Chapter 63: Movement and Mixing of GI (Discussion 8)

Question 1

Types of GI Movement

Answer 1

1. Mixing movements
2. Peristalsis: rhymical wave contraction gut wall smooth muscle
   
   • Moves food along intestinal tract
   • Stimulated by:
     
     • Distention of gut
     • Chemical/physical irritation of gut lining

Question 2

Mastication

Answer 2

Mechanical breakdown of food by mouth

Increase surface area for digestion

Breaks down indigestible cellulose membranes in plants (fiber)

Question 3

Swallowing

Answer 3

Food bolus moving from mouth –> esophagus –> stomach

• Epiglottis/larynx prevent close to food entering trachea
• Peristalsis/gravity move bolus down esophagus
• Gastroesophageal sphincter
  
  • Normally closed to prevent gastric reflux
  • Opens for bolus entry

Question 4

Motor Functions of the Stomach

Answer 4

1. Food storage
2. Mixing food + gastric juices (chyme)
3. Regulate chyme entry into duodenum
   
   • Pyloric pump: pumping of chyme through pyloric sphincter

Question 5

Duodenal Feedback

Answer 5

Factors that inhibit the pyloric pump:

• Too much chyme in duodenum
• Improper concentrations in chyme
• Digestion hormones (e.g. CCK, gastrin, secretin, GIP)

Question 6

Movement Types of Intestines

Answer 6

1. Mix chyme through segmentation
2. Propel chyme through peristalsis (“mass movements” in colon)

Question 7

Colon Functions (basic)

Answer 7

1. Absorb water/electrolytes
2. Store fecal matter

Question 8

Defecation

Answer 8

1) Fecal matter in rectum stimulates defecation reflex
2) Relaxation of involuntary internal anal sphincter
3) Relaxation of voluntary external anal sphincter
4) = poop