1. Digestive System

2. Functions of the Digestive System
Ingestion = Food
enters the mouth.

3. Functions of the Digestive System
Ingestion = Food enters the
mouth.
Digestion =
Process that breaks
food down into
small molecules

4. Functions of the Digestive System
Ingestion = Food enters the
mouth.
Digestion = Process that
breaks food down into small
molecules
Mechanical digestion =
Food is chewed and
churned.
Chemical digestion =
Breaks down large food
molecules into smaller
molecules to be
absorbed by cells

5. Functions of the Digestive System
Ingestion = Food enters the
mouth.
Digestion = Process that
breaks food down into small
molecules
Absorption =
Small molecules of
food are taken into
the body cells.

6. Functions of the Digestive System
Ingestion = Food enters the
mouth.
Digestion = Process that
breaks food down into small
molecules
Absorption = Small
molecules of food are taken
into the body cells.
Elimination =
Wastes made of
unabsorbed food
molecules pass out of the body.
Large Intestine

7. Organs of the Digestive Tract
Mouth = Digestion starts here.

8. Organs of the Digestive Tract
Mouth = Digestion starts here.
The tongue & teeth mechanically break food up.

9. Organs of the Digestive Tract
Mouth = Digestion starts here.
The tongue & teeth mechanically break food up.
Saliva chemically digests food.
Saliva = Mostly made of
water, also contains mucus
and enzymes

10. Organs of the Digestive Tract
Mouth = Digestion starts here.
The tongue & teeth mechanically break food up.
Saliva chemically digests food.
Saliva = Mostly made of
water, also contains
mucus and ptyalin (an
enzyme)
When swallowing, the epiglottis
(a small flap of tissue) automatically closes over the trachea (windpipe).

11. Organs of the Digestive Tract
Esophagus
Smooth muscles force food into the mucus-lined esophagus.
Rhythmic muscular
contractions
(peristalsis) push food
downward.

12. Organs of the Digestive Tract
Stomach
Food undergoes mechanical digestion when stomach muscles churn the food.
Chemical digestion
happens when hydrochloric
acid (HCl) and pepsin
break down the complex
proteins.
Peristalsis pushes the food
toward stomach’s exit.

13. Organs of the Digestive Tract
Small Intestine (6 meters long)
Most digestion happens here.
Intestinal juice
(full of enzymes)
breaks down food.

14. Organs of the Digestive Tract
Small Intestine (6 meters long)
Most digestion happens here.
Intestinal juice (full of enzymes) breaks down food.
Digestive Helpers
Liver = Bile is
produced here (Bile
breaks up fats like
dish detergent
breaks up grease.).

15. Organs of the Digestive Tract
Small Intestine (6 meters long)
Most digestion happens here.
Intestinal juice (full of enzymes) breaks down food.
Digestive Helpers
Liver = Bile is produced
here (Bile breaks up fats
like dish detergent breaks
up grease.).
Gall bladder = Bile
is stored here until
released into the small intestine.

16. Organs of the Digestive Tract
Small Intestine (6 meters long)
Most digestion happens here.
Intestinal juice (full of enzymes) breaks down food.
Digestive Helpers
Liver = Bile is produced
here (Bile breaks up fats
like dish detergent breaks
up grease.).
Gall bladder = Bile is
stored here until released
into the small intestine.
Pancreas = Produces
pancreatic juices that
are released into the small intestine to break down proteins, starches, and fats

17. Organs of the Digestive Tract
Small Intestine (6 meters long)
Most digestion happens here.
Intestinal juice (full of
enzymes) breaks down food.
Digestive Helpers
Liver
Gall bladder
Pancreas
Digested food is
absorbed through the villi in the small intestine into a network of blood vessels that carry the nutrients to all parts of the body.

18. Organs of the Digestive Tract
Small Intestine (6 meters long)
Most digestion happens here.
Intestinal juice (full of enzymes)
breaks down food.
Digestive Helpers
Liver, Gall bladder, Pancreas
Digested food is absorbed
through the villi into a network of
blood vessels that carry the
nutrients to all parts of the body.
e) By the time food leaves the small intestine, it is empty of all nutrients except water.

19. Organs of the Digestive Tract
Large Intestine (1.5 meters long)
Undigested food spends 18–24 hours here, and most of the water is absorbed.

20. Organs of the Digestive Tract
Large Intestine (1.5 meters long)
Undigested food spends 18–24 hours here, and most of the water is absorbed.
Helpful bacteria
living in the large
intestine make
vitamins K and B.

21. Organs of the Digestive Tract
Large Intestine (1.5 meters long)
Undigested food spends 18–24 hours here, and most of the water is absorbed.
Helpful bacteria living in the
large intestine make vitamins
K and B.
Materials not
absorbed form into
solid waste (dead
bacteria, some fat and
protein, undigested
food, dried out parts of
digestive juices, and old intestinal cells).

22. Organs of the Digestive Tract
Large Intestine (1.5 meters long)
Undigested food spends 18–24 hours here, and most of the water is absorbed.
Helpful bacteria living in the large
intestine make vitamins K and B.
Materials not absorbed form into
solid waste (dead bacteria,
some fat & protein, undigested
food, dried out parts of digestive
juices, and old intestinal cells).
Solid waste passes
into the rectum and is stored until it is eliminated from the body through the anus.