Transcript Digestive System

DIGESTIVE SYSTEM
PATH OF DIGESTION
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Food is grasped and collected into the oral cavity
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This is called prehension
Mastication (chewing) breaks food into smaller
pieces
 Deglutition moves chewed food into the pharynx
and on into the esophagus
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The epiglottis closes off the entrance to the trachea
Food moves down the esophagus by gravity and
peristalsis
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Peristalsis is a series of wavelike contractions of smooth
muscle
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-stalsis means contraction
PERISTALSIS VERSUS SEGMENTATION
Food moves through
the small intestines
by peristalsis and
segmentation
 Peristalsis is a
series of wavelike
contractions that
move ingesta
caudally toward
the anus
 Segmentation
involves the side-toside mixing of
ingesta
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STRUCTURES AND FUNCTIONS
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The organs of the gastrointestinal tract (GI) form
a tubelike passage through the body cavaties.
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From the mouth to the anus by way of the pharynx,
esophagus, stomach, and intestines
The main functions of this system is
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Prehension
Transport
Breakdown of food
Absorption of nutrients
Eliminate waste
STRUCTURES AND FUNCTIONS
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Food moves through the digestive system aided by
peristalsis, an involuntary, wavelike movement.
The digestive tract in all mammals generally has the
same parts
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Mouth
Teeth
Tongue
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
THE MOUTH
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Lips form the entrance to the mouth. The lips of
sheep, goats, and horses are soft and flexiable
and aid in picking up food.
Lips of cattle and swine are stiff and immobile
and do little more than close the mouth.
TEETH
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The number of deciduous (baby teeth) and
permanent teeth vary with the species and the
natural diet of an animal.
Teeth provide a variety of functions
Cutting and grinding of food
– Defense mechanism
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Ruminants do not have upper incisors, just a pad.
SALIVARY GLANDS
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Saliva is produced in 4 salivary glands
Parotid
 Sublingual
 Mandibular
 Zygomatic
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Referred to as exocrine glands
Saliva begins the breakdown of some foods
(carbohydrates) in the mouth.
 Moistens food, lubricant for the bolus.
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DIGESTION
Digestion is the process of breaking down foods
into nutrients that the body can use
 Metabolism is the processes involved in the
body’s use of nutrients
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Meta- means change or beyond
 Anabolism is building up of body cells
 Catabolism is breakdown of body cells
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ABSORPTION
 Absorption
is the process of taking
digested nutrients into the circulatory
system
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also called assimilation
 Absorption
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Villi are tiny hairlike projections that help
increase the surface area of the small intestine
allowing more nutrients to be absorbed
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occurs in the small intestine
Vill/i means tuft of hair
The valleys that result from the projections of
the small intestine are called crypts
DIGESTIVE SYSTEMS
Man and pig have a simple stomach with an
extensive intestinal system
 Ruminants have a complex stomach with a
simpler intestinal system
 Horses and rabbits have a simple stomach with
an extensive intestinal system and an enlarged
cecum
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3 MAJOR DIGESTIVE SYSTEMS
 All
3 systems will be addressed in detail
in the lesson to follow:
 Ruminants—have four stomach
compartments
 Monogastric—have one stomach
 Modified Monogastric—have one stomach
but the ability to digest roughages
Ruminant Digestive System
DIGESTIVE SYSTEM
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Small Intestine: long coiled tube connecting
stomach to large intestine
rest of the digestion and absorption takes place here
 surface covered with villi (surface area)
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3.5 times the length of animal – dog 18’
Large Intestine: Cecum, colon, rectum
absorbs water (makes feces more solid)
 some vitamins and minerals absorbed here
 Cecal Fermenters (Horse): similar to rumen
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DIGESTIVE SYSTEM
Accessory organs:
 Pancreas secretes enzymes to break down fat
 Liver (largest internal organ) secretes bile, which
digests fats
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also stores iron
DIGESTIVE SYSTEMS
Man and pig have a ________stomach with an
extensive intestinal system
