Flashcards in GI Defences Deck (44)
What toxins can the GI tract be exposed to?
Nematodes (round worms)
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
Small intestine secretions including bile, proteolytic enzymes, lack of nutrients
Shedding of epithelial cells
Rapid transit - peristalsis
Mucus to protect colonic epithelium
What innate cellular defences are there in the GI tract?
Natural killer cells
Tissue mast cells
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?
What infectious consequences are there of xerostomia?
Parotitis caused by Staph aureus
What can cause achlorydia? (Lack of gastric acid)
Proton pump inhibitors
What infections are patients at a higher risk of if they have achlorydia?
Hospital patients on PPIs - C. difficile
Which bacteria are resistant to gastric acid?
Which viruses are resistant to stomach acid?
What causes recruitment of mast cells in the gut and what do they cause?
Gut infections which activate complement
Recruit mast cells
Causes vasodilation and increased capillary permeability
Massive fluid loss
What is the mortality of cholera if left untreated?
What infection of the gut can cause right iliac fossa pain?
Mesenteric adenitis caused by adenovirus or coxsackie virus. Affects ileocaecal GALT
What can cause appendicitis?
Lymphoid hyperplasia of the appendix base leading to obstructed outflow. Stasis and infection
Faecolith (calcified faecal matter)
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
What can compromise blood flow to the gut?
Intestinal venous thrombosis
Causes of liver failure?
Drugs eg paracetemol, halothane
What can you be more susceptible to with liver failure?
What is hepatic encephalopathy?
High blood concentration of ammonia
How is ammonia produced?
Deamination of amino acids
How do oesophageal varices occur?
Vein? drains into hepatic portal vein
If there is cirrhosis, can cause portal hypertension
Blood backs up in the oesophageal veins and causes them to dilate
What is caput medusae caused by?
Ligamentum teres opens up and blood radiates out from the umbilicus
How do haemorrhoids develop?
At anorectal junction, vein? joins with hepatic portal vein. If pressure is increased in portal vein, can cause the junction to open up and causes haemorrhoids
How does the liver handle bile pigments?
Conjugates bilirubin and secretes it into the faeces which can then be excreted.
What is the most abundant plasma protein and what is it essential for?
Maintaining osmotic pressure needed for proper distribution of body fluids.
What coagulation factors does the liver produce?
V, VII, IX, X, XI
Protein C, protein S, antithrombin
What is thrombopoietin and what does it do?
A glycoprotein hormone
Regulates production of platelets by bone marrow
What does a high level of alkaline phosphatase indicate and why?
When liver's biliary ducts are obstructed
It is an enzyme in the cells of these ducts
What does low albumin indicate?
Chronic liver disease
What does an increased prothrombin time show?
The clotting tendency of the blood
Would show if there is liver damage?
Signs of hyperbilirubinaemia?
Yellow pigmentation of skin
Yellow conjunctival membranes over the sclerae
What should bilirubin levels in the blood be below normally and when is it an issue?
Clinically detectable above 44mmol/L
What is pre-hepatic jaundice caused by?
-red cell membrane defects
-mechanical (eg RBCs running across the metal heart valve)
What is hepatocellular jaundice caused by?
Deranged hepatocyte function
Can be an element of cholestasis
Lab findings in pre-hepatic jaundice?
High LDH (contained in RBCs)
Low haptoglobin (normally bound to bilirubin)
Lab findings in hepatocellular jaundice?
Mixed conjugated and unconjugated hyperbilirubinaemia
High ALT and AST
Normal/high ALP (alkaline phosphatase??)
Causes of hepatocellular jaundice?
Cirrhosis caused by
Hepatic tumours: hepatocellular carcinomas, metastases
What is post-hepatic/cholestatic jaundice?
Obstruction of biliary system affecting drainage of bile
Causes a back up of bile acids into the liver
Can be inta or extra hepatic
Passage of conjugated bilirubin is blocked
Lab findings in post-hepatic jaundice?
Bilirubin in urine (dark)
Increased canalicular enzymes (ALP)
Normal or raised ALT/AST due to mild hepatocyte damage from pressure
Causes of post-hepatic jaundice?
-primary biliary cirrhosis
Extra-hepatic (obstruction distal to bile canaliculi)
Where can carcinomas be which cause extra-hepatic jaundice?
Head of pancreas