1. The Digestive System

2. Anatomy of the Digestive System
The digestive System has two main parts:
The Digestive tract
Digestive
Glands

3. The Digestive Tract
The Digestive Tract is a long tube that starts at the mouth and ends at the anus (30ft long)
This long tube is a passageway of several organs that help to breakdown food

4. It can take up to 24 hours for food to cover the length of the digestive tract.

5. Made up of:
1)The Mouth
2) Pharynx
3) Esophagus
4) Stomach
5) Small Intestine
6) Large Intestine(colon)

6. The Mouth Contains: Teeth: mechanically break down food.
Oral Cavity where food enters the body.
Contains:
Teeth: mechanically break down food.
Tongue: tastes and manipulates food.
Enclosed by: Lips, Cheek, Palate
*Uvula: small flap hanging at back of throat, lifts to close nasal cavity when swallowing
*Salivary glands: produce saliva that lubricate food and start chemical digestion of sugars

7. uvula
teeth
tongue

8. The Pharynx At back of throat Passageway for both food and air.
Epiglottis:
flap that closes
the airway (respiratory tract)
when food is swallowed.

9. The Esophagus Elastic muscular tube that connects pharynx to stomach
2.5 cm wide and 25 cm long

10. FUNCTION: Churn, digest, store food
STOMACH
Muscular, j-shaped bag
about 12 cm wide
Left side of abdomen
FUNCTION: Churn, digest, store food
Two Sphincters: (Muscular rings)control the entrance and exit of food
1)Cardia is at entrance to the stomach after the esophagus. It prevents food from going back up.
2) Pyloric Sphincter controls what leaves stomach and goes to small intestine.

11. The Small Intestine (largest organ)
Muscular tube ~ 3m long (folded several times)
Most nutrient digestion and absorption takes place here
Lined with intestinal villi: small folds lining small intestine which increase surface area for absorption of nutrients.

12. Large Intestine (Colon)
Muscular tube, 1.5 m long, with smooth mucus lining to facilitate the passage of waste.
Absorbs most of the water.
Rectum- storage of waste(feces)
Anus- opening for elimination of waste

14. Digestive Glands: are glands that secrete enzymes to help break down food for digestion
These include:
1) Salivary Glands
2) Liver
3)Pancreas
4) Gastric Glands
5) Intestinal Glands

16. Salivary Glands Found in Mouth Located at level of upper,
lower jaws and under tongue.
Secretes about 1-2 liters of saliva a day
Function:
**Saliva contains an enzyme called AMYLASE
Which starts the chemical digestion of Carbohydrates
**Saliva also protects against bacteria

17. The Liver Located on the right side of the abdomen
Largest gland in the human body
Produces bile (1L a day) which helps the break down of fats by physically separating fat molecules.
Bile is stored in the gall bladder

18. Pancreas Located on the left side of the abdomen beneath the stomach
Secretes 2 things: pancreatic juices and insulin
Pancreatic juices (1.3L a day), contain enzymes that help chemically digest fats, proteins and carbs.
Insulin is a hormone which regulates blood sugar levels.

19. Gastric Glands
Line the inside of the stomach
About 35 million of them
Produce 2-3 L of Gastric Juices a day
Gastric Juices contain hydrochloric acid (HCl) and Pepsin(enzyme) which starts the chemical digestion of proteins
Mucin – mucus layer to protect the stomach from digesting itself because of all the acid that the gastric juices have.
***Acid in stomach is the reason for heartburn or acid reflux

20. Intestinal Glands
Located at the bottom of the villi that line the surface of the small intestine
50 million of them
Secrete intestinal juices into that contain enzymes that complete the chemical digestion of fats, proteins and carbs.

22. Stages of Digestion Ingestion of food- taking in of food
Digestion of food- the breakdown of food
Absorption of nutrients-the taking up of nutrients
Elimination of waste – the removal of waste materials from the body.

23. We ingest carbs, fats, proteins, water, vitamins and minerals.
**Water, minerals, vitamins are absorbed directly as they go through digestive tract at the level of the intestines.

24. **Fats, carbs and proteins are more complex and cannot be directly absorbed but need to be broken down through digestion:

25. Digestion: is the transformation of complex molecules contained in food into simpler molecules that the body can use.
For food absorption to occur, the food has to be broken down into smaller nutrients

26. Breakdown!!! Carbohydrates = glucose (simple glucose)
Fats = glycerol and fatty acids
Proteins = amino acids
Glucose, amino acids, glycerol and fatty acids are the nutrients that will be absorbed

28. 2 types of Food Transformations
Mechanical Transformation
nature of substance remains the same, only physical appearance changes
Ex: chewing
Chemical Transformation Bonds of molecules are broken, which gives rise to new substances
Ex. Complex Molecules broken down by stomach acid into simpler molecules

29. Mouth Insalivation: saliva is mixed with food
Mechanical Transformations
Mastication (Chewing): using teeth to break food into smaller pieces. Tongue helps move food around.
Insalivation: saliva is mixed with food
Bolus: lump of food after it has been
chewed and covered in saliva
Swallowing (Deglutition) tongue helps push bolus back

30. Chemical Transformations
Salivary Amylase
The salivary amylase begins the digestion of carbohydrates (starch) by breaking them down into smaller chains of glucose.

31. Pharynx Mechanical Transformations Swallowing (Deglutition)
How it works:
*Tongue pushes bolus back
*Uvula raises to close off access
to nasal cavity
*Epiglottis lowers to cover trachea
(respiratory tract)
*Bolus goes through the pharynx
into the esophagus

32. Esophagus Mechanical Transformations After swallowing, food enters
Peristalsis is the muscular contractions
of the esophagus which moves the
food through the esophagus down to the
stomach

33. Stomach Mechanical Transformations Churning: muscular contractions
of the stomach wall
*Purpose: to soak food and mix it with gastric juices.
*After mixing for a few hours the bolus becomes chime
Peristalsis: Muscular contractions of stomach will move food to next section of digestive tract.

34. Stomach
Chemical Transformations
Pepsin digests proteins by breaking them down into smaller chains of amino acids.
Pepsin needs an acidic environment to work.
Gastric juices, which include hydrochloric acid, help pepsin work.

36. Small Intestine
Mechanical Transformations
Peristalsis: Muscular contractions of stomach will move food to next section of digestive tract.
Churning: to mix with digestive juices and make absorption easier.

37. Small Intestine Chemical Transformations
Bile from the liver turns fat into smaller pieces to make digestion of fats easier.
The pancreatic and intestinal juices(containing enzymes) complete the digestion of carbohydrates, proteins and fats.
All the chains of complex molecules will be broken down to their simplest form:
Carbohydrates = Simple glucose
Proteins= simple amino acids
Fats = glycerol and fatty acids

38. Movie

39. Large Intestine
Mechanical Transformations
Peristalsis: Muscular contractions of large intestine will move food to its exit of the body

40. Movie

41. Small Intestine is where most absorption of
Nutrients obtained through digestion must be absorbed to be used by the blood and lymphatic systems.
Small Intestine is where most absorption of
glucose, amino acids, fatty acids and glycerol happens.
Large Intestine absorbs water, minerals and vitamins

43. (last part of digestion)
Elimination of Waste
(last part of digestion)
Rectum (last section of large intestine) stores fecal matter (poop)
Defecation is the process of removing poop from the body.
Fecal matter is made up of bacteria, debris, fibre, and nutrients that have not been absorbed.

45. Movie