Gastric Secretion Flashcards
What is ingestion?
Taking in food
What does mechanical digestion involve?
Chewing (mouth)
Churning (stomach)
Segmentation (small intestine)
What is propulsion?
Swallowing (oropharynx)
Peristalsis (oesophagus, stomach, small and large intestine)
What are the absorption mechanisms?
Lymph vessels
Blood vessels
What is defecation
Getting rid of waste out of anus
What two sphincters are involved in the stomach?
Cardiac (oesophagus)
Pyloric (duedenum)
What are the three layers of muscularis externa?
Longitudinal layer
Circular layer
Oblique layer
What curvatures are involved in the stomach?
Lesser curvature
Greater curvature
What is the fundus?
Top section of the stomach wall
What are the rugae of mucosa?
Ridges inside the stomach
What are the layers of the stomach wall?
Mucosa
Submucosa
Muscularis externa
Serosa
What do gastric pits do?
Lead to gastric glands
What do gastric glands do?
Produce gastric juice
What types of cells make up the mucosa of the stomach
Simple columnar epithelium
What do mucous neck cells do?
They make up the neck of the gastric pits
What are the gastric glands cells?
Parietal
Chief
Mucous neck
What cells are at the bottom of the gastric pit?
Enteroendocrine cells
Where is most of the gastric juice produced?
Glands in the fundus and body (oxyntic glands)
What does gastric juice consist of?
Hydrochloric acid
Pepsinogen
Intrinsic factor
Mucus
What do parietal cells do?
Secrets intrinsic factor and HCl
What does intrinsic factor do?
Required for absorption of vitamin B12
What does HCl do?
Kills microbes
Denatures proteins
Activates enzymes
What ph is HCL?
1-3
What do chief cells do?
Secretes pepsinogen and gastric lipase
What does pepsinogen do?
Breaks down peptide bonds
Converted to pepsin by HCL
What does gastric lipase do?
Splits short chain triglycerides into fatty acids and monoglycerides
What do mucous cells do?
Secrete mucus
What two mucous cells are there?
Superficial epithelia
Mucuous neck cells
What does mucus do?
Forms a protective barrier
Has alkaline properties
What is gastropathy?
When the stomach goes wrong…
What can cause damage to the stomach?
Drugs Infection Stress Alcohol Radiotherapy
What does helicobacter pylori do?
Often leads to ulcers
What mechanisms regulate gastric secretion?
Neural and hormonal mechanisms
What are the phases of gastric secretion?
Cephalic phase (reflex)
Gastric phase
Intestinal phase
When does the cephalic phase occur?
A few minutes prior to food entry
When does the gastric phase happen?
3-4 hours after food enters the stomach
When does the intestinal phase happen?
When food enters duodenum
Followed by inhibitory effects
What happens in the cephalic phase?
Smell, site, thought and taste of food activates CNS
Nerves activated
Glands activated
Prepares mouth and stomach for food
What nerves activate cephalic phase?
Facial
Glossopharyngeal
Vagus
What glands activate during the cephalic phase?
Salivary and gastric
What happens in the gastric phase?
Food distended the stomach and stimulates stretch receptors
Chemoreceptors detect increase in pH…
…Perisatalisis and gastric juice secretion.
Chyme emptied into duodenum
pH and distension decreases
What is gastric phase an example of?
Negative feedback loop
What is gastric phase regulated by?
Gastric
Where is gastrin produced?
Released by G cells of gastric glands
When is gastrin released?
In response to food in stomach and stimulation of parasympathetic system
Gastrin is released into the…
Bloodstream
What does gastrin stimulate?
Gastric juice secretion
What does gastrin prevent?
Acid reflux
When does gastrin production stop?
When pH is less that 2
Negative feedback
When does the intestinal phase occur?
When food enters small intestine
What does the intestinal phase inhibit?
Inhibits exit of chyme from stomach by inhibiting gastric motility and contraction of the pyloric sphincter
Inhibits gastric secretion
What does intestinal phase promote?
Digestion of food in small intestine
