1. Digestive System

2. Humans as Heterotrophs Hetero=another Trophe= nutrition
As heterotrophs we cannot convert carbon therefore we ingest carbon in our food.
All of our cells require nutrition for;
Growth
Repair
Maintenance
Humans as Heterotrophs Hetero=another Trophe= nutrition
Inorganic Carbon= CO2, Carbon Fixation= Autotrophs

3. Functions of the Digestive System
Break down of food into nutrients.
Nutrients absorbed in the body.
Transported throughout the circulatory system.
Nutrients in the cell can be used as a
source of energy OR
Used for the synthesis of chemical compounds

4. Stages of the Digestive System
Absorption
Egestion
Ingestion
Digestion

5. 1. Ingestion Ingestion occurs when food enters the mouth.
It is mechanically broken down by teeth
1. Ingestion

6. Chewing stimulates the release of saliva from the salivary organs.
Saliva contains a mixtures of water, mucus and enzymes.
1. Ingestion: Cont.
Starch to sugars

7. Enzyme that breaks starch down into simple sugars.
1. Ingestion: Amylase

8. Food that has been chewed and mixed with saliva becomes a bolus.
1. Ingestion: Bolus
The epiglottis, a flap of skin directs food down the esophagus.
Pharynx: Either food or air can enter here. Before the Larynx (air) and the Esophagus.

9. 1. Ingestion: Peristalsis
When the bolus has entered the esophagus muscle contractions (peristalsis) move it towards the stomach.
1. Ingestion: Peristalsis

10. 2. Digestion: Stomach Digestion occurs initially in the stomach.
The stomach is J-shaped, it stores food, and has a capacity of 1.5 L
2. Digestion: Stomach

11. 2. Digestion: Sphincters
Food enters and exits the stomach through sphincters.
Sphincters are muscles surrounding a tube-like structure
The bolus enters the stomach when the cardiac sphincter relaxes.
2. Digestion: Sphincters

12. 2. Digestion: Gastric Juice
The stomach contains gastric juice secreted by the stomach lining.
Gastric juice contains a mixture of:
HCL (hydrochloric acid)
Enzymes
Mucus
2. Digestion: Gastric Juice

13. 2. Digestion: Gastric Juice
HCL
Breaks down fibres & Bacteria
Mucus
Protect stomach lining from HCL
If stomach lining is destroyed ulcers form.
2. Digestion: Gastric Juice
Gastric juices are eating through the lining, digesting itself since there is no protection from the mucus.

14. Heliobacter pylori
H. Pylori attaches itself to the stomach lining using flagella penetrating the mucus lining. It will harm the stomach and the duodenum causing ulcers and gastritis. Present in about 50% of the world** Verify. Focus on stomach ulcers. The Nobel Prize in Physiology or Medicine 2005
Barry J. Marshall and J. Robin Warren
"for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease"

15. 2. Digestion The stomach absorbs: Water Alcohol
Some medications (Aspirin)
2. Digestion

16. Chyme travels out of the stomach by the pyloric sphincter into the small intestine.
Chyme is a mixture of:
Water
Digested food
Gastric Juices
2. Digestion: Chyme

17. 2. Digestion: Small Intestine
After the pyloric sphincter chime enters the duodenum
Duodenum is first 25cm of the small intestine.
7m in length, 2.5m in diameter.
2. Digestion: Small Intestine

18. 2. Digestion: Duodenum Majority of digestion occurs here.
Secretions from pancreas and duodenum enter via a duct.
2. Digestion: Duodenum

19. 2.Digestion: Liver Has four functions in digestion: Synthesis
Breakdown
Detoxification
Storage
2.Digestion: Liver

20. Synthesis Produces bile which breaks down fats.
Bile is stored in the gallbladder
Synthesis

21. Bile is an emulsifier (a compound used to mix immiscible substances)
This allows for the breakdown of fats and for travel through the digestive system.
1. Synthesis: Bile
Emulsification-Mayo

22. 1. Synthesis: Gallstones
Gallstones occur when too much bile or concentrated bile is produced in the gallbladder.
The bile will crystalize into gallstones blocking the gallbladder.
1. Synthesis: Gallstones

23. Process of removing Nitrogen group from Amino Acids to create urea.
2. Breakdown

24. When there is a blockage of the gallbladder Jaundice can occur (yellowing of the skin).
2. Breakdown: Jaundice

25. 3. Detoxification Removes toxins from the body including Alcohol
Chemicals
3. Detoxification

26. 4. Storage
Vitamins and carbohydrates are stored in the liver.

27. Increases the pH of chyme from 2
Increases the pH of chyme from 2.5 to 9 due to the production of sodium bicarbonate.
Secretes enzymes for digestion
Lipase (fats)
Trypsin (proteins)
Pancreas

28. Small Intestine Secretes Maltase (maltose - > glucose)
Peptidase (protein breakdown)
Duodenum (beginning), Jejunum (middle), Ileum (end).

29. Food & Enzymes Carbohydrates -> Glucose Proteins -> Amino Acids
(amylase & maltase)
Proteins -> Amino Acids
(pepsin & peptidase)
Fats (triglycerides) -> Fatty Acids & Glycerol
(bile & lipase)
Food & Enzymes
Amylase: Enzyme in the saliva Starch to sugars.

30. The jejunum and ileum contain villi (finger like projections) which increase the surface area.
The villi help with absorption of
Glucose
Amino Acids
Fatty Acids
Glycerol
3. Absorption

31. Once nutrient are absorbed through the villi they enter the blood stream and are dispersed throughout the body
3. Absorption

32. Digestive System

33. 3. Absorption: Large Intestine
Water absorption
Bacteria living in colon releasing Vitamin K & B, also absorbed.

34. Cellulose aids in the ejection of material from the bowels.
Lack of cellulose in the diet can lead to colon cancer.
4. Egestion
Celery dietary roughage. Sphincter

35. Digestive System
The entire process takes hours.

36. Homeostasis
The ability of the body to regulate according to the fluctuating internal and external environment
Homeostasis:

37. Digestion & Homeostasis
Nervous and hormonal system aid digestion before we eat.
Seeing, smelling and tasting food stimulates production of gastric secretions.
Digestion & Homeostasis

38. Digestion & Homeostasis Cont.
Swallowing stimulate the production of gastric juices.
Gastrin (hormone) stimulates the release of gastric juice before food arrives.
Digestion & Homeostasis Cont.

40. Digestion Speed of Digestion:
Large meals with digest quickly due to strong stomach contractions and faster emptying.
Fatty meals slow down digestion due to a hormone response from the small intestine.
Digestion

41. Homeostasis Receptors in the body sense: Blood Sugar levels Body T
Oxygen level
Disruption in homeostasis -> Signal to brain for correction
Homeostasis

42. Homeostasis: Blood Sugar
Concentration crucial to well being
Too low body shuts down (coma)
Eating increases blood sugar (glucose)
Homeostasis: Blood Sugar

43. Homeostasis: Blood Sugar
Body releases insulin from pancreas to bring glucose inside cells.
Extra glucose taken by liver cells and convert to glycogen and stored.
Homeostasis: Blood Sugar
Insulin: Activates cell surface.

44. Homeostasis: Blood Sugar
normal glucose
high glucose
food
low glucose
insulin release
(pancreas)
cells take up excess
glucose, liver makes
glycogen
glucagon release
glycogen release
as glucose (liver)
Decrease in blood sugar pancreas will be activate to release glucagon
Glucagon (hormone) will convert glycogen (in liver), back to glucose, which will be released into the blood.
Homeostasis: Blood Sugar