Download DIGESTIVE PHYSIOLOGY

Digestive Physiology
For:
ADVS 1110
Introduction to Animal Science
Digestion – Digestive Systems
Simple Monogastric Systems:
Animal
Food Class
Humans
Omnivore
Monkey
Omnivore
Pig
Omnivore
Dog
Carnivore
Poultry
Omnivore
Digestion – Digestive Systems
Polygastric Systems:
Animal
Food Class
Cow
Herbivore
Sheep
Herbivore
Goat
Herbivore
Digestion – Digestive Systems
Monogastric – Functional Cecal Systems:
Animal
Food Class
Horse
Herbivore
Rabbit
Herbivore
Guinea Pig
Herbivore
Hamster
Omnivore
Rat
Omnivore
Mouse
Omnivore
Digestion – GI Tract
FUNCTIONS OF THE GI TRACT:
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Movement of food.
Secretion of digestive juices.
Absorption of the digested nutrients, water and electrolytes.
Storage – body of the stomach, or fecal matter in the descending
colon.
Digestion – stomach, duodenum, jejunum and ileum.
Absorption – of the digestive-end-products (DEPs) in the entire
small intestine and proximal half of the colon (large intestine).
Digestion – GI Tract
Amount of ingested food determined by:
1.
Hunger – the intrinsic desire for food, regardless
of food type or preference.
2.
Appetite – the specific type of food that is
preferentially sought.
3.
Capacity—body size, GI tract
size
Digestion – GI Tract
The mechanical aspects of food ingestion:

Mastication – includes chewing as well as
ingestion.
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Incisors – cutting and food intake action @ 55 psi.
Molars – grinding action @ 200 psi.
Swallowing – also referred to as ‘deglutition’.
Digestion – GI Tract
DENTITION:

Temporary & Permanent Dentition:
 Horses
 Cattle
 Sheep
 Pig
 Dog
 Cat
Digestion – GI Tract
DENTITION/TEETH: (front to back)
 Incisors = I*
 Canines = C*
 Premolars = P
 Molars = M
* Usually absent in the mare.
Digestion – GI Tract
DENTITION – SECTION THROUGH A MOLAR
TOOTH:
Digestion – GI Tract
TWO TYPES OF MOVEMENT IN THE GI TRACT:
1.
Mixing Movements – keeps intestinal contents
homogenous.
2.
Propulsive Movements – causes the food to
move anal-ward along the tract at an appropriate
rate for digestion and absorption.
Digestion – GI Tract
OTHER TYPES OF MOVEMENTS:

Peristalsis – basic propulsive movement. Peristalsis is the
rhythmic contractions and movements by which the GI tract
propels it’s contents.

Distension – is the usual stimulus for peristalsis.

Analward Peristaltic Movements – peristalsis can occur in
either direction, from a stimulated point, but normally dies out
rapidly in the oral direction.

