Transcript Gastrointestinal System Biomedicine Review

Gastrointestinal System
Biomedicine Review
Felix Hernandez, M.D.
Anatomy/Physiology
Responsible for the intake,
digestion of food, absorption of
nutrients, and elimination of
solid waste.
Alimentary Canal (GI tract)
Accessory Digestive Organs
Teeth
tongue
salivary glands
liver
gallbladder
pancreas
Teeth
Maxillary
arch (upper)
Mandibular
arch (lower)
•
anterior teeth for biting and tearing
•
posterior teeth for chewing and grinding
Oral Cavity
Palate, hard and soft
bolus
Pharynx
Uvula
Esophagus
Epiglottis
Esophagus
chyme
cardiac,
or lower
esophageal or
gastroesophageal
sphincter
Stomach
Fundus
Body,
fundus
pylorus
rugae
pyloric
sphincter
Body
Small Intestine
small
bowel
villi
Parts
•
duodenum
•
jejunum
•
ileum
ileocecal
valve
Large Intestine
Large
Bowel
colon
cecum
vermiform
appendix
Large Intestine
 Colon
•
ascending
•
hepatic flexure
•
transverse
•
splenic flexure
•
descending
 Sigmoid
 Rectum
 Anus
Liver
Functions
•
production of bile
•
glucose - glycogen
•
storage of vitamins, B12, A, D, E, K
•
erythrocytolysis (pigment released eliminated in
bile called bilirubin)
•
bilirubin gives stool its characteristic dark color
•
removes toxins from blood
•
manufactures blood proteins
Pancreas
internal
- endocrine function
•
insulin
•
glucogon
external
- exocrine function
•
amylase - carbohydrates
•
trypsin, chymotrypsin - proteins
•
lipase - fats
enzymes
inactive until reach duodenum
Gallbladder
pear-shaped
sac under the liver
chol/e
means bile or gall
cyst/o
means cyst or sac
gallbladder
contracts forcing bile out cystic duct
into common bile duct.
Bile
bile
is a digestive juice- emulsifier acts on fat in a
way that lipid enzymes can digest fat
travels
via hepatic duct to cystic duct to gall
bladder, where stored
bile
consists of water, bile salts, cholesterol, and
bilirubin (a colored substance resulting from
breakdown of hemoglobin)
bilirubin
gives bile yellow or orange color
Stomach during Digestion
Gastric
juices
•
HCL - activates
enzymes
•
protease
•
pepsin
•
lipase
Chyme
Small Intestine during Digestion
digestion
completed in small
intestine
chyme
mixed with bile and
pancreatic juices
emulsification
absorption
Large Intestine
receive
fluid waste products and
store until released from body.
excess
feces,
water absorbed
stools
defecation,
or bowel movement
Diseases of the Esophagus—Clinical Presentations
Dysphagia
Esophageal (retrosternal) pain
Aspiration or regurgitation
Diseases of the Esophagus
Developmental abnormalities—atresia with or
without esophageal-tracheal fistula
Esophagitis
Hernia
Achalasia
Varices
Esophageal Atresia
Figure 1004A
Hiatal Hernia
Figure 1004B
Achalasia
Figure 1004C
Esophageal Varices
Figure 1004D
Esophagitis
Reflux of gastric juice (“peptic esophagitis”)
Infection—viruses, fungi (immunosuppressed
persons), and bacterial superinfection
Chemical irritants—exogenous chemicals or
drugs
Carcinoma of the Esophagus
Squamous cell carcinoma in
upper or lower esophagus
Adenocarcinoma in lower
esophagus developing in
Barrett’s esophagus
Diseases of Stomach and Duodenum—Symptoms
Pain—midline, upper abdomen
Vomiting
Bleeding—acute with hematemesis or chronic
with melena
Dyspepsia
Systemic consequences—e.g., iron deficiency
anemia caused by chronic blood loss, vitamin
B12 malabsorption–related megaloblastic
anemia
Gastritis
Acute (erosive)—stress related, shock, food,
exogenous chemicals and drugs
Erosions
Ulcerations
Chronic atrophic gastritis with or without intestinal
metaplasia
Helicobacter pylori related
Autoimmune (with pernicious anemia)
Peptic Ulcer—Etiology and Pathogenesis
Multifactorial!
Contributing factors include:
Gastric juice—HCl, pepsin
Mucosal barrier defects—stress, shock,
NSAIDs, smoking reduce resistance
Helicobacter pylori—found in most patients
Acid Reducing Agents
Histamine Receptor Blockers:
MOA: Histamine receptor Antagonist
Indications: duodenal/gastric ulcer,
hypersecretion of acid, GERD
Interactions: increases concentration of
anticoagulants
Drugs:
Cimetidine (Tagamet)
Ranitidine (Zantac)
Proton Pump Inhibitors
Drugs: Omeprazole (Prilosec), Lansoprazole
(Prevacid), Esomeprazole (Nexium), Pantoprazole
(Protonix)
MOA: inhibits hydrogen/potassium ATPase (Proton
pump) of the parietal cells thus reducing acid
secretion.
