HBHD 13e Ch19

Copyright © 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 19
The Digestive System

Copyright © 2015 Wolters Kluwer • All Rights Reserved
Overview

Key Terms
absorption esophagus pancreas
bile gallbladder peptic ulcer
chyle hydrolysis peristalsis
chyme ingestion peritoneum
defecation intestine saliva
deglutition lacteal sphincter
digestion liver stomach
duodenum mastication villi
emulsify mesentery

General Structure and Function of the
Digestive System
Learning Objectives
1.Name the three main functions of
the digestive system.
2.Name and locate the two main
layers and the subdivisions of the
peritoneum.
3. Describe the four layers of the
digestive tract wall.

Organs of the Digestive Tract
Learning Objectives
4.Describe the two types of muscular
contractions important in the
digestive process.
5.Name and describe the functions of
the digestive tract organs.
6.Name and locate the different types
of teeth.

The Accessory Organs
Learning Objectives
7.Name and describe the functions of
the accessory organs of digestion.
8. Describe how bile travels into
the digestive tract and functions in
digestion.

Enzymes and the Digestive Process
Learning Objectives
9. Explain the role of enzymes in
digestion, and list enzymes involved
in the digestion of fats,
carbohydrates, proteins and nucleic
acids.
10. Define the term hydrolysis, and
explain its role in digestion.
11.Name the digestion products of
fats, proteins, and carbohydrates.

Absorption
Learning Objective
12.Define absorption, and state how
villi function in absorption.

Control of Digestion and Eating
Learning Objectives
13. Explain nervous control of
digestion and the role of the enteric
nervous system.
14. List four hormones involved in
regulating digestion, and explain the
function of each.

Disorders of the Digestive System
Learning Objective
15. Describe common disorders of
the digestive tract and its accessory
organs.

Case Study
Learning Objective
16. Using the case study,
describe the colonoscopy
procedure and its role in
diagnosing certain colon
disorders.

Word Anatomy
Learning Objective
17. Show how word parts are used to build words
related to digestion.

Digestive System
General Functions
•Digestion
•Absorption
•Elimination
Divisions
•Digestive tract
•Accessory organs

Figure 19-1 The digestive system.
Which accessory organs of digestion secrete into the
mouth?

Digestive System (cont.)
Peritoneum
•Lines the abdominopelvic cavity; covers abdominal
organs
•Layers of the peritoneum
– Parietal
– Visceral
•Subdivisions
– Mesentery
– Mesocolon
– Greater omentum
– Lesser omentum

Figure 19-2 The abdominopelvic cavity and peritoneum.
Which part of the peritoneum is around the small
intestine?

The Wall of the Digestive Tract
•Mucosal membrane, or mucosa
•Submucosa
•Smooth muscle, the muscularis externa
•Serous membrane, or serosa

Figure 19-3 Wall of the digestive tract.
What type of tissue is between the submucosa and the
serous membrane in the digestive tract wall?

✓
Checkpoints
19-1 Why does food have to be digested before cells
can use it?
19-2 What is the name of the large serous membrane
that lines the abdominopelvic cavity and covers the
organs it contains?
19-3 What are the four layers of the digestive
tract wall?

?
Pop Quiz
19.1 Which of the following is the correct order from the
outermost to innermost layer?
A) Submucosa, serous membrane, smooth muscle,
mucous membrane
B) Smooth muscle, serous membrane, mucous membrane,
submucosa
C) Serous membrane, smooth muscle, submucosa,
mucosa
D) Mucous membrane, submucosa, smooth muscle, serous
membrane

?
Pop Quiz Answer
19.1 Which of the following is the correct order from the
outermost to innermost layer?
A) Submucosa, serous membrane, smooth muscle,
mucous membrane
B) Smooth muscle, serous membrane, mucous
membrane, submucosa
C) Serous membrane, smooth muscle, submucosa,
mucosa
D) Mucous membrane, submucosa, smooth muscle,
serous membrane

Organs of the Digestive Tract (cont.)
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine

The Mouth
•Also called oral cavity, processes food by:
– Ingestion
– Mastication
– Mixing with saliva
– Deglutition
•Tongue

Figure 19-4 Gastrointestinal motility.
Which type of motility would be most useful in the
esophagus, where the contents should move quickly?

