Motility of the Large Intestine

• What is the primary function of the small intestine in terms of motor activity?

  There is no storage function in the small intestine.
• What is the transit time for the small intestine?

  The transit time is a few hours.
• What is the gradient basal electrical rhythm (BER) in the small intestine?

  It is a rhythmic electrical activity that coordinates motor activity.
• What is the motor motility complex (MMC) in the small intestine?

  It is a pattern of motor activity that occurs in the small intestine.
• What type of movement occurs in the small intestine?

  There is no retrograde movement or mass movement in the small intestine.
• What type of muscle is present in the small intestine?

  There is continuous longitudinal muscle in the small intestine.
• What is the primary function of the large intestine in terms of motor activity?

  The large intestine has a storage function.
• What is the transit time for the large intestine?

  The transit time is a few days.
• What is the difference in electrical rhythm between the small and large intestine?

  The large intestine has no gradient basal electrical rhythm.
• What type of movement is frequent in the large intestine?

  There is frequent retrograde movement and mass movement in the large intestine.
• How many bands of longitudinal muscle are present in the large intestine?

  There are 3 discrete bands of longitudinal muscle in the large intestine.
• What are the types of colonic motility and their consequences?

  • Mixing movements: occur in the proximal colon, facilitate absorption of salts and water, no net movement.
  • Haustral migration: net movement of chyme in an aboral direction.
  • Mass movement: least common, occurs in central and distal colon, sweeps feces towards the rectum.
• Where do mixing movements primarily occur in the colon?

  Mixing movements occur primarily in the proximal colon.
• What is the purpose of haustral migration?

  Haustral migration is the net movement of chyme in an aboral direction.
• What is the least common type of colonic motility?

  Mass movement is the least common type of colonic motility.
• What triggers reflexive defecation?

  The initial process is triggered by stool entering the rectum and causing muscle contractions.
• What happens to the internal anal sphincter during reflexive defecation?

  The internal anal sphincter relaxes involuntarily.
• What is the role of the external anal sphincter during defecation?

  The external anal sphincter allows for conscious control of defecation.
• What is the myenteric reflex?

  The myenteric reflex is the intrinsic neural pathway that triggers rectal muscle contractions.
• How does the parasympathetic nervous system contribute to defecation?

  The parasympathetic nervous system contributes to rectal muscle contraction and internal sphincter relaxation.
• What differentiates voluntary control from intrinsic control during reflexive defecation?

  Voluntary control involves conscious actions, while intrinsic control is involuntary and automatic.
• What activates stretch receptors during reflexive defecation?

  The stretching of the rectal walls by stool activates stretch receptors.
• What is the consequence of rectal distention during defecation?

  Rectal distention initiates a reflex contraction of the rectal muscles.
• What role does abdominal muscle contraction play in defecation?

  Voluntary contraction of the abdominal muscles can assist defecation.
• What are the primary substrates for colonic bacterial metabolism?

  Undigested carbohydrates (fiber) in the diet
• What do bacteria ferment undigested carbohydrates to produce?

  Short-chain fatty acids like acetate, propionate, and butyrate
• What types of dietary fiber are included as non-digestible carbohydrates?

  • Cellulose
  • Hemicellulose
  • Pectin
• What is resistant starch?

  A type of starch that resists digestion in the small intestine
• What are oligosaccharides also known as?

  Prebiotics
• What are some sugars that can escape digestion in the small intestine?

  Some sugars that are not fully broken down during digestion
• What are the main products of colonic bacterial metabolism?

  Hydrogen, carbon dioxide, and sometimes methane
• What are the short-chain fatty acids produced by colonic bacteria?

  • Acetate
  • Propionate
  • Butyrate
• How can the composition of gases produced in the colon be affected?

  By the type of substrate available and the dominant bacterial species present
• What effect does higher fiber intake have on short-chain fatty acid production and gas formation?

  It leads to increased short-chain fatty acid production and gas formation