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Chapter 22


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  • 1. Chapter 22 Oral & Gastrointestinal Diseases
  • 2. Overview of Digestive System
    • Organs are separated into 2 groups
      • Alimentary canal (GI tract)
        • Continuous muscular tube (30 ft); open to external environment at both ends
        • Site of digestion and absorption
        • Includes mouth, pharynx, esophagus, stomach and the intestines
      • Accessory organs
        • Teeth, tongue, liver, gallbladder, pancreas and salivary glands
        • Glands are outside GI tract; connected by ducts; produce digestive enzymes and various other secretions
  • 3.  
  • 4. Digestive Processes
    • Six essential activities
      • Ingestion
      • Propulsion
        • Involves peristalsis – wave-like contractions
      • Mechanical digestion
        • Chewing of food in mouth stomach
        • Churning and segmentation in stomach
      • Chemical digestion
        • Series of catabolic steps facilitated by enzymes
      • Absorption
        • Passage of foodstuffs from GI tract into blood and lymph
      • Defecation
        • Elimination of indigestible substances
  • 5.  
  • 6.
    • Mouth – oral cavity
      • Common portal of entry for microbes; has normal flora
      • Lined with stratified squamous epithelium,slightly keratinized to protect against abrasions, produces defensins
      • Contains tongue, teeth and salivary glands
      • Primary functions; mastication and chemical digestion
      • Salvia has several functions
        • cleans mouth, dissolves food chemicals for taste, contains enzymes like lysozymes to destroy microbes
      • Each tooth has a crown covered with enamel above the gum and a root covered with cementum below the gum
      • Under these coverings is a porous substance called dentin, a central pulp cavity and the root canals where blood vessels and nerves are located
  • 7. A section through a typical tooth and gum
  • 8.
    • Pharynx – throat; has three divisions
      • Oropharynx, laryngopharynx (common passages for air and food) and the nasopharynx (plays no role in digestion)
      • Has external muscle layer to propel food into esophagus below
    • Esophagus – muscular tube that is collapsed when not involved in food propulsion
      • Pierces diaphragm and empties into the stomach
      • Heartburn occurs when acidic stomach juice (pH 4) is regurgitated into esophagus
  • 9.
    • Stomach – site of protein digestion and more mechanical digestion
      • Food is converted into a creamy paste called chyme
      • The epithelial lining has goblets cells which produce a protective alkaline mucus coating
      • Lining is doted with millions of gastric glands which produce hydrochloric acid & pepsin (protein digesting enzyme)
      • Alcohol and aspirin and some lipid-soluble drugs pass across the mucous barrier to blood
  • 10.  
  • 11.
    • Small intestine is the body’s main digestive organ
      • Site of virtually all absorption
    • Three subdivisions
      • Duodenum – beginning portion; drains stomach; curves around pancreas; bile duct and main pancreatic duct converge here
      • Jejunum – middle portion
      • Ileum – end portion; joins large intestine
      • Villi – finger-like projections
        • Increase surface area form absorption, contain blood & lymph vessels
      • Microvilli – tiny folds in plasma membranes of absorptive cells
        • Secrete enzymes that complete the digestive process
  • 12.
    • As food enters the duodenum it is mixed with secretions from the liver and pancreas
      • The liver secretes bile & cholesterols which help digest fats
      • The pancreas produces a broad spectrum of enzymes that help complete digestion of starches & proteins
    • Sugars & amino acids are absorbed into the blood while fats are absorbed into the lymph
    • The ileum contains special lymphoid tissues called Pyer’s patches to filter out microbes
  • 13.  
  • 14.  
  • 15.
    • Large Intestine’s (colon) major function is to absorb water from indigestible foods and eliminate them from body as feces
    • The beginning portion is a sac-like cecum, with a worm-like appendix extending off the back
    • Most bacteria entering the large intestine are dead – the few that survive and those entering the anus make up the bacterial flora of the colon
      • Ferment indigestible carbohydrates releasing acids and gasses
      • They also produce vitamin K needed for the liver to produce clotting factors and complex B vitamins
      • In addition to absorbing water the colon absorbs these vitamins
  • 16.  
