Guyton Ch. 64 Propulsion and Mixing of Food in the Alimentary Tract
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Questions and Answers

What controls the timing of mixing and propulsion activities in the alimentary tract?

  • Appetite
  • Intrinsic desire for food
  • Hormonal mechanisms
  • Automatic nervous mechanisms (correct)

Which chapter discusses the mechanisms of food ingestion, especially mastication and swallowing?

  • Chapter 48
  • Chapter 64 and Chapter 72
  • Chapter 64 (correct)
  • Chapter 72

What type of teeth provide a strong cutting action for chewing?

  • Molars
  • Canines
  • Incisors (correct)
  • Premolars

What determines the amount of food that a person ingests?

<p>Hunger (A)</p> Signup and view all the answers

Which teeth provide a grinding action for chewing?

<p>Molars (D)</p> Signup and view all the answers

What is discussed in Chapter 72 in relation to the body's nutrition?

<p>Mechanisms for maintaining an adequate nutritional supply (D)</p> Signup and view all the answers

What is the primary function of the intense peristaltic contractions in the stomach during stomach emptying?

<p>Forcing up to several milliliters of chyme into the duodenum (A)</p> Signup and view all the answers

What is the role of the pyloric sphincter in stomach emptying?

<p>To prevent passage of food particles until they become almost fluid consistency (B)</p> Signup and view all the answers

Which factor promotes increased emptying from the stomach?

<p>Stretching of the stomach wall (D)</p> Signup and view all the answers

Which factor can initiate enterogastric inhibitory reflexes from the duodenum?

<p>Presence of breakdown products of fats in the chyme (A)</p> Signup and view all the answers

What is the effect of the hormone gastrin on stomach emptying?

<p>Promotes stomach emptying (A)</p> Signup and view all the answers

What happens if the pH of the chyme in the duodenum falls below about 3.5 to 4?

<p>Stops further release of acidic stomach contents into the duodenum (C)</p> Signup and view all the answers

What is the primary effect of enterogastric inhibitory reflexes?

<p>Inhibit stomach emptying (A)</p> Signup and view all the answers

What are the types of factors that are continually monitored in the duodenum to initiate enterogastric inhibitory reflexes?

<p>Distention of the duodenum, presence of irritation of the duodenal mucosa, and acidity of the chyme (A)</p> Signup and view all the answers

What is the role of the intense peristaltic contractions in causing stomach emptying?

<p>Gradually pinching off food in the body of the stomach (C)</p> Signup and view all the answers

What effect does increased food volume in the stomach have on stomach emptying?

<p>It elicits local myenteric reflexes that accentuate activity (D)</p> Signup and view all the answers

What is a significant effect of stretching of the stomach wall on stomach emptying?

<p>It accentuates activity of the pyloric pump (D)</p> Signup and view all the answers

Which factor elicits inhibitory enterogastric reflexes to slow or stop stomach emptying?

<p>Breakdown products of fats (A)</p> Signup and view all the answers

Which cranial nerve innervates most of the muscles of chewing?

<p>Fifth cranial nerve (C)</p> Signup and view all the answers

What force can all the jaw muscles working together close the molars with?

<p>200 pounds (A)</p> Signup and view all the answers

What initiates reflex inhibition of the muscles of mastication during chewing?

<p>Presence of a bolus of food in the mouth (A)</p> Signup and view all the answers

Why is chewing especially important for most fruits and raw vegetables?

<p>They have indigestible cellulose membranes around their nutrient portions (D)</p> Signup and view all the answers

What is the principal reason that grinding the food to a very fine particulate consistency aids digestion?

<p>Increases surface area exposed to digestive secretions (B)</p> Signup and view all the answers

What initiates a series of automatic pharyngeal muscle contractions during the involuntary pharyngeal stage of swallowing?

<p>Bolus of food entering the posterior mouth and pharynx (D)</p> Signup and view all the answers

What is the main role of the pharynx during swallowing?

<p>Subserves respiration and swallowing (D)</p> Signup and view all the answers

What prevents reflux of food into the nasal cavities during the involuntary pharyngeal stage of swallowing?

<p>Soft palate is pulled upward to close the posterior nares (D)</p> Signup and view all the answers

What is the function of the valvelike mechanism of the lower esophagus?

<p>To prevent high intra-abdominal pressure from pushing stomach contents into the esophagus (B)</p> Signup and view all the answers

What is the role of vagovagal reflex in the stomach?

<p>To reduce the tone in the muscular wall of the stomach (D)</p> Signup and view all the answers

What initiates the mixing waves in the stomach?

<p>Basic electrical rhythm of the stomach wall (D)</p> Signup and view all the answers

What is the main role of the peristaltic constrictor rings in the antrum of the stomach?

<p>To squeeze antral contents upstream through retropulsion (A)</p> Signup and view all the answers

What determines the degree of fluidity of chyme leaving the stomach?

<p>The degree of digestion that has occurred (C)</p> Signup and view all the answers

What causes hunger pangs in individuals after prolonged fasting?

