27 Gastrointestinal Motility (Mid And Hindgut)

Front 1

What composes the midgut?

Back 1

Duodenum

Jejunum

Ileum

Front 2

What type of muscle is the small intestinal composed of?

Back 2

Longitudinal and circular

Front 3

The SI has slow waves that _______ in frequency in the aboral direction.

Back 3

decrease

Front 4

What are the two controllers of the SI?

Back 4

Neural (ENS) control

Endocrine control

Front 5

What are the two types of neural (ENS) controls?

Back 5

Peristalsis - activation of inhibitory neutrons =

relaxes muscles

-Excitatory neurons = contracts muscles

Segmentation - inhibitory neurons = inhibit circular muscle contraction (relaxation)

Front 6

What is the endocrine control compose of, stimulated by, and inhibited by?

Back 6

Jejunal smooth muscle

Stimulated by gastrin

Inhibited by secretin and glucagon

Front 7

What are the three types of contractile patterns of the SI?

Back 7

Peristaltic waves

Stationary Contractions

Cluster of Contractions

Front 8

Peristaltic waves - location, stimulus, and function

Back 8

Location: total SI

Stimulus: Non Caloric meal (always happening)

Function: Transport of chyme/mass propulsion (~2h intervals)

Front 9

Stationary contractions - location, stimulus, and function

Back 9

location: Proximal SI

stimulus: Protein meal

function: Segmenting/mixing and protein digestion

Front 10

Cluster of contractions - location, stimulus, and function

Back 10

location: Proximal SI (stationary); Total SI (aboral migrating)

stimulus: Fat meal

function: Lipid digestion

Front 11

What are Aboral Giant(power) Contractions?

Back 11

-Ileum

-Interdigestive period in dogs humans and horses

-Digestive period in pigs

**Large amplitude and long duration - CLEAN INTESTINE ('STRIPPING WAVE')

Front 12

What are two types of pathological contractile patterns of the proximal intestine?

Back 12

Anti peristaltic waves

Giant contractions in the duodenum

Front 13

Anti peristaltic waves....

Back 13

Proximal SI (Jejunum)

Distal gastrectomy

Front 14

Giant Contractions in the duodenum....

Back 14

-Proximal SI

-Oral propagating: vomitting stimuli

Aboral: strong stimuli (acetic acid, distal gastrectomy) DIARRHEA

Front 15

Interdigestive motility patterns - Migrating Myoelectric Complex (MMC) - What is the function and how is it regulated?

Back 15

Function = clean small intestines of residues and prevent bacterial growth

Regulated by

- Motilin - initiates in esophagus, stomach, proximal duodenum

- Intrinsic nerves (ENS) - distal duodenum and jejunum

- Inhibition - hormones and vago-vagal reflex

Front 16

What is the MMC interrupted by in Carnivores & adult birds and uninterrupted by in herbivores & young birds?

Back 16

Carnivores & adult birds: interrupted by feeding (Fed MMC = phase II)

herbivores & young birds: uninterrupted by feeding

Front 17

Explain the phases of MMC..

Back 17

Phase 1: quiet period. No physical contraction but slow waves

Phase 2: slight degree of contraction. Some spontaneous (action potential) = segmenting contractions and single peristaltic waves

Phase 3: frequency and amplitude of contractions go up = forceful peristaltic waves (slow and spikes)

Front 18

Birds Gastroduodenal motility sequence - what happens?

Back 18

Gizzard = contraction of thin muscle -> duodenum = peristaltic waves (aboral passage of ingesta) -> Gizzard = contraction of THICK muscle (oral passage of ingesta to proventriculus) -> proventriculus -> Gizzard -> Duodenum -> jejunum/ileum

Front 19

In birds, what happens if there is an intestinal reflux (reverse peristalisis)?

Back 19

Jejunum/illium -> duodenum -> gizzard

Front 20

What is the hindgut composed of? (LI)

Back 20

cecum and colon

Front 21

What are the 4 movements of large intestines?

Back 21

1. Peristaltic and antiperistalic waves

2. Aborally migrating segmental contractions

3. Haustral movements

4. Aboral giant movements (dogs, cats, humans)

Front 22

What are peristaltic and antiperistalic waves of the LI?

Back 22

-Characteristics of the cecum and colon controlled by the colon 'pace makers'

-shallow constrictions - low propulsion and retropulsion (mixing)

- Anti-peristalsis in colon (ruminants, birds, rodents) allows filling of the cecum and H2O absorption

Front 23

What are aborally migrating segmental contractions in the LI?

What is it called in dogs and horses?

What happens in sheep?

Back 23

Move aborally (unique to LI)

-LONG lasting contractions that SEPARATE digesta into boil

Colonic motor complex - dogs and horses

Sheep - segmenting contractions in spiral colon - produce fecal boli/pellets

Front 24

What are austral movements in the LI?

Back 24

-Alternating contractions and relaxations for mixing of digesta

-Aboral/oral rolling movement for liquid transport

**especially pigs

Front 25

What are aboral giant movements in the LI? (Dogs vs pigs)

Back 25

Dogs: 'migrating spike bursts' from the colon pacemaker = prolonged burst of spikes and powerful contractions of circular muscles

-evacuate the colon!

Pigs: empty the ileum

**large amplitude contractions for bowel movements

Front 26

What is the defecation reflex? (recto-sphincter reflex)

Back 26

-the normal response (defecation) to the presence of an accumulation of feces in the rectum

Front 27

How does the defecation reflex work?

Back 27

-Afferent impulses stimulated by movement of feces into rectum to sacral spinal cord

-parasympathetic efferent impulses (pelvic nerves) stimulate peristalic contractions of rectum and relaxation of the internal sphincter (smooth muscle)

-voluntary signals (sympathetic) (pudendal nerve) controls the external sphincter (striated muscle)

Front 28

Peristalsis (normal intestinal motility) - what happens when bolus stimulates 5HT to the myenteric plexus (ENS)?

Back 28

Myenteric plexus stimulates...

1. Excitatory motor neurons (cranial to bolus) -> Ach, Substance P -> increase motor activity -> CM contracts and LM relaxes

2. Inhibitory motor neurons (caudal to bolus) -> NO, VIP -> decrease motor activity -> CM relax and LM contraction

Front 29

What are the two types of disorders of intestinal motility?

Back 29

1) Mechanical Ileus (mechanical obstruction)

2) Adynamic Ileus (surgery or peritonitis)

Front 30

Explain what happens with Mechanical Ileum...

Back 30

-Foreign body in the GI tract is similar to bolus so the pathways are similar but just LARGER MAGNITUDE

-If this is not sufficient then it goes to a higher center

Front 31

What happens if the normal pathways are not sufficient in reliving technical ileum?

Back 31

-Myenteric plexus stimulates the prevertebral ganglia!

-sympathetic output -> NE and NPY

= decrease in motor activity (shut down)

Front 32

Explain Dynamic ileum

Back 32

Surgery or peritonitis

-gut may not heal 100% causing shut down due to stress (prevertebral ganglia)