Lecture 4 (we're getting there!!!) Flashcards
What is the only part of the GI tract for ingestion
The mouth
What do mumps infect
Parotid glands
What do parotid glands release
Watery (serous) secretions
What percent of saliva do the parotid glands create
25%
What percent of saliva does the submandibular glands create
70%
What kind of saliva do the submandibular glands secrete
serous and mucous
What percent of saliva does the sublingual glands secrete
5%
What kind of saliva do sublingual glands produce
Mucousy
What is another word for swallowing
Deglutition
What are the 2 phases of swallowing
Buccal
Pharyngeal-esophageal
What phase of swallowing is voluntary
Buccal phase
Describe the buccal phase
Tongue forced against hard palate
tongue forces food into oropharynx
What phase of swallowing is involuntary
pharyngeal-esophageal
What is the pharyngeal-esophageal phase controlled by
The swallowing center
Where is the swallowing center located
Medulla
Lower pons
What phase of swallowing involves blocking off every path except to the stomach
Pharyngeal-esophageal
Where is the gastro esophageal sphincter located
Between esophagus and stomach
What is a hiatal hernia
When the diaphragm is not properly positioned and the stomach pushes up
What is barrett’s esophagus
when esophageal tissue is exposed to stomach acid, and tissue becomes to look more similar to stomach tissue
What can barrett’s esophagus progess to
Esophageal cancer
What is food converted to in the stomach
Chyme
Where is casein found
Milk
What is the function of rennin
digest casein
What does pepsin do
Digest proteins
What enzyme digests proteins
Pepsin
What two lipid soluble drugs are easily absorbed by the stomach
Anti-inflammatory drugs and alcohol
What is the function of intrinsic factor
absorption for B12
What is B12 necessary for
RBC
What transforms pepsinogen into pepsin
HCl
What denatures proteins and nucleic acids in the stomach
HCl
What are the 3 phases of gastric secretion
Cephalic
Gastric
Intestinal
What phase of gastric secretion occurs before food enters the stomach
Cephalic
How long is the cephalic phase
only a few minutes
What is the function of the cephalic phase
To “prime” the stomach for food
What inputs the hypothalamus vagal nuclei of medulla oblongata leading to secretion of gastric juice
Olfactory taste buds
How long is the gastric phase
3-4 hours long
What phase provides about 2/3 of gastric secretions
Gastric
What 3 things initiate the gastric phase
Distension of stomach
Peptides
Low acidity
How does stomach distension initiate the gastric phase
Mechanoreceptors’s vagal reflexes release Ach and increase output of gastric juices
What are the more important triggers for the gastric phase
Peptides and low acidity
What cells secrete gastrin
G cells
Where do you find G cells
Stomach pyloric antrum
What do G cells secrete
Gastrin
What do peptides and low acidity lead to
Secretion of gastrin and histamines
Does caffeine increase or decrease gastrin secretions
Increase
Proteins are _______ to increase stomach pH
Buffers
Gatrin secretion is _______ when pH is below 2
inhibited
What does gastrin do
Increases gastric juice secretion (especially HCl)
What cells secrete HCl
Parietal cells
What cells secrete intrinsic factor
Parietal
Parietal cells secrete what
Intrinsic factor
HCl
What do chief cells secrete
pepsinogen
What do enteroendocrine cells secrete
Hormones and paracrines
What are the two components of the intestinal phase
excitatory
inhibatory
What is the excitatory component of the intestinal phase mediated by
Intestinal gastrin
What is the excitatory component of the intestinal phase triggered by
Low pH and foodstuffs as chyme enters the duodenum
What happens when during the inhibitory component of the intestinal phase
Enterogastric reflex:
vagal nuclein in medulla inhibited
Local reflexes inhibited
Sympathetic fibers activated - pyloric sphincter tightens
What are the two main enterogastrones
Secretin
Cholecystokinin
What happens when enterogastrons are released
Gastric secretion decreases
Gastric emptying slows
What are secretin and cholecystokinin
enterogastrones
Is H+ secretion into stomach lument active or passive
active
What is H+ secretion in response to
Gastrin
Ach
Histamine
What is H+ derived from
Carbonic acid
What follows H+ and why
Cl- to maintain electrical balance
What is the other product of HCL secretion
HCO3-
What is the alkaline tide
rise in plasma/urinary pH from efflusx of HCO3- into blood in exchange for Cl-
When does the alkaline tide occur
After a meal
What is tagamet
Treatment for an ulcer
What does tagamet do
inhibits the histamine-H2 receptor interaction
How does tagamet inhibit the histamine-H2 receptor interaction
Tagamet binds to H2 to prevent it from binding to histamine
What is accommodation
smooth muscle allowing stomach to stretch without increasing tension
What are the interstitial cells of cajal
they depolarize every 20 seconds and regulate stomach constriction
Rate of stomach emptying is largely dependent on what
signalling from the duodenum