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Five functions of the digestive system
- 1. Ingestion
- 2. Mastication
- 3. Digestion
- 4. Absorption
- 5. Elimination
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Seven parts of the digestion system
- 1. Mouth
- 2. Pharynx
- 3. Esophagus
- 4. Stomach
- 5. Small intestine
- 6. Large intestine
- 7. Accessory glands
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Three types of accessory glands
- 1. Salivary glands
- 2. Liver
- 3. Pancreas
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Four layers of the digestive tract
- 1. Mucosa (inside)
- 2. Sub-mucosa
- 3. Muscle
- 4. Serosa (outside)
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Incisors
- Front teeth
- Numbered from center of mouth
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Canine
- Eye teeth
- Bridle teeth
- Tusks
- Normally absent in the mare, gelding & ruminant
- Wolf teeth of young horse
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Hypsodont
- Long crown
- Herbivores
- Grow continuously
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Four types of taste receptors
- 1. Filiform
- 2. Fungiform
- 3. Circumvallate
- 4. Foliate
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Filiform
- Hair like in appearance
- Give horses tongue velvety feel
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Fungiform
- Shaped like toadstool
- Contain taste buds
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Foliate
- Resemble leaves
- Contain taste buds
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Circumvallate
Large circular projection surrounded by deep groove
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Hard palate
- Forms roof of mouth
- "Lampers" in house is inflammation of the mucosa of hard palate
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Soft palate
- Directly behind hard palate
- Separates mouth from pharynx
- Elongated soft palate causes snoring
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What are tonsils made of?
Lymphoid tissue
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Three types of lymphoid tissue
- 1. Palatine
- 2. Lingual
- 3. Pharyngeal
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Palatine
- Seen most in canine and human
- Lack membrane covering tonsils, causes tonsillitis
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Lingual
- Seen most in horse, cow & pig
- Located at base of tongue
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Pharyngeal
Enlargement of these are called adenoids
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Pharynx
- Common passageway for food and air
- Includes mouth, 2 nares, 2 Eustachian tubes, esophagus, & larynx
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Esophagus
- Muscular tune extending from the pharynx to the stomach
- Dorsal to trachea
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Simple stomach
Located behind the left side of the diaphragm
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Epithelium surface of stomach
Gastric pits
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Folds in stomach
Rugae folds
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Cardiac glands
- Closest to cardia
- Produce mucus
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Pyloric glands
- Located in pylorus region
- Produce mucus & gastrin
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Gastrin
- Hormone that stimulates release of HCl & formation of pepsin
- Aids in release of pancreatic enzymes & gall bladder contraction
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Fundic glands
- Located in remainder of stomach
- Contain parietal cells & chief cells
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Parietal cells
Produce HCl which split pepsinogen to form pepsin
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Pepsin
Main component of digestive juices
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Chief cells
Produce pepsinogen & rennin
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Parts of the ruminant stomach
- 1. Rumen
- 2. Reticulum
- 3. Omasum
- 4. Abomasum
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Rumen
- Largest
- Huge storage vat
- Fermentation of feed
- Involves cuddling & bloat
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Reticulum
- Most cranial compartment
- Closest to heart
- "Honeycomb"
- Involves "Hardware Disease" or traumatic reticular pericarditis
- Main digestive function in young calves
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Omasum
- Located to right of rumen & caudal to liver
- Grinds roughage before entering abomasum
- Aka "book" stomach
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Abomasum
- True stomach
- Where digestion begins
- Located ventral to omasum on caudal side of rumen
- Involves twisted stomach
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Small intestine parts
- 1. Duodenum
- 2. Jejunum
- 3. ileum
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Duodenum
- Proximal portion of small intestine
- Ducts from the pancreas & liver enter here to excrete enzymes to aid in digestion
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Jejunum
Central portion of small intestine
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ileum
Distal portion of small intestine
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Where are most nutrients absorbed?
Small intestines
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Most animals have sort large intestine except the _____?
Horse
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Equine large intestine includes
- 1. Cecum
- 2. Right ventral colon
- 3. Sternal flexure
- 4. Left ventral colon
- 5. Pelvic flexure
- 6. Left dorsal colon
- 7. Diaphragmatic flexure
- 8. Right dorsal colon
- 9. Transverse colon
- 10. Small colon
- 11. Rectum
- 12. Anus
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Crypts of Lieberkuhn
- Located between villi
- Secrete mucus in S.I.
- Secrete enzyme enteeokinase
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Enterokinase enzyme
Activates pancreatic secretion of trypsinogen & small amount of amylase
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Brunner's glands
- Located in duodenum
- Secrete mucus for moisture
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Peyer's Patches
Lymph nodules located in ileum
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Auerbach's Plexus
Nerve supply for intestinal tract
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Salivary glands include
- 1. Parotid
- 2. Mandibular
- 3. Submandibular
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Pancreas
- Lobulated organ located between liver, kidneys & stomach
- Has exocrine & endocrine functions
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Exocrine of pancreas
Sodium bicarbonate & digestive enzymes into duodenum
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Endocrine of pancreas includes
- 1. Alpha cells
- 2. Beta cells
- 3. Delta cells
- Aka Islets of Langerhans
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Alpha cells
- Secrete glucagons
- Elevates blood sugar
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Beta cells
- Secrete insulin
- Affects metabolism of carbs, proteins & fats
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Delta cells
- Secrete somatostatin
- Thought to inhibit secretion of glucagon & insulin
- Acts as buffer
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Pancreatic amylase
Breaks down starch
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Pancreatic lipase
Breaks down fats
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Pancreatic trypsinogen
Breaks down protein
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Trypsin digestion test
- Test for protein absorption
- When protein is absorbed, trypsinogen is produced
- Test will eat X-ray film when trypsinogen is present
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Normal fasting glucose
80-120
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Liver
- Filtration device
- Waste removal
- Storage for blood & fat
- Filters food & meds
- Contains lobes
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Rumenal bloat / Rumenal Tympany
- Located in paralumbar fossa
- First sign is rubbing against tree or barn
- Painful, difficulty breathing
- Pass nasal gastric tube to remove gas, contents & or replace with meds
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Colic in horses
Treat with gastric tube, mineral oil, pain reliever or surgery as last resort
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Herbivore teeth
- Don't have upper incisors
- Have dental pad
- Flat teeth that grow continuously
- ie: horses, cows
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Carnivore teeth
- Sharp, pointy teeth for shearing & tearing
- ie: cat
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Omnivore teeth
- Not as sharp, pointy
- Not as substantial
- ie: dog
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When do calves start to ruminate?
About 3 weeks of age
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Dog and cat teeth growth
- Deciduous: 3-4 weeks old
- Permanent: 4-6 months old
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Cows teeth growth
- Deciduous: 8 days old
- Permanent: 18 months old to 4 years old
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Horse teeth growth
- Deciduous: 8 days, 8 weeks, 8 months old
- Permanent: 2 1/2, 3 1/2, 4 1/2, & 5 years old
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