Have you ever eaten your favorite food, only to ask yourself how it gets digested and moves through your body? Well, here’s what happens. There are a few organs that help with the digestion process.
Mouth
The first organ is your mouth. The minute your food enters your mouth, it starts breaking it down through chewing. That helps with another process later. While your mouth is chewing your food, a digestive fluid called saliva is released and mixes with it, containing an enzyme called amylase to help break it down. Your tongue molds your mushed food into a soft ball called a bolus and shoves it to the back of your throat so it can be swallowed. Your mouth has a few parts you probably know: the teeth, tongue, and a few more. But there is more to your mouth. Let’s start with your teeth. Your teeth are made of the hardest substance in your body. It’s enamel. Your teeth are also made of other materials called dentin and pulp. Then we also have the tongue. To start, your tongue is a muscular organ covered with tiny bumps called papillae. Many papillae contain taste buds to help sense taste.
Esophagus/gullet
Your esophagus is a muscular tube. Its main job is to link your mouth to your stomach. It’s very flexible and is about 10 inches long. Your esophagus has 4 layers. The deepest layer is called the mucosa. It is made of stratified squamous epithelium, a type of body tissue that serves as a protective barrier. Below the mucosa is the submucosa, which holds connective tissue, blood vessels, nerves, and mucus-secreting glands, as your esophagus is covered in mucus. The next layer is the muscularis externa. It includes mostly skeletal muscle in the upper segment, a mixture of skeletal and smooth muscle in the middle segment, and smooth muscle in the lower segment, allowing controlled swallowing followed by peristalsis. The external layer is the adventitia, and it links the esophagus to its environment.
Stomach
Your stomach continues the digestion and breaking down process that begins in your mouth. Your stomach has the most complicated anatomy in the digestive system. Your stomach has 4 layers similar to those of your esophagus. The mucosa, muscularis externa, submucosa, and serosa. We will begin with the mucosa. The mucosa is filled with gastric pits and glands that secrete hydrochloric acid, pepsinogen, and protective mucus. Next, there is the muscularis externa. It is made of 3 layers. The longitudinal, circular, and oblique layers are important for strong mixing. Your stomach lining forms ripple-like folds called rugae, which allow your stomach to enlarge when food enters. Stomach acid helps activate enzymes such as pepsin, which digest proteins, and helps get rid of harmful microorganisms and other bacteria. On the other hand, mucus stops the stomach from digesting its own tissue and part of itself. Your food leaves your stomach through the pyloric sphincter.
Small Intestine
Your small intestine is where most nutrient absorption occurs. It makes up a few layers. The first one is the mucosa. The mucosa consists of villi, which are tiny finger-like structures that increase the surface area so nutrients can be absorbed. The cells covering the villi have thousands of even smaller projections called microvilli. Villi form brush-like bristles, increasing the surface area. The next layer is the submucosa. It is filled with blood vessels, lymphatic vessels, and nerve networks that adjust the secretion and motion. The muscularis externa is a ring of smooth muscle layers that form a specialized mixing motion called segmentation to help stir your food. Peristalsis also helps move the food forward. The serosa provides protection and produces a slippery fluid that reduces friction around your small intestine. This type of structure makes it easier for nutrients to flow. Enzymes break down carbs into sugars, proteins into amino acids, and fat into fatty acids and glycerol.
Pancreas
Your pancreas is a combination of exocrine tissues and endocrine tissues. The exocrine segment contains acinar cells. These specialized cells can produce enzymes such as lipase, protease, and amylase. The enzymes are carried through tubes called ducts to the small intestine. The pancreas also lets go of bicarbonate. Bicarbonate is a chemical that neutralizes stomach acid to protect the intestinal lining. The endocrine segment consists of clusters called islets of Langerhans, which contain different hormone-producing cells. These cells release hormones like insulin, which lowers glucose levels by helping cells take glucose out of your bloodstream, and glucagon, which raises glucose levels by signaling the liver to let go of stored sugar. Food doesn’t visit the pancreas, but it is a crucial part of the digestive system as it helps with the liver and gallbladder.
Liver and Gallbladder
Let’s start with your liver. Your liver is made of very fundamental units called lobules. Lobules consist of specialized cells called hepatocytes. These hepatocytes secrete an important fluid called bile, help with the process of metabolism, remove dangerous components, and store energy. The bile travels to the gallbladder through channels and ducts. The gallbladder is a muscular, sac-like organ with a stem to make it look like a tree. It’s lined with simple epithelium, which is a layer of squeezed cells packed together. When fat reaches the small intestine, the gallbladder is signaled to send out bile to break large fat droplets into smaller droplets.
Large intestine/colon
Your large intestine is made of the same four layers as the other organs in the system. The mucosa doesn’t consist of villi, but it does hold cells called goblet cells that secrete mucus, a sticky liquid, to make waste movement less complicated. The muscularis externa contains bands of muscle called taeniae coli, which help form pouch-like structures called haustra that slow down movement for more water absorption. The large intestine absorbs water, sodium, and many other electrolytes, turning liquid chyme into solid feces. It’s home to billions of good bacteria that ferment remains from different materials and give out vitamins. This is extremely crucial and needed to help with immunity and metabolism.
Anus
Your anus is the final step in digestion. It’s a part of the anal canal, which has the mucosa, submucosa, and muscle layers with an important change of lining: the upper portion has columnar epithelium, while, on the other hand, the lower portion has stratified squamous epithelium to help with friction. Your anus is controlled by two muscles. The internal anal sphincter is made of smooth muscle and is controlled automatically. Then there is also the external anal sphincter, which is made of skeletal muscle and can be controlled voluntarily. These muscles help control your stool.
| Organ | Approximate Time |
|---|---|
| Mouth | 60-120 secs |
| Esophagus | 5-10 secs |
| Stomach | 2-4 hours |
| Small Intestine | 3-6 hours |
| Large Intestine | 12-48 hours |
| Rectum | Stores stool until you’re ready to go |
| Anus | Stool passes through during a bowel movement |
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