Stomach and duodenum Flashcards
What is stomach: secretory function
- epithelial lining is composed of- goblet cells that produce a coat alkaline mucus this mucus surface layer traps a bicarbonate-rich fluid beneath it.
- gastric pits contain gastric glands that secrete gastric juice, mucus, and gastric
Namer the secretory cells and function
A= mucus neck cells= secrete acid mucus
B= parietal cells= secrete HCI and intrinsic factor
C= chief cells= produce pepsinogen (pepsinogen is activated to pepsin by.)
1. HCI in the stomach
2. Pepsin it self via a positive feedback mechanism
D=enters endocrine cells- secrete gastrin, histamine, endorphins, serotonin,cholecystokinin and somatostatin into the laming propria
Explain the process of gastric secretion
Neural and hormonal mechanism regulate the release of gastric juice stimulator and inhibitory events occur in three phases:
Name phases of gastric secretion and explain
- Cephalic (reflex) phase: prior to food entry
- gastric phase: once food enters the stomach
- intestinal phase: as partially digested food enters the duodenum
Explain cephalic phase
Excitatory events include:
= sight or thought of food
= stimulation of taster or smell receptors
Intribitory events include:
= loss of appetite or depression
= decrease in stimulation of the parasympathetic division
Explain gastric inhibitory and excitatory events
Excitatory events include=
stomach distension,
activation of stretch receptors neural activation,
activation of chemoreceptors by peptides, caffeine and rising ph
release of gastric to the blood
Inhibitory events:
• A ph lower than 2
• emotional upset that overrides the parasympathetic division
Explain intestinal phase excitatory and inhibitory events
Excitatory= low ph, partially digested food enters the duodenum and encourages gastric gland activity
Inhibitory= distension of duodenum, presence of fatty, acid, or hypertonic chyme, and/or it rants in the duodenum
- initiates inhibition of local reflex and vague nuclei
- closes the pyloric sphincter
-releases enterogastiones that inhibit gastric secretion
Explain how gastric filling works
- stomach pressure remains constant until about 1L of food is ingested
- relative unchanging pressure results from reflex-mediated relaxation and plasticity
What is included in reflex mediated events
Receptive relaxation = as food travels in the oesophagus stomach muscles relax
Adaptive relaxation= the stomachdialates in response to gastric filling
In gastric filling what does plasticity mean
It is the intrinsic ability of smooth muscle to exhibit the stress-relaxation response.
(peristaltic waves move toward the pelorus at the rate of 3 per minute)
What initiates the basic electrical rhythm in gastric filling
Pacemaker cells called cells of Cajal
Where is the most vigorous peristalsis
Near the pylorus
Explain how chyme is delivered
It is derived is small amounts to the duodenum or
Forced back ward into the stomach for further mixing
Which two mechanisms assist in gastric emptying
The neural enterogastic reflex
Hormonal (enterogastrone) mechanism
What is the function of mechanisms of gastric filling
To inhibit gastric secretion and duodenal filling
• carbohydrate-rich chyme quickly moves through the duodenum
O fast laden chyme is cligested move slowly causing food to remain in the stomach longer
What affect gastric emptying
• fluidity of chime • volume of gastric contents • Osmolality of chime • caloric density eg fats • acidity of chime • body position • hormones= cholecystokin, secreting somatostatin slow GE;motilitin t3 and Insulin enhance GE
Explain vomiting
• forceful expulsion of gastric and intestinal contents through mouth
• usually preceded by nausea (ANS response)
• controlled by vomiting centre (VC) in medulla
• efferent impulses= diaphragm and abdominal muscles
• following irritation or stimulus vomiting begins with deep
(inspiration = glottis closes = soft palate is elevated= abdominal muscles
Contract increased intra-abdominal pressure)= cardiac sphincter and stomach body relates = gastric contents are forced upward
What is the epithelium of duodenum mucosa made up of
• absorptive cells and goblet cells
• Enteroendocrine cells
Interspersed T cells called intraepithetial lymphocytes (IELS) (IELS immediately release cytokines upon encountering Ag
What is the function of duodenum
1= movement of contents by peristalsis- parasympathetic stimulation 2= secretion of intestinal juice- parasympathetic stimulation
3= completion ct chemical digestion of carbohydrates protein and fats in the enterocytes of the villi
4= protection against infection by microbes that have survived theantimitrobial action of the hydrochloric acid in stomach by the solitary
Lymph follicles and aggregated lymph follicles
5= secretion of the hormones cholecystokinin (CCK) and secretion
6= absorption of nutrients
What secrets intestinal juice
Secreted by intestinal glands in response to distension cr irritation of mucosa
It is slightly alkaline and isotonic with blood plasma (5-34/d9)
Largely water, enzyme-poor, but contains mucus