The Teeth
•Sets of teeth
– Deciduous
– Permanent
•Types of teeth
– Incisors
– Cuspids
– Molars
• Six-year molars
• Premolars
• Third molars or wisdom teeth

The Teeth (cont.)
•Parts of a tooth
– Dentin
– Crown
– Enamel
– Root
•The gum
– Gingiva

Figure 19-5 The mouth and teeth.

The Pharynx
•Also called the throat
•Divisions
– Oropharynx
– Nasopharynx
– Laryngopharynx
•Soft palate
•Uvula

The Esophagus
•Muscular tube.
•Food is lubricated with mucus.
•Peristalsis.
•No digestion occurs here.
•Passes through esophageal hiatus of the diaphragm to
join stomach.

The Stomach
•Structure
– Greater curvature
– Lesser curvature
– Fundus
– Body
– Pylorus
•Sphincters
– Lower esophageal sphincter (LES)
– Pyloric

Figure 19-6 Longitudinal section of the stomach.
Which additional muscle layer is in the wall of the stomach
that is not found in the rest of the digestive tract?

The Stomach (cont.)
•Functions
– Storage pouch
• Rugae
– Secrete substances to form gastric juice
• Hydrochloric acid prepares proteins for digestion.
• Pepsin digests proteins.
– Delivery of chyme to the small intestine

The Small Intestine
•Subdivisions of the small intestine
– Duodenum
– Jejunum
– Ileum
•Functions of the small intestine
– Secretion
– Motility
– Digestion
– Absorption

Figure 19-7 The intestines.
Which portions of the small and large intestines join at
the ileocecal valve?

The Large Intestine
•Subdivisions of the large intestine
– Cecum
• Ileocecal valve
• Appendix
– Ascending colon
– Transverse colon
– Descending colon
– Sigmoid colon
– Rectum
– Anal canal
– Anus

• Functions of the large intestine
– Production of mucus
– Reabsorb some water
– Form feces (stool)
– Defecation

✓
Checkpoints
19-4 Which form of motility occurs in the esophagus? In
the small intestine?
19-5 What type of food is digested in the stomach?
19-6 What are the three divisions of the small intestine?
19-7 How does the small intestine function in the
digestive process?
19-8 What are the functions of the large intestine?

?
Pop Quiz
19.2 Which organ receives food flowing through the
pyloric sphincter?
A) Stomach
B) Jejunum
C) Duodenum
D) Esophagus

?
Pop Quiz Answer
19.2 Which organ receives food flowing through the
pyloric sphincter?
A) Stomach
B) Jejunum
C) Duodenum
D) Esophagus

The Accessory Organs (cont.)
• Release secretions through ducts into the digestive
tract.
• Salivary glands open to mouth.
• Other organs release secretions into the duodenum:
– Liver
– Gallbladder
– Pancreas

Salivary Glands
•Functions
– Secrete saliva
• Moistens food
• Facilitates mastication and deglutition
• Helps keep teeth and mouth clean
•Three pairs:
– Parotid glands
– Submandibular glands
– Sublingual glands

Figure 19-8 Salivary glands.
Which salivary glands are directly below the tongue?

The Liver
•Structure of the liver
– Largest accessory organ
– Right, left lobes
– Portal vein
– Hepatic artery

The Liver (cont.)
•Functions of the liver
– Manufactures bile
– Controls blood glucose levels
– Modifies fats
– Stores some vitamins, iron
– Forms blood plasma proteins
– Destroys old red blood cells
– Synthesizes urea
– Detoxifies harmful substances

The Liver (cont.)
•Bile
– Manufactured in the liver.
– Bile leaves the liver by ducts.
• Common hepatic duct
• Cystic duct
• Common bile duct

Figure 19-9 Accessory organs of digestion.
Into which part of the small intestine do these accessory
organs secrete?

