GI Defences Flashcards
What are the innate physical defences of the GI?
Sight, smell and memory Saliva which contains lactoperoxidase, IgA, complement, polymorphs and washes toxins into the stomach Gastric acid Small intestine secretions including bile, proteolytic enzymes, lack of nutrients Anaerobic environment Shedding of epithelial cells Rapid transit - peristalsis Mucus to protect colonic epithelium
What toxins can the GI tract be exposed to?
Chemicals Bacetrial Viruses Protozoa Nematodes (round worms) Cestodes (tapeworm) Trematodes (flukes)
What innate cellular defences are there in the GI tract?
Neutrophils Macrophages Kupffer cells Natural killer cells Tissue mast cells Eosinophils
What are Kupffer cells and why do we need them?
Specialised macrophages in the liver
All venous blood from the GI tract passes through the liver
What are the adaptive defences of the GI tract?
B lymphocytes - produce antibodies including IgA and IgE. Effective against extracellular microbes
T lymphocytes - directed against intracellular organisms
Gut-associated lymphoid tissue (GALT) - diffusely distributed. Found in tonsils, appendix and Peyer’s patches
What is infection if the salivary glands called?
Parotitis
What infectious consequences are there of xerostomia?
Parotitis caused by Staph aureus
Hairy tongue
What can cause achlorydia? (Lack of gastric acid)
Pernicious anaemia
H2 antagonists
Proton pump inhibitors
What infections are patients at a higher risk of if they have achlorydia?
Shigellosis
Cholera
Salmonella
Hospital patients on PPIs - C. difficile
Which bacteria are resistant to gastric acid?
H pylori
Mycobacterium tuberculosis
Which viruses are resistant to stomach acid?
Enteroviruses
- hep A
- polio
- coxsackie
What causes recruitment of mast cells in the gut and what do they cause?
Gut infections which activate complement Recruit mast cells Release histamine Causes vasodilation and increased capillary permeability Massive fluid loss
What is the mortality of cholera if left untreated?
60%
What infection of the gut can cause right iliac fossa pain?
Mesenteric adenitis caused by adenovirus or coxsackie virus. Affects ileocaecal GALT
Appendicitis
What can cause appendicitis?
Lymphoid hyperplasia of the appendix base leading to obstructed outflow. Stasis and infection
Faecolith (calcified faecal matter)
Worm
What complication in the gut can typhoid fever lead to?
Inflamed Peyer’s path in the terminal ileum which can perforate and kill the patient.
What infectious complication occurs if blood supply to the GI tract is compromised?
Cannot carry out defence mechanisms
Overwhelming sepsis and rapid death within hours