SUPPLEMENTAL RESOURCE FOR DIGESTION CHAPTER

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DIGESTION
SUPPLEMENTAL
RESOURCE
POWERPOINT

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4.1 Overview of the Digestive System
Learning Outcomes
1. Identify the major components of the digestive system
and the key functions of each.
2. Describe the distinct layers of the gastrointestinal tract
wall.
3. Identify the location, anatomical name, and function of
each sphincter involved in the digestive system.
4. Explain the differences between chemical and
mechanical digestion.
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The Digestive System
The primary roles of the digestive system are:
• To breakdown food into nutrients
• To absorb nutrients
• To eliminate solid waste products
Digestion is the process of breaking down large food
molecules into nutrients that the body can use
Absorption is the process of nutrient uptake from the
gastrointestinal (GI) tract for transport through the
circulatory or lymphatic systems
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Components of the Digestive System 1
The digestive system has two major components:
• GI tract (also called the digestive tract, alimentary canal,
or gut)
• Hollow, muscular tube ̴16-ft long
• Accessory organs
• Assist functioning of GI tract
• Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
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Components of the Digestive System 2
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Layers of the Wall of the GI Tract3
The wall of the stomach is
the thickest and strongest of
the GI tract
• Has a third type of muscle,
diagonal (oblique) muscle
By relaxing and contracting, the muscle layers:
• Mix substances in the lumen
• Control movement (motility) of material through the tract
Muscle layers of the
stomach
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Sphincters Control the Flow of GI Contents
Sphincters - thickened regions of circular muscle that
control the flow of contents at various points in the GI tract
• When relaxed:
• Passageway opens, GI contents flow through it
• When contracted:
• Passageway closes, flow is restricted
Sphincters help control rates of digestion and absorption
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Mechanical and Chemical Digestion
Mechanical digestion - the physical breakdown of food as it
passes through the GI tract
Chemical digestion - the breakdown of large nutrient
molecules in food into smaller components, primarily by the
action of stomach acid and various enzymes, proteins that
allow chemical reactions to occur at a rapid rate
• Water, cholesterol, minerals and most vitamins do not
need to undergo digestion, as they are absorbed intact
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Assess Your Progress 4.1
1. List the primary and accessory components of the GI
tract.
2. What is a sphincter? Why are sphincters important for the
function of the GI tract?
3. Explain the difference between mechanical and chemical
digestion.
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4.2 The Mouth
Learning Outcomes
1. Describe the mechanical and chemical digestion that
occurs in the mouth.
2. Identify and explain the effects of smell and taste
disorders in humans.
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Digestion Starts in the Mouth
Oral cavity is another term for mouth
• Digestion starts here
Teeth chew (masticate) food
• Mastication is a type of mechanical digestion that prepares
food for swallowing and chemical digestion
Tongue helps direct the bolus into the throat (pharynx), the
section of alimentary canal that connects the nasal cavity
with the top of the esophagus
• Bolus - mass of food that has been chewed and mixed
with saliva and mucus
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Salivary Glands
Salivary glands - structures that produce saliva and secrete
the fluid into the oral cavity
Saliva - the watery fluid that contains mucus and a few
enzymes
• Lysozyme – is an enzyme in saliva that can destroy some
bacteria that are in food or the mouth
• Salivary amylase - enzyme in saliva that begins starch
digestion
• Lingual Lipase - enzyme secreted into saliva that begins
fat digestion
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Location of Salivary Glands
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Taste Buds
Certain molecules in food dissolve in saliva and stimulate
specialized sensory cells in taste buds that help distinguish
six basic tastes:
• Sweet
• Sour
• Salty
• Bitter
• Savory (or umami)
• Fat
Close-up of taste buds
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Sense of Smell
• The sense of smell
(olfaction) contributes to the
ability to taste food
• Airborne chemicals in
chewed food stimulate the
olfactory region of the nasal
passages
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Disorders of Smell
Anosmia - the complete inability to detect odors
Partial or total loss of the sense of smell may be caused by:
• Advancing age
• Obstruction of nasal passageways
• Brain tumors
• Dental disease
