Lab 1: Presentation 1 Flashcards
What does melena mean?
Black stool as a result of an upper GI bleed
At what stage of the GI tract if there was a bleed it would be black and why is it black?
A bleed before the jejunum will be black in the stool (melena)
It is black because it has been partially digested
What should be done initially when a patient is in heamorrhagic shock?
Give fluids by intervenous injection to increase the blood pressure.
Sample the blood to determine haemoglobin levels (to show if blood needs to be give)
What is the normal haemoglobin levels for a female and male?
Female: 110
Male: 130
What are the two ways to stop the bleeding for a peptic ulcer?
- Inject with adrenaline as it is a vasoconstrictor
- Coagulate the area with a heat probe
What is the pH of gastric juice?
1.5-3.5
What are these?
Gastric pits and Gastric glands
Can be one gastric pit and multiple gastric glands
What are the two types of gastric glands that are found in the stomach?
Oxyntic and pyloric glands
What region of the stomach are the oxyntic glands found?
The fundus and body of the stomach
What region of the stomach are pyloric glands found?
In the pyloric antrum
What are the differences between a oxyntic and pyloric gland?
Oxyntic:
Found in the fundus and the body
More parietal cells
High secretion of hydrochloric acid and intrinsic factor
Pyloric:
Found in the pyloric antrum
Less parietal and more G cells
High secretion of gastrin
What are the components of gastric juice?
Hydrochloric acid (secreted by parietal cells)
Pepsin (secreted in the form of pepsinogen by chief cells)
Mucin (large glycoprotein, which is a structural component of mucus)
Intrinsic factor (secreted by parietal cells)
When the pH begins to fall what gets secreted?
Somatostatin from D cells
What cells does the vagus nerve innervate?
ACh (released by the vagus nerve) inhibits D cells, stimulates G cells and parietal cells
What receptor does ACh innervate on the parietal cell?
M3 receptor
What receptor does the gastrin innervate on the parietal cell?
CCK 2 receptor
What cells does the ACh innervate?
Inhibits D cells
Stimualtes parietal cells
Stimulates G cells
Name these receptors?
Name these cells?
What does gastrin do?
Stimulates ECL cells to produce histamine
Stimulates parietal cells to produce acid
What does ACh do in the gastric secretion process?
Stimulates G cell to produce gastrin
Stimulates parietal cell to produce acid
What does somatostatin do in the gastric secretion process?
Secreted by the D cells
Inhibits parietal cell acid secretion
Inhibits ECL cell histamine secretion
What does histamine do in the acid secretion process?
Stimulates parietal cell to produce acid via H2 receptor
Inhibits D cells somatostatin secretion, thus stimulates acid secretion
What are the 3 functions of the gastric acid?
Aids digestion- converts pepsinogen to pepsin
Absorption of iron, vitamin B12 and calcium
Antimicrobial
What is the main defence against the gastric acid in the stomach? Why is it such a good defence
The gastric mucus is the main defence
Physical and chemical barrier
Chemical: its rich in bicarbonate which neutralises the hydrochloric acid
Give examples of too much attack causes that results in peptic ulcer disease?
Zollinger Ellison Syndrome- benign gastric producing tumour
H.pylori infection
Which cyclooxygenase is important in mucus production?
COX-1
Why are NSAIDs so dangerous in the stomach?
NSAIDS are non selective inhibitors of COX1 and COX2
COX1 is important for the production of mucus, hence NSAIDs are dangerous and it lowers this protective barrier from the gastric acid
Give examples of too little defense causes that results in peptic ulcer disease?
Non steroidal anti-inflammatory drugs aka NSAIDs
“Stress” ulceration
H.pylori infection
How does the H.pylori result in peptic ulcer disease?
Is it too much attack or too little defense?
Why?
Both attack and defense
Attack: Blocks D cells, limiting in the inhibition of parietal cells and it secretes ammonia which neutralises the acid. Triggering more acid production
Defense: causes chronic inflammation of the lining
What are “stress” ulceration?
It is when an ulceration results in a patient who is under a lot of physiological stress e.g. surgery.
What does a peptic ulcer look like in an endoscope?
Looks similar to a mouth ulcer
White circular shape on the lining
What are some complications of peptic ulcer disease?
Perforation
Bleeding
Penetration
Gastric outlet blockage
What is the main cause of peptic ulcer disease?
H.pylori
Describe the difference in the outcome of H.pylori as a result of geographical design?
Asia
H.pylori predominately results in pangastritis
Pangastritis: Atrophy of the parietal cells leading to hypochlorhydria (low levels of acid). Increasing the risk of gastric cancer. Effects the entire stomach lining.
West
H.pylori predominately results in antral predominant gastritis
Antral predominant gastritis: Excessive acid production but does not cause atrophy. Found in the antrum.
What is the main cause of duodenal ulcers?
Usually are a result of acid hypersection from the stomach.
The acid moves into the duodenum when chyme travels through.
How does H.pylori live in the stomach?
It metabolises urea via urease, into ammonia. Ammonia is an alkaline which is secreted around the H.pylori creating a buffer zone , as the ammonia neutralises the acid.
What are the 5 ways to detect Helicobacter pylori ?
Serological (blood) test
Stool test
Urea breathe test
Barium swallow
Biopsy urease test
What are the pros and cons of the blood test to detect Helicobacter pylori?
The test detects IgG antibodies
85% sensitive
Can only be used once
Describe the urea breathe test for detecting Helicobacter pylori?
Patient ingests 13C-Urea (isotope 13 for Carbon)
If H. pylori is present they will convert the 13C-urea into 13CO2 and ammonia
Test the levels of 13CO2
Describe how the barium swallow test can be used to detect H.pylori?
Ingests barium
If a peptic ulcer is present, it will be filled with barium
Can be seen on an X-ray
Describe the biopsy urease test (also known as rapid urease test) to detect Helicobacter pylori?
A biopsy is taken
The biopsy is added to a substrate that contains urea and phenol red (hence the red colour)
If H.pylori is present, it will convert the urea into ammonia, and this will increase the pH.
This causes a colour change from red to yellow- positive indication of H.pylori
What colour is the rapid urease test initially and after a positive result?
Initially it is yellow
Positive result, red
What are the 4 treatments for peptic ulcer disease?
- Eradication therapy- antibiotics
- Medication
- Lifestyle changes
- Surgical treatment
Describe the medications available to test peptic ulcer disease?
H2 receptor antagonist
Proton pump inhibitors
Give an example of a H2 receptor antagonist?
Ranitidine
Give an example of a proton pump inhibitor?
Omeprazole
Describe the way H2 receptor antagonist works in reducing acid secretion?
Competitive and reversibility bind to the H2 receptor on the parietal cells
Histamine released by the ECL cell bind to the H2 receptor. Hence the H2 receptor antagonist reduces the histamine effect
Reduces acid secretion
What are some cons of the H2 receptor antagonist?
Interacts with other drugs
“Drug holidays” are required- this is when you have to take breaks when taking a medication because you become tolerant
Describe the mechanism of action for proton pump inhibitors?
Taken orally
Absorbed in the small intestine
It inhibits the potassium/hydrogen ion pump located on the apical membrane of the parietal cell
What are some cons of the proton pump inhibitors?
Slight increase in the risk of food poison
Rebound acid hypersecretion- when PPI are stopped, there is an increase in acid secretion (higher than it was prior to PPI)
