1. Digestive System
•
Two groups of organs
1. Alimentary canal (gastrointestinal or GI tract)
•
Digests and absorbs food
•
Mouth, pharynx, esophagus, stomach,
small intestine, and large intestine
Copyright © 2011 Pearson Education, Inc.

2. Digestive System
2. Accessory digestive organs
•
Teeth, tongue, gallbladder
•
Digestive glands
•
Salivary glands
•
Liver
•
pancreas
Copyright © 2011 Pearson Education, Inc.

3. Mouth (oral cavity)
Tongue
Esophagus
Liver
Gallbladder
Duodenum
Jejunum
Small
intestine Ileum
Anus
Copyright © 2011 Pearson Education, Inc.
Parotid gland
Sublingual gland Salivary
Submandibular
glands
gland
Pharynx
Stomach
Pancreas
(Spleen)
Transverse colon
Descending colon
Ascending colon
Large
Cecum
intestine
Sigmoid colon
Rectum
Vermiform appendix
Anal canal
Figure 22.1

4. Digestive Processes
•
Six essential activities
1. Ingestion
2. Propulsion
3. Mechanical digestion
4. Chemical digestion
5. Absorption
6. Defecation
Copyright © 2011 Pearson Education, Inc.

5. Ingestion
Mechanical
digestion
• Chewing (mouth)
• Churning (stomach)
• Segmentation
(small intestine)
Chemical
digestion
Food
Pharynx
Esophagus
Propulsion
• Swallowing
(oropharynx)
• Peristalsis
Stomach (esophagus,
stomach,
small intestine,
large intestine)
Absorption
Lymph
vessel
Small
intestine
Large
intestine
Defecation
Copyright © 2011 Pearson Education, Inc.
Blood
vessel
Mainly H2O
Feces
Anus
Figure 22.2

6. Blood Supply: Splanchnic Circulation
• Arteries
• Hepatic, splenic, and left gastric
• Inferior and superior mesenteric
• Hepatic portal veins
• Drains nutrient-rich blood from digestive
organs
• Delivers it to the liver
Copyright © 2011 Pearson Education, Inc.

7. TISSUES OF THE
ALIMENTARY CANAL
Copyright © 2011 Pearson Education, Inc.

8. Histology of the Alimentary Canal
• Four basic layers (tunics)
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa
Copyright © 2011 Pearson Education, Inc.

9. Mucosa
Inner layer of lumen
Three sublayers:
1. Epithelium – simple columnar and goblet cells
•
Secrete mucus and enzymes
1. Lamina propria – areolar basement membrane
2. Muscularis mucosae– thin layer of smooth muscle
Copyright © 2011 Pearson Education, Inc.

10. Simple Columnar with Microvilli
Copyright © 2011 Pearson Education, Inc.

11. Submucosa, Muscularis Externa and Serosa
Submucosa
• Connective tissue
• Blood and lymphatic vessels
Muscularis externa
• Responsible for segmentation and peristalsis
• Smooth muscle
Serosa
• Fibrous covering (visceral peritoneum)
Copyright © 2011 Pearson Education, Inc.

12. ORAL CAVITY
Mouth, teeth, salivary glands and tongue
Copyright © 2011 Pearson Education, Inc.

13. Mouth
• Oral (buccal) cavity
• Bounded by lips, cheeks, palate, and tongue
• Lined with stratified squamous epithelium
Copyright © 2011 Pearson Education, Inc.

14. Oral Cavity
• Lips form anterior border
• Cheeks form lateral border
• Palate forms superior border
• Hard palate: maxillae and palatine bones
• Ridges help create friction
• Soft palate: closes the nasopharynx for swallowing
• Uvula projects down from free edge
Copyright © 2011 Pearson Education, Inc.

15. Tongue
Oral cavity muscle
• Assists in chewing
• forming bolus
• swallowing, speech, and taste
Contains taste buds
Frenulum attaches tongue to the floor of oral cavity
Copyright © 2011 Pearson Education, Inc.

16. Salivary Glands
Extrinsic salivary glands
•Secrete saliva, contains digestive enzymes
1.Parotid gland – buccal area
•
Duct opens near 2nd molar
1.Submandibular – medial mandible
•
Duct opens under tongue
1.Sublingual – anterior to submandibular,
under tongue
Copyright © 2011 Pearson Education, Inc.

17. Tongue
Teeth
Parotid
gland
Ducts of
sublingual
gland
Frenulum
of tongue
Sublingual
gland
Mylohyoid
muscle (cut)
Anterior belly of
digastric muscle
(a)
Submandibular
gland
Parotid duct
Masseter muscle
Body of
mandible (cut)
Posterior belly
of digastric
muscle
Submandibular
duct
Mucous
cells
(b)
Copyright © 2011 Pearson Education, Inc.
Serous cells
forming
demilunes
Figure 22.9

18. Teeth
• 32 permanent teeth
• Covered by enamel – hardest substance in body
• Periodontal ligament
• Forms fibrous joint called a gomphosis
• Incisors - chisel shaped for cutting
• Canine - fanglike
• Premolars (bicuspids) and molars
• Have broad crowns for grinding or crushing
Copyright © 2011 Pearson Education, Inc.