• Nasal irritation due to common cold and allergies
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Disorders of Taste
Hypogeusia - the diminished ability to taste substances
Ageusia - the total loss of the ability to taste substances
Taste disorders may be caused by:
• Upper respiratory or middle ear infections
• Radiation treatment and certain medications
• Head injury and degenerative nerve diseases
• Poor dental health
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Fresh Tips - Tasting Foods
People that are unable to taste foods can be encouraged to:
• Use a variety of spices
• Add fruits and vegetables that have interesting textures or
appealing colors to meals and snacks
• Avoid combination dishes that mix together too many
strongly flavored ingredients
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COVID-19
Loss of taste and smell are common symptoms of COVID-19
• Nearly 40% of patients report anosmia and/or ageusia as
their first and/or only symptom
• One study found that 98% of patients had at least some
loss of smell
• Loss of these senses may be permanent in some
individuals
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Did You Know? - Organs Can Also Taste Foods
The gut and pancreas also have taste receptors
• They are nutrient receptors that help the body prepare to
metabolize incoming nutrients
• Evidence suggests that artificial sweeteners may stimulate
these receptors
• May affect our metabolism
• May stimulate hormone release, like real sugar
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Assess Your Progress 4.2
5. Explain what normally happens to food once it enters the
mouth.
6. Describe the key components of saliva.
7. List the taste sensations that human taste buds detect.
8. Discuss disorders of taste and smell, including their
causes.
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4.3 The Esophagus
Learning Outcomes
1. Describe the action of swallowing and what it
accomplishes.
2. Identify the muscular activity that propels a mass of food
through the esophagus.
3. Explain the functions of the two esophageal sphincters.
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The Esophagus
After being swallowed, the food bolus travels through the
esophagus
• Muscular tube that extends about 10 inches from the
pharynx to the upper portion of the stomach
• Its primary function is to transfer a bolus into the stomach
• Entrance is near the larynx (“voice box”)and opening of
trachea (“windpipe”)
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What Happens When You Swallow
The epiglottis is a flap of tough tissue that prevents the food
from entering the larynx and trachea
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Peristalsis
Peristalsis - waves of muscular contractions that help move
material through most of the digestive tract
• Involuntary response
Peristalsis in the
esophagus
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Assess Your Progress 4.3
9. Describe peristalsis and how a bolus of food moves
through the esophagus.
10. Explain the key function of the epiglottis and what would
happen if the epiglottis was not working properly.
11. Under normal circumstances, what keeps stomach
contents from reentering the esophagus?
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4.4 The Stomach
Learning Outcomes
1. Identify the types of cells in the gastric glands and what
each secretes.
2. Describe the kinds of mechanical and chemical digestion
that occur in the stomach.
3. List the components of gastric juice.
4. Discuss factors that may influence stomach emptying.
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Secretions of the Stomach1
The stomach is a muscular sac that stores and mixes food
Gastric glands located in the stomach synthesize and
secrete gastric juice
• A collection of stomach secretions that includes mucus,
hydrochloric acid, intrinsic factor, and digestive enzymes
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Secretions of the Stomach2
Mucous cells secret mucin, a carbohydrate-rich substance
that forms mucus when combined with water
Parietal cells secrete hydrogen and chloride ions (which form
hydrochloric acid, HCl) and intrinsic factor
• Intrinsic factor is a substance necessary for the
absorption of vitamin B‒12
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Secretions of the Stomach3
Chief cells secrete gastric lipase and some chemically
inactive digestive enzymes like pepsinogen
• Pepsinogen is an example of a zymogen, the inactive
form of a digestive enzyme stored in cells until use
• Once secreted, zymogens are converted to their enzyme active
form by stomach acid or other enzymes
G cells secrete gastrin, a hormone that stimulates stomach
motility and gastric gland secretions
• Gastrin is a hormone, a chemical messenger that
conveys information to “target” cells
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Gastric Gland and Its Secretory Cells
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Gastric Gland Cells
Gastric Gland Cells Secretion Major Functions
Mucous Mucus Protects stomach mucosa
