L5 The Stomach Flashcards
What are the different areas of the stomach?
- LES - The lower esophageal sphincter (LES) is a bundle of muscles at the low end of the esophagus, where it meets the stomach.
- Cardia - The part of the stomach that is closest to the esophagus
- Fundus - the upper part of the stomach, which forms a bulge above the level of the opening of the oesophagus (furthest from the pylorus).
- Body of the Stomach
- Antrum - The antrum is the lower part of the stomach. The antrum holds the broken-down food until it is ready to be released into the small intestine. It is sometimes called the pyloric antrum. The pylorus is the part of the stomach that connects to the small intestine.
- Pylorus
What secretions occur at the cardia and LES?
Mucus and Bicarbonate
What secretion occur at the fundus and body of the stomach?
Protons, Intrinsic factor, Mucus, Bicarbonate (protects the stomach from being digested by its own enzymes and the HCl), Pepsinogens and Lipase
What secretions occur at the antrum and the pylorus?
Mucus and bicarbonate
What is the different function of parts of the stomach?
LES and cardia - control of food into the stomach. Prevention of reflux. Belching.
Fundus and body - Food is stored and mixed. Acts as a reservoir. Tonic force during emptying. Not high motile compared to the antrum and pylorus and so the peristaltic waves are not as great. Stores food and mixes it with secretions. Initial digestion of carbohydrates. Accommodates food and passes it to the pylorus.
Antrum and pylorus - where mixing, grinding and sieving takes place. regulation of emptying.
What is the vago-vagal reflex?
Vagovagal reflex refers to gastrointestinal tract reflex circuits where afferent and efferent fibers of the vagus nerve coordinate responses to gut stimuli via the dorsal vagal complex in the brain. This reflex also allows for the accommodation of large amounts of food in the gastrointestinal tracts. It helps tell the stomach to expand to accommodate the food without increasing pressure. After a litre, you will then feel you are full.
How is gastric emptying controlled?
- Size of the particles, particles larger than 1-2 mm cannot pass the pyloric sphincter
- Duodenum delivery of acid, amino acids and lipids and secretes hormones (CCK, Secretin, GIP) which decreases gastric emptying
- Carbohydrates leave faster than fatty meals
- Enteric nervous system
- feedback from the duodenum
What are the different phases of gastric secretion?
Cephalic phase - when you smell or see food or think of food. This causes messages to the brain to prepare the stomach to prepare fro the food. accounts for 1/3.
Gastric phase - stomach distention activates stretch receptors. Food chemicals and rising pH activate chemoreceptors. This leads to vagostimulation and g cells secreting gastrin.
Intestinal phase - Presence of low pH and partially digested food in the duodenum as the stomach empties leads to intestinal gastrin release into the blood to stimulate stomach secretory activity.
What are gastric pits and glands?
There are pit in the mucosa leading to gastric glands. There are different glands in the stomach depending on where you are. There are different cell types such as endocrine cells, chief cells and parietal cells.
Where is gastrin released from?
G cells
What is gastrin homologous with?
CCK-PZ
What are the different forms of gastrin?
G17 - main form secreted from antrum
G34 - main from secreted from the duodenum
What is the release of gastrin stimulated by?
- Partially digested proteins in the stomach. This leads to an increase in pH. This is sensed by the parasympathetic system and causes G cells to release gastrin.
- Parasympathetic input (cephalic and gastric)
What is the release of gastrin inhibited by?
Lumenal proton - pH in the lumen decrease causes a negative feedback
What is the role of somatostatin?
Inhibit gastrin
Released in response to increased lumenal proton concentration and inhibited by ACh. Acts on G cells to inhibit the release of gastrin and also CCK and secretin.