19. Tooth Structure
Copyright © 2011 Pearson Education, Inc.

20. Pharynx and Esophagus
Muscular tubes allow passage of water and
food
Esophagus uses peristalsis to move food
• Travels through diaphragm
• Esophageal sphincter
Copyright © 2011 Pearson Education, Inc.

21. STOMACH AND INTESTINES
Copyright © 2011 Pearson Education, Inc.

22. Stomach Regions
• Cardiac region
• Connects to esophagus
• Fundus
• Dome region below
diaphragm
• Body
• midregion
Copyright © 2011 Pearson Education, Inc.
• Pyloric region:
• antrum, pyloric canal,
and pylorus
• Connects to
duodenum via pyloric
sphincter
• Greater curvature
• Lesser curvature

23. Cardia
Esophagus
Fundus
Body
Lesser
curvature
Lumen
Greater
curvature
Duodenum
(a)
Copyright © 2011 Pearson Education, Inc.
Pyloric
Pyloric
canal
antrum
Pyloric sphincter
(valve) at pylorus
Figure 22.14a

24. Stomach: Layers
• Four tunics
• Three muscular layers and outer tunic (serosa)
• Muscularis externa
1.longitudinal
2.circular
3.oblique
• Covered by omentums
• Greater & lesser
Copyright © 2011 Pearson Education, Inc.

25. Stomach: Tissues
• Mucosa
• Simple columnar epithelium with mucus covering
• Contain gastric pits
• Produce gastric acid = HCl
Copyright © 2011 Pearson Education, Inc.

26. Digestive Processes so Far…
• Physical digestion (chewing)
• Teeth and tongue
• Creates bolus
• Enzymatic digestion
• Enzymes in saliva
• Gastric acid
• Delivers chyme to the small intestine
• Creamy food mass
Copyright © 2011 Pearson Education, Inc.

27. Small Intestine
•
Major organ of absorption
•
Pyloric sphincter to ileocecal valve (2-4 m long)
•
Subdivisions
1. Duodenum : beginning portion
•
connects to stomach via pyloric sphincter
1. Jejunum : intermediate portion(~8ft)
2. Ileum : end portion (~12ft)
•
Connects to large intestine via ileocecal valve
Copyright © 2011 Pearson Education, Inc.

28. Small Intestine
Copyright © 2011 Pearson Education, Inc.

29. Duodenum
• Ducts for gallbladder and pancreases empty into
the hepatopancreatic ampulla
• Bile duct
• Main pancreatic duct
• Enter at the duodenal papilla
• Are controlled by the hepatopancreatic
sphincter
Copyright © 2011 Pearson Education, Inc.

30. Absorption of Small Intestine
• Modification help increase surface area
(absorption):
1. Circular folds (plicae circulares)
2. Villi
3. Microvilli
Copyright © 2011 Pearson Education, Inc.

31. Villi and Microvilli
Villi
• fingerlike extensions of mucosa
• Simple columnar absorptive cells
• With microvilli – increase surface area
• Goblet cells – produce mucus
Copyright © 2011 Pearson Education, Inc.

32. Large Intestine
• Compacts fecal mater (food waist) and
propels it out
• Regions
1. appendix
2. cecum
3. colon
4. rectum
5. anus
Copyright © 2011 Pearson Education, Inc.

33. Colon
• Regions of colon
• Ascending colon
• Right (hepatic) flexure
• Transverse colon
• Left (splenic) flexure
• Descending colon
• Sigmoid colon (S – shaped)
• Contains pocketlike sacks haustrum
Copyright © 2011 Pearson Education, Inc.

34. Large Intestine
Copyright © 2011 Pearson Education, Inc.

35. Rectum and Anus
• Rectum
• Inferior holding chamber
• Anal canal
• Last segment of the large intestine
• Sphincters
• Internal anal sphincter —smooth muscle
• involuntary
• External anal sphincter —skeletal muscle
• voluntary
Copyright © 2011 Pearson Education, Inc.

36. Functions of the Large Intestine
• Major function: propulsion of feces toward the
anus
• Reclaims : vitamins, water, and electrolytes
• Colon is not essential for life
Copyright © 2011 Pearson Education, Inc.

37. Motility of the Large Intestine
• Haustral contractions
• Slow segmenting movements
• Haustra sequentially contract in response to
distension
• Gastrocolic reflex
• Initiated by presence of food in the stomach
• Three slow powerful peristaltic waves per day
in the colon (mass movements)
Copyright © 2011 Pearson Education, Inc.

38. Defecation
• Mass movement of feces into rectum
• Distension initiates defecation reflex
• Parasympathetic signals
• Stimulate contraction of the sigmoid colon and
rectum
• Relax internal anal sphincter
• Conscious control relaxation of external anal
sphincter
Copyright © 2011 Pearson Education, Inc.

39. Rectal valve
Rectum
Hemorrhoidal
veins
Levator ani
muscle
Anal canal
External anal
sphincter
Internal anal
sphincter
Anal columns
Pectinate line
Anal sinuses
Anus
(b)
Copyright © 2011 Pearson Education, Inc.
Figure 22.29b