How the Digestive System Works With the Respiratory System (and Why They’re Important)
You may understand the respiratory and digestive systems as separate entities but, in many ways, the two are intimately connected.
For example, breathing provides oxygen to help your digestive tract function, and digestion provides nutrients to fuel your respiratory system. These systems work together to provide energy to cells and help your entire body function at its best.
Here’s an overview of the digestive and respiratory systems and how they work together.
How the Digestive System Functions
Your digestive system comprises organs like your liver, pancreas, and gallbladder and your gastrointestinal (GI) tract. Your GI tract includes your mouth, esophagus, stomach, small intestine, large intestine, and anus. Your digestive system helps your body digest the foods and fluids you take in every day. It breaks down nutrients so your body can absorb them and use them for fuel, growth, and repairing cells.
Here are the stages of digestion:
You chew your food and pass it into your esophagus.
Once you swallow, your body automatically activates a process called peristalsis. This is when the muscles in your GI tract sequentially relax and contract to push food through your digestive system.
As food moves through your esophagus, your sphincter muscle relaxes so it can pass food into your stomach.
Food mixes with digestive juices in your stomach that help break it down.
Food then passes into the small intestine, where it mixes with more digestive juices from your liver, pancreas, and intestine to further break down. During this process, your small intestine absorbs fluid and nutrients.
Peristalsis moves the leftover waste materials down your GI tract, where the large intestine absorbs water to turn them into stool.
Peristalsis moves stool to your rectum, which is the end of the large intestine, eventually pushing it out your anus during a bowel movement.
How the Respiratory System Functions
Your respiratory system is a group of organs and tissues that help you breathe. It comprises your mouth, nose, sinuses, throat, trachea, bronchial tubes, lungs, diaphragm, larynx, ribs, blood vessels, and the muscles and tissues that help these parts function.
The respiratory system takes in oxygen from your environment and moves it through your body. Your respiratory system allows you to breathe, talk, and smell. It also helps deliver oxygen to cells, protect your airways, remove waste gases, and more.
Here are the steps of respiration:
Your mouth and nose pull in air from your environment.
The air travels to your lungs.
Your lungs remove oxygen from the air and pass it into your bloodstream.
Blood carries oxygen throughout your body to nourish organs, tissues, and cells.
Your blood carries carbon dioxide and other waste, which is released from your body when you exhale.
How Digestion Depends on Respiration
Your digestive system needs your respiratory system to provide oxygen to support its functions, including fueling peristalsis — when the muscles in your GI tract relax and contract — to move food through the digestive process.
Reducing oxygen supply directly reduces cellular activity necessary for intestinal epithelial transport. This is the movement of substances like nutrients, ions, and water across the intestinal lining (epithelium).
The respiratory system also aids the digestive system by removing waste products that cells produce during digestion, such as carbon dioxide.
How Respiration Depends on Digestion
Your respiratory system also depends on digestion.
Your digestive system provides your respiratory organs and tissues with the nutrients they need to work properly. Lungs are highly metabolically active organs, meaning they require a great deal of energy to function.
Most especially, without adequate fuel, your muscles wouldn’t have the energy they need to contract, which moves oxygen through your airways and into the rest of your body.
The Gut-Lung Axis
There’s a substantial body of research focusing on the gut-lung axis, or the communication and interaction between our digestive system and lungs.
For example, research suggests that an imbalanced gut microbiome — the bacteria and other microbes living in our intestines — can contribute to respiratory conditions like asthma, allergies, and COPD. The imbalance may also make us more vulnerable to respiratory infections.
Researchers are studying how microbes in the gut can travel to the lungs and influence their function, particularly their immunity, with the ultimate goal of informing and improving gut interventions for respiratory illnesses.
The Takeaway
Your digestive system relies on oxygen from the respiratory system for essential functions like peristalsis, while the respiratory system needs nutrients from digestion for energy.
The respiratory system also helps remove waste, like carbon dioxide, produced during digestion, and the digestive system provides the vital fuel your respiratory organs need to function.
Emerging research highlights a significant connection between your gut microbiome and lung health, suggesting that an imbalanced gut microbiome can affect respiratory conditions and vulnerability to infections.
