1. What do humans need to live?
Humans make energy using:
food
oxygen
Animals build bodies using:
food for raw materials
amino acids, sugars, fats, nucleotides
ATP energy for synthesis
food
ATP O2
mitochondria

2. Getting & Using Food Ingest Digest Absorb Eliminate taking in food
mechanical digestion
breaking up food into smaller pieces
chemical digestion
breaking down food into molecules small enough to be absorbed into cells
enzymes
Absorb
absorb nutrients across cell membranes
diffusion
active transport
Eliminate
undigested material passes out of body

3. Digestive System
ABSORPTION – Nutrient molecules absorbed from gut into bloodstream
INGESTION – Act of taking in food and drink into body
ELIMINATION – Ridding the body of undigested food waste
DIGESTION BREAKDOWN – Chemical and Physical

4. Mechanical/Physical Digestion
-food is broken down -more surface created Examples:
Chewing with teeth -churning food in stomach
-No new molecules are produced

5. Chemical Digestion
-food molecules are broken down -produce brand new smaller molecules.
-requires digestive enzymes and water as a substrate (hydrolysis reactions.)

6. In many parts of the digestive tract both types of digestion are happening simultaneously. For example: in the stomach.

7. Fig. 12.1

8. Human digestive system
After chewing and swallowing, it takes 5 to 10 seconds for food to pass down the esophagus to the stomach, where it spends 2 to 6 hours being partially digested.
Final digestion and nutrient absorption occur in the small intestine over a period of 5 to 6 hours.
In 12 to 24 hours, any undigested material passes through the large intestine, and feces are expelled through the anus.

9. Mouth Functions mechanical digestion chemical digestion (saliva) teeth
break up food
chemical digestion (saliva)
amylase enzyme
digests starch
mucus
protects soft lining of digestive system
lubricates food for easier swallowing
buffers
neutralizes acid to prevent tooth decay
anti-bacterial chemicals
kill bacteria that enter mouth with food
All that in spit!

10. Fig. 12.2a

11. Tonsils at the back sides of the mouth protect against infections.
Tonsillitis results when the tonsils become inflamed; the infection can spread to the middle ears.
Three pairs of salivary glands (parotid, sublingual, submandibular) send saliva (containing salivary amylase for digestion of starch to maltose) into the mouth.

12. mouth
break up food
digest starch
kill germs
moisten food

13. Swallowing (& not choking)
Epiglottis
flap of cartilage
closes trachea (windpipe) when swallowing
food travels down esophagus
Peristalsis
involuntary muscle contractions to move food along

14. Peristalsis in Esophagus
The ESOPHAGUS
Peristalsis in Esophagus
The esophagus is a muscular tube that conducts food through the thoracic cavity and diaphragm into the stomach.
Peristalsis begins in the esophagus; this collapsed tube moves the bolus of food downward after swallowing occurs.
Heartburn is a burning pain when acidic stomach contents enter the esophagus.
Peristalsis is a rhythmic contraction that pushes food through the digestive tube. When peristalsis occurs with no food present, it produces a sensation of a lump in the throat.
When vomiting occurs, a contraction of the abdominal muscles and diaphragm propels the contents of the stomach upward through the esophagus.

15. PERISTALSIS

16. Stomach Functions disinfect food food storage digests protein
hydrochloric acid = pH 2
kills bacteria
food storage
can stretch to fit ~2L food
digests protein
pepsin enzyme
Still, the epithelium is continually eroded, and the epithelium is completely replaced by mitosis every three days.
Gastric ulcers, lesions in the stomach lining, are caused by the acid-tolerant bacterium Heliobacter pylori.
Ulcers are often treated with antibiotics.
Pepsin is secreted in an inactive form, called pepsinogen by specialized chief cells in gastric pits.
Parietal cells, also in the pits, secrete hydrochloric acid which converts pepsinogen to the active pepsin only when both reach the lumen of the stomach, minimizing self-digestion.
Also, in a positive-feedback system, activated pepsin can activate more pepsinogen molecules.
But the stomach is made out of protein!
What stops the stomach from digesting itself?
mucus secreted by stomach cells protects stomach lining

17. Stomach Functions
1. Storage of a meal – most expanded structure along the alimentary canal

18. 2. Mechanical Digestion of food – Stomach is very muscular and it squeezes to churn and mix food to physically break it down

19. 3. Chemical Digestion of food – Adds PEPSIN enzyme to start chemically breaking proteins into small peptide chains

20. 4. Protection against Germs – HCl helps activate enzymes but it also helps kill many of the bacteria that we ingest.

21. GASTRIC GLANDS
-produce gastric juice which consists of mucous, HCl, Pepsinogen and water.
In the presence of HCl the Pepsinogen converts to active Pepsin. This Pepsin is a PROTEASE enzyme, breaking proteins into smaller peptide chains

22. mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
sphincter
sphincter

23. This is where all the work is done!
Small intestine
Functions
digestion
digest carbohydrates
amylase from pancreas
digest proteins
trypsin & chymotrypsin from pancreas
digest lipids (fats)
bile from liver & lipase from pancreas
absorption
nutrients move into body cells by:
diffusion
active transport
This is where all the work is done!
About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles.
As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient-rich broth known as acid chyme.
At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine.
A squirt at a time, it takes about 2 to 6 hours after a meal for the stomach to empty.