from HCl and enzymes
Parietal Components that form
HCl (hydrogen ions [H+]
and chloride ions [Cl−])
Intrinsic factor
Activates pepsinogen,
destroys many food-borne
microbes
Facilitates the absorption of
vitamin B-12
Chief Pepsinogen
Gastric lipase
Digests protein after
conversion to pepsin
Digests small amounts of fat
G cell Gastrin Stimulates stomach motility
and gastric gland activity
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Lower Portion of the Stomach
• The main function of the lower portion of the stomach is
mixing food with gastric juice to form chyme, a semiliquid
mass
• The pyloric sphincter is a circular muscle that regulates
the flow of chyme into the small intestine
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Digestion in the Stomach1
The presence of food in the stomach stimulates peristalsis
• Mixes food with gastric juice
• Some protein and fat in chyme are broken down
Few substances are absorbed in the stomach
• A few drugs, like aspirin
• Alcohol
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Digestion in the Stomach2
HCl is a strong acid that contributes to the low pH of gastric
juice
The pH scale is used to measure the hydrogen ion (H )

concentration of solutions
• Neutral solutions have a pH of 7
• Acidic solutions have a pH value lower than 7
• pH of chyme is 2.0

• Alkaline (basic) solutions have a pH value higher than 7
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The pH Scale
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Acid in the Stomach
Acidic environment of stomach causes:
• Salivary amylase activity to cease
• Lingual lipase to become active
• Pepsinogen to be converted to pepsin, which is the active
enzyme that begins the enzymatic digestion of proteins
Mucus is a slippery secretion that protects the stomach from being
damaged by its acid and digestive enzymes
• Produced by stomach’s mucous cells
• If the layer of mucus breaks down, HCl and gastric enzymes
contact the stomach wall and gastric or peptic ulcers can form
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Stomach Emptying
Stomach empties in about 4 hours following a meal, but this
varies with contents and size of meal
• Watery meals spend less time in stomach, fatty and high-
fiber meals spend more
• Larger meals take longer to empty than smaller ones
Dumping syndrome - a disorder that occurs when chyme
flows too rapidly from the stomach into the small intestine
• Often develops after surgeries of the esophagus or
stomach
• Changing the types of food eaten, eating smaller meals,
and taking certain medications can help
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Fresh Tips - Sense of Stomach Fullness
The longer a food stays in the stomach, the more full the
person will feel after eating
Plant foods that contain fiber often delay stomach emptying
Eat a high-fiber food for breakfast to increase your sense of
stomach fullness
• Bowl of oatmeal
• Whole-grain bagel
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Assess Your Progress 4.4
12. Identify the four different gastric gland cells and list their
secretions.
13. Describe the digestive processes that occur in the
stomach.
14. Explain how the stomach protects itself from digestion.
What conditions might occur if this protection fails?
15. List factors that influence stomach emptying.
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4.5 The Small Intestine
Learning Outcomes
1. Identify the three sections of the small intestine and
indicate where most nutrient digestion and absorption
occurs.
2. Describe the functions of the accessory organs of the
digestive system.
3. Discuss the functions of intestinal villi and microvilli.
4. List the key GI hormones and describe their functions in
digestion.
5. Compare and contrast the ways nutrients are absorbed.
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The Small Intestine
The small intestine is the primary site for nutrient digestion
and absorption
It has three sections:
• Duodenum - first segment of the small intestine
• Jejunum - middle segment of the small intestine
• Ileum - last segment of the small intestine
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Parts of the Small Intestine
Chyme moves out of the
ileum into the large
intestine, passing through
the ileocecal sphincter,
which is a circular muscle
that controls the rate of
emptying undigested
material into the large
intestine
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Accessory Organs1
The liver, gallbladder, and
pancreas are accessory
organs of the
gastrointestinal system
• Play a major role in
digestion as they secrete
important substances
into the GI tract.
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Accessory Organs2
The liver:
• Processes and stores many nutrients
• Synthesizes cholesterol
• Makes bile, a greenish-yellow fluid stored in the
gallbladder until it is needed for fat digestion and
absorption
The gallbladder stores and concentrates bile
The pancreas produces and secretes digestive enzymes and
bicarbonate ions (HCO3
-) to neutralize the highly acidic
chyme coming in from the stomach.
