Summary
The mouth, stomach, intestines and accessory organs that break down food and absorb nutrients.
In depth
Mouth (mechanical and amylase), oesophagus (peristalsis), stomach (acid, pepsin), small intestine (digestion and absorption), liver, pancreas, gallbladder, large intestine (water absorption, faeces). Stages: ingestion, digestion, absorption, egestion.
Mechanical and chemical digestion occur together. Peristalsis moves food. Sphincters regulate passage. Gut hormones coordinate.
Example: stomach acid (pH 1 to 2) kills most microbes.
The tube runs from mouth to anus, about 9 m long, with accessory organs (salivary glands, liver, gall bladder, pancreas). The wall has layers: mucosa, submucosa, muscularis and serosa, with the enteric nervous system coordinating movement. Mechanical digestion includes chewing, churning and segmentation. Chemical digestion needs enzymes, acid and bile. About 8 to 9 litres of fluid enter the gut a day (food, drink, secretions), and the colon absorbs most remaining water.
The large intestine houses microbes producing vitamin K and short-chain fatty acids. Typical disorders include reflux, ulcers (often from Helicobacter pylori, which won Marshall and Warren the 2005 Nobel Prize), coeliac disease, lactose intolerance and inflammatory bowel disease.
Example: food takes 2 to 6 hours to leave the stomach, and a total of about 24 to 72 hours to pass through the gut.
Frequently asked questions
What is Digestive System?
The mouth, stomach, intestines and accessory organs that break down food and absorb nutrients.
Which area of biology covers Digestive System, and how advanced is it?
Digestive System is one of the 51 topics in Human Physiology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Digestive Enzymes, Small Intestine Absorption, Excretory System.
Can you give an example of Digestive System?
The intestine is about 6 m long.
What should I learn before Digestive System?
Digestive System is a Beginner topic, so no earlier topic is required. Other Beginner topics in Human Physiology that pair well with it include Homeostasis, Tissues and Organs, Skeletal System.
What topics are related to Digestive System?
The closest topics to Digestive System are Digestive Enzymes, Small Intestine Absorption, Excretory System, Circulatory System. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Digestive System?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Digestive System. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Digestive System different from Digestive Enzymes?
Digestive System: The mouth, stomach, intestines and accessory organs that break down food and absorb nutrients. Digestive Enzymes: Amylase, proteases and lipases break carbohydrates, proteins and fats into absorbable units. Read both side by side and note what each one explains.
How should I study Digestive System step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Digestive Enzymes and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.