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32 Cards in this Set
- Front
- Back
What composes the midgut? |
Duodenum Jejunum Ileum |
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What type of muscle is the small intestinal composed of? |
Longitudinal and circular |
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The SI has slow waves that _______ in frequency in the aboral direction. |
decrease |
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What are the two controllers of the SI? |
Neural (ENS) control Endocrine control
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What are the two types of neural (ENS) controls? |
Peristalsis - activation of inhibitory neutrons = relaxes muscles -Excitatory neurons = contracts muscles
Segmentation - inhibitory neurons = inhibit circular muscle contraction (relaxation) |
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What is the endocrine control compose of, stimulated by, and inhibited by? |
Jejunal smooth muscle
Stimulated by gastrin
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What are the three types of contractile patterns of the SI? |
Peristaltic waves Stationary Contractions Cluster of Contractions |
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Peristaltic waves - location, stimulus, and function |
Location: total SI
Stimulus: Non Caloric meal (always happening)
Function: Transport of chyme/mass propulsion (~2h intervals) |
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Stationary contractions - location, stimulus, and function |
location: Proximal SI
stimulus: Protein meal
function: Segmenting/mixing and protein digestion |
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Cluster of contractions - location, stimulus, and function |
location: Proximal SI (stationary); Total SI (aboral migrating)
stimulus: Fat meal
function: Lipid digestion |
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What are Aboral Giant(power) Contractions? |
-Ileum -Interdigestive period in dogs humans and horses -Digestive period in pigs
**Large amplitude and long duration - CLEAN INTESTINE ('STRIPPING WAVE') |
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What are two types of pathological contractile patterns of the proximal intestine? |
Anti peristaltic waves
Giant contractions in the duodenum |
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Anti peristaltic waves.... |
Proximal SI (Jejunum)
Distal gastrectomy |
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Giant Contractions in the duodenum.... |
-Proximal SI
-Oral propagating: vomitting stimuli
Aboral: strong stimuli (acetic acid, distal gastrectomy) DIARRHEA |
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Interdigestive motility patterns - Migrating Myoelectric Complex (MMC) - What is the function and how is it regulated? |
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 |
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What is the MMC interrupted by in Carnivores & adult birds and uninterrupted by in herbivores & young birds? |
Carnivores & adult birds: interrupted by feeding (Fed MMC = phase II)
herbivores & young birds: uninterrupted by feeding
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Explain the phases of MMC..
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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) |
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Birds Gastroduodenal motility sequence - what happens? |
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 |
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In birds, what happens if there is an intestinal reflux (reverse peristalisis)? |
Jejunum/illium -> duodenum -> gizzard |
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What is the hindgut composed of? (LI) |
cecum and colon |
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What are the 4 movements of large intestines? |
1. Peristaltic and antiperistalic waves 2. Aborally migrating segmental contractions 3. Haustral movements 4. Aboral giant movements (dogs, cats, humans) |
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What are peristaltic and antiperistalic waves of the LI? |
-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 |
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What are aborally migrating segmental contractions in the LI?
What is it called in dogs and horses? What happens in sheep? |
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 |
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What are austral movements in the LI? |
-Alternating contractions and relaxations for mixing of digesta -Aboral/oral rolling movement for liquid transport
**especially pigs |
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What are aboral giant movements in the LI? (Dogs vs pigs) |
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
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What is the defecation reflex? (recto-sphincter reflex) |
-the normal response (defecation) to the presence of an accumulation of feces in the rectum |
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How does the defecation reflex work? |
-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)
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Peristalsis (normal intestinal motility) - what happens when bolus stimulates 5HT to the myenteric plexus (ENS)? |
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 |
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What are the two types of disorders of intestinal motility? |
1) Mechanical Ileus (mechanical obstruction) 2) Adynamic Ileus (surgery or peritonitis) |
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Explain what happens with Mechanical Ileum... |
-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 |
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What happens if the normal pathways are not sufficient in reliving technical ileum? |
-Myenteric plexus stimulates the prevertebral ganglia! -sympathetic output -> NE and NPY = decrease in motor activity (shut down) |
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Explain Dynamic ileum |
Surgery or peritonitis -gut may not heal 100% causing shut down due to stress (prevertebral ganglia) |