The Gallbladder
•Muscular sac
•Located on inferior surface of the liver
•Stores bile

The Pancreas
•Gland that produces enzymes
•Releases large amounts of sodium bicarbonate (NaHCO3)
•Also functions as an endocrine gland

✓
Checkpoints
19-9 What are the names and locations of the salivary
glands?
19-10 Which accessory organ secretes bile, and what is
the function of bile in digestion?
19-11 What is the role of the gallbladder?
19-12 What accessory organ secretes sodium bicarbonate,
and what is the function of this substance in digestion?

(cont.)
• Fundamental chemical process of digestion
• Enzymes
– Required for digestion
– Catalysts
– Highly specific proteins

(cont.)
Role of Water
•Hydrolysis
•Seven liters of water secreted into the digestive tract
daily
•Produces digestive juices
•Dilutes food
•Used in the chemical process of digestion

Figure 19-10 Hydrolysis.

Digestion, Step by Step
Digestion in the Mouth
•Chews food, mixes with saliva
•Some starches changed to sugars via salivary amylase
Digestion in the Stomach
•Secretes HCl, enzymes
– Denatures proteins
•Secretes mucus
•Forms chyme

Digestion, Step by Step (cont.)
Digestion in the Small Intestine
Most digestion occurs in the duodenum.
•Fats
•Carbohydrates
•Proteins
•Nucleic acids

(cont.)
✓
Checkpoints
19-13 What is an enzyme?
19-14 What process means “splitting by means of water,”
as in digestion?
19-15 Which organ produces the most complete digestive
secretions?

Absorption (cont.)
• Villi in mucosa of the small intestine:
– Arteriole and venule bridged with capillaries
• Capillaries absorb:
– Simple sugars
– Small proteins
– Amino acids
– Simple fatty acids
– Water
• Portal system transports nutrients to the liver.

Absorption (cont.)
• Absorption of fats
– Lacteals absorb fat.
– Fat/lymph mixture (chyle) drains from the small
intestine.
– Chyle merges with lymphatic circulation, enters
blood in veins near the heart.
– The liver further processes absorbed fats.

Absorption (cont.)
• Absorption of vitamins and minerals
– Vitamins and minerals are absorbed from the small
intestine.
– Minerals and some vitamins mix with water and are
absorbed directly into the blood.
– Other vitamins are incorporated in fats and
absorbed along with fats.
– Vitamin K and some B vitamins are produced by
bacterial action in the colon and are absorbed from
the large intestine.

Figure 19-11 Carbohydrates.
Name the two monosaccharide components of sucrose.

Absorption (cont.)
Checkpoint
19-16 What is absorption?
✓

(cont.)
?
Pop Quiz
19.3 Which enzyme digests carbohydrates?
A) Amylase
B) Pepsin
C) Lipase
D) Trypsin

(cont.)
?
Pop Quiz Answer
19.3 Which enzyme digests carbohydrates?
A) Amylase
B) Pepsin
C) Lipase
D) Trypsin

Control of Digestion and Eating (cont.)
Control of Digestion
Two types of control over digestion—nervous and hormonal
•Nervous control of digestion
– Parasympathetic stimulation increases activity
– Sympathetic stimulation decreases activity
•Hormonal control of digestion
– Digestive organs produce hormones
• Gastrin
• Gastric inhibitory peptide (GIP)
• Secretin
• Cholecystokinin (CCK)

Control of Hunger and Appetite
•Hunger
– Desire for food
– Regulated by hypothalamic centers
– Respond to nutrient levels
– Satisfied by adequate meal
•Appetite
– No relationship to need for food
– May not be satisfied by adequate meal

• Short-term regulation of hunger
– Hypothalamus induces hunger sensations
– Ghrelin hormone
– Food consumption
• Long-term regulation of body weight
– Leptin hormone produced by adipocytes

Figure 19-12 Regulation of food intake.

