis.  Here how peristalsis works: When you swallow, muscles in the wall of your esophagus create synchronized waves, one behind the other than push the bolus down. The muscles of the esophagus below the bolus relax, while the muscles above it contract. This allows the bolus to be squeezed down the esophagus without resistance. 

At the bottom of your esophagus there is a valve, known as the esophageal sphincter. When the sphincter senses pressure from a bolus reaching the lower end of the esophagus, it opens and allows the bolus to enter the stomach.  People get something known as heartburn when the esophageal sphincter doesn't keep the esophagus tightly closed between swallows. When that happens, acid from the stomach comes back up the esophagus and creates a burning sensation (heartburn).

Your Stomach

As you just learned, gastric juices and enzymes, pour out of glands that line your stomach and break down food into a thick, creamy fluid called chyme. Chyme continues mixing in your stomach until it is released by the pyloric sphincter into the small intestine. It is a slow process. The pyloric sphincter releases less than an eighth of an ounce of chyme at a time. 

The stomach is composed of four main layers. Starting from the inside of the stomach, and working our way out, the innermost layer is called the mucosa. Digestive juices are made in the mucosa layer. The next layer is called the submucosa. The submucosa is surrounded by the muscularis, a layer of muscle that moves and mixes the stomach contents. The outermost layer, the serosa is the wrapping for the stomach.

Your Liver

The liver is the largest and one of the most complex organs in your body. The liver holds about 13 percent of your blood supply at any given moment.  Let's review the important things the liver does for us: The liver aids in digestion by helping in the absorption of fat and certain vitamins, including vitamins A, D, E, and K.  It helps distribute the nutrients found in food.    

The liver also acts like a filter. It helps "clean" the blood by removing medications, toxins and bacteria.    The liver produces important proteins that affect the blood, such as chemicals that are essential in making the blood clot after an injury.    The liver produces bile which aids in the digestion and absorption of fats.

Your Gallbladder

As you have learned, bile is produced by the liver. Bile travels to the gallbladder, a pear shaped organ, where it is stored. As fatty food enters the upper portion of your small intestine (the duodenum), the gallbladder contracts and forces bile into the small intestine through the common bile duct.   Sometimes the substances contained in bile crystallize in the gallbladder, forming gallstones. These are more common in people over 40, and can cause inflammation of the gallbladder. Ouch!   If a stone becomes lodged in the bile duct, it produces severe pain. Gallstones may pass out of the body spontaneously; but sometimes surgery is necessary.

Your Pancreas

The pancreas makes enzymes that break down food in the intestines, and hormones such as insulin, that regulate the blood's glucose level.  The pancreas is made up of two types of tissue: exocrine and endocrine.       The exocrine tissue secretes digestive enzymes which help break down carbohydrates, fats, proteins, and acids in the duodenum. The exocrine tissue also secretes a bicarbonate to neutralize stomach acid in the duodenum.  The endocrine tissue in the pancreas produces hormones such as insulin and glucagon which regulate the level of glucose in the blood.

Your Small Intestine

The small intestine is divided into the duodenum, jejunum, and ileum.  In your duodenum, chyme from the stomach mixes with a variety of digestive juices from your pancreas, liver and gallbladder. When bile and pancreatic digestive juices produced by these organs mix with other juices secreted by the wall of your small intestine, the digestive process really gets going.   

In the jejunum, the chyme is broken down into smaller molecules of nutrients that can be absorbed. Then it travels into the last and longest part of your small intestine, the ileum, where all of the remaining nutrients are absorbed through the lining of the ileum's wall.  

The absorption of nutrients in your small intestine takes place through hair like structures known as villi. The villi increase the surface area for absorption in the small intestine many times over. Each villi is filled with a network of tiny vessels through which nutrients are absorbed. The absorbed substances are then transported via the portal vein to the liver and then distributed throughout the body in the form of nutrients.

Your Large Intestines

By the time your food reaches the large intestine all that is left is water and waste products, such as fruit and vegetable fiber.  The first stop is the cecum, a pouch at the beginning of the large intestine. The appendix, a finger-like pouch, hangs at the end of the cecum.    Once through the cecum, food residue passes through the colon, where nearly all of the water is absorbed, leaving a usually soft but formed substance called stool or poop.

Muscles in the wall of your colon separate the waste into small segments that are pushed into your rectum.      As the rectal walls are stretched, they signal the need for a bowel movement. When the sphincter muscles in your anus relax, the rectal wall muscles contract to increase pressure. Sometimes you have to use your stomach muscles, which press on the outside of the colon and rectum. These coordinated muscle contractions expel your poop through your anus.

Your Kidneys and Bladder

Your kidneys, bladder and urinary tract create and expel urine by filtering wastes from your blood. Urine is a concentrated solution of wastes that mostly contains water, salts, amino acids, ammonia, and urea, a waste product of the digestion of proteins.  These wastes are the produced by your body as it goes through its normal functions. Without the kidneys, waste products would build up in your blood to levels that are very harmful. Every minute, more than 1 quart of blood is filtered by the kidneys.  The kidneys also ensure the body's balance of water, so that that our tissues receive enough water to remain healthy.   

Your urine is transported out of the kidneys through the ureters to be stored in the bladder. When the bladder is full, nerve endings in the bladder communicate with your brain. When you are ready to urinate, the bladder walls contract, a valve opens and urine then flows from the bladder and out of the body through the urethra, a tube-like structure.

About the Wonder Rotunda

The Wonder Rotunda is an online educational theme park (for ages 7-12) that sparks curiosity, helps kids find their interests and passions, and inspires them to think about making a mark in the world. Topics explored include marine life, space exploration, animal life, classical music, nutrition, American government, globalization, climate change, money and business, the visual and performing arts, film making and climate change. Take the Free Tour.

About the Digestive System Adventure

A personal size submarine takes you on a trip through the human body’s digestive system that begins in the mouth, winds through a turbulent stomach, and transports you through the small and large intestines. A bout with nausea and a humorous finale make this adventure one of the most popular in the park.