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Digestion in the Small Intestine1
The small intestine is the primary site of chemical and
mechanical digestion
Each day it secretes ~1,440 mL of fluids containing mucus
and enzymes
• Provide lubrication to small intestine walls
• Facilitate passage of chyme
• Protect mucosa from damage as material moves through
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Digestion in the Small Intestine2
Cells in the mucosa of duodenum and jejunum release
secretin
• Secretin - hormone that stimulates the pancreas and liver
to release a bicarbonate-rich solution into the small
intestine
Bicarbonate neutralizes the pH of chyme
• Protects small intestine mucosa from stomach acid effects
• Raises pH, creating favorable environment for the activity
of pancreatic and intestinal enzymes
• These enzymes break down large nutrient molecules
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Digestion in the Small Intestine3
As fat and partially digested proteins enter the duodenum,
cells in the mucosa secrete cholecystokinin
• Cholecystokinin (CCK) - hormone that stimulates the
gallbladder to contract and the pancreas to release
pancreatic juice into the small intestine
• Gallbladder releases bile into duodenum
• Facilitates fat digestion and absorption
• Pancreatic juice is enzyme-rich
CCK also reduces gastric secretions and motility
• Helps to control chyme flow from stomach
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Major Pancreatic and Intestinal Enzymes
Enzyme Source Action
Pancreatic amylase Pancreas Digests starch
Pancreatic lipase Pancreas Digests fat
Trypsin, chymotrypsin Pancreas Partially digests proteins
Carboxypeptidase Pancreas Breaks down certain
partially digested
proteins
Nuclease Pancreas Digests DNA and RNA
into nucleotides
Peptidase Small intestine Breaks down certain
partially digested
proteins
Sucrase, maltase,
lactase
Small intestine Breaks down certain
sugars into simpler
sugars
Intestinal lipase Small intestine Digests fat
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Actions of Key Digestive Hormones in the GI Tract
Hormone
Primarily
Released
from
Secreted in
Response to Key Actions
Gastrin Stomach Food entering the
stomach
Triggers parietal cells to release
HCl and chief cells to release
pepsinogen
Stimulates stomach and small
intestinal motility
Secretin Small intestine Acidic chyme
entering the
duodenum and first
part of jejunum
Stimulates the release of a
bicarbonate-rich solution from the
liver and pancreas
Cholecysto-
kinin (CCK)
Small intestine Fat and breakdown
products of proteins
(peptides) entering
the small intestine
Stimulates release of bile from the
gallbladder into the small intestine
Stimulates the release of pancreatic
enzymes, decreases stomach
secretions, and slows stomach
motility
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Villi and Surface Area
The small intestine mucosa is highly folded and covered by villi
(singular: villus)
• Villi - tiny, fingerlike projections of the small intestinal mucosa
that are involved in nutrient digestion and absorption
The folds and villi provide a surface area of ~200 m2
• Enable efficient nutrient absorption
Each villus has an outer layer of absorptive cells called
enterocytes
• The part of the enterocyte exposed to chyme contains
microvilli, tiny, hair like projections that form “the brush border”
of an enterocyte
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Small Intestinal Absorption
• Microvilli contain “brush border enzymes” that help digest
protein and carbohydrates
• Enterocytes remove nutrients from chyme and enable
them to enter the intestinal blood or lymph vessels
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Nutrient Absorption
Depending on various
factors, including type and
amount of nutrient, nutrient
absorption can occur by:
• Simple diffusion
• Facilitated diffusion
• Active transport
• Osmosis
• Endocytosis
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Nutrient Transport
The core of the villus contains:
• Arteriole (tiny arteriole)
• Blood capillary network
• Venule ( a vein)
• Lacteal - a vessel of the lymphatic system
Nutrients from chyme are absorbed into either the capillary
network or the lacteal
Water-soluble nutrients and certain fats are absorbed into the
capillary network
• Travel to the liver via the hepatic portal vein
Most lipids undergo specialized processing before they enter the
lacteals
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Bioavailability of Nutrients
Bioavailability is the amount of a nutrient that can be
effectively digested, absorbed, and used by the body
• Important when determining the true nutritional value of
foods
• Affected by:
• Dietary factors, including chemical form of the nutrient, how food
was processed and prepared, other foods and nutrients consumed
around same time
• Physiological factors, including individual differences in digestion,
nutrient and health status, age, sex, ethnicity
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Assess Your Progress 4.5
16. List the three primary sections of the small intestine and identify
where most nutrient digestion and absorption occurs.