Gradient Theory – is that there are more frequent neural
impluses (peristaltic) analward than in the oral direction.
Digestion – GI Tract
THE HERBIVORE GI TRACT – DESCENDING ORDER:
1. Oral Cavity
8. Abomasum (True Stomach)
2. Incisors
9. Small Intestine: a. Duodenum; b.
Jejunum; c. Illeum
3. Molars
10. Cecum
4. Esophagus
11. Large Intestine (Colon): a.
Ascending, b. Descending
5. Rumen (Paunch)
12. Rectum
6. Reticulum (Hardware Stomach;
Honeycomb; Tripe)
13. Anus
7. Omasum (Manyplies)
Beef Cattle GI Tract
Ruminant Ailments
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Bloat-excess accumulation of rumen gas
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Frothy bloat caused by rapidly digesting protein
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Occurs within about an hour of consumption or the
second or third day (rapid onset and often fatal)
Prevention/treatment with antifoaming agents including
oils, dish soap, synthetic nonionic surfactants
(poloxalene)
Free-gas (secondary) bloat caused by high grain
diet, anatomical issues, or esophagus obstruction
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Can result in chronic bloating (20% fatal)
Ruminant Ailments
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Bloat Risk Factors
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Irregular feeding (hunger), sudden feed changes,
weather events (frost), genetic pre-disposition,
Pneumonia
Twisted Stomach(Displaced Abomasum)
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Abomasum normally rests on the ventral floor
of the abdomen.
Occasionally it twists to the left or the right.
(LDA or RDA)
LDA most common and requires surgery
RDA usually fatal within 12-24 hours
Risk Factors
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Irregular feeding, sudden feed changes,
weather events, genetic pre-disposition
80% occur within 1 month of parturition due
to hypocalcemia, hypokalemia, mastitis,
metritis, endotoxemia (all result in decreased
rumen fill)
Periparturient changes in intra-abdominal
organ position
Colic (Horses)
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Abdominal pain
Clinical signs may include: pawing, looking
at flank, curling upper lip and arching neck,
repeatedly raising a rear leg or kicking at
abdomen, lying down, rolling side to side,
sweating, stretching out as if to urinate,
straining to defecate, distension of abdomen,
loss of appetite, depression, decreased
bowel movements
Reasons for Colic
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Intestinal wall stretched excessively by gas,
fluid, or ingesta (possible foreign material)
Intestinal displacement (tension on
mesentery)
Restricted blood supply (Ischemia)
Inflammation: Entire intestinal wall (enteritis)
or abdominal cavity lining (peritonitis)
Prevention/Treatment
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Consistent feeding
Adequate water
Deworm
Treat the symptoms
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Pain
Dehydration
Intestinal lubricants/laxatives
Surgery may be required
Digestion – GI Tract
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1.
2.
3.
4.
5.
6.
7.
Terminology: Food As It Moves Through The Digestive
System
Feed or Feedstuff.
Ingesta – after swallowing.
Cud – after leaving rumen.
Chyme – after leaving the true stomach or only stomach.
(Small Intestine)
Digestive End Products (DEPs) – those nutrient ingredients
absorbed after digestion.
Fecal Material or Non-Digested End Products – lower end
of large intestine or large colon.
Feces – waste matter removed from the rectum after all
digestive processes, and deposited outside the body.
Digestion – GI Tract
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The ruminant system is large in relation to the size of the
animal.
It’s four (4) compartments are bunched and joined together
to form a compact structure.
Digestion
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The most important products of the rumen “fermentation
vat” process as illustrated in a diagrammatic form, are the
“Volatile Fatty Acids” (VFA’s)
VFA’s represent the major source of energy derived from
the feed in a usable form.
Digestion – GI Tract
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In the digestive process most feed materials follow
pathways indicated by arrows.
The rumen, consisting of several different regions, is much
larger than the three (3) other compartments combined.
Digestion – GI Tract
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The possible routes of feed
in ruminants:
Digestion – GI Tract
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The stomach of a monogastric animal is much smaller than
that of the ruminant stomach in relation to the size of the
animal and other parts of the digestive tract:
Digestion – GI Tract
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Approximate relative capacity of ruminant stomach
compartments:
Compartment
At Birth
(%)
At 4 Months (%)
At Maturity (%)
Rumen
25
75
80
Reticulum
5
5
5
Omasum
10
9
7
Abomasum
60
11
8
Total
100
100
100
Digestion – GI Tract
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In contrast with the ruminant system, the stomach of
