Session 7 Flashcards
What are the 2 main branches of defences in the GI tract?
Innate (Physical and cellular)
Adaptive
What are some of the physical defences in the GI tract?
Sight Smell Taste Saliva Gastric acid Peristalsis (If slowed, infections are prolonged)
What does saliva contain to aid defence?
Lysozyme
Lactoperoxidase
Complement
IgA
How does saliva aid defence?
Its contents
Helps wash food down to the stomach which the stomach acid can kill it
What is Xerostomia?
Decreased salivary flow. It can lead to microbial overgrowth in the mouth eg parotitis caused by Staphylococcus aureus - swelling of parotid gland
How does the oesophagus aid GI defences?
Aiding the flow of liquids
Peristalsis
How does the stomach aid GI defences?
Gastric acid
Sterilisation
Low pH which kills most bacteria
Why do some patients have an increased risk of Clostridium difficile?
Because they are on proton pump inhibitors, therefore their stomach pH is higher than it should be and more pathogens can survive
What pathogens are resistant to gastric acid?
Mycobacterium TB (Can do gastric washings to collect bacteria for diagnosis) Helicobacter pylori (Produces urease which acts on urea to make a protective cloud of ammonia Norovirus
How does the small intestine aid GI defences?
Bile Proteolytic enzymes Lack of nutrients Anaerobic conditions Shredding of epithelial cells Peristalsis
What protects the epithelium of the colon?
The thick mucus layer
What are some of the cellular defences of the GI system?
Neutrophils Macrophages Eosinophils (Parasites) Natural Killer Cells (Especially good for Viruses) Mast cells
Why can infections that activate Mast cells be very dangerous?
They release the Histamine which causes vasodilation and increased capillary permeability leading to mass fluid loss
Which areas of the body have a very large population of Macrophages?
Lung
Liver
Spleen
How does the portal system work in the Liver?
2 capillary systems work in series (The hepatic lobule and villus) - Hepatic portal system and Hypothalamus hypophyseal portal system
Define Cirrhosis
Hepatic fibrosis
What are Caput Medusae?
The appearance of distended and engorged paraumbilical veins, which are seen radiating from the umbilicus across the abdomen
What can cause Caput Medusae?
Cirrhosis causes portal venous hypertension which then causes portosystemic shunting and therefore toxic shunting. Leads to oesophageal varicies – > Haemorrhoids and Caput Medusae
What is acute alcoholic hepatitis?
Acute enlargement of the liver
Painful
Usually occurs when the patient has been drinking a lot in a short space of time
What are some of the adaptive defences of the GI system?
B lymphocytes (Produce antibodies, best against extracellular microbes) T lymphocytes (Directed against intracellular microbes)
How many layers does the anorectal junction have?
3 layers of sphincters
2 muscular and 1 mucosal
Where is the GI system is lymphoid tissue nodular?
Tonsils
Appendix
Peyer’s patches (In lumen on Ileum)
Non nodular lymphoid tissue is diffusely distributed
Define tonsil
A mass of lymphoid tissue
What are the 3 main tonsils?
Linguinal (on tongue, drains to cervical lymph node)
Palatine (on tongue)
Nasopharyngeal (Also called aderoids)