17. Where is bile synthesized and stored?
18. Explain the importance of the pancreas as an accessory organ for
nutrient digestion.
19. Discuss the three major gut hormones, including the tissues from
which they are released, the factors causing their release, and their
key actions.
20. Explain how the structure of villi increases the surface area
available for absorption.
21. Identify the five ways that nutrients can be absorbed by enterocytes.
22. Describe some of the dietary and physiological factors that affect
nutrient bioavailability.
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4.6 The Large Intestine
Learning Outcomes
1. Identify the sections of the large intestine.
2. Describe the role of the large intestine in nutrient
absorption and waste elimination.
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Parts of the Large Intestine
After moving through the ileocecal
sphincter, unabsorbed water and
undigested material enter the:
• Cecum
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon
• Rectum
• Last section of the large intestine
• Anus
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Functions of the Large Intestine1
Other than water and some minerals, little additional
absorption takes place.
The large intestine mucosa contains numerous goblet-cells
that secrete mucus, its primary secretion
• Primary secretion of the large intestine
As food residue passes through the colon, water is absorbed,
forming semisolid feces
• Consist mostly of water, resident intestinal bacteria and
undigested fiber
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Functions of the Large Intestine2
Fecal material moves through colon by muscular
contractions until reaching the internal anal sphincter, the
circular muscle that allows feces to be moved from the
sigmoid colon into the rectum
• Under involuntary control
• Increased pressure causes its relaxation, allowing
passage of feces into rectum causing the urge to defecate
Defecation is expulsion of fecal material from the body
• Occurs through the external anal sphincter
• Under voluntary control
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Summary of GI Tract Organs and Functions
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Assess Your Progress 4.6
23. List the main sections of the large intestine from the
ileocecal sphincter to the anus.
24. What is the primary function of the large intestine?
25. Trace the pathway of food from the mouth to the anus,
including key organs and their functions.
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4.7 Microbes in the Digestive Tract
Learning Outcomes
1. Discuss the importance of bacteria in the digestive tract.
2. Describe the role of prebiotics and probiotics in human
health, and provide an example of each.
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Gut Microbiota
A healthy person generally has few microbes in their small
intestine, especially in the duodenum and jejunum.
The large intestine hosts vast numbers of various types of
bacteria and other microorganisms
• Gut microbiota - Populations of microorganisms that
reside in the large intestine
The composition of the gut microbiota varies due to individual
differences in diet, genetics, age, environmental conditions,
use of medications
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Actions of Intestinal Bacteria
The gut microbiota provides benefits to the human host
• Help digest foods that are indigestible to humans, like fiber
• Produce important molecules including vitamins and
neurotransmitters (serotonin and GABA)
• Protect the body by warding off pathogens, eliminating
toxins, helping develop the immune system, controlling
inflammation
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Gut Microbiota in Health and Disease
Source: Valdes AM and others: Role of the gut microbiota in nutrition and health. BMJ 361,
k2179, 2018. DOI:10.1136/bmj.k2179. https://www.bmj.com/content/361/bmj.k2179.full
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Did You Know? - The Body’s Microbiota
The gut microbiota is not the only microbiota in the body
• Every surface of the body that comes in contact with the
outside world is populated with microbes
• Our skin microbiota can protect us from unwanted
pathogens
• It also contributes to our body odor and can attract or repel
mosquitoes
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Probiotics and Prebiotics
Probiotics are live, beneficial, microbes that promote good
health for their human hosts, or products that contain such
microbes (for example Lactobacillus and Bifidobacterium)
• Reliable scientific evidence for their long-term safety and
effectiveness is still being collected and evaluated
Prebiotics are substances in food that promote the growth of
beneficial microbes
• Different fibers found in various foods, including fruits,
most vegetables, some grains
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Fermented Foods
Fermented foods are foods made through the controlled
activity of live microbes to change their chemical composition
• An alternative way to consume probiotics and prebiotics
• May be better sources of probiotic bacteria than capsules
• Fermentation preserves foods and enhances their
nutritional quality
• Some experts suggest they should be added to national dietary
recommendations
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Fecal Microbiota Transplantation
Fecal microbiota transplantation (FMT) is the introduction
of stool from one person into another person’s large intestine
• Used to treat Clostridium difficile (C. diff) infection
• May benefit people with chronic intestinal disorders
• Ulcerative colitis
• Crohn’s disease
• More research is needed to determine its long-term safety
and effectiveness
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Assess Your Progress 4.7
26. Summarize the roles of the gut microbiota in human
health.