 Ruminants have a ___________ stomach with a
simpler intestinal system
 Horses and rabbits have a simple stomach with
an extensive intestinal system and an
enlarged__________
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DIGESTIVE SYSTEM
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Mouth: “Prehension” tool (grasps food)
___________________secrete juices containing enzymes
(digest food)
 Chewing food breaks down
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____________: muscular tube that connects mouth to
stomach
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Peristaltic Movement: sequential contraction of ring
like___________
Reverse ___________= blowing chunks
SIMPLE STOMACH
Muscular contractions break down food
 Enzymes break down food:
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Gastric: ___________
 Liver and ____________: fats
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Ruminant Digestive System
Ruminant Facts (Bovine)
 Chews cud
 40,000-60,000 jaw movements/day
 No upper incisors - dental pad
 Does not “bite” grass - wraps tongue
 Uses fermentation to digest plants
I thought Dumbo
was an elephant
 Symbiotic relationship with bacteria
 Produces 13 gallons of gas/hour
 Produces 40 liters of saliva/day
RUMINANT STOMACH
Stomach occupies 3/4 of abdominal cavity, mostly on
the left side
 Rumen (paunch): 80% of stomach, lighter food
collects here
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microbes digest cellulose
 lots of water
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Reticulum (hardware stomach): 5% of stomach,
heavy foreign items are trapped here
RUMINANT STOMACH
Omasum (many plies): 8% of stomach, absorbs
water
 Abomasum (true stomach): 8% of stomach,
typical enzyme activity
 Rumination: regurgitation, rechewing of food
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Rumen
 Largest compartment
 On left side of animal
 Contains micro-organisms
 Ferments cellulose
 Absorbs VFA’s
 Divided into chambers
 Continually contracting
 Contains papillae
 Produces CO2
 pH close to neutral (6 - 7)
Reticulum
 Smallest compartment
 Lies close to the heart
 Small sac - part of rumen body
 Catches dense, heavy feed for later
rumination
 Contracts for regurgitation
 “Honeycomb” lining
 Catches hardware and stores it
Omasum
 Third compartment
 Globe-shaped
 Lining called “many plies”
 Reduces feed particle size
 Absorbs water and dries out ingesta
 Absorbs volatile fatty acids
Abomasum
 Final compartment
 Tubular in design
 “True” stomach (glandular)
 Secretes HCl and enzymes for
chemical digestion
 Reduces pH to 2.5
 Dissolves minerals
 Kills rumen bacteria
 Breaks down proteins
 Passes ingesta to small intestine
Ruminant Digestion
Ruminant Digestion
 Intake
 Mastication (chewing)
 Swallowing
 Regurgitation
 Remastication
 Fermentation
 Eructation
 Absorption
 Digestion
Rumination
Fermentation
 Anaerobic bacteria
break down cellulose
 VFA’s released by
bacteria passed to
bloodstream through
papillae
 CO2 and CH4 produced
by bacteria
 Bacteria controlled by
protozoa
 Ingesta passed to
omasum by contractions
DIGESTIVE SYSTEM
Converts feed into a form that can be used for
maintenance, growth, and reproduction
 In a light horse, the tract is approximately 100 feet
long and capacity of 40-50 gallons.
 Includes:
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Mouth, esophagus, stomach, intestines, anus, liver, teeth,
pancreas, and salivary glands
EQUINE DIGESTIVE SYSTEM
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Mouth
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Lips, pharynx, soft palate
Lips pick up loose feed which is then passed into the
mouth by the tongue
Pharynx
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Short, funnel shaped tube between the mouth and
the esophagus
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Food and water cannot return through the mouth after
passing through
 Horse that chokes has food pass through nose
DIGESTIVE SYSTEM
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Esophagus is a long muscular tube from the
pharynx to the stomach.
Stomach is a U shaped muscular sac
Peristalsis moves food through
 Gastric juices are expressed by the stomach walls.
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HORSE DIGESTIVE SYSTEM
1. Esophagus
5. Large intestine (80 quarts)
2. Stomach (8-16 quarts)
6. Pelvic flexure
3. Small intestine (48 quarts) 7. Colon
4. Cecum (28-32 quarts)
8. Rectum
LARGE INTESTINE, HORSES
 The
large intestine makes up
approximately 60% of the total digestive
tract.
 Divided into cecum, large colon, small
colon and rectum.
 Cecum is an important organ in horses.
Horses can use large amounts of roughage
because of the presence of bacteria in the
cecum and colon.
 These bacteria digest cellulose and ferment
carbohydrates.
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LARGE INTESTINE, HORSES
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IMPORTANT- because the large intestine of the
horse usually contains substantial quantities of
ingested material, impaction occurs easily.
This impaction is the start of what horse
ailment?
Signs and symptoms
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Kicking at abdomen, rolling, lying down and standing
up repeatedly, restlessness .