1. The Gastrointestinal System and
its functions

2. Retrieved from Images from Purves et al., Life: The Science of
Biology, 4th Edition, by Sinauer Associates and WH Freeman .
The human digestive system

3. Functions of Digestive System.
 The mechanical and chemical
breakdown of food .
 Absorption of digested nutrients.
 Supplying essential nutrients to
fuel the other organs and body
system.

4.  Movement: propels food through the digestive system
 Secretion: release of digestive juices in response to a
specific stimulus
 Digestion: breakdown of food into molecular
components small enough to cross the plasma
membrane
 Absorption: passage of the molecules into the body's
interior and their passage throughout the body
 Elimination: removal of undigested food and wastes
Stages in the Digestive Process

5. The Gastrointestinal Tract Organs
 The Mouth
 The Pharynx and
Esophagus
 The Stomach and
Small Intestine
 The
Colon, Rectum, and
Anus
 Pancreas
 Liver
 Gallbladder
The GI tract or alimentary canal
The accessory glands and
organs

6.  Ingestion of food.
 Propulsion of food and wastes
from the mouth to the anus
 Secretion of mucus, water and
enzymes
 Mechanical digestion of food
particles
 Chemical digestion of food
particles.
 Absorption of digested food.
 Elimination of waste products by
defecation.
 The Liver, gall bladder and
exocrine pancreas all secrete
enzymes for the digestion of
chyme.
The GI tract or alimentary
canal
The accessory glands and organs
The Gl Tract Organs functions

7. The mouth
 The mouth is the beginning of the digestive
system.
 Chewing and salivation soften, make it easy to
swallow.
 An enzyme in saliva, ptyaline, converts
starches to sugars.
 The tongue rolls the masticated food into a
ball, known as bolus and pushes it to the
posterior end of the mouth into the pharynx.

8. Retrieved from Image from Purves et al., Life: The Science of Biology, 4th
Edition, by Sinauer Associates and WH Freeman .
Structure of the throat and the mechanics of swallowing.

9. The Pharynx and Esophagus
 The esophagus is a muscular tube connecting
the pharynx to the stomach that is part of
the upper gastrointestinal tract.
 Mucus moistens food and lubricates the
esophagus. Bicarbonate ions in saliva
neutralize the acids in foods.
 Swallowing moves food from the mouth
through the pharynx into the esophagus and
peristaltic waves propel food to the stomach.

10. The Stomach
 a hollow organ, or "container, "holding food, it
serves as the mixer and grinder of food.
 Secretes acid and powerful enzymes that
continue the process of breaking the food
down and changing it to a consistency of liquid
or paste.

11. Small Intestine
 Made up of three segments -- the
duodenum, jejunum, and ileum
 the 'work horse' of digestion, as this is where
most nutrients are absorbed. Peristalsis
moving food through and mixing it up with the
digestive secretions from the pancreas and
liver, including bile.
 Carbohydrates, lipids and proteins are broken
down and digested.

12. Large Intestine
 made up of the ascending (right) colon, the
transverse (across) colon, the descending
(left) colon and the sigmoid colon.
 is responsible for processing waste so that
defecation (excretion of waste) is easy and
convenient.
 absorb water and mineral salts from the
digested food

13. Rectum, and Anus
 the rectum is to receive waste material or
feces from where the sigmoid colon is
stored, until it is excreted out of the body via
the anus.
 Stool is stored in the sigmoid (S-shaped) colon
until a "mass movement" empties it into the
rectum, usually once or twice a day.

14. Accessory Digestive Organs
 Liver :chemical "factory” the raw materials
absorbed by the intestine. second largest
organ. Weighs around 3 pounds.
 make and secrete bile.
 detoxifies potentially harmful chemicals. It
breaks down and secretes many drugs.
 Gallbladder a storage sac for excess bile, and
then releases it into the duodenum to help
absorb and digest fats.

15. Retrieved from Images from Purves et al., Life: The Science of
Biology, 4th Edition, by Sinauer Associates and WH Freeman
The liver and associated organs

16. Accessory Digestive Organs
 Pancreas : the chief factory for digestive
enzymes that are secreted into the duodenum.
These enzymes break down protein, fats, and
carbohydrates.
 more than 1000 ml of digestive enzymes daily.
 production of several hormones, such as
glucagon and insulin.

17. Retrieved from Images from Purves et al., Life: The Science of
Biology, 4th Edition, by Sinauer Associates and WH Freeman
The liver and associated organs

18. Regulation of Appetite
 The hypothalamus in the brain has two centers
controlling hunger.
 the appetite center.
 the satiety center.

19. Regulation of Appetite
 The presence of protein in the stomach stimulates secretion
of gastrin , which causes increased stomach acid secretion
and mobility of the digestive tract to move food.
 Food passing into the duodenum causes the production of
secretin, which promotes release of alkaline secretions from
the pancreas, stops further passage of food into the intestine
until the acid is neutralized.
 Cholecystokinin (CCK) is released from intestinal epithelium
in response to fats, and causes the release of bile from the
gall bladder and lipase (a fat digesting enzyme) from the
pancreas.


20. Retrieved from Images.search.yahoo.com/images/view
Structures and functions of Gastrointestinal tract.

21. References
 McCance, K.L., Heather, S.E., Brasher, V.L., & Rote, N.S.
(Eds.). (2006). Structure and Function of Digestive
System. Pathophysiology: The Biologic Basis for Diseases in
Adults and Children (5th ed.). St. Louis, MO: Elsevier Mosby.
 Margaret Eckman, Debra Share(Eds.) (2013).Gastrointestinal
System. Pathophysiology made Incredibly Easy (5thed.)
Wolters Kluwer, Lippincott Williams & Wilkins

22. References
 Digestive system. Retrieved from http://www.webmd.com
 Digestive system .Retrieved from
http://www.buzzle.com/articles/digestive-system-fuction
 Digestive system. Retrieved from
http://www.cchs.net/health/healthinfo/docs/1600/1699.asp?in
dex=7041function.html
 Digestive system. Retrieved from
http://www.estrellamountain.edu/facutly/farebee/biobk/BioBoo
k DIGEST.html