27. Explain the difference between a probiotic and a
prebiotic, and give an example of each.
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Sustainability and Your Diet
Composting is a way to use bacteria to beak down food
waste to recycle food’s nutrients back into the soil
• Waste materials, like leftover food and tree trimmings, are
combined with a source of bacteria in appropriate
containers
• Wood chips are added to speed up breakdown
• Exposure to high temperatures kills pathogens and allows
compost to “mature”
Many colleges are expanding their composting efforts to
raise awareness and reduce landfill waste
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4.8 Common Digestive Tract Disorders
Learning Outcomes
1. Describe common gastrointestinal health problems.
2. Discuss preventative measures and treatments for
gastroesophageal reflux, vomiting, gastric ulcer,
constipation, diarrhea, irritable bowel syndrome
inflammatory bowel disease, diverticulosis, and
diverticulitis.
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Digestive Disorders
60 to 70 million Americans in the U.S. suffer from digestive
disorders
• Each year, over 13 million require hospitalization
• Treatment accounts for a significant percentage of all
surgical procedures
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Gastroesophageal Reflux
• Gastroesophageal reflux (GER) - commonly called
heartburn or acid reflux; is a burning sensation generally
felt in the back of the throat and upper chest that results
from the passage of acidic contents from the stomach into
the esophagus
• Gastroesophageal reflux disease (GERD) - a chronic
condition characterized by frequent heartburn that can
damage the esophagus
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Factors That Contribute to or Worsen GER
• Having excess body fat, especially around the waistline
• Drinking alcohol and coffee
• Overeating
• Eating chocolate, peppermint, and greasy or spicy foods
• Eating foods that contain tomatoes
• Smoking or inhaling secondhand smoke
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Acid Reflux Damage
If not treated properly, GERD irritates the lining of the
esophagus and contributes to the development of
esophageal ulcers
David M. Martin, M. D./Science Source
• An endoscopic view of the
esophagus near the
opening of the stomach
• The reddened areas are
signs of damage caused
by acid reflux
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Recommendations to Reduce the Risk of Heartburn
1. Lose excess body weight.
2. Do not lie down within 3 hours after eating a meal.
3. Do not overeat at mealtimes.
4. Avoid smoking cigarettes or breathing secondhand
smoke.
5. Elevate the head of the bed so it is about 6 to 8 inches
higher than the foot of the bed.
6. Do not wear tight belts or clothes with tight waistbands.
7. Learn to recognize foods and beverages that cause
heartburn.