✓
Checkpoints
19-17 What are the two types of control over the digestive
process?
19-18 What is the difference between hunger and
appetite?

?
Pop Quiz
19.4 Which portion of the autonomic nervous system
inhibits digestion?
A) Somatic
B) Parasympathetic
C) Sympathetic
D) Visceral

?
Pop Quiz Answer
19.4 Which portion of the autonomic nervous system
inhibits digestion?
A) Somatic
B) Parasympathetic
C) Sympathetic
D) Visceral

Disorders of the Digestive System
Learning Objective
15. Describe common disorders of the
digestive tract and its accessory
organs.

Disorders of the Digestive System (cont.)
Peritonitis
•Inflammation of the peritoneum following infection of an
organ covered by peritoneum
– Localized
– Generalized
• Examples of causative factors: ruptured appendix,
perforated ulcer, penetrating wound

Diseases of the Mouth and Teeth
•Dental caries
•Gingivitis
•Periodontitis
•Vincent disease
•Oral thrush
•Parotitis

Disorders of the Esophagus and Stomach
•Hiatal hernia and gastric reflux
– Heartburn
– Chronic reflux or gastroesophageal reflux disease
(GERD)
•Nausea and vomiting (emesis)
•Stomach cancer
•Gastritis and peptic ulcer
•Pyloric stenosis

Figure 19-13 Disorders involving the esophagus and stomach.

Intestinal Disorders
•Inflammatory disorders
– Appendicitis
– Inflammatory bowel disease
• Crohn disease
• Ulcerative colitis
– Celiac disease
– Irritable bowel syndrome (IBS)
– Enteritis and gastroenteritis
– Diverticulitis

Intestinal Disorders (cont.)
•Diarrhea
•Constipation
– Spastic constipation
– Flaccid constipation
•Intestinal obstruction
– Intussusception
– Volvulus
•Colon and rectal cancer
– Sigmoidoscope
– Colonoscope

Figure 19-14 Intestinal obstructions.

Figure 19-15 Imaging of the colon.

Cirrhosis and Other Liver Diseases
•Cirrhosis
– Active liver cells replaced by inactive connective
(scar) tissue.
– Alcoholic (portal) cirrhosis is most common type.
– Varicose veins (varices) of the digestive tract.
•Jaundice
•Hepatitis
– Types of hepatitis virus: A, B, C, D, E
•Liver cancer

Gallstones
• Cholelithiasis
• Cholecystitis
Pancreatic Disorders
•Pancreatitis
•Pancreatic cancer

Figure 19-16 Gallstones.

✓
Checkpoints
19-19 What are six common diseases of the mouth
and teeth?
19-20 What does GERD stand for?
19-21 Which two diseases fall into the category of
inflammatory bowel disease?
19-22 What are the two forms of constipation?
19-23 What is hepatitis?
19-24 What is the common term for cholelithiasis?

Effects of Aging and the Digestive System
• Decreased digestive organ activity
– Decrease in saliva
– Tooth loss
– Poor nutrient absorption
– Slowing of peristalsis
• Decreased tissue replacement
• Increased risk of cancer

Case Study
Learning Objective
16. Using the case
study, describe the
colonoscopy procedure and
its role in diagnosing
certain colon disorders.

Case Study (cont.)
Colonoscopy
•Recommended for people over the age of 50 years as
baseline; every 10 years thereafter for low-risk persons
•Used to detect colorectal cancers
•Preparation:
− Nothing to eat from the evening prior to the
examination
− Bowel cleansing
•Types of colonoscopies:
− Flexible lighted endoscope
− Virtual colonoscopy using computerized x-rays
•May remove polyps and abnormal tissue with endoscope

Word Anatomy (cont.)

HBHD 13e Ch19

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HBHD 13e Ch19