1. HUMAN DIGESTION

2. Fun Facts We eat about 500kg of food per year.
1.7 liters of saliva is produced each day
You can swallow even if you are standing on your head.
Every day 11.5 liters of digested food, liquids and digestive juices flow through the digestive system, but only 100mls is lost in feces. 
Food stays in your stomach for 2-6 hours.
Small intestine, 5-6 meters long
Esophagus is 25 cm long
The food stays in the small intestine from 1-4 hours
The food stays at the colon for 10 hours or for a several days 2

3. Fart Facts
Most of us pass somewhere between 200 and 2,000 ml of gas per day (average, about 600 ml) in roughly passages.
These emissions are composed of five gasses: nitrogen (N2), oxygen (O2), carbon dioxide (CO2), hydrogen (H2), and methane (CH4).
produce more gas than meat-eaters because the intestinal enzymes can't digest the cellulose in vegetables' cell walls
Does your poop float? If so, that means bacteria in your gut are producing methane
The noise created by passing gas is not from the two buttocks vibrating together, as many believe. The noise created occurs as the gas passes through the anal sphincter. It's influenced by a combination of the volume of gas, the force with which it's expelled and the tightness of the anal sphincter.

4. Digestion
Digestion is the breakdown of large, complex organic molecules into smaller components that can be used by the body.
Molecules need to be small enough to pass across the membrane of your intestine to your blood stream
Digestion animation

5. Ingestion
Food enters the human digestive tract through the mouth (aka oral cavity).
Physical breakdown of food begins with the teeth grinding the food and increasing its surface area. An increase surface area allows for easier chemical digestion

6. Alimentary Canal
The human digestive tract is often referred to as the alimentary canal.
The alimentary canal of a normal adult is approximately 6.5 to 9 meters long.
It runs from mouth to anus!
What organs/structures make up the alimentary canal? Which contribute to digestion? Which don’t?

7. Saliva
Saliva is released from the salivary glands and begins chemical digestion of starches. Saliva contains the enzyme salivary amylase which breaks down starches into simpler carbohydrates.
Saliva also moistens and lubricates food, making it easier to swallow.
Swallowing

8. Esophagus
The bolus of food moves down the esophagus propelled by wave-like muscular contractions known as peristalsis.
Peristalsis moves food all the way through the gastrointestinal tract.

9. Stomach
The stomach acts as a temporary storage site for food. Food usually spends about 4 hours in the stomach. It has ridges which allow it to expand to store about 1.5 litres of food.
The stomach is also the site of initial protein digestion.
Endoscopy

10. Stomach
Movement of food into and out of the stomach is controlled by circular muscles known as sphincters.
One at the top of the stomach allows food from the esophagus to enter and prevents food from going back up into the esophagus.
Another located at the bottom slowly releases partially digested food into the small intestine. The partially digested food is called chyme.
Stomach pyloris

11. Stomach
Millions of cells lining the stomach secrete various fluids known collectively as gastric fluids.
Gastric fluid consists of mucus, hydrochloric acid, pepsinogens (an enzyme) and other substances.
Mucus coats and protects the lining of the stomach. Hydrochloric acid kills any harmful substances that have been ingested and it also converts pepsinogen into pepsin.
Pepsin is a protein digesting enzyme that breaks large protein chains into smaller chains.

12. Stomach pH
The pH environment of the stomach normally ranges between 2.0 and 3.0 on the pH scale.
The high acidity allows pepsin to work and makes the HCL effective at killing pathogens

13. Small and Large Intestine
The intestines are named for their diameter, not length.
The small intestine is up to 7 m in length but only 2.5 cm in diameter.
The large intestine is only 1.5 m in length but 7.6 cm in diameter.

14. Small Intestine
In mammals the length of the small intestine is directly related to their diet.
Due to the fact that meats are easier to digest than plant materials, carnivores (lion) will have a shorter intestine than herbivores (rabbit). The length of the digestive tract of omnivores falls somewhere in the middle.

15. Anatomy of the Small Intestine
The majority of chemical digestion occurs in the first of three sections of the small intestine known as the duodenum.
This section also contains an opening from the bile duct and pancreatic duct through which bile and pancreatic enzymes enter the small intestine.

16. Small Intestine
Food enters the small intestine as a semi-solid mixture known as chyme. The chyme is acidic due to the HCl in the stomach so it needs to be neutralized.

17. Pancreas
The pancreas is an accessory organ of the digestive system. It releases chemicals to aid in digestion.
Secretin will stimulate the pancreas to release a solution containing bicarbonate ion into the small intestine where it will neutralize the acidic chyme and raise the pH from 2.5 to This inactivates the pepsin.

18. Pancreas and Digestion
The pancreas also releases digestive enzymes that break down the three macromolecules: carbohydrates, lipids and proteins.

19. Liver
The liver is a large accessory organ of the digestive system that is constantly producing a fluid known as bile.
Bile is stored in the gall bladder until it is needed in the small intestine.

20. Liver and Gall Bladder
The presence of lipids in the small intestine trigger the release of bile from the gall bladder.
Bile contains bile salts that emulsifies fats which means it breaks them into smaller droplets so they can be digested.

21. Absorption of Materials
Now that nutrients are small enough they need to be absorbed into the blood stream in the small intestine.
Chemical digestion of nutrients is completed by the time it reaches the large intestine.

22. Large Intestine
The large intestine or colon stores waste products long enough so that water can be reabsorbed from the wastes.
Along with the water, some inorganic salts, minerals and vitamins are absorbed.

23. Large Intestine
The large intestine is home to several different types of bacteria.
These bacteria use waste materials to make vitamins B and K. This is an example of a symbiotic relationship.

24. Cellulose
Cellulose is more commonly known as fiber. Fiber helps to remove wastes and therefore toxins from the body.
Humans cannot digest cellulose however it provides bulk which promotes the movement of the waste products out of the colon.
If you have a diet low in fiber you will have fewer bowel movements which means toxins remain in your body for longer periods of time.

25. It all comes down to poo…