Transcript Peptic Ulcers - Mount Carmel Academy

Chapter 14 – Part 5
The Digestive System
Digestive Activities of the Mouth
1. Mechanical Breakdown
 Food is physically broken down by chewing
2. Chemical Digestion – Begins
carbohydrate digestion
 Food is mixed with saliva
 Breaking of starch into maltose by salivary
amylase
Activities of the Pharynx and
Esophagus
 These organs have
no digestive function
 Serve as
passageways to the
stomach
 Food propulsion
only
Deglutition (Swallowing)
 Deglutition – Swallowing
 Complicated process that includes
the coordinated efforts of the tongue,
soft palate, pharynx, and esophagus
 It has two phases:
1. Buccal Phase
2. Pharyngeal-Esophageal Phase
Deglutition (Swallowing)
 Buccal Phase
 Voluntary
 Occurs in the mouth
 Food is formed into a bolus (food mass)
 The bolus is forced into the pharynx by the
tongue
Deglutition (Swallowing)
 Pharyngeal-esophageal phase
 Involuntary transport of the bolus through
the pharynx and esophagus
 All passageways except to the stomach are
blocked
 Tongue blocks off the mouth
 Soft palate (uvula) blocks the
nasopharynx
 Epiglottis blocks the larynx
Deglutition (Swallowing)
 Pharyngeal-esophogeal phase (cont.)
 Peristalsis moves the bolus toward the
stomach
 When food reaches the end of the
esophagus, it presses against the
cardioesophageal sphincter, causing it to
open, and the food enters the stomach
Deglutition (Swallowing)
Food Breakdown in the Stomach
 Secretion of gastric juice
 Regulated by neural and hormonal
factors
 Under normal conditions, 2-3 liters are
produced each day
 Sight, smell, and taste of food increase
the secretion of gastric juice
 Presence of food or falling pH causes
the release of the hormone gastrin
Food Breakdown in the Stomach
 Gastrin causes the stomach glands to
produce:
1. Protein-digesting enzymes
(pepsinogens)
2. Mucus
3. Hydrochloric acid
Acid Environment in the Stomach
 Hydrocholoric acid makes the stomach
contents very acidic
 The extremely acidic environment is
necessary because it:
1. Activates pepsinogen to pepsin for
protein digestion
2. Provides a hostile environment for
microorganisms
Heartburn
 Heartburn – Pain caused
when gastric juice backs up
into the esophagus when the
cardioesophageal sphincter fails to close
tightly
 The esophagus has little mucus protection
(unlike the stomach)
 If uncorrected, it can cause inflammation of
the esophagus (esophagitis) and even an
ulceration to the esophagus
What are Peptic Ulcers?
 Peptic Ulcers – Craterlike
erosion in the mucosa of any
part of the GI tract that is
exposed to the secretions of the stomach
 Affects 1 out of every 8 Americans
 Most occur in the pyloric part of the stomach
(gastric ulcers) or the first part of the
duodenum (duodenal ulcers)
 Develop most frequently between the ages of
50-70 years
Peptic Ulcers: Symptoms
 After developing, they tend to recur healing, then flaring up periodically - for
the rest of one’s life if not treated
 Produce a gnawing or burning pain in
the abdomen that appears 1-3 hours
after a meal and is relieved by eating
 Other symptoms: loss of appetite,
burping, nausea, and vomiting
Peptic Ulcers: Cause
 Cause remains incompletely understood
 A stressful lifestyle does seem to aggravate
existing ulcers
 Recent studies indicate that many ulcers
are actually caused by a strain of acidresistant bacteria (Helicobacter pylori)
Peptic Ulcers: Treatment
1. First step is to avoid smoking,
alcohol, ibuprofen, and aspirin (all
aggravate ulcers)
2. Antacid drugs to neutralize the stomach
acids
3. Triple drug therapy to promote healing
and prevent reccurence
Digestion and Absorption in the
Stomach
 Other than the beginning of protein
digestion, little chemical digestion occurs
in the stomach
 Protein digestion enzymes
1. Pepsin – an active protein digesting
enzyme
2. Rennin – works on digesting milk protein
 Virtually no absorption occurs in the
stomach (Exception: alcohol and aspirin)
Food Propulsion in the Stomach
 Food must first be well mixed
 Rippling peristalsis occurs in the lower
stomach
Propulsion in the Stomach