monogastric animals has only one principal digestive cavity,
including one (1) non-glandular and three (3) glandular
regions:
Digestion – GI Tract
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Digestive System of the Horse:
Digestion - Avian
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Digestive Tract of the
Chicken:
Digestion – GI Tract
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The Cecum in Various Animal Species:
Digestion – GI Tract
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Digestive tract sizes and capacities of mature ruminant animals:
Species
Part of Digestive
Tract
Cow
Ewe
Rumen
40 gal
5 gal
Reticulum
2 gal
2 qt
Omasum
4 gal
1 qt
Abomasum
4 gal
3 qt
Small Intestine
15 gal (130 ft)
2 gal (80 ft)
Large Intestine
10 gal
6 qt
Stomach
Digestion – GI Tract
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Comparative capacities of monogastric (simple stomach) animals:
Part of
Digestive Tract
Horse
Pig
Man
Stomach
20 qts
8 qts
1 qt
Small Intestine
48 qts
8 qts
2 qts
Large Intestine
120 qts
(cecum also)
8 qts
2 qts
Digestion – GI Tract - Summary
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The Digestive Pathway in Monogastrics:
Mouth
Esophagus
Simple
Stomach
Small Intestine
(duodenum, jejunum, ileum)
Cecum
Large Intestine
Rectum
Anus
Digestion – GI Tract - Summary
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The Digestive Pathway in Poultry:
Mouth
Esophagus
Crop
Esophagus
Proventriculus
(stomach)
Gizzard
Small Intestine (duodenum, jejunum, ileum)
Ceca
Large Intestine
Cloaca
Vent
Digestion – GI Tract - Summary
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The Digestive Pathway in Ruminants:
Mouth
Esophagus
Reticulo-rumen
Regurgitated, Rechewed, reinsalivated, reswallowed
Reticulo-rumen
Omasum
Abomasum
Small Intestine (duodenum, jejunum, ileum)
Cecum
Large Intestine
Rectum
Anus
Digestion – Circulation of Blood in Mammals:
Annual Manure Production of
Animals:
Species
Animal Weight
(lb.)
Total Manure
Production
(tons/yr)
Dairy Cattle
1,400
21.00
Beef Cow
1,000
11.50
Beef Feeder
600
6.60
Swine
200
3.60
Sheep
100
0.75
4
0.05
1,000
8.50
Poultry Broiler
Horses
Digestion - GI Tract
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The Human Alimentary
Canal (GI Tract):
Digestion - Avian
Digestion - Avian
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Mouth – no teeth; therefore coarse feed must move to gizzard.
Fowl break their feed into a size that can be swallowed by
pecking with their beaks or by scratching with their feet.
Crop – is an esophageal diverticulum and serves as a storage
area for recently digested food.
Proventriculus – is similar to the stomach in carnivorous
animals.
Gizzard – primary function is the reduction of the size of food
particles by a grinding action.
Pepsin is present, an acid-base activity takes place, along with
meager proteolysis.
Digestion - Avian
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Small Intestine – digestive activity here is similar as in
mammals.
 Enzymes of the pancreas and the ‘brush border’ aid in digestive
activity.
 Monosaccharides and amino acids are carried by active transport
through the gut wall.
 Fat absorption takes place in lower half of small intestine and
enhanced by the presence of bile.
Ceca – most of the fiber digestion takes place here via
fermentation.
Large Intestine – concerned with water absorption.
Cloaca – chamber into which the urinary and genital tracts also
open into.
Digestion
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A diagram of a cross-section of the intestinal tract showing
it’s tissue layers:
Digestion - Ruminant
Digestion of Feed Nutrients Ruminants
Digestion - Ruminant
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Routes of carbohydrate utilization in ruminants:
Digestion - Non-Ruminant
Digestion of Feed Nutrients – NonRuminants
Digestion – Non-Ruminant
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Routes of carbohydrate utilization in nonruminants:
Digestion – Chemistry
Location
Digestive Juice
Enzyme
Kind of Food
Acted Upon
Mouth
Saliva
Ptyalin
Starch >
Maltose
Stomach
Gastric
Pepsin
Proteins >
Peptones >
Proteoses
Stomach
Gastric
Rennin
Casein >
Paracasein
Stomach
Gastric
Lipase
Fats > Higher
Fatty Acids,
Glycerol
Digestion – Chemistry
Location
Digestive Juice
Enzyme
Kind of Food
Acted Upon
Pancreas
Pancreatic
Trypsin
Proteins >
Proteoses &
Peptones,
Peptides >
Amino Acids
Pancreas
Pancreatic
Amylase
Starch >
Maltose >
Glucose
Pancreas
Pancreatic
Steapsin
(Lipase)
Fats > Higher
Fatty Acids &
Glycerol
Digestion – Chemistry
Location
Digestive Juice
Enzyme
Kind of Food
Acted Upon
Liver
Bile
Bile
Emulsification
of fats (Liquid)
Small Intestine
Intestinal
Juices
Erepsin
Peptides >
Amino Acids
Small Intestine
Intestinal
Juices
Invertases
(Sugar
Enzymes)
Digestion – Chemistry
Location
Small Intestine
Digestive Juice
Intestinal
Juices
Enzyme
Kind of Food
Acted Upon
Invertases
(Sugar
Enzymes)
Maltase
Maltose > 2
Glucose
Sucrase
Sucrose >
Glucose &
Fructose
Lactase
Lactose >
Glucose &
Galactose
Digestion - Monosaccharides
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The more common carbohydrates, sources and functions:
