1. The Journey of a Cracker

2. Amalyse
Mouth
Digestion of the cracker begins here. Teeth physically (mechanically) crush and chop the food while the tongue mashes the food around. Saliva which is excreted by salivary glands, contains water, mucus, and the enzyme amalyse which chemically breaks large starch molecules, also called polysaccarides, into smaller sugar molecules called monosaccarides. (glucose) Only starches (carbohydrates) are digested here. Enzymes are proteins that speed or assist chemical reactions. Starch and sugar are called organic molecules because they contain carbon as part of their chemical structure.
Today, hand out a single saltine cracker to each student. Have them place it on their tongue, without chewing and without talking for 1 minute. They should pay close attention to any change in flavor.

3. Esophagus
Wavelike muscle action called peristalsis moves the bolus (chewed food) from the mouth to the stomach. (no digestion takes place, though physical changes in shape and texture occur).
Epiglottis
The epiglottis is a small flap of tissue that closes over the opening of the trachea, or wind pipe (breathing tube) when you swallow, keeping food out of your lungs.

4. Monday’s Board Notes

5. Pepsin
Stomach
Food enters the stomach through a valve. The stomach is a “j” shaped muscular organ that churns and mixes food mechanically like a blender. Gastric juices (Hydrochloric acid, enzymes such as pepsin and mucus) break it down chemically and change it into chyme (malt-like liquid). The cracker is now a thin liquid and leaves the stomach after about 4 hours by way of another sphincter valve.
Demo Something’s Churning for regulars. Read and discuss WHY renin is important for babies.

6. Discussion Questions – Something’s Churning Lab
1. What effect did the rennet tablet have on the milk?
2. Define qualitative and quantitative data.
3. Describe the milk before and after.
4. How does the enzyme rennin increase the efficiency of the digestive process in infants?

8. Small Intestine
The thin liquid enters the first curve of the small intestine called the duodenum. Most chemical digestion and absorption of nutrients into the blood stream takes place here (first 10 inches). After digestion, absorption of the nutrients through the intestinal wall (the villi) takes place. The cracker is now glucose molecules which leave the villi and enter the blood stream, which carries them to cells for energy production.
Demo Intestine digestion, have students try Stringing Along, throwing in the paper towel

9. Stringing along data Tube Prediction Actual A – no liner ml
B – cotton fabric
C – cotton washcloth
Line
Length, cm
Villi, microvilli
AB straight 18
AB bold line 60
3, 0
AB squiggles
200
3, 76

10. Data and Discussion Questions

11. Liver
Manufactures bile – an enzyme that mechanically breaks down lipids (fat) into smaller fat droplets. Food does not enter the liver. Bile is secreted into the small intestine through a tiny tube.
Gall Bladder
Small sac under the liver that stores the bile until needed. The bile is released into the duodenum of the small intestine. Food does not enter the gall bladder.

12. Pancreas
Gland which produces enzymes such as insulin which break down proteins, starches, and fats chemically. These enzymes are secreted into the duodenum also. Food does not enter the pancreas. If the pancreas fails to produce the right amount of insulin, diabetes or hypoglycemia can result. The pancreas also produces trypsin which breaks down proteins into amino acids and lipase, which breaks down fats into fatty acids and monoglycerides.
Insulin
Glucose

13. Large Intestine
Water, salt and minerals are absorbed from the undigested material forming solid waste called feces. Bacteria break down some fiber. Vitamins B and K are also produced here by bacteria and absorbed into the blood. Cellulose from the cracker provides fiber for peristalsis to work. The large intestine is often called the colon.

14. Rectum
The last vertical section of the large intestine through which solid waste (feces) travels.
Anus
Muscular opening where solid waste is released (excreted) from the body.

15. Organic Molecules Fats chemically break down into fatty acids.
Proteins chemically break down into amino acids.
Carbohydrates(starches) chemically break down into simple sugars.
They all have Carbon as an element in their chemical structure, which makes them organic molecules.

16. The Path of Food
Main Organs/Structures of Digestion the Food Passes Through (all lined with epithelial tissue).
Organs/Structures of Digestion that Food Does NOT Enter (Accessory Organs)

17. Physical or Chemical Change?
Action
Physical or Chemical
Teeth chop, crush and grind food
Saliva has chemicals called enzymes (Amylase) that break down starches into sugar
Involuntary contractions of smooth muscles, called Peristalsis, moves chewed food down the esophagus to the stomach (and through the rest of the digestive system), changing shape and texture
Gastric juices including the enzyme pepsin breakdown proteins into amino acids
Stomach blends food into a liquid
Enzymes and chemicals from the pancreas and gall bladder are secreted into the small intestine to break down fats, proteins and sugars into smaller units
Bile from the gall bladder cuts lipids into smaller pieces of lipids
Villi in the small intestine absorb nutrients into the blood stream
Water from food is absorbed back into the blood stream in the large intestine
Bacteria in the large intestine convert some wastes into vitamins B and K.
In the rectum, waste is compressed into solid form and then eliminated through the anus.

18. Major functions of the digestive system
To ingest (take in) food
To digest (break down) large molecules of food such as starches into smaller molecules such as sugars, fats into fatty acids and proteins into amino acids that the body can use
To absorb nutrients from digested food into the bloodstream to be delivered to cells
To excrete (eliminate) undigested wastes from the body