  • 17.  
  • 18. Normal Flora of the Digestive System
    • Mouth has over 400 species of bacteria
    • Esophagus has no permanent flora
    • Stomach is usually too acidic for bacteria to colonize
    • Some G- anaerobes colonize the lower small intestine and into the colon
      • E. coli, Bacteroides, Clostridium
    • Food may remain in the colon for over 60 hours allowing lots of time for colonization
      • About 50% of the weight of feces is bacteria
  • 19. Bacterial Diseases of Mouth
    • Dental plaque
      • continuously formed coating of the teeth with microbes and organic matter
      • 1 st step in tooth decay and gum disease
      • May become so firmly attached it requires professional removal
      • Plaque consists of over 30 different genera of bacteria and their metabolic products
        • Plaque forming bacteria include Streptococcus mutans and Streptococcus sanguis
      • May accumulate near the gum line and cause gingivitis
        • Actinomyces, Veillonella, Fusobacterium and Streptococci
      • May mineralize causing the formation of tarter (calculus)
  • 20.
    • Dental caries (tooth decay)
      • Chemical dissolution of enamel, dentin and pulp
      • The most common infectious disease in developing countries because of refined sugar in diet
      • May form an abscess that damages the peridontal ligaments and bone supporting the tooth
        • Periodontal disease
      • Sugars diffuse through plaque then the acids produced by bacteria from fermentation of the sugars becomes trapped against tooth
      • Preventable by reducing sugar, frequent brushing and fluoride treatment
        • Hardens surface enamel
        • Water supply, toothpaste, mouthwash, gel treatments
  • 21. Viral Diseases of the Mouth
    • Mumps – caused by paramyxovirus
      • Transmitted in saliva & droplets
      • Swelling of parotid glands (salvia glands)
      • Common in children (6-10 yrs)
      • Preventable with MMR vaccine
      • May cause orchitis in post-pubertal males
        • Inflammation of testes that predisposes them to testicular cancer
      • Other complications include inflamation of ovaries and pancrease, eye and ear infections, and meningoencephalitis
  • 22. paramyxovirus
  • 23.
    • Other diseases of the mouth
    • Herpes simplex
      • Primarily HHV type 1
      • cause fever blisters or cold sores
    • Thrush
      • Caused by the yeast Candida albicans
      • Characterized by milky patches of inflammation on oral mucus membranes
      • Prevalent in infants, diabetics and immunosuppressed individuals
  • 24. Bacterial Gastrointestinal Diseases
    • Bacterial food poisonings
      • Food poisoning is caused by ingesting food contaminated with bacterial toxins, pesticides, heavy metals or other toxic substances
      • Preventable by following proper food handling procedures
      • If bacteria are consumed they can continue to produce toxins
        • Tissue damage is a result of the action of the toxin not the growth of the bacteria
      • Bacteria producing such toxins include Staphylococcus aureus, Campylobacter jejune, Clostridium species and Bacillus cereus
  • 25.
      • S. aureus causes enterotoxicosis by releasing enterotoxins A or D which are actually exotoxins
        • damages intestinal wall and inhibits water reabsorbtion causing abdominal pain, vomiting and diarrhea usually within 1-6 hrs of ingestion
        • Usually clears itself up in healthy adult; no immunity
      • C. perfringens releases an enterotoxin only during sporulation under anaerobic conditions
        • Main symptom is diarrhea usually 8-24 hrs after exposure
        • May also be transmitted by introducing spores to open wounds causing gangrene
      • C. botulinum produces the botulism neurotoxin which mainly affects the nervous system
      • B. cereus secretes a toxin that induces vomiting
        • often associated with contaminated rice
        • Symptoms occur within 12 hrs of exposure and are short lived
  • 26. S. aureus C. perfringens C. botulinum B. cereus
  • 27.