Indications: reflux esophagitis, duodenal ulcers,
hypersecretory states
Side Effects: Constipation (few side effects)
Mucosal Protectant
Misoprostol
MOA: increases bicarbonate and mucin
release in the GI tract and reduces acid
secretion
Indications: prevention of ulcers caused by
aspirin and other NSAIDS
Side Effects: Abortion (uterine contraction)
Contraindications: PREGNANCY!!!!
Is a prostaglandin analog
Diverticulosis of the Colon
Figure 1008
Inflammatory Bowel Disease
Crohn’s disease—incidence is 70 to 150 per
100,000 persons per year in the United States
Ulcerative colitis—incidence is 20 to 40 per
100,000 persons per year in the United States
Cause unknown but may be familial
Features of Crohn’s Disease
and Ulcerative Colitis
Clinical Features
Crohn’s Disease
Ulcerative Colitis
Familial
++
++
Peak age
15–25 years
15–25 years
Immune disturbances
+
+
Extraintestinal
complications
+
+
Treatment
+
+
Features of Crohn’s Disease
and Ulcerative Colitis
Pathology
Crohn’s Disease
Ulcerative Colitis
Distribution
Segmental, including
ileum
Diffuse, colon only
Transmural
++
(−)
Granuloma
+
(−)
Fistula
+
(−)
Megacolon
(−)
+
Cancer
+
++
Inflammatory Bowel Agents
Mesalamine and Sulfasalazine
MOA: anti inflammatory
Indications: inflammatory bowel syndrome,
UC or Crohn’s
Comparison of Diarrhea Caused by Small and Large
Intestinal Disease
Stool Characteristic
Small Intestinal
Large Intestinal
Volume
Large
Small
Appearance
Watery
Mucoid
Blood
Rare
Common
Leukocytes
(−)
+/− or +
Proctoscopy
(−)
+
Antidiarrheal Agents
Opiates
Diphenoxylate and Atropine (Lomotil)
MOA: diphenoxylate is an agonist at opiate receptors in the GI tract and
atropine blocks muscarinic receptors. Both of these actions inhibit peristalsis
Indications: Diarrhea
Side Effects: few such as constipation, abdominal/bowel distention
Contraindications: Parasitic or bacterial infections, obstructive jaundice
Increased risk of paralytic ileus with antimuscarinics
Loperamide (Imodium)
No drug interactions
Treat OD with Naloxone
Antidiarrheal Agents
Bismuth Subsalicylate (Pepto-Bismol)
MOA: absorbs toxins produced by bacteria and other GI irritants
Indications: Diarrhea, prophylaxis for traveler’s diarrhea
Side Effects: Impaction
Contraindications: Aspirin sensitivity
Kaolin/Pectin (Kaopectate)
MOA: adsorbent and protection that is of questionable efficacy
Indications: diarrhea
Acute Appendicitis
Figure 1012A
Acute Appendicitis
Figure 1012B
Acute Appendicitis
Figure 1012C
Intestinal Obstructions—Hernia
Figure 1013A
Intestinal Obstructions—Intussusception
Figure 1013B
Intestinal Obstructions—Volvulus
Figure 1013C
Malabsorption Resulting from Defective Uptake of
Nutrients
Celiac sprue
Gluten
Tropical sprue
Infectious
Dysmotility Agent
Metoclopramide (Reglan)
MOA: increases rate of gastric emptying by
an unknown mechanism
Indications: reflux esophagitis, gastroparesis,
pre-op gastric emptying
Bulk Forming Agents
Psyllium (Metamucil)
MOA: nondigested plant cell wall absorbs
water into feces thus softening the stool
Indications: constipation, hard stools
Side Effects: flatulence, impaction if the bolus
is obstructed
Milk of Magnesia
Milk of Magnesia (saline solutions)
MOA: magnesium or sodium salts are poorly
absorbed and thus draw water into the lumen.
High dose rids bowel of parasites and
empties bowel preoperatively
Side Effects: precipitation of cardiac, renal,
convulsive disorders or hypocalcaemia
Docusate (Colace)
MOA: improves penetration of water and fat into
feces
Side Effects: diarrhea, abdominal cramps.
Obesity Management
Orlistat (Xenical)
MOA: reversible lipase inhibitor therefore it
inhibits the absorption of fats from the intestine
Should be accompanied by a balanced
reduced calorie diet
Multivitamin supplements are needed because
vitamin absorption is decreased by the drug
Patient will have fatty/oily stool