1. The Digestive System

2. Major Functions
Digestion- Break down food into the nutrients the body can absorb.
Absorption- Take out nutrients out of the food we eat and deliver it to the cells in our body.
Eliminate solid wastes that is not needed by the body.

3. Digestion Processing of food Types Mechanical (physical)
Chew
Tear
Grind
Mash
Mix
Chemical- uses catabolic reactions and enzymes to break down food
Saliva
Stomach Acids
Bile used to break down fats
Examples of Mechanical Digestion

4. Digestion Phases Ingestion Movement Digestion Absorption
Further digestion

5. Digestive System Organization
Gastrointestinal (Gl) tract
Tube within a tube
Direct link/path between organs
Major Organs:
MouthPharynx Esophagus Stomach  Small Intestines Large Intestines Rectum

6. Digestive System Organization
Accessory Organs
Not in tube path
Organs
Teeth
Tongue
Salivary glands
Liver
Gall bladder
Pancreas

7. Mouth- where digestion begins
Teeth- Mechanical Digestion
Salivary Glands- Chemical digestion of compounds such as starch

8. Teeth- Mechanical Digestion

9. Surface of the Tongue

10. The Major Salivary Glands

11. Deglutition (swallowing)
__________________
Deglutition (swallowing)
Peristalsis
Sequence
A. Voluntary stage
Push food to back of mouth
B. Pharyngeal stage
Raise pallate
- C. Esophageal stage- Contract pharyngeal muscles, open esophagus, start peristalsis

12. Esophagus Usually collapsed (closed) Functions Secrete mucous
Transport food to the stomach

13. Peristalsis
Contractions of smooth muscles that push food down the digestive tract

14. Esophagus Sphincters Abnormalities Upper Lower Achalasia Atresia
Hernia
Barret’s esophagus
Esophageal varices

15. Stomach Usually “J” shaped Mucous membrane G cells – make gastrin
Goblet cells – make mucous
Gastric pit – Oxyntic gland – Parietal cells – Make HCl
Chief cells – Zymogenic cells
Pepsin
Gastric lipase
Very Acidic, but the cells are produced faster than they die

16. Anatomy of the Stomach

17. Stomach Functions 5. Absorbs 1. Mix food- Mechanically
2. Reservoir- Store food
3. Start chemical digestion of
Protein
Nucleic acids
Fats
4. Destroy some bacteria
5. Absorbs
Alcohol
Water
Lipophilic acid
B 12

18. Stomach
Function- To mix, break down (chemically and mechanically), and store food.
Inner surface thrown into folds – Rugae
Contains enzymes that work best at pH 1-2 (VERY ACIDIC)

19. Stomach
Food leaves the stomach as a soupy mixture called chyme

20. Small Intestine
Function- Major site of chemical digestion and absorption.
Movements
Peristalsis
Absorbs
80% ingested water
Vitamins
Minerals
Carbonates
Proteins

21. Structure of the Villi in the Small Intestine
Villi- Increase surface area for absorption.

22. Small Intestine- Accessory Organs
Liver- Creates bile that is used to break down fats.
Gal bladder- Stores bile and releases it into the small intestines
Pancreas- Creates pancreatic juices that neutralize the chyme.

24. Anatomy of the Large Intestine

25. Large Intestine
Function- To reabsorb water from digested wastes to make solid wastes.
- No villi
No permanent circular folds
Smooth muscle
Chyme dehydrated to form feces

26. Feces Formation and Defecation “whats in it?”
Chyme dehydrated to form feces
Feces composition
Water
Inorganic salts
Epithelial cells
Bacteria
Byproducts of digestion
Defecation
Peristalsis pushes feces into rectum
Rectal walls stretch until full

27. Anatomy of the Large Intestine

28. The Organs and Positions in the Abdominal Cavity

29. Video of the digestion of food- The whole picture

30. Digestive Disorders
Chrone’s Disease (inflammatory bowel syndrome)- Inflammation of the intestines

31. Digestive disorders
Blind loop syndrome-
Blind loop syndrome occurs when part of the intestine becomes bypassed, so that digested food slows or stops moving through the intestines. This causes bacteria to grow too much in the intestines and leads to problems in absorbing nutrients.
Diarrhea- increased frequency of watery feces. Causing dehydration and abdominal pain.

32. Digestive Disorders
Phenylketonuria (PKU)- is a rare condition in which a baby is born without the ability to properly break down an essential amino acid called phenylalanine.

33. Symptoms Lighter skin and hair color Delayed mental and social skills
Bad breath and odor from skin and urine.

34. PKU is a recessive trait and therefore both parents must carry the allele to pass the trait.

35. Salivary gland
Mouth
Esophagus
Liver
Stomach
Gal Bladder
Pancreas
Small Intestines
Large Intestines
Rectum
Anus