 The pylorus meters out chyme into the
small intestine (30 ml at a time)
 The stomach empties in four to six
hours
Vomiting
 Vomiting – Essentially a reverse
peristalsis occurring in the stomach
 Accompanied by contraction of the
abdominal muscles and the diaphragm,
which increases the pressure on the
abdominal organs
 Caused by:
1. Local irritation of the stomach such as
food poisoning
2. Disturbances of the equilibrium
apparatus of the inner ear
Digestion in the Small Intestine
 Food entering the small
intestine is only partially
digested
 Carbohydrate and
protein digestion have
been started
 Virtually no fats have been digested up to
this point
 By the time food reaches the end of the
small intestine, chemical digestion is
complete and nearly all food absorption has
occurred
Enzymes of the Small Intestine
1. Brush border enzymes
 Break double sugars into
simple sugars
 Complete some protein
digestion
2. Enzyme-rich pancreatic
juice (play the major
digestive function)
Small Intestine: Pancreatic Enzymes
 Pancreatic enzymes play the major
digestive function:
1. Help complete the digestion of starch
2. Carry out about half of all protein
digestion
3. Totally responsible for fat digestion
4. Digest nucleic acids
5. Alkaline content neutralizes acidic
chyme coming in from the stomach
Absorption in the Small Intestine
 Water is absorbed along the length of the
small intestine
 Absorption of the end products of
digestion along the length of the small
intestine
 Most substances are absorbed by active
transport through cell membranes
 Lipids are absorbed by diffusion
 Substances are then transported in the
blood to the liver by the hepatic portal vein
Absorption in the Small Intestine
 At the end of the small intestine (ileum),
all that remains is:
 Some water
 Indigestible food materials
 Large amounts of bacteria
Propulsion in the Small Intestine
 Peristalsis is the major
means of moving food
 Segmental movements
 Mix chyme with
digestive juices
 Aid in propelling food
Food Breakdown and Absorption in
the Large Intestine
 No digestive enzymes are produced
 Resident bacteria digest remaining nutrients
 Make some vitamins (Vitamin K and B)
 Release gases (methane and hydrogen
sulfide) that contribute to the odor of feces
 The only absorption: Remaining water,
vitamin K, and vitamin B
 Remaining materials are eliminated via
feces
Food Breakdown and Absorption in
the Large Intestine
 Feces – The more or less solid product
delivered to the rectum
 Contains:
 Undigested food
residues
 Mucus
 Millions of bacteria
 Just enough water to allow their smooth
passage
Food Breakdown and Absorption in
the Large Intestine
 About 500 ml of gas (flatus) is produced
each day
 Much more gas is produced when
certain carbohydrate-rich foods (such
as beans) are eaten
Propulsion in the Large Intestine
 Two major types of propulsive
movements occurring in the large
intestine:
1. Sluggish peristalsis
2. Mass movements – Long, slow-moving,
but powerful contractile waves that move
over large areas of the colon
 Occurs three to four times per day
 Forces the contents towards the rectum
Propulsion in the Large Intestine
 When feces are forced into the rectum
by mass movements and its wall is
stretched, a defecation reflex is initiated
 Internal anal sphincter is relaxed
 Defecation occurs with relaxation of the
voluntary (external) anal sphincter
 As feces are forced through the anal canal,
you have time to make a decision as to
whether the external voluntary sphincter
should remain open or be constricted to stop
the passage of feces
Diarrhea
 Diarrhea – Watery stools
 Results from any condition
that rushes food residue
through the large intestine
before that organ has had time to absorb
the water
 Some Causes: Irritation of the colon by
bacteria
 Prolonged diarrhea may result in
dehydration (lose fluids and ions)
Constipation
 Constipation - Hard stool
 Too much water is absorbed
(food remains in the large
intestine for too long)
 Stool becomes difficult to pass
 May result from:
 Lack of fiber in the diet
 Poor bowel habits (“failing to heed the
call”)
 Laxative abuse