Chapter 11 - stomach, intestines, rectum, anus Flashcards
What is the esophagus?
a muscular tube that extends from the pharynx (throat) to the stomach
What is the esophagus’ function?
transports swallowed material from the pharynx to the stomach
Where does the esophagus enter?
enters the stomach at an angle in cardia region - surrounded by the cardiac sphincter muscle
As the stomach expands, what happens?
folds of the stomach against esophagus closes the lower end of the esophagus -
- reduces the risk for reflux
- in some species the closure is strong enough to prevent reflux or vomiting (horse, rabbit)
What are the 5 different areas in a monogastric stomach?
cardia, fundus, body, pyloric antrum, pyloris
What is the cardia?
opening from the esophagus
What is the body and what does it do?
distensible middle section
contracts to help mix food
What is the fundus?
distensible blind pouch; expands as more food is swallowed
Fundus and body contain and do what?
numerous glands
relax with swallowing of food
Gastric glands contain…?
parietal cells
chief cells
mucous cells
What are parietal cells?
produce hydrochloric acid
What are chief cells?
produce the enzyme pepsinogen
What are mucous cells?
produce the protective mucus
What does the pyloric antrum do?
grinds up swallowed food; regulates hydrocholoric acid
increases contractions in response to swallowing; stimulates mixing, grinding, and propulsive contractions that move food toward the pylorus
has glands that contains G cells - secrete gastrin
What is pylorus and what does it do?
muscular sphincter
regulates the movement of chyme from the stomach into the duodenum
prevents backflow of duodenal contents into the stomach
What is peristalsis that occurs in stomach and small intestines?
the succession of waves of involuntary muscular contraction of various bodily tubes
What layers does the stomach contain?
mucosal layer
submucosa
muscular layer (longitudinal and circular muscle fibers)
outer serosal layer
Smooth muscle in stomach wall responds to…?
hormones, peptides, nervous system controls
Parasympathetic stimulation causes ______ to relax and ______ contractions in the antrum.
fundus
increases
Sympathetic stimulation can cause a _______ in motility - gastric atony,
decrease
What is gastric atony?
a large distended stomach lacking in tone as seen in a horse that is a windsucker and continuously swallows air. Predisposes to chronic indigestion.
What is gastrin?
produced by the G cells in the antrum of the stomach
increases production of hydrochloric acid
inhibits muscle activity of the fundus
What is enterogastric reflex?
distension of the intestines or increased acidity in the duodenum inhibits stomach contraction - delays gastric emptying
What is secretin?
released from duodenum in response to excess stomach acid in small intestine
- can cause fundus to relax
- can inhibit peristalsis of the body and antrum of the stomach to slow gastric emptying
What is antrum?
The pyloric end of the stomach, partially shut off during digestion from the cardiac end by sphincter muscles in the stomach wall.
What is cholecystokinin (CCK)?
released in response to large amounts of fats or proteins in duodenum
- decreases contraction of the antrum, body and fundus
What is pepsinogen?
secreted by chief cells; precursor for the enzyme pepsin
-breaks proteins into chains of amino acids
Intrinsic factor is ?
secreted from glands in submucosa
-in some species, intrinsic factor must combine with vitamin B12 in order for B12 to be absorbed from the small intestine
What is mucus?
complex of substances; provides protective coating for the stomach against acidic gastric environment
-must be secreted continuously
What is mucins?
produced by goblet cells in gastric glands; main constituent of the mucous coating
What are goblet cells?
a goblet-shaped epithelial cell that secretes mucin
What does a bicarbonate ion do?
alkalinizes the mucus
What is hydrochloric acid?
- hydrogen H+ and chloride Cl- ions - secreted by parietal cells in the gastric glands then combine in the stomach to produce hydrochloric acid
- receptors on parietal cells for gastrin, histamine, and acetycholine involved in regulation of H= and Cl- secretion
- selectively blocking one of these receptors decreases the production of stomach acid
What is prostaglandins (PGs)?
- inhibit gastrin release
-stimulate the gastric glands to produce the bicarbonate ion - enhance blood flow to the stomach
- stabalize lysosomes within gastric cells
regulate the activity of macrophages and mast cells
What are ruminants?
- cattle, sheep, goats
- one true stomach and 3 forestomachs
- swallow their food, regurgitate it to chew on it some more before swallowing it again (rumination)
What is another word for true stomach?
abomasum
What is reticulum?
- smallest, most cranial compartment of the forestomach compartments
- separated from the rumen by the ruminoreticular fold
- lining composed of honeycomb arrangements of folds
- reticulum and rumen - coordinated contractions
What are the three forestomachs called?
reticulum, rumen and omasum
Ruminants _______ their food.
ruminate - swallow food and then bring it back up the esophagus to their mouth (regurgitate) to chew on it some more before swallowing it again (rumination)
What’s another name for rumination?
chewing the cud
What is rumen?
series of muscular sacs partially separated from one another by long muscular folds of rumen wall called pillars
Pillars aid in ______ and ______ of ruminal contents.
mixing and stirring
What is reticuloruminal contractions?
- allow partially digested plant food to be regurgitated
- allow built-up carbon dioxide or methane gas to be expelled from the rumen