<p>Decreased levels of blood sugar (D)</p> Signup and view all the answers

What happens when hunger contractions become extremely strong in the body of the stomach?

<p>They fuse to cause a continuing tetanic contraction (A)</p> Signup and view all the answers

How are hunger contractions affected by gastrointestinal tonus?

<p>They are most intense in individuals with high gastrointestinal tonus (B)</p> Signup and view all the answers

What promotes stomach emptying?

<p>Intense peristaltic contractions in the antrum (D)</p> Signup and view all the answers

What is the main role of cholecystokinin (CCK) in inhibiting gastric emptying?

<p>Inhibiting the pyloric pump and increasing the strength of contraction of the pyloric sphincter (C)</p> Signup and view all the answers

What stimulates the release of inhibitory hormones from the upper intestine?

<p>Fats entering the duodenum (B)</p> Signup and view all the answers

Which hormone has a general but weak effect of decreasing gastrointestinal motility?

<p>Gastric inhibitory peptide (GIP) (D)</p> Signup and view all the answers

What are the two main conditions under which the rate of stomach emptying is slowed by inhibitory feedback signals from the duodenum?

<p>Too much chyme in the small intestine and excessively acidic chyme (D)</p> Signup and view all the answers

What is the main effect of gastric inhibitory peptide (GIP) at physiological concentrations?

<p>Stimulates secretion of insulin by the pancreas (A)</p> Signup and view all the answers

What is the main role of secretin in relation to stomach emptying?

<p>Inhibiting gastric emptying (B)</p> Signup and view all the answers

What is one of the factors that can limit the rate of stomach emptying?

<p>Inhibitory feedback signals from the duodenum (D)</p> Signup and view all the answers

What is the primary function of the esophagus?

<p>To conduct food rapidly from the pharynx to the stomach (A)</p> Signup and view all the answers

Where are the most sensitive tactile areas for initiating the pharyngeal stage of swallowing located?

<p>Around the pharyngeal opening, with greatest sensitivity on the tonsillar pillars (C)</p> Signup and view all the answers

Which nerves transmit impulses from the sensitive areas of the mouth and pharynx to the medulla oblongata?

<p>Trigeminal and glossopharyngeal nerves (B)</p> Signup and view all the answers

What controls the orderly sequence of swallowing reflex?

<p>Reticular substance of the medulla and lower portion of the pons (A)</p> Signup and view all the answers

What term is used to collectively describe the areas in the medulla and lower pons that control swallowing?

<p>Deglutition center (A)</p> Signup and view all the answers

Which type of peristalsis results from distention of the esophagus by retained food?

<p>Secondary peristalsis (A)</p> Signup and view all the answers

What causes initiation of secondary peristaltic waves in the esophagus?

<p>Reflexes initiated by vagal afferent fibers to the esophagus (D)</p> Signup and view all the answers

Which nerves control peristaltic waves in the upper third of the esophagus?

<p>Glossopharyngeal and vagus nerves (B)</p> Signup and view all the answers

What happens when vagus nerves to the esophagus are cut?

<p>The myenteric nerve plexus becomes excitable enough to cause strong secondary peristaltic waves without support from vagal reflexes (C)</p> Signup and view all the answers

What is receptive relaxation of the stomach?

<p>'Digestive relaxation' that prepares the stomach for receiving food from the esophagus (D)</p> Signup and view all the answers

What is another name for the lower esophageal sphincter?

<p>'Cardiac sphincter' (D)</p> Signup and view all the answers

What is the main role of segmentation contractions in the small intestine?

<p>To divide the intestine into spaced segments (A)</p> Signup and view all the answers

What determines the maximum frequency of segmentation contractions in the small intestine?

<p>Frequency of electrical slow waves in the intestinal wall (A)</p> Signup and view all the answers

Under what conditions does the maximum frequency of the segmentation contractions occur?

<p>When extreme stimulation is exerted on the intestinal wall (A)</p> Signup and view all the answers

What is the role of electrical slow waves in the intestinal wall?

<p>To determine the frequency of segmentation contractions (B)</p> Signup and view all the answers

What effect does stretching of the intestinal wall have on segmentation contractions?

<p>Initiates a new set of segmentation contractions (B)</p> Signup and view all the answers

How do segmentation contractions contribute to food mixing with secretions in the small intestine?

<p>By dividing the intestine into spaced segments (D)</p> Signup and view all the answers

What is the velocity of peristaltic waves as they move toward the anus in the small intestine?

<p>0.5 to 2.0 cm/sec (C)</p> Signup and view all the answers

What is the main cause of the increased peristaltic activity in the small intestine after a meal?

<p>Beginning entry of chyme into the duodenum (D)</p> Signup and view all the answers

What is the role of serotonin in relation to small intestinal motility?

<p>Enhances intestinal motility (D)</p> Signup and view all the answers

What is the primary function of the peristaltic waves in the small intestine?

