1. Digestive System
Chapter three

2. Learning Goal
To learn in more detail about the digestive tract and its components
To learn more about some disorders that affect the digestive tract

3. The digestive system
The human digestive system is made up of organs working together to transform food
The job of the digestive systems is to use the food we eat and break it down onto molecules that our body can easily use to keep us alive
This is done in Four Steps:
Ingestion
Digestion  
Absorption
Elimination

4. The digestive system

5. Parts of the digestive system
The function of digestion is to reduce a mouthful of food into smaller molecules so that our cells can use easier
This reduction of food into smaller pieces happens as we chew our food, mix it up in our mouth, and churn it with our teeth = Mechanical Digestion
The reduction of food in our mouth also uses enzymes = Chemical Digestion

6. Digestion in the Mouth
The digestive structures in the mouth are the teeth and the salivary gland
There are different types of teeth in your mouth, like fang shaped for biting into food or your molars at the back that grind your food into smaller pieces

7. Digestion in the Mouth
Together all of your teeth start mechanical digestion of the digestive system
In the mouth there are salivary glands that release saliva to help the breakdown of food into smaller pieces because inside our saliva are enzymes that help this digestion
Chemical digestion begins with saliva

8. Digestion in the Mouth
Mechanical Digestion also begins in your mouth as you bite, tear, and grind food into smaller pieces
This also exposes more of the surface area of the food to the saliva, making it more accessible for chemical digestion

9. The Esophagus
The chewed mass of food passes down your throat (pharynx)
When you swallow, your epiglottis muscle opens for food to pass through the pharynx into the esophagus
This is done using wave –like muscle contractions that push the food downward through peristalsis as muscles contract above the chewed food and relax below it
A ring-like muscular structure called a sphincter controls how the food enters the stomach from the esophagus

10. The Esophagus

11. The Stomach
The stomach is a J-shaped muscular bag that continues to carry our physical and chemical digestion
It also temporarily stores food while further chemical and mechanical digestion take place
The stomach is small when empty and can open up a lot when full (up to 4 L of food)
Here, chunks of food are broken down into smaller pieces as peristalsis churns food in the stomach (breakdown)

12. The Stomach
The stomach is filled with millions of gastric glands that secrete gastric juices, when food is present
Gastric juice is made up of Hydrochloric acid (HCl), salts, enzymes, water, & mucous
The mucous coats the walls of the stomach – protecting it from being attacked from strong acidic gastric juices
Gastric juices continue chemical digestion within the body

13. The Stomach
The mixture of food gets digested by the muscles in the stomach into smaller pieces and gastric juices that is churned up in the stomach becomes chyme
At regular intervals small amounts of chyme are squirted from the stomach to the small intestine – where food will travel through next

14. The stomach
The stomach is surrounded by a network of nerves that help regulate the activities of the digestive system
These nerves start stomach contractions that release partially digested food into the small intestine (next phase)

15. The Small Intestine (SI)
Chyme (mixture of food and gastric juices) enters the small intestine from the stomach contains molecules at different stages of being digested
The 2 functions of the small intestine are to:
Finish digesting nutrients in their smallest form
Absorb these small molecules into the bloodstream so they can be transported to where they are needed

16. The Small Intestine (SI)
The small intestine can be divided into 3 parts: duodenum, jejunum, and ileum
Each section has different roles and functions that help absorb nutrients from the food we eat

17. The Small Intestine (SI)
The Duodenum
Makes up the first 25 cm of the small intestine
Is the shortest and the widest of the 3 parts
Large surface area IMPORTANT for ABSORBTION
Helps the digestion of chyme from the stomach
Ducts (like valves) connected to the duodenum from the liver and pancreas join together

18. The Small Intestine (SI)
The Duodenum
The surface of the duodenum has tiny finger-like projections along it called villi and even smaller microvilli that help increase the surface area for absorption
Their job is to absorb the nutrients from food and allow them to enter into the blood system through lymph vessels from the circulatory system

19. The Small Intestine (SI)

20. The Small Intestine (SI)

21. The Small Intestine (SI)
The Jejunum
Is 2.5 meters long and continues nutrient digestion (if any left) and mainly absorption of nutrients into the blood stream
The Ileum
Is 3 meters long
Contains less villi and microvilli than other parts of SI
Its function is to absorb nutrients as well as push the remaining undigested food into the Large Intestine (LI)

22. Accessory organs Role of Accessory Organs
Includes the pancreas, liver, and gall bladder
These organs are not part of the digestive tract directly, but help it digest food

23. The Large Intestine (LI)
The material that is left over from the small intestine after all the absorption of nutrients has taken place enters the large intestine
Even though it is called the large intestine it’s actually shorter. We say “long” because its wider than the small intestine

24. The Large Intestine (LI)
Digestion no longer takes place from the large intestine on – now it is strictly absorption, to be more specific, it’s the absorption of water
Another name for the large intestine is colon
Anything left over turns into feces – which leave the colon through the rectum and the anal canal

25. Time for Digestion?

26. Magic School Bus
(7 – 20)

27. Things still questioning
Post gizmo lab

28. 1) Where does diffusion / osmosis take place?
In the digestive tract, we have food broken down via mechanical and chemical digestion into smaller pieces
Where our macromolecules (fat, protein, & carbohydrates) are broken down into smaller pieces (i.e carbs = glucose)
These smaller pieces will DIFFUSE from the small intestine (duodenum & jejunum) into the capillary bed surrounding the small intestine or lymphatic system (only small amounts of fat will diffuse into the lymph system).
Osmosis takes place mainly on the LARGE INSTESTINE where water is absorbed back into the body via the capillaries (end up increasing volume of interstitial space and blood volume)

29. 2) Why does absorption increase with pancreas?
The pancreas is responsible for releasing INSULIN to the small intestine to help with the absorption of carbohydrates (glucose).
This is why when you add the pancreas to the duodenum (SI) that the % of absorption increases

30. What do parietal / Chief cells do
A gastric chief cell is a cell in the stomach that releases enzymes that are part of the GASTRIC JUICES
Parietal cells are another type of cell found in the stomach that work with the chief cells in helping the digestion of protein in the digestive system

31. Check that I understand…
This is up to YOU!!
If YOU are not confident in the material, remember… there is EXTRA HELP after school on TUESDAY AND THURSDAYS
... FREE TUTORING!!

32. Bonus questions Thank you for brining this to my attention
Haven’ t done them in the past, but see their rewards
So I WILL try to add more bonus question in either assignments / final tests