    • Peptic ulcers & gastritis
      • Etiological agent: Helicobacter pylori
      • Peptic ulcers are lesions in membrane lining GI tract
      • Require 46,000 surgeries & cause 14,000 deaths annually
      • Correlated to 89% of stomach cancers
      • Chronic gastritis is stomach inflammation; may lead to ulceration
      • H. pylori generates ammonia from urea; ammonia neutralizes acidic stomach juices
      • Unclear portal of exit or route of infection
      • Experimental antibiotic treatments and antacids
  • 28. Knobs at end of flagella help it move through mucus that traps other normally flagellated bacteria Helicobacter pylori
  • 29.
    • Bacterial enteritis & enteric fevers
      • Enteritis is an inflammation of the intestine
        • bacteria invade and damage the intestinal lining and deeper tissues
        • Infection not intoxication like food poisoning
      • Mainly affects the small intestine causing diarrhea
      • If it affects the colon it is often called dysentery
        • Severe diarrhea usually contains mucus, blood or pus
      • Some infections spread to the blood and cause systemic infections called enteric fevers
      • Salmonellosis, Typhoid Fever, Shigellosis, Cholera, Vibriosis, Traveler’s Diarrhea (Montezuma’s revenge) and Yersiniosis
  • 30.
    • Salmonellosis
      • Etiological agent: Salmonella species
        • S. typhi, S. choleraeusuis & S. enteritidis
      • Various harmless animal hosts
      • Transmitted through contaminated food, water and chicken eggs
      • Abdominal pain, fever and diarrhea with blood or mucus
      • No vaccine; antibiotics may induce a carrier state
      • Health adults usually recover within a week with no treatment
      • Certain serovars have the ability to enter the blood and cause enterocolitis – enteric fever
      • Chronic infections are not uncommon
  • 31. Salmonella enteriditis
  • 32.
    • Typhoid Fever
      • One of the most serious epidemic enteric infections
      • Etiological agent: Salmonella typhi
      • Common in areas with poor water & sewage treatment
      • Transmitted in contaminated food or water and invades small intestine and lymphoid tissue
      • Survive and multiply in phagocytes
      • Headache, fever, malaise, enlargement of spleen, abdominal distension & tenderness but no diarrhea
      • May result in internal hemorrhage, perforation of bowel and pneumonia
      • Treatment: chloramphenicol (some strains are resistant)
      • Vaccine is available but requires booster every 3 yrs.
  • 33. Salmonella typhi --the cause of typhoid fever
  • 34.
    • Typhoid Mary
    • Mary Mallon: an immigrant, Irish woman who made her way as a cook
    • Well liked and respected ("good with the children")
    • Probably exposed to typhoid fever around 1900
    • Between 1900 and 1907, she infected 22 people with typhoid fever; one died
    • Quarantined on North Brother Island (age 37) for three years
    • Released by the new health officer after promising never to cook again
    • Traced to Sloan Maternity Hospital as cook!
      • 25 more people infected
      • 2 died
    • Returned to quarantine on North Brother Island
    • Died of a stroke 23 years later (in 1938)
  • 35.  
  • 36.
    • Shigellosis (bacillary dysentery)
      • Etiological agent: several species of Shigella
        • S. dysenteriae, S. flexneri, S. sonnei, S. boydii
      • Transmitted by contaminated food, fingers, water, flies, feces and fomites; only 10 organisms are enough to cause infection
      • Cramps, fever & extreme diarrhea with blood
      • All strains produce fever inducing endotoxins but S. dysenteriae produces a neurotoxin as well
      • Combination of antibiotics is used to treat
        • Ampicillin, tetracycline and nalidixic acid (DNA synthesis inhibitor)
        • Temporary immunity follows recovery & an oral vaccine is being developed
  • 37. A colorized TEM of S higella --the cause of shigellosis
  • 38.
