Digestion

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Across the whole planet, humans eat on average between one and 2.7 kilograms of food a day
That's over 365 kilograms a year per person, and more than 28,800 kilograms over the course of a lifetime
Every last scrap of food makes its way through the digestive system
Digestive system 
Comprised of ten organs covering nine meters
Contains over 20 specialized cell types
One of the most diverse and complicated systems in the human body
Digestive system 
Continuously works in unison to transform the raw materials of food into the nutrients and energy that keep you alive
Main components of the digestive system
Gastrointestinal tract
Pancreas, gallbladder, and liver
Body's enzymes, hormones, nerves, and blood
Mesentery
Gastrointestinal tract 
A twisting channel that transports food
Has an internal surface area of between 30 and 40 square meters, enough to cover half a badminton court
Pancreas, gallbladder, and liver 
Break down food using an array of special juices
Body's enzymes, hormones, nerves, and blood 
Work together to break down food, modulate the digestive process, and deliver its final products
Mesentery 
A large stretch of tissue that supports and positions all digestive organs in the abdomen, enabling them to do their jobs
Digestive process 
1. Anticipation of food triggers saliva production
2. Chewing and saliva turn food into a moist lump called the bolus
3. Peristalsis propels the bolus into the stomach
4. Stomach walls break down the bolus into chunks
5. Hormones trigger release of acids and enzymes to dissolve and break down food
6. Bile, pancreatic and intestinal juices break down fats, proteins and carbohydrates in the small intestine
7. Villi in the small intestine absorb the molecules into the bloodstream
8. Leftover fiber, water and dead cells make it to the large intestine where most fluid is drained out
9. Remaining soft mass is squeezed into the rectum and expelled as stool through the anus
The digestive process typically lasts between 30 and 40 hours