1. Two groups of organs Digestive System
1. Alimentary canal (gastrointestinal or GI tract)
Mouth to anus
Digests food and absorbs fragments
Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
© 2013 Pearson Education, Inc.

2. 2. Accessory digestive organs
Digestive System
2. Accessory digestive organs
Teeth, tongue, gallbladder
Digestive glands
Salivary glands
Liver
Pancreas
© 2013 Pearson Education, Inc.

3. Ingestion Food Mechanical breakdown Pharynx Esophagus Chewing (mouth)
Figure Gastrointestinal tract activities.
Ingestion
Food
Mechanical
breakdown
Pharynx
Esophagus
Chewing (mouth)
Churning (stomach)
Propulsion
Segmentation
(small intestine)
• Swallowing
(oropharynx)
• Peristalsis
(esophagus,
stomach,
small intestine,
large intestine)
Digestion
Stomach
Absorption
Lymph
vessel
Small
intestine
Blood
vessel
Large
intestine
Mainly H2O
Feces
Anus
Defecation
© 2013 Pearson Education, Inc.

4. Figure 23.3 Peristalsis and segmentation.
From
mouth
Peristalsis: Adjacent segments of alimentary tract organs alternately contract and relax, moving food along the tract distally.
Segmentation: Nonadjacent segments of alimentary tract organs alternately contract and relax, moving food forward then backward.
Food mixing and slow food propulsion occur.
© 2013 Pearson Education, Inc.

5. GI Tract Regulatory Mechanisms
Mechano and chemoreceptors
Respond to stretch, changes in osmolarity and pH, and presence of substrate and end products of dig
Initiate reflexes that
Activate or inhibit digestive glands
Stimulate smooth muscle
© 2013 Pearson Education, Inc.

6. Central nervous system
Figure Neural reflex pathways initiated by stimuli inside or outside the gastrointestinal tract.
External stimuli
(sight, smell, taste,
thought of food)
Central nervous system
Long reflexes
Visceral afferents
Extrinsic visceral (autonomic)
efferents
Chemoreceptors,
osmoreceptors, or
mechanoreceptors
Local (intrinsic)
nerve plexus
("gut brain")
Internal
(GI tract)
stimuli
Effectors:
Smooth muscle
or glands
Short reflexes
Gastrointestinal
wall (site of short
reflexes)
Response:
Change in
contractile or
secretory activity
Lumen of the
alimentary canal
© 2013 Pearson Education, Inc.

7. Peritoneum - serous memb of abd cavity
Visceral peritoneum on surface of organs
Parietal peritoneum lines body wall
Peritoneal cavity
Between two peritoneums
Fluid lubricates mobile organs
Peritonitis
Abdominal adhesions are bands of fibrous scar tissue that form on organs in the abdomen, causing the organs to stick to one another or to the wall of the abdomen.
© 2013 Pearson Education, Inc.

8. Two schematic cross sections of abdominal cavity illustrate
Figure 23.5a The peritoneum and the peritoneal cavity.
Abdominopelvic
cavity
Vertebra
Dorsal
mesentery
Parietal
peritoneum
Ventral
mesentery
Visceral
peritoneum
Peritoneal
cavity
Alimentary
canal organ
Liver
Two schematic cross sections of abdominal cavity illustrate
the peritoneums and mesenteries.
© 2013 Pearson Education, Inc.

9. Peritoneum and Peritoneal Cavity
Mesentery - double layer of peritoneum
Routes for BV, lymphatics, and nerves
Holds organs in place; stores fat
© 2013 Pearson Education, Inc.

10. Alimentary canal organ in a retroperitoneal position
Figure 23.5b The peritoneum and the peritoneal cavity.
Mesentery
resorbed
and lost
Alimentary
canal organ
Alimentary canal organ in
a retroperitoneal position
Some organs lose their mesentery and move,
becoming retroperitoneal, during development.
© 2013 Pearson Education, Inc.

11. Blood Supply: Splanchnic Circulation
Branches of aorta
Hepatic, splenic, gastric, mesenteric arteries
Hepatic portal circulation
© 2013 Pearson Education, Inc.

