Stomach and Rumen Motility Flashcards
What is the esophagus considered?
a conduit from the mouth to the stomach
What is the cricopharyngeus muscle also known as?
the upper esophageal sphincter
What is the function of the upper esophageal sphincter?
keeps the esophagus closed except when swallowing, keeps air out, allows buildup of negative pressure in the esophagus, prevents reflux in the pharynx
What is the function of the lower esophageal sphincter?
prevents acid reflux into the esophagus, normally kept closed until bolud needs to enter the stomach
During gastric distension, the lower esophageal sphincter contracts tighter. What controls this?
gastrin
As food reaches the lower esophageal sphincter, what tells it to relax and let the food enter?
vasoactive intestinal peptide
What species uniquely has anti-peristaltic waves?
ruminants
What do anti-peristaltic waves do?
they push food back into the mouth
What is the striated muscle in the esophagus of the ruminants controlled by?
the myenteric plexus
What is mega-esophagus?
distension of the esophagus and pooling of food
What is the congenital cause of megaesophagus?
perisistent right aortic arch - constricts the esophagus
Aside from something congenital, what else can cause megaesophagus?
ack of vagal stimulation inhibiting coordinated peristalsis
What are the muscle layers of the stomach?
inner circular, oblique layer, and outer longitudinal
What are the 4 types of mucosa in the stomach?
esophageal, cardiac, fundus, and pyloric
What type of mucosa does the esophageal part of the stomach have?
non-glandular
What type of mucosa does the cardiac part of the stomach of?
glandular-mucous
What type of mucosa dpes the fundus part of the stomach have?
glandular - secretes HCL, enzymes, mucous
What type of mucosa does the pyloric part of the stomach have?
glandular- mucous, gastrin secreted
What is adaptive relaxation?
the stretching of the stomach wall that occurs as the organ fills during eating
Where does the peristaltic wave of the stomach begin?
mid-fundus
What is the peristaltic wave of the stomach controlled by?
the vagus nerve, enteric nervous system, and hormones
Explain the proocess of stomach churning action.
distension of the fundus activates stretch receptors, the myenteric plexus and vagus efferents then cause peristaltic contraction, the peristaltic wave reaches the pylorus causing the sphincter to breifly relax, chyme is expelled, it closes and the solid material moves towards the cranial part of the fundus
What is gastrin produced by and in response to what?
pyloric neuroendocrine cells in response to stretch or vagal stimulation secreted in bloood
What does gastrin do?
it stimulates stomach motility and stimulates chief cells and parietal cells
What do chief cells release?
pepsinogen
What do parietal cells secrete?
HCl
What is secretin?
a hormone made when pH drops in the duodenum
What does secretin stop?
the release of acid in the duodenum
What is cholecystokinin?
a hormone made when fat enters the duodenum
What does cholecystokinin do?
it stops the stomach from sending more fat into the duodenum
What is gastric emptying dependent on?
rate and strength of stomach peristalsis, degree of relaxation of pyloric valve, and fluidity of chyme
What is the speed of stomach emptying mediated by?
Vagal tone - increased speeds it up, decreased slows it down
What speeds up emptying of the stomach?
increased distension pressure in the stomach
What can slow the emptying of the stomach?
stronger contraction of the pylorus
What does the pyloric sphincter tighten in the presence of?
acid, amino acids, or fat in the duodenum
What hormones is gastric emptying mostly mediated by?
cholecystokinin and secretin
Order these diets in rates of emptying from fastest to slowest: high protein, high fat, high carbohydrates.
high CHO, high protein, high fat
What is the hallmark symptom of pyloric stenosis?
projectile vomiting
In adults, what is pyloric stenosis secondary to?
scarring of the pylorus
What is pyloric stenosis in infants caused by?
atresia of myenteric complex in th epyoric area or improper formation of the duodenum
What is eructation?
burping
How does eructation in non-ruminants work?
peristalsis forces gas to the cardia of the stomach, pressure builds causing the lower esophageal sphincter to open, peristaltic waves force the gas back, the animal must consciously force the gas out
What type of epithelium is in the rumen, reticulum, and omasum?
stratified squamous epithelium
What is the function of the omasum?
it absorbes water and volatile fatty acids
What are the 3 types of ruminant stomach contractions?
mixing, eructation, and regurgitation
How do mixing contractions work?
material is poured from the dorsal sac of the rumen to the ventral sac to the caudal dorsal blind sac and back again
How long does it take mixing contractions to complete?
30-50 seconds
How many mixing contractions can be heard every 2 minutes?
3
What are mixing contractions interrupted by?
eructation or regurgitation contractions
What is the purpose of eructation contractions?
to get rid of CO2 and some CH4
What is the flow of contractions in eructation contractions?
contractions start in the caudal rumen and move forward from caudodorsal blind sac to the dorsal sac
What is the effect of the eructation contractions?
it drops the fluid level around the cardia region so that gas is at the level of the esophageal sphincter
What is the main criteria for eructation contractions to occur?
the cardia has to be free of fluid or froth so that the lower esophageal sphincter relaxes and allows gas into the esophagus
Where does the gas expelled during eructation contraction go?
out the mouth and in the lungs
When do eructation contractions usually occur?
every 3-5 primary contractions
What is bloat in ruminants?
the blockage of the esophagus that leads to build up of gasses in the rumen
What are common causes of bloat?
tetanus of the esophagus or frothy bloat
What is frothy bloat caused by?
feeding legume pasture or amylolytic bacteria and protozoa producing a slime with foaming properties
Why is froth a problem?
during eructation, when the caudoventral sac relaxes the fluid level can drop but froth on the cardia region is interpreted as fluid and signals LES to remain tightly closed
Why are ruminants especially susceptible to sulfur toxicity?
because when fed high sulfur diets, their bacteria produce H2S and during the eructation phase it gets into the lungs and leads to rapid death
What is the purpose for regurgitation contractions?
to chew the cud
How do regurgitation contractions work?
contraction of the mid dorsal sac forces ingesta to the cardia area, negative pressure created by an open upper esophageal sphincter causes the bolus to move past the lower esophageal sphincter and an anti-peristaltic contraction propels the bolus into the mouth
How often do regurgitation contractions occur?
about every 1-2 minutes while ruminating
If a cow eats a piece of hardware, how does it get to the reticulum?
rumen contractions eventually cause anything with higher density than water to move to the bottom of the reticulum
If an object goes through a cows peritoneum what happens?
peritonitis, no rumen motility, and fever
If an object goes through a cows diaphragm and into the thoracic cavity what happens?
pleuritis
If an object goes through a cows diaphragm and into the pericardial sac what happens?
pericardial effusion leading to hardware
How can you prevent hardware disease?
feed the cow a magnet
How does the rumenoreticular groove reflex work?
Reticulum lifts up to form a groove to direct liquids directly from the esophagus into reticulo-omasal orifice – bypassing the rumen
What is the purpose of the rumenoreticular groove reflex?
to bypass the rumen and get milk/colostrum into the abomasum quickly
What can elicit the ruminoreticular groove reflex in adults?
highly hyperosmotic fluids, salty solutions, copper sulfate solutions, injecting vasopressin IV
What is papillae development dependent on in calf and lamb rumen development?
butyrate produced from the fermentation of grains
