From ingestion to egestion: follow food through the mammalian digestive system, and see how dentition reveals whether an animal is a herbivore, carnivore, or omnivore.
| Process | Description |
|---|---|
| Ingestion | Taking food into the mouth |
| Digestion | Breaking food down — mechanically (chewing, peristalsis) and chemically (enzymes) |
| Absorption | Digested food molecules pass into the blood, mainly across the wall of the small intestine |
| Assimilation | Absorbed nutrients are incorporated into and used by body cells (largely via the liver) |
| Egestion | Removal of undigested waste from the body as faeces |
Mechanical digestion physically breaks food into smaller pieces — chewing, and peristalsis (rhythmic muscle contractions that push food along the gut). Chemical digestion uses enzymes to break large molecules into small, absorbable ones: carbohydrases break down carbohydrates, proteases break down proteins, and lipases break down fats.
The small intestine is the main site of absorption — its inner wall is covered in tiny finger-like projections called villi, which greatly increase surface area for absorbing nutrients. Absorbed food travels via the hepatic portal system to the liver, which assimilates glucose and amino acids, and breaks down (deaminates) excess amino acids as well as alcohol and other drugs.
A mammal's teeth are adapted to its diet. Compare herbivores, carnivores, and omnivores in the Explore tab.
Click each diet type to compare its teeth and see how they suit that way of feeding.
| Animal | Body length (m) | Gut length (m) |
|---|---|---|
| Cat (carnivore) | 0.60 | 1.80 |
| Human (omnivore) | 1.70 | 8.50 |
| Sheep (herbivore) | 1.20 | 30.0 |