Transcript GI-Pt2Yola

Gastrointestinal Tract
Part 2
The Simple Stomach/
Monogastric
• Main sections:
– Fundus: rounded section
above esophageal
opening
• Expands with contents
– Body: middle section
• Also distensible
– Pyloric antrum: lower,
small end
Sphincter Muscles
• sphincters are muscles in a ring shape that close an
opening when they contract
• CARDIAC SPHINCTER – located between the esophagus
and stomach.
• Food enters when it relaxes.
• Sphincter tightens when digestion is taking place. (Prevents
reflux)
• PYLORIC SPHINCTER – located between the pylorus and
the duodenum.
• Contracts to prevent stomach contents from escaping during
digestion.
• Relaxes to allow contents to leave stomach and continue to
intestines.
Gastric Layers and Glands
• Outer serosa layer
• Muscular layer
• Circular muscle
• Longitudinal muscle
• Oblique muscle
• Submucosa
• Contains blood vessels
• Mucosal lining
• Contains many tubular gastric glands that secrete
digestive enzymes, mucin, and HCl
Gastric Layers and Glands
PERISTALSIS: involuntary, wavelike movement of the intestinal tract propelling contents
through the GI tract.
Produced by circular and longitudinal muscle fibers of tubular structures.
• CHYME = viscous, highly acidic, semiliquid
contents of stomach after digestion. Moves
through digestive tract via peristalsis.
Ruminants
• RUMINATION:
– regurgitation, remastication,
insalivation, and reswallowing of
partially digested food.
– this process allows fermentation of food
by bacteria and protozoa which digest
cellulose and produce energy for the
body
– Occurs in RUMINANTS (ex: cattle, goats,
sheep, llamas, camels, deer).
Ruminant Stomach
4 CHAMBERS:
Reticulum
Rumen
Omasum
Abomasum
Three forechambers to true stomach are called diverticula.
They help ferment food by soaking it and subjecting it
to digestive microorganisms.
Rumination
The Reticulum
• Smallest, most cranial
chamber
• Honeycomb in appearance
(increase surface area for
absorption)
• Separated from heart by
diaphragm
• Hardware disease:
– Heavy objects drop into
reticulum and can pierce
diaphragm and pericardium
• Also called “the paunch”
• Large sac extending from the
diaphragm to the pelvis
• Left side of abdominal cavity
• Makes up 20% of the animal’s
body weight
• Made up of numerous long
papillae.
• Divided into the ventral and
dorsal sac.
The Rumen
The Omasum
• The “book”
stomach
• Round, lined with
short, blunt
papillae in-folds
that grind
roughage before
entering the
abomasum
The Abomasum
• “True stomach”
• Only glandular
portion of the
stomach.
• Functions like a
monogastric
stomach
• Secretes digestive
enzymes to break
down food particles
• Pylorus opens into
small intestines.
Other Structures of the
Abdomen
• PERITONEUM –
membrane that
lines the
abdominal cavity
and holds organs in
place
– Visceral
peritoneum
– Parietal
peritoneum
OMENTUM
• Fold of
peritoneum,
extending from
stomach, overlying
organs (like an
apron).
• Lace-like in
appearance
MESENTERY
• Peritoneal fold that attaches the
intestines to the dorsal abdominal
wall
The intestinal digestive juice
containing mucus and enzymes is
stimulated by a hormone called
secretin. It is produced by the
intestinal glands as chyme reaches
the small intestine. The digestive
process is completed in the small
intestine and the digested food is
absorbed through the intestinal
walls by villi. Villi are small thread
like projections, it is these villi that
are sloughed when a dog contracts
parvo virus
SMALL INTESTINE
• Majority of nutrient absorption occurs here
• Entero- refers to intestines
• VILLI of the small intestine (threadlike projections
that line the mucosa) is where absorption takes
place.
Parts of Small Intestine
• DUODENUM
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Shortest, widest section
Attaches to the pylorus of the stomach
Pancreatic and bile ducts empty here
Digestion and absorption
• JEJUNUM
• Middle section
• Held in place by mesentery
• Vigorous peristaltic wave action moves contents into the ileum
• ILEUM
• Empties into cecum at ileocecal valve
Large Intestine
• Provides
fermentation for
monogastric
animals
• Recovers fluid and
electrolytes
• Stores feces
• Made up of cecum,
colon, and rectum
Cecum
• Pouch that forms the first
portion of the large intestine
• Joins with the colon
• Larger in herbivores (due to
fermentation)
• Primary function is to break
down fibrous material
• Appendix is attached to
cecum.
• Home for whipworms
Colon
• Ascending, Transverse,
Descending
• Diameter is wider than
small intestine and wall is
thinner.
• Haustra (a series of
pouches), allow expansion
and elongation of colon
(like an accordion).
• Taenia are longitudinal
bands of muscle of colon.
Species Variations in Colon
Rectum
• Section of descending
colon, located within
the pelvis that dilates
to store feces until
expulsion.
• ANUS – termination of
the digestive tract made of both smooth
and skeletal muscle
• COPROPHAGYingestion of fecal
material
• Normal activity for
rabbits
PANCREAS
• Elongated gland located near the first part of
the duodenum.
• Exocrine and endocrine gland.
– Exocrine cells secrete pancreatic enzymes needed
for digestion and transfer them through a duct
into the small intestine.
– Endocrine cells produce and secrete insulin and
glucagon directly into the blood (no duct
required).
Pancreas
LIVER
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Hepat/o = liver
largest gland in the body
Exocrine gland located immediately caudal to diaphragm
Soft, pliable; red/brown in color
Major functions:
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Produces and secretes bile for digestion
Metabolizes protein, fat, and carbs
Filters and destroys foreign matter and neutralizes toxins
Stores iron, glycogen, and vitamins
Synthesizes most proteins in the body
Liver
GALLBLADDER
• Stores bile from the liver, which is secreted
into the duodenum during digestion
• Bile is a fluid that aids in the digestion of fat
• Chole - means bile Cholecyst = gallbladder
• RATS and HORSES do not have a gall bladder,
their bile flows continuously from liver into
the duodenum.
Gallbladder
Liver & Gallbaldder