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Flashcards in GI Motility - Karius Deck (23)
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1

Peristalsis

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

2

Mixing motions

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

3

The mouth
Mixing:
Propulsion:

M: Mastication
P: Swallowing

4

Is mastication required for complete digestion?

No

5

Stage 1 swallowing

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

6

Stage 2 swallowing

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

7

Stage 3 swallowing

Esophageal Phase
Presence of bolus in esophagus initiates peristalsis

8

The stomach
Mixing:
Propulsion:

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

9

Pyloric pump

Stronger waves of peristalsis force the chyme through the pyloric sphincter

10

Factors that increase gastric emptying

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

11

Factors that decrease gastric emptying

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

12

Small intestine
Mixing:
Propulsion

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

13

Peristalsis frequency in different areas of small intestine?

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

14

Chyme in small intestine

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

15

Peristaltic Rush

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

16

Migrating Motor Complex

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

17

What prevents back flow?

Ileocecal valve

18

Ileocecal valve

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

19

Colon
Mixing:
Propulsion:

M: Haustrations
P: Mass movement

20

Haustrations

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

21

Mass movement

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

22

3 Things that control defecation

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

23

Esophagus
Mixing:
Propulsive:

M: None
P: Swallow