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Vomiting1
Vomiting is an effective body strategy for expelling noxious
substances from the body
• Prevents potentially harmful foods and beverages from
entering the small intestine
• Can also be a response to:
• Blocked intestines
• Head injury
• Motion and morning sickness
• Migraine headaches
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Vomiting2
Vomiting generally
does not last longer
than 24 hours
Repeated vomiting can
lead to dehydration
• Children are more
vulnerable
Vomiting Danger Signs
1. Lasts longer than a few hours
(children under 6 years of age)
2. Lasts longer than a day (people
over 6 years of age)
3. Is accompanied by:
Blood in vomit (looks like coffee
grounds)
Signs of dehydration
Diarrhea
Fever
Weakness
Headache or stiff neck
Severe abdominal pain
Confusion or decreased alertness
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Gastric Ulcer
A gastric, or peptic, ulcer is a sore that occurs in the lining of
the stomach or the upper small intestine
• HCl digests the lining of the stomach mucosa
• Infection with Helicobacter pylori (H. pylori) is responsible
for most cases
• Symptoms include:
• Deep, dull upper abdominal pain
• Feeling of fullness 2 hours after eating
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Factors That Increase the Risk of Gastric Ulcers
• Infection with H. pylori
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Alcohol consumption
• Genetics
• Smoking
• Excess stomach acid production
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Helicobacter pylori
Science Photo Library/Getty Images
People infected with H.
pylori are given antibiotics,
as well as medications that
reduce stomach acid
production
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Constipation
Constipation - infrequent bowel movements and feces that
are difficult to eliminate
• Can be caused by
• Antibiotic exposure
• Certain medications, including opiates
• Lack of dietary fiber
• Low water intake
• Psychological disturbances like anxiety and depression
• Changes in typical routine like a long trip or major surgery
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Hemorrhoids
Hemorrhoids - clusters of
small veins in the anal
canal
Chronic constipation and
straining during bowel
movements play a role in
the development of
inflamed and swollen
hemorrhoids
• May protrude out of the
anus, causing pain,
itching, and bleeding
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Diarrhea
Diarrhea is a condition characterized by frequent, loose or
watery bowel movements
• Abnormal balance of water secreted into or absorbed from
the large intestine leads to excess water remaining
• Severe cases cause mineral losses and dehydration
• Children and older adults are more vulnerable
• Most cases are the result of body’s attempt to flush out
bacterial or viral infections
• Infectious agents can also produce toxic substances that increase
GI tract motility, reducing water absorption
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Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) - a condition characterized by
intestinal cramps and abnormal bowel function
• Diarrhea, constipation, or alternating episodes of both
• Women are more likely to suffer than men
• Cause is unknown
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Dietary Changes to Treat IBS Symptoms
• Avoid or eliminate foods containing gluten, such as wheat,
rye and barley products
• Reduce foods containing carbohydrates that are more
difficult to digest, such as dairy products, wheat products,
and some fruits and vegetables
• Increase consumption of dietary fiber from some fruits,
vegetables and gluten-free grains
• Reduce or eliminate foods and beverages that contain
large amounts of artificial sweeteners
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Inflammatory Bowel Disease 1
Inflammatory bowel disease (IBD) - a condition that is
characterized by chronic inflammation of the GI tract
• Autoimmune disorder of unknown cause
• Typical signs and symptoms:
• Diarrhea
• Rectal bleeding
• Abdominal cramps
• Fever
• Unintentional weight loss
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Inflammatory Bowel Disease 2
• Crohn’s disease - a type of IBD that causes inflammation
and abscesses to form in the superficial mucosa of the
small and large intestine
• Ulcerative colitis (UC) - a type of IBD that causes deep
ulcers to form in the mucosa of the colon and rectum
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Comparison of IBS and IBD
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Diverticulosis and Diverticulitis
Diverticula - Small pouches that form in the inner lining of
the large intestine and push through weak regions of the
colon wall
• Diverticulosis - the condition characterized by the
presence of diverticula
• Diverticulitis - the condition characterized by inflamed
diverticula
• Bacteria or feces become trapped in the little pouches
• Blood vessels may become damaged and cause rectal bleeding
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Assess Your Progress 4.8
28. Identify potential health effects of untreated, frequent
gastrointestinal reflux disease (GERD).
29. What factors contribute to the development of gastric
ulcers?
30. Explain the differences between constipation and
diarrhea and the consequences if they are untreated.
31. What dietary recommendations would you provide to a
person experiencing irritable bowel syndrome (IBS)?
32. Describe the differences between Crohn’s disease and
ulcerative colitis.
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