Gastrointestinal Tract
Med Term
Pharynx
• Common passageway for air and food.
• Commonly referred to as the throat.
The Esophagus
• Muscular tube from the pharynx through the diaphragm
to the stomach
• Dilates as food passes through, lumen is typically closed
otherwise.
• http://www.medicalvideos.us/videos/1804/
The art of swallowing
• 3 phases
• voluntary – passage of food from the mouth to the
pharynx. At this point, the larynx is blocked by the
epiglottis, so food should only go in the correct direction.
Tongue also helps by pressing against the hard palate.
• 1st involuntary – reflex phase that passes the food from
esophagus to the stomach. Respiration is suppressed as
to keep food from going into the trachea.
• 2nd involuntary – muscles contract the food through the
cardiac sphincter into the stomach
• http://www.youtube.com/watch?v=vBtJ1D3S_p8
• http://www.youtube.com/watch?v=wqMCzuIiPaM&featur
e=related
The Simple Stomach/ Monogastric
• - 3 main sections: FUNDUS, BODY, PYLORUS
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.
LAYERS OF THE INESTINAL
WALL
• Mucosa, Submucosa, Muscle layer, Serosa
• CHYME = semifluid contents of stomach after digestion.
Moves through digestive tract via peristalsis.
Ruminant Stomach
4 CHAMBERS:
rumen
reticulum
omasum
abomasum
Three forechambers to true stomach are called
diverticula and help ferment the food.
Terms used in Ruminant Stomach
• Rumination- Includes regurgitation, remastication,
ensalivation, and reswallowing of partially digested food.
“Chewing of the cud”
• Remastication- Rechewing the food.
• Cud- bolus containing fiber, other food particles, rumen
liqud, and flora; regurgitated by ruminants.
• Fermentation- anaerobic conversion of organic
compounds, such as carbohydrates, to simpler
compounds, producing energy.
The Reticulum
• Most cranial chamber and is honeycomb in appearance.
• Where hardware disease can occur.
The Rumen
• Also called “the paunch”
• Large sac extending from
the diaphragm to the
pelvis, makes up 20% of
the animal’s body weight,
made up of numerous long
papillae.
• Divided into the ventral
and dorsal sac.
The Omasum
• “book”
• round, lined with short, blunt papillae in folds that grind
roughage before going on to the abomasum
The Abomasum
• “True stomach”
• Only glandular portion of the stomach.
• Secretes digestive enzymes to break down food
particles, has a pylorus, opens into small intestines.
Structures of found in the abdomen
• PERITONEUM – membrane that lines the abdominal
cavity; holds viscera in place
• OMENTUM – fold of peritoneum overlying organs, esp
stomach. lace-like in appearance
• MESENTERY- peritoneal fold that attaches the
intestines to the dorsal abdominal wall
Small Intestine
• where digestive process is completed
• 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:
• attaches to the end the stomach ; pancreatic and
bile ducts empty here; digestion and absorption occur
here
•
• JEJUNUM:
• middle section; held in place by mesentery; vigorous
peristaltic wave action
•
• ILEUM:
• most food absorption takes place here
• Food moved through by peristalsis and stimulated by
hormone secretin
Large Intestine
• Fermentation occurs here.
• Made up of:
• Cecum
• pouch that forms the first portion of the large
intestines
• joins with the colon
• larger in herbivores
• breaks down fibrous material
• Colon
• ascending transverse, descending portions
• cecum and colon have HAUSTRA in the rabbit, pig
and horse (sacculated bands)
• Rectum
• section of descending colon that dilates to store feces
• ANUS – termination of the digestive tract. made of
both smooth and skeletal muscle
•
• COPROPHAGY-ingestion of fecal material
• Rabbits
Pancreas
• elongated gland adjacent to the duodenum
• EXOCRINE and ENDOCRINE gland
•
-secretes substances with or without using ducts
•
-enzymes are needed for digestion (amylase,
lipase), so they empty into the duodenum
•
-also secretes insulin
Liver
• “hepat” = liver
• largest gland in the body, an exocrine gland located
immediately caudal to diaphragm that is red/brown in
color
• FUNCTIONS:
• secrete bile for digestion;
• metabolizes protein, fat, and carbs;
• destroys/neutralizes toxins;
• stores iron, glycogen, and vitamins
Gallbladder
• stores bile from the liver, which is brought to the
duodenum during digestion
• bile is a fluid that aids in the digestion of fat
• “chole”- means bile
• RATS and HORSES do not have a gall bladder
• bile flows continuously from liver to duodenum