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This is an abbreviated table and provides only a partial list of the carbohydrates (CHO’s); but includes
the important animal science ones.
Name
Sources
Functions
Monosaccharides
Pentoses (5-carbon)
Not as common
Hexoses (6-carbon )
Glucose
Corn syrup, fruit
Principal blood sugar
Fructose
Fruit, honey
Converted to glucose
Galactose
One of the two
molecules in milk
Converted to glucose
Digestion - Disaccharides
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The more common carbohydrates, sources and functions:
Name
Sources
Functions
Disaccharides
Lactose
Milk
Yields glucose and
galactose in digestion
Maltose
Germinating seeds
Yields two (2) units of
glucose in digestion
Sucrose
Cane & Sugar Beets
Yields glucose and
fructose in digestion
Digestion - Polysaccharides
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The more common carbohydrates, sources and functions:
Name
Sources
Functions
Polysaccharides
Pentosans
Hexosans
Starch
Seeds, tubers
Principal energy source for
monogastrics
Cellulose
Plant leaves & stems
(cell walls)
Major source of energy for
ruminants; requires microbial
enzyme cellulase
Glycogen
Limited supply in animal
tissues
Reserve form of glucose in
muscles and liver
Digestion
The Liver is vital to digestion, filtering and absorption of
nutrients
Liver Function:
 Produces exocrine secretion named bile.
 Bile is stored in the gall bladder until it is required for
digestive purposes.
 Synthetic Reactions:
 Synthesis of certain amino acids, plasma proteins,
prothrombin, antibodies, urea, creatine, cholesterol.
 Glycogen and glucose (gluconeogenesis).
 Phospholipids ( for cell membranes).
 Fatty acids.
 Ketone bodies.
Digestion
Liver Function: (continued)
 Metabolic Reactions:
 Breakdown of glucose, glycogen, fatty acids, glycerol,
amino acids
 Metabolism of hormones (insulin, aldosterone, testerone,
estrogens, and thyroid hormone).
 Inter-conversion of certain amino acids to simple sugars
and vice-versa.
 Adenine Tri-Phosphate formation. (ATP)
 Embryonic formation of blood cells.
 Destruction of aged blood cells.
Digestion
Liver Function: (continued)
 Storage:
 Glycogen
Amino acids
 Fats
 Vitamins (A, B complex, D and E)
 Iron and Copper.
Detoxification
 Conversion of toxic substances to
harmless compounds.
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Digestion
Hormones Other Than Those of the Pituitary:
Hormone
Source
Primary Function
Thyroxin
Thyroid
Growth, metabolic rate
Thyrocalcitonin
Thyroid
Lowers blood calcium and
phosphate
Parathyroidhormone
Parathyroid
Elevates blood calcium,
lowers blood phosphate
Epinephrine
Adrenal Medulla Mobilization of glycogen,
increased blood flow
Digestion
Hormones Other Than Those of the Pituitary:
Hormone
Source
Primary Function
Insulin
Pancreas
Lowers blood glucose,
increase utilization of
glucose, and synthesis of
protein and fat, decreases
glucogenesis
Glucocorticoids
(Cortisol,
Corticosterone)
Adrenal Cortex
Promotes synthesis of
carbohydrates; protein
breakdown
Mineral Corticoids
(Aldosterone)
Adrenal Cortex
Sodium retention and
potassium loss through
kidney
Digestion
Hormones Important in Gastro-Intestinal Function:
Hormone
Origin
Releasing
Mechanism
Function
Gastrin
Pylorus
Distension and
movement of
stomach
Stimulation of acid
secretion by gastric
glands
Entero-gastrone
Duodenum
Fat and fatty acids Inhibition of gastric
+ bile in duodenum secretion and
motility
Secretin
Duodenum
Acids and
peptones in
duodenum
Stimulation of
pancreatic secretion
(water &
electrolytes)
Digestion
Hormones Important in Gastro-Intestinal Function:
Hormone
Origin
Releasing
Mechanism
Function
Pancreozymin
Duodenum
Acids and
peptones in
duodenum
Stimulation of
pancreas secretion
(enzymes)
Chole-cystokinin
Duodenum
Fat in duodenum
Contraction of gall
bladder and
relaxation of the
sphincter of ‘oddi’
Enterocrinin
Jejunum
Food digestion
products
Simulation of
intestinal secretions:
1) sucrase; 2) maltase; 3)
lactase; & 4) Intestinal
lipase
Digestion - Blood
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Distribution of total blood volume in different portions of the
cardiovascular system:
Part of Cardiovascular System
Percent of Total
(%)
Arterioles & Capillaries
7
Heart
9
Arteries
11
Pulmonary Circulation
12
Veins & Venules
61
Digestion - Blood
Components of blood:
 Plasma:
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Liquid portion of blood
Straw colored
55-57% of blood volume
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Water
Electrolytes (Na+, K+, Ca++, Cl-, HCO3-, PO4)
Carbohydrates (Glucose)
Lipids
Vitamins
Urea
CO2 (Gases from lungs or tissue)
O2
Digestion - Blood
Components of blood: (continued)
 Proteins (Mostly manufactured from liver, some from cell
disintegration)
 Important – All of the prior components, Plasma and Proteins are
absorbed from the gut.
 Formed Elements of blood:
 Erythrocytes – RBC
 Leukocytes – WBC
 Platelets:
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Non-nucleated
Aids in clotting
Digestion - Blood

Mammalian Heart in
Longitudinal Section:
Digestion - Blood
Digestion
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