The Stomach Flashcards
Name the 4 regions of the stomach
Cardia
Fundus
Corpus
Pylorus (antrum and sphincter)
How does the horse stomach differ to a common monogastric?
Large fundus (saccus cecus) and two distinct glandular and non-glandular regions split down the margo plicatus
What holds the stomach in place in the abdominal cavity?
Lesser omentum (cranial) Greater omentum (caudal)
What are the 4 main blood vessles supply oxygenated blood to the stomach?
Coeliac artery
hepatic
Splenic
Left Gastric
Describe the muscle layers of the stomach
Outer layer = longitudinal (continuous with the oesophagus)
Inner layer = circular (only in body and pylorus - not around fundus)
Internal oblique -> fundus and greater curvature
Describe the innervation of the stomach
Innervated by PSNS fibres within the two vagal trunks
By SNS fibres that reach stomach with arteries
PSNS fibres extend from vagus and synapse within the submucosa between the muscle coats onto the intramural plexuses where ti exerts control over the stomach.
Vagal stimulation:
- Proximal stomach: suppresses muscular contractions -> relaxation
Distal stomach: causes intense peristaltic activity (ACh)
Intramural plexus -> local reflexes
Only PSNS fibres reach secretory glands
What are the three main functions of the stomach?
store food
mechanical degradation of food
secretion of gastric juice
What cell type produces HCL in the stomach?
Parietal (stimulated by gastrin and short/long reflexes and vagal nerve stimulation)
What is the main function of HCL?
Kill bactera, activate pepsinogen, denature protein
What cell type secretes pepsinogen?
Chief cells (stimulated by vagal nerve impulses and short/long reflexes)
What is the function of pepsinogen?
Inactive (proenzyme) of pepsin, activated by HCL (autocatalysis). Pepsin then uses hydrolysis to undo peptide linkages within protein molecules -> break down to shorter peptides
Which region of the stomach are Parietal cells found in?
Fundus
Corpus
Which region of the stomach are chief cells found?
Fundus
Corpus
Which region of the stomach are ECL cells found?
Corpus
How is HCl made?
H+ generated by carbonic anhydrase (CO2 converted o carbonic acid then hydorgen and bicarb
What regulates the secretion of HCl?
Ach (Cholinergic neurons), Gastrin and Histamine
What is gastrin?
Gastric is a digestive tract hormone, released in response to peptides stimulating G-cells (Gastrin cells), + vagal stimulation (from +sight/smell/taste)
Where are G cells found?
Pylorus
What causes the release of histamine?
Stimulation of ECL and gastin release
What cell type produces mucin in the stomach and where is it found?
Cardia - mucous cells
Explain the action of gastrin
G cells release gastrin from vagal nerve impulses -> gastrin is i the blood which acts on parietal cells -> causing them to release HCL.
ALSO
Peptides can stimulate gastrin release -> act on parietal cells
ALSO
Short and long reflex also act on the G cells + gastrin release
What are the 3 stages of the normal secretion cycle?
Cephalic phase, Gastric phase and Intestinal phase
Describe the cephalic phase
CNS stimulation -> senses pick up food -> prepares stomach for it -> neural output.
Vagal fibres -> mucous cells, cheif cells, parietal cells and G cells -> causes a release of gastric juices
Describe the gastric phase
trigger = food arriving in the stomach
Neural component:
stretch and chemoreceptors - trigger myenteri and submucosal reflexes -> Ach released at parietal cells -> HCL secretion
Hormonal
Gastrin secreted enter circulation where stimulates parietal and chief cells -> increases secretion rates
Describe the intestinal phase
chime pushed into SI
Neural response
stretch stimualtion -> enterogastric reflex
Hormonal
Lipid, CHO in duodenum -> CCK released and gastric inhibitory peptide -> causes a reduction in gastric secretions and contractions (slow it down for absorption)
Duodenal drop in pH causes secretin to be released -> inhibits parietal and chief cells -> buffer release
