1. The Digestive System
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2. Organs of the Digestive System
Two main groups
Alimentary canal or GI tract
Accessory digestive organs
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3. Organs of the Alimentary Canal
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4. Accessory Digestive Organs
Salivary glands
Teeth
Pancreas
Liver
Gall bladder
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5. The Mouth (Oral Cavity)
Lips – sense temp. and texture; protect mouth
Hard palate and Soft palate – form the roof
Uvula – fleshy projection at the back of the soft palate
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6. The Mouth (Oral Cavity)
Tonsils
palatine tonsils - on either side of the back of the mouth
lingual tonsils– at the back of the tongue
both play a role in the immune system
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

7. Digestive Processes in the Mouth
mastication (chewing) of food
mixing of masticated food with saliva (secreted by salivary glands)
saliva contains enzymes that begin the digestion of carbohydrates
initiation of “deglutition” (swallowing) by the tongue
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

8. The Pharynx (throat) food and air share this passageway
muscular tube that moves food into the esophagus
when we swallow food, a flap of tissue known as the “epiglottis” covers the trachea
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

9. The Esophagus
muscular tube that runs from pharynx to stomach through the diaphragm
moves food by peristalsis (slow rhythmic contractions)
cardiac sphincter (lower esophageal sphincter)
group of muscles, at the bottom of the esophagus, that contracts and closes the entrance to the stomach when food is present – this prevents backflow

10. The Stomach
pouch-like organ in the left hypochondriac region of the abdominal cavity
regions of the stomach:
cardiac region – portion closest to the heart
fundus – upper rounded portion
body – middle portion
pylorus – narrow bottom portion
pyloric sphincter – circular muscle at the base of the stomach which controls the emptying of the stomach’s contents into the small intestine
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11. Stomach Anatomy the lining of the stomach is thick and has many
folds called “rugae”
as the stomach fills
up, the wall distends
and the folds
disappear
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

12. Digestive Processes in the Stomach
food is mixed with gastric juice (contains hydrochloric acid and enzymes)
pepsin begins to break down protein
muscle movements of the stomach form a semifluid mass called “chyme” (processed food)
muscles move chyme, in small batches, into the small intestine
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

13. The Small Intestine
it is about 20 feet long from stomach to large intestine
lined with villi (tiny, one-cell-thick fingerlike projections with capillaries) through which digested nutrients are absorbed into the bloodstream
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14. Subdivisions of the Small Intestine “Dogs Just Itch!”
Duodenum
10 inches long
chyme mixes with bile (digests fat), pancreatic juice (digests starch, proteins, and fat) and intestinal juice (digests sugars)
Jejunum
8 feet long
Ileum
connects small intestine to large intestine
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

15. Subdivisions of the Small Intestine “Dogs Just Itch!”
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

16. The Large Intestine about 5 feet long
forms a rectangle around the tightly packed small intestine
waste products usually remain in the large intestine from 12 – 24 hours
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

17. Large Intestine
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18. Subdivisions of the Large Intestine
Cecum
saclike first part of the large intestine
has 3 openings: one from the ileum into cecum, one from the cecum into the colon, and one from the cecum into the appendix
Appendix is filled with lymphatic tissue and can become inflamed (appendicitis)
Water and necessary substances are absorbed into the bloodstream and feces is formed
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

19. Subdivisions of the Large Intestine
Colon
ascending colon: extends upward
transverse colon: extends across
descending colon: extends downward, where it connects to the sigmoid colon
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

20. Subdivisions of the Large Intestine
Sigmoid Colon
S-shaped body that goes across the pelvis to the middle of the sacrum, where it connects to the rectum
Rectum
attaches to the anal canal
sphincter muscles of the anus open during the release of feces from the body (defecation)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings