GI Motility Phys Flashcards
The entire GI tract is -0—– muscle except for what regions?
Entire GI tract is smooth muscle except for upper 1/3 of esophagus (striated) and external anal sphincter (striated).
What triggers a contraction in the upper pharynx?
A bolus of food touching the back of the throat
How does swallowing occur?
1) Upper constrictors will contract
2) Epiglottis will close the opening of the airway allowing the bolus to move down the pharynx.
3) Upper esophageal sphincter relaxes and allows the bolus into the esophagus.
Pressures in the esophagus at rest are?
Below the atmospheric pressure when you are in the sction of esophagus above the diaphragm because they lie within the thorax.
Once you move below the diaphragm the resting esophageal pressures are positive again.
Note: during a swallow, the regions of the esophagus located above the diaphragm increase in pressure to above atmospheric.
Swallowing center located where
medulla
If the vagus nerve is severed, which part of the esophagus will not work?
The upper 1/3 because it is striated muscle and is innervated directly by the vagal efferents, therefore if vagal nerve is cut, it cannot be stimulated.
Why is the lower 2/3 of the esophagus not impacted in a similar way?
Because the myenteric plexus has increased control over the smooth muscle of the lower 2/3. Not directly innervated by vagus.
What part of the stomach contains oxyntic galnds
Body and Fundus
What part of the stomach contains pyloric glands or is referred to as the pyloric gland area?
Antrum
What is the pressure of the lower esophageal sphincter at rest?
above atmospheric pressure…..drops to around 0 during swallowing
What is the pressure of the fundus at rest
Positve….drops to just barely over atmospheric pressure during swallowing
KNOW, the upper part of the stomach has very weak contractions whereas the lower part of the stomach has 3-5 contractions per minute in order to mix food and breakdown size
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KNOW…only small amounts of a bolus are pushed through the pyloric sphincter at one time. The rest of the bolus is propelled back into the stomach in order to be mixed
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Gastric slow waves are always present and come from where?
interstitial cells of cajal
If the stomach is empty, very few of these slow waves generate a degree of depolarization that is sufficient to generate a contraction. If there is afood in the stomach, its a different story. Most of them will generate a contraction
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It is IMPORTANT to realize that the frequnecy of slow waves does not vary! What varies is the height of the depolarizations and thus the number of contractions
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How long does it generally take for a meal to leave the human stomach
3 hours…the more liquid present, the quicker everything moves through.
What are some things that prevent gastric emptying from occurring at a rate which impedes the ability of the duodenum to digest it.
- Fat content- the more fat content, the slower the gastric emptying is b/c the fat is not water soluble
- Increased acid- high acid = slower peristalsis through a neural reflex
- CCK- slows gastric emptying
During persitalsis, what is the length of most contractions ( in regards to distance?
4-5 cm
What is different about slow waves in the small intestine in comparison to those discussed for the stomach
In the small intestine, the amplitude (degree of polarization) is always the same, in the stomach it varies depending on how full the stomach is. In the small intestine however, you must have a corresponding action potential for the small waves to generate a contraction.
At rest, is the UES below atmospheric pressure?
No, it is above…drops down to around atmpospheric pressure during a swallow
Receptive relaxation of the stomach controlled by
vagal-vagal reflex….triggered by swallowing
What types of glands are found in the oxyntic gland area?
parietal cells
What moves through the stomach fastest?
Isotonic glucose
The ileocecal sphincter relaxes with distension of which part of the colon?
Ileum…so food can pass through
IT CONTRACTS AGIAN HOEWVER AS COLON distends
Does the ileocecal sphincter require neuronal input?
NOPE
Migrating motor complex triggered by release of
Motilin
What is the migrating motor complex?
housekeeping
When the rectum is distended by a mass movement it will contract as the internal anal sphincter relaxes. If you don’t want to use the bathroom, you can voluntarily contract the external anal sphintcter . Internal anal sphincter will slowly tighten back up
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