12. Myenteric nerve plexus
Figure Basic structure of the alimentary canal.
Intrinsic nerve plexuses
Myenteric nerve plexus
Submucosal nerve plexus
Glands in
submucosa
Mucosa
Epithelium
Lamina propria
Muscularis
mucosae
Submucosa
Muscularis externa
Longitudinal muscle
Circular muscle
Serosa
Epithelium
(mesothelium)
Nerve
Connective tissue
Artery
Gland in mucosa
Lumen
Vein
Duct of gland outside
alimentary canal
Mucosa-associated
lymphoid tissue
Mesentery
Lymphatic vessel
© 2013 Pearson Education, Inc.

13. Enteric Nervous System
Intrinsic nerve supply – enteric neurons
Major nerves to GI tract; control motility
Submucosal nerve plexus
Regulates glands and smooth muscle in mucosa
Myenteric nerve plexus
Controls GI tract motility
Sympathetic inhibit dig activities
Parasympathetic stimulate dig activities
© 2013 Pearson Education, Inc.

14. Sagittal section of the oral cavity and pharynx
Figure 23.7a Anatomy of the oral cavity (mouth).
Soft
palate
Palatoglossal
arch
Uvula
Hard
palate
Oral cavity
Palatine
tonsil
Tongue
Oropharynx
Lingual tonsil
Epiglottis
Hyoid bone
Laryngopharynx
Esophagus
Trachea
Sagittal section of the oral cavity and pharynx
© 2013 Pearson Education, Inc.

15. Upper lip Gingivae (gums) Superior labial frenulum Palatine raphe
Figure 23.7b Anatomy of the oral cavity (mouth).
Upper lip
Gingivae
(gums)
Superior
labial
frenulum
Palatine
raphe
Palatoglossal
arch
Hard
palate
Palatopharyngeal
arch
Soft
palate
Uvula
Palatine
tonsil
Posterior wall
of oropharynx
Tongue
Sublingual
fold with
openings of
sublingual
ducts
Lingual frenulum
Opening of
Submandibular
duct
Gingivae (gums)
Oral vestibule
Inferior labial
frenulum
Lower lip
Anterior view
© 2013 Pearson Education, Inc.

16. Epiglottis Palatopharyngeal arch Palatine tonsil Lingual tonsil
Figure Dorsal surface of the tongue, and the tonsils.
Epiglottis
Palatopharyngeal
arch
Palatine tonsil
Lingual tonsil
Palatoglossal
arch
Terminal sulcus
Foliate papillae
Vallate papilla
Medial sulcus
of the tongue
Dorsum of tongue
Fungiform papilla
Filiform papilla
© 2013 Pearson Education, Inc.

17. Figure 23.9 The salivary glands.
Tongue
Teeth
Parotid
gland
Ducts of
sublingual
gland
Parotid duct
Masseter muscle
Frenulum
of tongue
Body of mandible (cut)
Sublingual
gland
Posterior belly of
digastric muscle
Mylohyoid
muscle (cut)
Submandibular
duct
Anterior belly of
digastric muscle
Submandibular
gland
Mucous cells
Serous cells
forming demilunes
© 2013 Pearson Education, Inc.

18. Two types of secretory cells
Salivary Glands
Two types of secretory cells
Serous cells
Watery, enzymes, ions, bit of mucin
Mucous cells
Mucus
Parotid, submandibular glands mostly serous; sublingual mostly mucous
© 2013 Pearson Education, Inc.

19. 97–99.5% water, slightly acidic
Composition of Saliva
97–99.5% water, slightly acidic
Electrolytes—Na+, K+, Cl–, PO4 2–, HCO3–
Salivary amylase and lingual lipase
Mucin
Metabolic wastes—urea and uric acid
Lysozyme, IgA, defensins, and a cyanide compound protect against microorganismsa
PLAY
Animation: Rotating head
© 2013 Pearson Education, Inc.

