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Day 1. I can identify the organs and describe the functions of the Digestive System . 1. 2. 3. Science Starter Identify the organs of the Excretory System. 4. Digestive System. http :// song Finlay.

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day 1
Day 1

I can identify the organs and describe the functions of the Digestive System.





Science Starter

Identify the organs of the Excretory System.



Digestive System song Finlay



The digestive system is made up of the digestive tract—a series of hollow organs joined in a long, twisting tube from the mouth to the anus—and other organs that help the body break down and absorb food.

Organs that make up the digestive tract are the mouth, esophagus, stomach, small intestine, large intestine—also called the colon—rectum, and anus. Inside these hollow organs is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tinyglandsthat produce juices to help digest food. The digestive tract also contains a layer of smooth muscle that helps break down food and move it along the tract.

Two “solid” digestive organs, the liver and the pancreas, produce digestive juices that reach the intestine through small tubes called ducts. The gallbladder stores the liver’s digestive juices until they are needed in the intestine. Parts of the nervous and circulatory systems also play major roles in the digestive system.


Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.

Mechanical digestion is the process of breaking food up into smaller pieces. Mechanical digestion takes place first in the mouth from chewing. The smooth muscles in the stomach and small intestines continue to mix and churn the food as it mixes with the digestive juices to make it break down even further.

Chemical digestion also occurs in the mouth (salivary glands) and in the stomach and small intestines. Enzymesandacids are produced in the mouth, stomach, and small intestines. The liver and the pancreas also provide digestive chemicals to the stomach. These digestive juices break or dissolve food down into the basic elements which can then pass into the blood vessels surrounding the small intestine.


The Mouth and Stomach

So, the digestive glands that act first are in the mouth— the salivary glands. Saliva produced by these glands contains an enzyme that begins to digest the starch from food into smaller molecules. An enzyme is a substance that speeds up chemical reactions in the body.

The next set of digestive glands is in the stomach lining. They produce stomach acid and an enzyme that digests protein. A thick mucus layer coats the mucosa and helps keep the acidic digestive juice from dissolving the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot.

Cone-shaped tongue papillae, seen here in a colored scanning electron micrograph, contain nerve endings that receive and transmit touch sensations to the brain. As we begin chewing, the tongue shapes food in a ball-shaped bolus for swallowing.


After the stomach empties the food and juice mixture into the small intestine, the juices of two other digestive organs mix with the food. One of these organs, the pancreas, produces a juice that contains a wide array of enzymes to break down the carbohydrate, fat, and protein in food. Other enzymes that are active in the process come from glands in the wall of the intestine.

small intestine
Small Intestine
  • 90% of absorption occurs in the small intestine

The second organ, the liver, produces yet another digestive juice-bile. Bile is stored between meals in the gallbladder. At mealtime, it is squeezed out of the gallbladder, through the bile ducts, and into the intestine to mix with the fat in food. The bile acids dissolve fat into the watery contents of the intestine, much like detergents that dissolve grease from a frying pan. After fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine.


Other important jobs of the liver include:

  • Filtering toxins from our blood before they get out into the body
  • Maintain a proper level of glucose (sugar) in our blood
  • Stores certain vitamins and minerals
  • Removes waste materials that result from digestion and the normal breakdown of the cells in our bodies. All the blood leaving the stomach and intestines passes through the liver.
  • Produces certain proteins necessary for making plasma
  • Production of cholesterol and special proteins to help carry fats through the body
  • Converts excess glucose into a substance called glycogen, a form of stored energy that can be converted back into glucose when the body needs it.
  • Stores iron which is needed for the hemoglobin of blood
  • Produces substances that help the body develop amino acids which are the building blocks of protein
  • Regulates blood clotting
  • Converts ammonia, a poisonous waste product of cellular activity, into urea (a component of urine)

When the liver has broken down harmful substances, its by-products are excreted into the bile or blood. Bile by-products enter the intestine and ultimately leave the body in the form of feces. Blood by-products are filtered out by the kidneys, and leave the body in the form of urine.