<p>Cause progression of chyme toward the ileocecal valve and spread out the chyme along the intestinal mucosa (D)</p> Signup and view all the answers

What initiates intense peristaltic contractions called 'peristaltic rush' in the small intestine?

<p>Intense irritation of the intestinal mucosa (C)</p> Signup and view all the answers

What is the role of muscularis mucosae in the small intestine?

<p>Cause short folds to appear in the intestinal mucosa and increase absorption (D)</p> Signup and view all the answers

What is the function of the ileocecal valve?

<p>Prevent backflow from the colon to the small intestine (B)</p> Signup and view all the answers

What is the resistance capability of the ileocecal valve against reverse pressure?

<p>&gt;50 to 60 centimeters of water (B)</p> Signup and view all the answers

What causes resistance to emptying at the ileocecal valve?

<p>Ileocecal sphincter constriction (C)</p> Signup and view all the answers

What is the typical rate of travel for net movement along the small intestine?

<p>~1 cm/min (C)</p> Signup and view all the answers

'Peristaltic rush' is initiated partly by intrinsic enhancement of which reflexes?

<p>(Myenteric plexus) reflexes in the gut wall (D)</p> Signup and view all the answers

What is a significant effect of stretching of the stomach wall on stomach emptying?

<p>Delay stomach emptying (A)</p> Signup and view all the answers

What prevents continual dribble of fecal matter through the anus?

<p>Conscious signals inhibiting the external sphincter constriction (C)</p> Signup and view all the answers

What converts the intrinsic myenteric defecation reflex into a powerful process of defecation?

<p>Parasympathetic defecation reflex involving the sacral segments of the spinal cord (A)</p> Signup and view all the answers

What causes automatic emptying of the lower bowel in newborns and some people with transected spinal cords?

<p>Lack of conscious control exercised through voluntary contraction or relaxation of the external anal sphincter (A)</p> Signup and view all the answers

What is the role of the peritoneointestinal reflex?

<p>Strongly inhibits excitatory enteric nerves, causing intestinal paralysis (B)</p> Signup and view all the answers

Which reflex inhibits intestinal activity as a result of kidney irritation?

<p>Renointestinal reflex (A)</p> Signup and view all the answers

What initiates enterogastric inhibitory reflexes to slow or stop stomach emptying?

<p>Stretching of the stomach wall (D)</p> Signup and view all the answers

What is one of the functions of vagovagal reflex in the stomach?

<p>Inhibition of excitatory enteric nerves (B)</p> Signup and view all the answers

What is one effect of increased food volume in the stomach on stomach emptying?

<p>Slowing down of stomach emptying (A)</p> Signup and view all the answers

What is the role of the cecum in controlling the ileocecal sphincter and ileal peristalsis?

<p>Intensifying contraction of the ileocecal sphincter (B)</p> Signup and view all the answers

Which factor promotes increased emptying from the stomach?

<p>Stimulation of intense peristaltic contractions (C)</p> Signup and view all the answers

How are reflexes from the cecum to the ileocecal sphincter and ileum mediated?

<p>By both the myenteric plexus and extrinsic autonomic nerves (C)</p> Signup and view all the answers

What happens when vagus nerves to the esophagus are cut?

<p>Loss of involuntary control over swallowing (A)</p> Signup and view all the answers

What characterizes the movements of the colon during absorption and storage functions?

<p>Slow and sluggish movements (D)</p> Signup and view all the answers

What is the main effect of gastric inhibitory peptide (GIP) at physiological concentrations?

<p>Slowing down stomach emptying (C)</p> Signup and view all the answers

What can be observed during mixing movements in the large intestine?

<p>Baglike sacs called haustrations due to combined circular and longitudinal muscle contractions (C)</p> Signup and view all the answers

What is one function of peristaltic constrictor rings in the antrum of the stomach?

<p>Initiation of intense peristaltic contractions in the stomach (C)</p> Signup and view all the answers

What is a characteristic of propulsive movements in the colon?

<p>A series of mass movements persisting for 60-90 minutes (C)</p> Signup and view all the answers

What initiates mass movements in the colon after meals?

<p>Distention of the stomach and duodenum (B)</p> Signup and view all the answers

What contributes to maintaining an empty rectum most of the time?

<ul> <li>Presence of a weak functional sphincter near the sigmoid colon-rectum juncture (B)</li> </ul> Signup and view all the answers

What effect does a mass movement have in causing the desire for defecation?

<ul> <li>Forcing feces into the rectum (B)</li> </ul> Signup and view all the answers

What stimulates mass movements after meals?

<p>Constriction at points distended or irritated in the colon (C)</p> Signup and view all the answers

What contributes to progressive absorption of fluid and dissolved substances in the large intestine?

<p>Haustral contractions rolling over fecal material (C)</p> Signup and view all the answers

What is a key characteristic of propulsive movements known as mass movements?

<p>Contraction force developing progressively for about 30 seconds (C)</p> Signup and view all the answers

What leads to defecation when a mass movement forces feces into the rectum?

<p>Relaxation of anal sphincters in response to rectal distention (B)</p> Signup and view all the answers

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