1. Ch 39 – Digestion & Excretion
39.2 Digestive system
39.3 Excretory system

2. Digestion is the breaking down of organic matter
Mechanical digestion
Chemical digestion

3. 39.2 Digestive system Ingest food. Transport food.
Digest food into smaller usable components.
Absorb the necessary nutrients into the bloodstream.
Expel the waste products from the body.

4. Path of digestion & excretion

5. Start of digestion - Mouth
Chem & mechanical
Saliva moistens & lubricates food
Salivary amylase begins to break down starches
(carbohydrates).

6. Esophagus Approximately 10” long No digestion
Moves food from the throat to the stomach
Muscle movement called peristalsis
If acid from the stomach gets in here that’s heartburn.
A good way to describe peristalsis is an ocean wave moving through the muscle.
These diagrams don’t separate the esophagus from the mouth functions, you might want to talk about what happens in the mouth too.

7. Stomach Sphincter separates esophagus & stomach
Stores the food you eat, breaks it down into tiny pieces –mech & chem
Mixes food with digestive juices
HCl and pepsin
Pepsin digests large proteins into smaller proteins
Mucus, bicarbonate, and blood circulation helps protect stomach tissues
The stomach takes around 4 hours to do it’s job on the food, depending on what kinds of food are digested.

9. Small Intestine Small intestines are roughly 20 feet long
Insides are coated with little ‘fingers’ called villi to increase surface area.
Lipases break down fat
Nutrients from the food pass into the bloodstream through the small intestine walls.

10. Small Intestine Pancreas Liver Gall bladder
** Most chemical digestion takes place in the small intestine with help of secretions from the
Pancreas
Liver
Gall bladder
Villus singular Villi plural

11. Large Intestine or Colon
About 5 feet long, not coiled
No digestion
Accepts what small intestines don’t absorb.
Absorbs water and minerals from the waste matter.
Last section is rectum
Depending on the maturity of the group, you can talk about the feces leaving via the anus.
Mention the appendix at the bottom of the ascending colon and that it might have been used long ago but is not today
Mention the portions of the large intestine, ascending, transverse, descending, sigmoid, and rectum (last one if the audience is mature enough)

12. Function of appendix – growing fetus: endocrine system, adult : immne system

13. Pancreas Produces compounds to digest fats and proteins
Neutralizes acids that enter small intestine
Regulates blood sugar by producing insulin
Explain the difference between the two types of diabetes. In type 1, the pancreas fails to produce enough insulin. In type 2, the body stops responding properly to the insulin it creates.

15. Liver Directly affects digestion by producing bile
Bile helps digest fat
Processes nutrients in the blood, filters out toxins and waste.
Is often called the body’s energy factory
About the size of a football (3 lbs) in a human
Livers can regenerate missing pieces if necessary. Is one of the largest organs in the body.

17. Gall Bladder Stores bile from the liver
Delivers bile when food is digested
Fatty diets can cause gallstones
Explain to students that removing the stones typically means removing the gallbladder, but that the body eventually adjusts to not having the bile stored.

18. Digestive system video

19. 39.3 Excretion 3 organs LUNGS KIDNEYS SKIN
Excretion is the process that rids the body of toxic chemicals, excess water, salts, CO2, while maintaining osmotic & pH balance
3 organs
LUNGS
KIDNEYS
SKIN

20. Kidneys
Each kidney is composed of about 1 million microscopic blood filtering units called nephrons
Kidneys filter out blood
toxins
urea (ammonia converted to less toxic nitrogenous waste)
water
salts
3 phases
Filtration
Reabsorption
Secretion

21. Kidney – science facts
Your blood passes through the kidneys 300 x a day.
The nephrons clean all your blood in 45 min. 
Every day the nephrons send about 6 cups of urine to the bladder.

22. Function of the nephron

23. Urine – formed from the water, urea, & salts that are left after absorption & secretion
Ureters – tubes that carry urine from kidney to urinary bladder
Urethra – urine leaves body and exits via urethra

24. Digestive Enzymes Pepsin Lipase large proteins into smaller proteins
Amylase
Pepsin
Lipase
fats into fatty acids and glycerol
starches into sugars
stomach
large proteins into smaller proteins
mouth
intestine 3

25. Mini quiz Proteins are made up of Fatty acids Glycerol Amino acids
monosaccharides

26. During digestion, food passes through the
mouth, esophagus, stomach, ________, &
large intestine.
Pancreas
Lungs
Gallbladder
Small intestine

27. Which of the following correctly pairs the
enzymes with the food molecules they
digest?
Lipases – starch
Amylases – fats
Lipases – fats
Pepsin – starches

28. Which substance is NOT a waste eliminated
from the body through the kidneys?
A. Urea
Water
Salts
Oxygen

29. The ________ are involved in excretion
Kidneys & stomach
Liver & pancreas
Pancreas & kidneys
Kidneys & lungs