20. Control of Salivation 1500 ml/day activated by parasympathetic when
Ingested food stimulates chemoreceptors and mechanoreceptors in mouth 
Salivatory nuclei in brain stem send impulses along parasympathetic fibers in cranial nerves VII and IX
Sympathetic inhibits salivation results xerostomia
© 2013 Pearson Education, Inc.

21. © 2013 Pearson Education, Inc.

22. Primary and permanent dentitions formed by age 21
Teeth
Primary and permanent dentitions formed by age 21
20 deciduous teeth erupt (6–24 months of age)
Roots resorbed, teeth fall out (6–12 years of age) as permanent teeth develop
32 permanent teeth
All but third molars in by end of adolescence
Third molars at 17–25, or may not erupt
© 2013 Pearson Education, Inc.

23. © 2013 Pearson Education, Inc.

24. Figure 23.10 Human dentition.
Incisors
Central (6–8 mo)
Lateral (8–10 mo)
Canine (eyetooth)
(16–20 mo)
Molars
First molar
(10–15 mo)
Deciduous
(milk) teeth
Second molar
(about 2 yr)
Incisors
Central (7 yr)
Lateral (8 yr)
Canine (eyetooth)
(11 yr)
Premolars
(bicuspids)
First premolar
(11 yr)
Second premolar
(12–13 yr)
Molars
First molar (6–7 yr)
Second molar
(12–13 yr)
Third molar
(wisdom tooth)
(17–25 yr)
Permanent
teeth
© 2013 Pearson Education, Inc.

25. Shorthand indicator of number/position of teeth
Dental Formulas
Shorthand indicator of number/position of teeth
Ratio of upper to lower teeth for 1/2 of mouth
Primary:
Permanent:
© 2013 Pearson Education, Inc.

26. Crown - exposed part above gingiva (gum)
Tooth Structure
Crown - exposed part above gingiva (gum)
Covered by enamel—hardest substance in body (calcium salts and hydroxyapatite crystals)
Enamel-producing cells degenerate when tooth erupts  no healing if decay or crack
Root - portion embedded in jawbone
Connected to crown by neck
© 2013 Pearson Education, Inc.

27. Cement - calcified connective tissue Periodontal ligament
Tooth Structure
Cement - calcified connective tissue
Covers root; attaches to periodontal ligament
Periodontal ligament
Fibrous joint called gomphosis
Anchors tooth in socket
Gingival sulcus - groove where gingiva borders tooth
© 2013 Pearson Education, Inc.

28. Dentin - bonelike material under enamel
Tooth Structure
Dentin - bonelike material under enamel
Maintained by odontoblasts of pulp cavity
Pulp cavity - surrounded by dentin
Pulp - connective tissue, BV, and nerves
Root canal - as pulp cavity extends to root
Apical foramen at proximal end of root
Entry for blood vessels, nerves, etc.
© 2013 Pearson Education, Inc.

29. Enamel Dentin Cement Root canal Bone
Figure Longitudinal section of a canine tooth within its bony socket (alveolus).
Enamel
Dentin
Crown
Dentinal
tubules
Pulp cavity
(contains
blood vessels
and nerves)
Neck
Gingival
sulcus
Gingiva
(gum)
Cement
Root canal
Root
Periodontal
ligament
Apical
foramen
Bone
© 2013 Pearson Education, Inc.

30. Tooth and Gum Disease
Dental caries (cavities) - demineralization of enamel and dentin from bacterial action
Dental plaque (film of sugar, bacteria, and debris) adheres to teeth
Acid from bacteria dissolves calcium salts
Proteolytic enzymes digest organic matter
Prevention: daily flossing and brushing
© 2013 Pearson Education, Inc.

31. Tooth and Gum Disease Gingivitis
Plaque calcifies to form calculus (tartar)
Calculus disrupts seal between gingivae and teeth
Bacteria infect gums
© 2013 Pearson Education, Inc.

32. Periodontitis -Immune cells attack
Tooth and Gum Disease
Periodontitis -Immune cells attack
Destroy periodontal ligament
Activate osteoclasts  dissolve bone
Tooth loss; may promote atherosclerosis
Risk factors ?
© 2013 Pearson Education, Inc.