24. Absorption in Small Intestines
Absorption through villi & microvilli
finger-like projections
increases surface area for absorption
SMALL INTESTINES 6 meters long, but can stretch to cover a tennis court

25. Fig. 12.6
Small Intestine

26. It’s all about surface area
1.Plicae 2. Villi Microvilli

27. VILLI
Microvilli

28. Its All About Active Transport
Products of Carbohydrate and Protein Digestion are actively transported from small intestine into the villus. These simple sugars and amino acids are taken into the capillary bed in the villus and transported to the Liver.
Products of Fat digestion are absorbed into the central lymphatic vessel called a LACTEAL

29. Duodenum  Jejenum  Ileum

30. DUODENUM Functions
The Duodenum is only about 45 cm (18 inches long) but it plays a couple of very important roles:
1. Receives incoming Stomach Chyme, Pancreatic Juices and Bile from Liver and Gall bladder.
2. Secretes digestive juces/enzymes from duodenal glands

31. mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
liver
produces bile
- stored in gall bladder
break up fats
small intestines
breakdown food
- proteins
- starch
- fats
absorb nutrients
pancreas
produces enzymes to
digest proteins & starch

32. Accessory Organs
PANCREAS
LIVER
GALL BLADDER

33. Pancreas Produces digestive enzymes Buffers digest proteins
trypsin, chymotrypsin
digest starch
amylase
digest lipids
lipase
Buffers
neutralizes acid from stomach
small intestine
pancreas

34. PANCREAS Function
-produces a variety of hydrolytic digestive enzymes that help chemically finish off the digestion of Carbohydrates, Fats and Proteins.

35. Pancreatic Juice INGREDIENTS: Sodium Bicarbonate – NaHCO3 LIPASES
PANCREATIC AMYLASE
TRYPSIN – same function as PEPSIN
NUCLEASES (work on Nucleic Acids)

36. Pancreatic Endocrine Function
When blood sugar is getting too high. The pancreas produces and secretes INSULIN into the bloodstream

37. Pancreatic Endocrine Function
When blood glucose levels start getting too low, the Pancreas will produce and secrete the hormone GLUCAGON. Glucagon will travel through the bloodstream to tell muscle and liver cells to break down their stored Glycogen back into glucose and send it back into the blood, to raise blood sugar levels

38. mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
pancreas
produces enzymes to
digest all foods

39. Liver & Gall Bladder Produces bile breaks up fats
gallbladder only stores bile
that’s why you can have your gall bladder removed
bile contains colors from old red blood cells collected in liver =
iron in RBC rusts & makes feces brown

40. Fig

41. Gall Bladder Function -sits inferior (below) the liver.
-stores bile that was produced in the liver.
-secretes this bile into the Duodenum.
-bile helps emulsify fats to create more surface area so that hydrolytic lipases (fat enzymes) can break the fat down chemically.

42. mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
liver
produces bile
- stored in gall bladder
break up fats
pancreas
produces enzymes to
digest proteins & starch

43. Large intestines (colon)
Function
re-absorbs water
use ~9 liters of water every day in digestive juices
if don’t reabsorb water would die of dehydration
> 90% of water re-absorbed
not enough water re-absorbed
diarrhea
can be fatal!
too much water re-absorbed
constipation
reabsorb by diffusion

44. Large Intestine Functions
1. Receives undigested waste and helps absorb fluid (water) from those wastes back into the bloodstream, to help keep us from dehydrating.
2. Helps compact and form feces.
3. Harbours helpful bacteria which can further break down wastes to free up minerals and some bacteria will help produce and free up some vitamins, such as Vitamin K

45. You’ve got company!
Living in the large intestine is a community of helpful bacteria
Escherichia coli: E. coli
digest cellulose
digests fruits & vegetables
produce vitamins
vitamin K & B vitamins
BUT generate gases
by-product of bacterial metabolism
methane, hydrogen sulfide
STINKY!
PEE-YOO!

46. Large Intestine/Colon
Fig. 12.8
Large Intestine/Colon

47. mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
liver
produces bile
- stored in gall bladder
break up fats
small intestines
breakdown food
- proteins
- starch
- fats
absorb nutrients
pancreas
produces enzymes to
digest proteins & carbs
large intestines
absorb water

48. Appendix
Vestigial organ

49. mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
liver
produces bile
- stored in gall bladder
break up fats
small intestines
breakdown food
- proteins
- starch
- fats
absorb nutrients
pancreas
produces enzymes to
digest proteins & carbs
large intestines
absorb water
appendix

50. So don’t forget to wash your hands!
Rectum
Last section of large intestines
eliminate feces
what’s left over?
undigested materials
mainly cellulose from plants
called roughage or fiber
keeps everything moving & cleans out intestines
masses of bacteria
So don’t forget to wash your hands!

51. Fig. 12.9