Stomach Flashcards
What type of parietal cell receptor can be blocked pharmacologically to reduce stomach acid secretion?
H2 receptor (e.g. with H2 antagonists such as Ranitidine)
Name three receptors on parietal cells which when stimulated increase acid production
- H2 receptors (histamine receptor)
- Muscarinic receptor (ACh receptor)
- Gastrin receptor/ CCK receptor (gastrin and CCK have similar structures)
How do proton pump inhibitors (PPIs) work?
E.g. Omeprazole. They block the H+/K+ ATPase (proton pump), which actively transports H+ out of parietal cells onto the epithelial surface of the stomach
How does the stomach physically disrupt food?
Muscular contractions of the antrum - the antrum has thicker muscluar walls than the fundus or body
What the the function of receptive relaxation in the stomach?
It allows the stomach to distend when food enters to maintain a steady intraluminal pressure, preventing reflux
Stomach acid production is under neural, paracrine and endocrine control. Which substance is involved in paracrine control of stomach acid production?
Histamine released from ECL (enterochromaffin-like cells) (stimulates acid production by parietal cells)
Stomach acid production is under neural, paracrine and endocrine control. Which substance is involved in neural control of stomach acid production?
ACh neurotransmitter - stimulation from vagal nerve
GRP (gastrin-releasing peptide) - Released by nervous detection of stomach distension, which stimulates gastrin secretion and therefore stimulates H+ production in parietal cells
Stomach acid production is under neural, paracrine and endocrine control. Which substance is involved in endocrine control of stomach acid production?
Gastrin - released from G cells stimulates H+ production in parietal cells
Where are G-cells found?
Antrum
What is the effect of the hormone somatostatin?
It inhibits gastrin secretion in G cells which reduces the stimulation of gastrin on parietal cells, therefore less H+ is secreted into the stomach
Where is somatostatin secreted from and what stimulates this secretion?
Somatostatin is secreted from D cells in response to stimulation by stomach acid
Which two factors inhibit HCl secretion in the stomach?
- Low pH-> D-cell activation -> somatostatin release
2. Reduction in stomach distension -> decreased vagal activity…
What specialised cells in the stomach are responsible for the secretion of pepsinogen?
Chief cells
Which cells in the stomach produce mucous?
Mucous neck cells and surface mucous cells
What do parietal cells secrete?
Stomach acid and intrinsic factor
What do enteroendocrine cells secrete?
E.g. C-cells, D-cells and ECL cells. Hormones like gastrin and somatostatin
What type of chronic gastritis can lead to megaloblastic anaemia?
Chronic autoimmune gastritis - a process which attacks parietal cells which secrete intrinsic factor. Intrinsic factor is essential for absorption of vitamin B12. B12 deficiency leads to megaloblastic anaemia (pernicious anaemia)
What is megaloblastic anaemia?
A type of pernicious anaemia caused by inhibition of DNA synthesis during red blood cell production
What type of anaemia can be caused by bacterial and reactive gastritis in severe cases?
Microcytic anaemia due to iron deficiency from blood loss
What is the major function of the stomach?
Initial digestion - though salivary amylase in the oral cavity starts digestion
What types of absorption occur in the stomach?
NO nutrient or water absorption
What is the name of the first part of the duodenum which joins the stomach and what is it a common site for?
Duonenal bulb - a common site for peptic ulcers
What is a peptic ulcer?
An umbrella term for any ulcer that happens in the stomach or duodenum
What is receptive relaxation?
Relaxation and distension of the UPPER (thin-walled) portion of the stomach to maintain a steady pressure within the stomach, preventing reflux of contents into the oesophagus