Everyone loves to eat yet few understand what happens with the food they ingest. How do we go from delicious food to nasty, brown poop that we flush down the toilet? Simple answer: the digestive system. The digestive system is a tract, having one way in and one way out. All food moves from the mouth to the anus, with many chemical transformations along the way that make it easy for our body to absorb and use the components in the food. Let’s start by looking at the organs involved in digestion!
Basic Anatomy of the Digestive System
The digestive system is pretty complex, having several unique parts to the system. Below is the function of each component, which can be matched to its location in the diagram above.
- Oral Cavity: Beginning of the digestive tract; mechanically digests food
- Salivary Glands: secrete saliva to break down carbohydrates in the mouth and soften food for swallowing
- Tongue: pushes food into throat to slide down the esophagus
- Esophagus: tube that connects the throat and stomach
- Stomach: holds food while being broken down by enzymes in the stomach
- Liver: secretes bile into small intestine for digesting fat and some vitamins, creates new chemicals for the body with digested molecules, processes nutrients from small intestine, and detoxifies the body from harmful substances (like drugs and alcohol)
- Gallbladder: stores and releases bile from liver into duodenum for fat digestion/absorption
- Pancreas: secretes enzymes to break down fats, carbohydrates, and protein; secretes insulin for maintenance of blood sugar level
- Pancreatic Duct:
- Common Bile Duct:
- Small Intestine: connects stomach to large intestine; takes semi-solid food mass and turns it into a liquid
- Duodenum: first section of small intestine, mostly breaks down food
- Jejunum: middle section of small intestine, absorbs nutrients
- Ileum: last section of small intestine, absorbs nutrients
- Large Intestine (Colon): processes waste for removal; connects small intestine to rectum
- Ascending Colon: first section of colon, absorbs leftover water and nutrients
- Transverse Colon: middle section of colon, absorbs water and electrolytes, moves stool forward to descending colon
- Descending Colon: final section of colon, stores stool/feces to be released from the rectum
- Rectum: connects colon to anus; holds stool until the brain signals a bowel movement
- Anus: final part of digestive tract; controls release of stool
Stages of Digestion
The digestive system processes food slowly, taking about 6-8 hours for food to move through the stomach and small intestine and then another 36 or so to move it through the colon. In general food will take 24-72 hours to move all the way through. This process is aided by the contraction of smooth muscle that lines most of the digestive tract. The involuntary contractions are wave-like to push food forward in the tract. This is called peristalsis. Peristalsis mainly occurs in the esophagus, small intestine, and colon since they are the major tubular structures for moving food along. Below are the various stages of digestion:
Want to know more about your body? Check out this article!
