1. The Digestive and Excretory Systems
EQ: How do organ systems work together to enable an organism to maintain homeostasis?

2. Functions of the Digestive and Excretory Systems
Digestive System
Excretory System
Getting food into your body
Digesting the food
Absorbing the nutrients you need
Eliminating solid waste
Getting the materials you don’t need out of your body.
Fluids: Liquids, gases

3. The Digestive System
You feel hungry because your brain receives signals that your cells need energy.
But eating is only the beginning of this story.
Your body must change a meal into substances you can use.
Your digestive system is a group of organs that work together to digest food so that it can be used by the body.

4. Two Types of Digestion
Mechanical
Chemical
The breaking, crushing, mashing and pulverizing of the food
Large molecules of food are broken down into the nutrients that the body needs for normal growth, maintenance and repair.

5. Organs of the Digestive System
Teeth
Esophagus
Stomach
Pancreas
Small Intestine
Liver
Gallbladder
Large Intestine

6. Teeth Teeth are very important organs for mechanical digestion,
They break and grind food into smaller pieces so they can be swallowed more easily.
As you chew, saliva moistens your food to make it slipperier.
Saliva also contains enzymes that begins the chemical digestive process.

7. Esophagus
Once your food is reduced to a soft mush, the tongue pushes it down the throat, which leads to a long, straight tube called the esophagus.
The esophagus squeezes the food down to the stomach with muscle contractions.
These contractions are called peristalsis.

8. Stomach Peristalsis forces your food into your stomach.
The stomach is a muscular, saclike organ.
The stomach continues to mechanically digest your food by squeezing it with muscular contractions.
While this squeezing takes place, enzymes and acids are being produced, which helps with the chemical break down of your food.
After a few hours of this mechanical and chemical digestion, your food is reduced to a soupy mixture called chyme.

9. The Pancreas
Most chemical digestion takes place after your food leaves your stomach.
When the chyme leaves the stomach, the chyme is very acidic.
The chyme never actually enters your pancreas, which is oval-shaped and between the stomach in small intestine
Instead, the pancreas produces fluid (pancreatic fluid) that contains enzymes that further breaks down the chyme and neutralizes the acids in the chyme.
These fluids flow into the small intestine.
The pancreas also helps produce hormones (endocrine system) to help regulate blood sugar.

10. Small Intestine
The small intestine is a muscular tube that is about 2.5 cm in diameter, and about 6 m in length.
Inside the small intestine, there are finger-like projections called villi.
The villi are covered with tiny, nutrient-absorbing cells.
Once the nutrients are absorbed, they enter the blood stream to deliver the nutrients to your body.

11. Liver
The liver is a large, reddish brown organ that helps with digestion.
It is about the size of a football.
The liver helps with digestion in the following ways:
Makes bile to break up fat
Stores nutrients to be released later
Breaks down toxins such as alcohol.

12. Gallbladder
Although bile is made by the liver, bile is temporarily stored in the gallbladder.
Bile is squeezed from the gallbladder into the small intestine, where the bile breaks large fat droplets into smaller droplets.

13. Large Intestine –The End of the Line
Material that cannot be absorbed into the blood is pushed into the large intestine.
The large intestine stores, compacts and eliminates indigestible material from the body.
It is about 1.5 meters long and 7.5 cm in diameter.
Undigested material enters the large intestine as a soupy mixture.
The large intestine absorbs most of the water and changes the liquid into a semisolid waste called feces.

14. Rectum The rectum is the last part of the large intestine.
It stores the feces until they can be expelled.
It generally takes 24 hours from the time your food enters your mouth until it is expelled from your body.

15. The Excretory System
The excretory system is very important to your body and has only a few parts.
In a similar way to removing solid waste from your body, you must also get rid of fluids.
Excretion is the process of removing waste products from your body.

16. Three of your body systems have a role in excretion
Your integumentary system releases water a waste by way of sweat.
Your respiratory system releases carbon dioxide and water when you exhale.
Your urinary system contains the organs that remove waste products from your blood.

17. Organs of the Urinary System
Kidneys – a filtering organ that constantly clean the blood.
Ureter – tubes leading from the kidneys to the urinary bladder.
Urinary bladder --- a sac which holds the urine until it is expelled from your body
Urethra – a tube through which the urine leaves your body