GI Motility - Karius

Question 1

Peristalsis

Answer 1

Food in one region
Relaxation of aboral (anal) region
Contraction of region with food
Food propelled on
Usually travels some distance along gut

Question 2

Mixing motions

Answer 2

Presence of chemicals/food
Contraction of region
Chyme moved to either side
With relaxation, chyme mixed

Question 3

The mouth
Mixing:
Propulsion:

Answer 3

M: Mastication
P: Swallowing

Question 4

Is mastication required for complete digestion?

Answer 4

No

Question 5

Stage 1 swallowing

Answer 5

Voluntary (buccal) Phase
Voluntary (cortical) control
Tongue rolls food back to entrance of pharynx

Question 6

Stage 2 swallowing

Answer 6

Pharyngeal Phase
Bolus of food stimulates afferents
Synapse in NTS
NTS initiates swallow and terminates inspiration
Block trachea - risk of aspiration

Question 7

Stage 3 swallowing

Answer 7

Esophageal Phase

Presence of bolus in esophagus initiates peristalsis

Question 8

The stomach
Mixing:
Propulsion:

Answer 8

M: Retropulsion - variant of peristalsis - hits pyloric sphincter and goes backward
P: Peristalsis - sometimes called pyloric pump

Question 9

Pyloric pump

Answer 9

Stronger waves of peristalsis force the chyme through the pyloric sphincter

Question 10

Factors that increase gastric emptying

Answer 10

1. Stretch of gastric wall - vagal and myenteric reflex
2. Gastrin
   * arise from stomach

Question 11

Factors that decrease gastric emptying

Answer 11

1. Enterogastric reflex - distension, acid, proteins in duodenum. Decrease motility, increase pyloric tone
2. Hormones - CCK-PZ and Secretin
   * arise from duodenum

Question 12

Small intestine
Mixing:
Propulsion

Answer 12

M: Segmentation
P: Peristalsis - major purpose is to distribute chyme in single layer over mucosa

Question 13

Peristalsis frequency in different areas of small intestine?

Answer 13

Varies
Duodenum - 11-12 minutes
Ileum - 8-9 minutes (get all the good shit out o’ the shit)

Question 14

Chyme in small intestine

Answer 14

Travels about 0.5 - 2 cm/second - faster proximally
Peristalsis travels about 5 cm before dying out
Move slowly - 1cm/mn
Fxn: move chyme to colon and spread chyme evenly

Question 15

Peristaltic Rush

Answer 15

Irritation within SI
Intense peristaltic event - may run length of SI
Clears of irritant

Question 16

Migrating Motor Complex

Answer 16

During fasting - 1.5-2 hour intervals
Starts in stomach, of moderates strength
Moves secretions throughout intestine

Question 17

What prevents back flow?

Answer 17

Ileocecal valve

Question 18

Ileocecal valve

Answer 18

Normally mildly contracted
Relaxation by - gastroileal reflex, gastrin
Contraction by - irritation, dissension of cecum

Question 19

Colon
Mixing:
Propulsion:

Answer 19

M: Haustrations
P: Mass movement

Question 20

Haustrations

Answer 20

Mixing motion in colon
Triggered by chyme
Near complete occlusion of lumen
Absorb water
Mix bicarbonate - counters the acids secreted by bacteria

Question 21

Mass movement

Answer 21

Propulsive motion
Travels > 20cm
Repeats every 10-30 minutes until defecation
Also initiated by: gastrocolic reflex, duodenocolic reflex, parasympathetic

Question 22

3 Things that control defecation

Answer 22

1. Local reflex - distension, not strong
2. Parasympathetic - distension, receptor in gut, stronger
3. Voluntary - relax EAS

Question 23

Esophagus
Mixing:
Propulsive:

Answer 23

M: None
P: Swallow