The job of the large intestine is to absorb water from the remaining indigestible food material and then to pass this useless waste material (feces) from the body through the rectum. review

day 2
Day 2

Parr digestive

I can identify the organs and describe the functions of the Digestive System.


What is the primary function of the digestive system?

The function of the digestive system is to break down food.

2. What is the function of the mouth?

The mouth breaks down food into smaller pieces and

secretes enzymes that begin digestion.

3. What is the function of the esophagus?

The esophagus transport food and water to the


4. What are the two primary types of digestive chemicals

produced by the digestive system?

Acids (particularly hydrochloric acid) and enzymes.


5. The liver, gall bladder, and pancreas have a similar digestive function.

How do these organs contribute to digestion?

Each produces or distributes some type of digestive chemical.

6. Breaking food into smaller pieces by chewing and the muscular

contractions of the stomach and small intestine to further break food

into smaller particles are examples of what type of digestion?


7. The action of digestive chemicals to dissolve food into microscopic

particles that can be absorbed into the blood stream.

Chemical digestion

8. Why does the hydrochloric acid produced by the stomach not destroy

the lining of the stomach and small intestine?

The lining of these structures is protected by a special layer of tissue.

9. The majority of digested nutrients enter our bloodstream through special

channels lining the ___________________, rather than the stomach.

small intestine

10. What are the two primary roles of the large intestine?

The main functions of the colon are to reabsorb excess water and move

solid waste from the body.


1. Bell Ringer (10 min) Complete the walk-through sheet.In the process of digestion, food is initially broken into smaller pieces through the action of ___________________. Digestive _______________________ are produced by special glands in the mouth, so both mechanical and _____________________ begin there. Food is transported to the stomach through the __________________________. The stomach produces more digestive __________________________ and a powerful type of acid known as ________________________________________. The ____________________ muscles lining the outside of the stomach ______________________ and relax in order to break the food down further. As this soupy material enters, the small intestine, the _______________________ releases bile (which breaks down ___________) into the small intestine. At the same time, the __________________ also release digestive enzymes into the small intestine. Once the food particles are broken down into molecules, they are able to pass through special channels in the lining of the small intestine and enter the blood stream through thousands of miles of tiny blood vessels called ______________________. The undigested material then passes into the ______________________________ where the excess water left over from digestion is reabsorbed. As the waste material (feces) becomes more compact, it is eventually expelled from the body through the __________________.

(Word Bank is on the White Board)

day 3
Day 3

I can identify the organs and describe the functions of the Digestive System.


Common Diseases of the Digestive System

  • All parts of the digestive and excretory system are prone to cancer, though cancer of the colon is one of the most common.

Ulcer- an ulcer is a hole in the mucosal lining of the stomach or small intestine. If serious enough, an ulcer can cause internal bleeding.


Acid Reflux- a medical condition where stomach acids rise or leak up from the stomach into the lower part of the esophagus. These powerful acids damage the tissue of the esophagus and can result in permanent, long-term damage.


Cirrhosis- a type of chronic liver disease characterized by the development of small nodules throughout the liver and gradual replacement of healthy liver tissue with scar tissue (which cannot carry out the function of the liver.) Cirrhosis is most commonly caused by alcoholism, Hepatitis B and C, and fatty liver disease.


1. The most common form of digestive system cancer occurs in which digestive organ?

The colon (large intestine.)

2. This digestive disorder is characterized by a backflow of stomach acid and partially digested food from the stomach upward into the esophagus.

Acid reflux.

3. Which substances in our food would a person have difficulty digesting if he or she suffered from gall stones?

The gall bladder stores and releases bile into the small intestine. Bile breaks down fats.



large intestines

absorb water


kills germs

break up food

digest proteins

store food


break up food

moisten food

digest starch

kill germs



produces bile

- stored in gall bladder

break up fats


small intestines

break down food

- proteins

- starch

- fats

absorb nutrients