    • Asiatic Cholera
      • Etiological agent: Vibrio choleae
      • Problematic in areas with poor sewage & water treatment
      • Enterotoxin (choleragen) binds to cells of small intestine making them highly permeable to water
      • Severe diarrhea, nausea and vomiting, death due to shock from fluid loss
      • Treatment: fluid and electrolyte replacement
      • No effective vaccine & immunity is temporary
    • Vibriosis
      • Caused mainly by Vibrio parahaemolyticus
      • Most common in Japan where raw fish is frequently consumed
      • Can also infect skin wounds
      • Releases endotoxin causing nausea, vomiting, diarrhea
      • No vaccine & usually no treatment is given
  • 39. A colorized SEM of Vibrio cholerae—the cause of Asiatic cholera
  • 40.
    • Traveler’s Diarrhea (Montezuma's revenge)
      • Most commonly caused by E. coli (40-70%)
      • Different from the strains found in colon
      • Transmitted in contaminated food & water
      • Mild to severe diarrhea, vomiting, nausea, bloating and malaise
      • May become irritable bowel syndrome & persist for years
      • Enter-hemorrhagic strains ( E. coli O157:H7) cause deadly outbreaks of bloody diarrhea (no more rare hamburger)
      • May lead to kidney failure (leading cause in children)
    • Yersiniosis
      • Caused by Yersinia entercolitica – most common in Western Europe
      • Transmitted in contaminated food (especially chitlins)
      • Releases endotoxin causing severe abdominal pain & increase in WBCs
  • 41. E. coli Yersinia enterocolitica
  • 42. Viral Gastrointestinal Diseases
    • Viral enteritis
      • major cause in children is the rotavirus
        • Double stranded RNA virus
      • Transmitted by the oral-fecal route, common in small children
      • Damages GI lining, causes watery diarrhea
      • Major cause of infant mortality in under developed countries
      • About ½ US cases caused by Norwalk virus
        • Affects mostly older children and adults
  • 43. rotavirus
  • 44.
    • Hepatitis
      • Inflammation of liver usually caused by viruses but also by an amoeba & various toxic chemicals
      • Most common viral form is Hepatitis A (infectious hepatitis) caused by hepatitis A virus (HAV)
        • Single RNA transmitted by fecal-oral route; contaminated food
      • Hepatitis B (serum hepatitis) caused by HBV
        • Double stranded DNA transmitted by blood; intravenous; direct contact & contaminated body secretions
      • Hepatitis C caused by more than 1 RNA virus (not HAV)
        • Transmitted parenterally by blood
      • Hepatitis D (delta hepatitis) particularly severe caused by both HDV and HBV
      • Hepatitis E caused by HEV
        • Transmitted by fecal-oral route; fecally contaminated water
      • 3 more viruses have been identified as potential hepatitis viruses
  • 45. Hepatitis B viruses                                             
  • 46. Protozoan Gastrointestinal Diseases
    • Giardiasis – caused by flagellated Giardia intestinalis
      • Inflammation of bowel, frothy diarrhea due to decreased fat absorption, dehydration & weight loss
      • Transmitted by contaminated food, water & hands
      • Giardia cysts are not killed by ordinary chlorination
    • Amoebic dysentery – caused by Entamoeba histolytica
      • Becomes chronic but can revert to acute
      • Transmitted through cyst infected water & food
    • Cryptosporidiosis – Cryptosporidium species transmitted from cyst infested feces of puppies & kittens
      • Opportunistic infection with no available treatment
      • Severe diarrhea and fluid loss
    • Cyclosporiasis – Cyclospora cayentanenisis
      • Transmitted by contaminated fruits and vegetables
      • Flu like symptoms, often with relapse
  • 47. Giardia intestinalis Cryptosporidium lining the intestinal tract
  • 48. Effects of Fungal Toxins on GI Tract
    • Fungi produce large numbers of toxins
      • Most come from species of Aspergillus & Penicillium
      • Various effects include loss of muscle coordination, tremors, weight loss and cancers
      • Aflatoxins – produced by Aspergillus flavus
        • Most potent carcinogen known
        • Transmitted from mold infected grain
      • Ergot – produced by Claviceps purpurea
        • Transmitted on contaminated rye and wheat
        • Causes fever, hallucinations, gangrene and death
  • 49. Claviceps purpurea                                     
  • 50. Helminth Gastrointestinal Diseases
    • Helminthes that infect humans have complex life cycle with 1 or more intermediate hosts
      • Acquired mainly in tropical regions
    • Fluke infections
    • Tapeworm infections
    • Trichinosis
    • Hookworm infections
    • Ascariasis
    • Pinworm infections
  • 51.
