GI motility (Fan) Flashcards
What is the result of mixing food content with various secretions?
reduction in particle size, increased digestion, and enhanced absorption of nutrients
What does aboral movement mean?
Towards the anus/away from the mouth (vomiting is the only exception to aboral movement)
What is the purpose of phasic contractions?
Generate the force to move material along the tract
What is the purpose of tonic contractions?
Normally occurs in sphincters. Creates resistance to movement
Function of mastication (chewing)?
(1) reduce particle size (depends on consistency of food)
(2) mixing food with saliva to lubricate the mass and increase exposure to salivary amylase (carbohydrate digestion) and lingual lipase (lipid digestion)
(3) enhance stimulation of taste buds and other receptors in the oral cavity (increase salivation and appreciation of food)
Oral phase of swallowing - involuntary or voluntary?
Both
When does primary esophageal peristalsis begin?
After the contraction of the UES
What is antral systole?
Simultaneous contraction of the terminal antrum and pylorus
What is the result of antral systole?
(1) retrograde movement of chyme back into the stomach, leading to effective mixing
(2) shearing forces (grinding of luminal contents), which reduces partil size
Personal factors that reduce the frequency of defecation?
- diet low in insoluble fiber
- insufficient fluid intake
- excessive delay of defecation
- narcotic drugs
- physical inactivity
- antibiotics
- old age (improvable and hopefully correctable)
What is the valsalva maneuver?
The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one’s mouth, pinching one’s nose shut while pressing out as if blowing up a balloon.
** Facilitates defecation **
Describe resting conditions in the colon
rectum is empty and relaxed, the internal anal sphincter is contracted to near maximum tone and the EAS is near minimum tone
During defecation, what innervation leads to movement of fecal material in the colon?
enteric and parasympathetic mediated reflexes lead to relaxaion of the internal anal sphincter and further colonic peristaltic contraction.
What is special about the external anal sphincter?
under sympathetic and voluntary control
how does morphine affect movement of chyme?
morphine increases resistance to movement of chyme/feces by stimulating generalized contractions. This reduces propulsive activity and can result in constipation.
what affect does caster oil (ricinoleic acid) have on chyme movement?
decreases resistance to movement of chyme/feces by stimulating generalized contractions
What are the three types of contraction occuring in the colon
- mass movement (rare)
- peistaltic activity - push stool aborally/to anus (occassional)
- Segmenting nonperistaltic contactions (also known as haustral shuttling)
What contractions occur in the small intestine?
- segmental type contractions
what is mass movement contraction?
sustain peristaltic wave
significance of segmenting nonperistaltic contractions (haustral shuttling)?
slows fecal steam; ensures absorption of water and electrolytes
How does inactivity affect bowel movements?
Physical inactivity for periods of time will inhibit mass movements (peristalsis). This may be rlated to the observation of constipation with bed rest or long plane trips
What are the two set of pacemaker cells in the large intestine motility?
(1) ECA ggenerating cells at the submucosal border of circular muscle
(2) myenteric potential oscillation cells
What are myenteric potential oscillation cells?
between circular and longitudinal cells. initiate additional low, irregular amplitude and high frequency chanes in the resting membrane potential. these changes are propagated for short distances. Haustra develop as a result of localized contractions.
where is the cecum?
beginning of the large intestine
what is the reflex for the ileo-cecal junction for ileal distension?
relaxation
what is the reflex for the ileo-cecal junction for cecal distension?
increased contraction
What are the functions of the ileocecal sphincter?
(1) to delay transit of chyme into the colon, allowing increased time for absorption
(2) to prevent bacterial overgrowth in the ileum