    • Fluke infections
      • Affect 40 million people worldwide
      • Sheep liver fluke ( Fasciola hepatica )
        • Intermediate host is snail
        • Cercaria encyst on water vegetation forming metacercaria
        • Diagnosed by eggs in stool
        • Treated with bithionol or other antihelminth
        • Prevented by avoiding uncooked water vegetation
      • Chinese liver fluke ( Clonorchis sinensis )
        • Has a second intermediate host – fish or crustacean
        • Diagnosed by eggs in stool
        • No effective treatment
        • Prevented by avoiding uncooked fish or crustaceans
  • 52.
    • Tapeworm infections
      • Caused by several species- most found worldwide
      • Contracted by eating undercooked pork, beef or fish and by contact with infected dogs
      • Pork tapeworm ( Taenia solium ) and Beef tapeworm (Taenia saginata)
        • Enter as larvae in undercooked meat
        • Develop into adult in intestine stealing nutrients from host
        • May form masses that block intestines
        • Eggs may invade blood stream and spread to other body sites
      • Echinococcus granulosus
        • Contracted through contact with infected dogs
        • Eggs produces cysts called hydatid cysts containing hundreds of immature worms
      • Diagnosed by eggs or proglottids in stool
      • Treated with niclosamide and other antihelminths
  • 53. Liver Fluke Pork Tapeworm
  • 54.
    • Trichinosis
      • Caused by round worm Trichinella spiralis
      • Enters as encysted larvae in undercooked pork, horse or game meat
      • Adults penetrate intestinal mucosa releasing toxins
      • Wandering larvae damage blood vessels an other tissues
      • Hard to diagnose – muscle biopsy or immunological tests may be effective
      • Treatment is restricted to alleviating symptoms
      • Prevented by thoroughly cooking meat
      • Average of 100 cases/yr in US
  • 55.
    • Hookworm infections
      • Often caused by 1 of 2 species of roundworms
        • Necator americanus or Ancylostoma duodenale
      • Complex life cycle with a single host
      • Free-living larvae burrow through skin and travel to heart or lungs
      • May be coughed up and swallowed where they reach the intestines mature, lay eggs and start the cycle again
      • 500 million cases worldwide
      • Diagnosed by worms or eggs in feces
      • Treatment: Tetrachloroethylene for Necator only; Bephenium and mebendazole effective for both worms
      • Preventable through sanitary disposal of human waste
  • 56.
    • Ascariasis
      • Caused by the large roundworm Acaris lumbricoides
      • Spread through water or food contaminated with eggs
      • Eggs hatch and larvae travel to lymph vessels and results in systemic immune response
      • Mature in small intestine and begin laying eggs
        • Single female lays 200,000 eggs/day and 26 million/ lifetime
      • Worldwide 25% of population is infested
      • Ascaris worms cause three forms of damage
        • Burrowing into lungs causes Ascaris pneumonitis
        • Malnutrition by stealing host nutrients
        • Wandering worms for abscess in liver and other organs
  • 57.
    • Pinworm infections
      • Caused by small round worm Enterobius vermicularis
      • Humans are the only known host
      • Has the greatest geographical distribution of all human worm parasites
      • 209 million infested worldwide (18 million in US and Canada)
      • Adults attach to intestinal wall
      • Females carrying 15,000 eggs travel to anus and lay the eggs on the exterior then travel back to intestines
      • Eggs are ealisly transmitted through contaminated bedding, clothing and hands
      • Eggs may become airbourne
      • Usually not debilitating, but very uncomfortable
      • Diagnosed by eggs around anus
      • Treated with piperazine or other antihelminth
      • All personal items (bedding, clothing) should by cleaned
  • 58. Adult Pin Worm Hookworm Round Worm
  • 59. Hydatid cysts in brain
  • 60. Ascaris lumbricoides mass