This document summarizes and compares the digestive systems of humans, ruminants, avians, horses, and fish. It describes the three basic types of digestive systems - monogastric, ruminant, and hind gut fermentors - based on their stomach structure. For each type, it provides details on the anatomy and functions of the mouth, esophagus, stomach, small intestine, large intestine and other organs. It also compares key aspects of digestion and nutrient utilization across these different digestive system types.

1. Comparative anatomy
( Chordates)
Digestive system
1 Human
2Ruminant
3-Avian
4-Horse
5-Fish

2. Digestive System

3. Introduction
• Three (3) basic types of digestive systems according
to their stomachs :
►Monogastric – simple stomach.
►Ruminant (cranial fermentor) – multi-compartmented
stomachs.
►Hind gut (caudal) fermentor – simple stomach, but very
large and complex large intestine

4. Types of Digestive Systems
Cats
Chickens Pigs
Dogs
Turkeys
Monogastrics Ruminants
Hind Gut
Fermentors
Beef Cattle Dairy Cattle
Deer
Sheep
Goats
Horses
Rabbits
Ostrich

5. Types of Digestive Systems
• Are divided into three groups based on their
food sources
1. Herbivores are animals that eat plants
exclusively
2. Carnivores are animals that eat other animals
3. Omnivores are animals that eat both plants and
other animals
5

6. Carnivore
• Eat primarily
other animals.
Herbivore
• Eat primarily
plant materials.
omnivore
• Eat combination
of plant and
animal material.

7. Introduction
• The digestive system is used for breaking down
food into nutrients which then pass into the
circulatory system and are taken to where they
are needed in the body.

8. Main Functions of Digestive Tract
• The major activities of GI tract
• 1-Ingestion: taking in food
2.Motility
• Propel ingested food from mouth toward
rectum
3.Secretion of juices e.g. saliva
• Aid in digestion and absorption
4.Digestion
• Food broken down into absorbable
molecules
5.Absorption
• Nutrients, electrolytes, and water are
absorbed or transported from lumen of
GIT to blood stream
6.. Egestion(Elimination) : removing any
leftover wastes

10. Digestion
• Types
– Mechanical (physical)
• Chew
• Tear
• Grind
• Mash
• Mix
– Chemical
• Enzymatic reactions to improve digestion of
– Carbohydrates
– Proteins
– Lipids

11. Anatomy of the Digestive Tract
GIT consists of;
– Oral cavity or mouth
– Pharynx
– Esophagus
– Stomach
– Small intestine
– Large intestine
– Rectum
– Anus

12. Mouth or oral cavity
• Ingestion - bringing food into the
body
– tongue - taste buds detect
chemical composition of food
• Mastication - chewing (physical
digestion)
– teeth and tongue
• Chemical digestion - saliva
– moistens food
– amylase - breaks down starch
– lysozyme - antibacterial agent

13. Esophagus
• Muscular tube connecting the pharynx to the
stomach.
• Functions include:
1.Secretes mucus
2.Moves food from the throat to the stomach
using muscle movement called peristalsis
 Cardiac Sphincter – connects esophagus and
stomach
• If acid from the stomach gets in here that’s
heartburn.

14. 17

15. Stomach
• Muscular sac-like organ
• Chemical and physical digestion
– forms chyme
• goblet cells – mucus
– forms a protective barrier against the high
acidity of the stomach content.
– parietal cells – HCl
– kills bacteria, denatures proteins
• chief cells - pepsinogen
– pepsinogen activated by HCl  pepsin
– pepsin breaks down proteins

16. Small intestine
Functions
Digestion
Digest carbohydrates : amylase from pancreas
Digest proteins : trypsin & chymotrypsin from
pancreas
Digest lipids (fats) bile from liver & lipase from
pancreas
Absorption
VILLI – small finger-like projections that increase the
surface area MICROVILLI – even smaller finger-like
projections on the VILLI
Capillaries – small blood vessels found on each villus
(Absorbs all nutrients )

17. The Parts of Small intestine
1.Duodenum - most digestion occurs
here
2.Jejunum - some digestion and
some absorption occur
3.Ileum - mostly absorption

18. SMALL INTESTINE
• The small
intestine is divided
• duodenum
• jejunum
• ileum.

19. • Pancreas has 2 functions:
a) Endocrine functions: secretes insulin and glucagon from
islets of Langerhans
b) Exocrine function: secretion of pancreatic juice
• It has 2 components: aqueous and enzymatic components.
• Aqueouscomponent(contains HCO3) is important for
neutralizing stomach acid in the duodenum so pancreatic
enzymes can function properly
• Enzymatic component is essential for the proper
digestion and absorption of carbohydrates, fats, and
proteins
• Pancreatic enzymes include trypsin, chemotrypsin,
lipase, and amylase
Functions of the Pancreas

20. 24

21. Liver
Functions of the Liver:
1)Metabolic regulation
•Store absorbed nutrients, vitamins
•Release nutrients as needed
2)Hematological regulation
•Plasma protein production
•Remove old RBCs
3)Production of bile
•Required for fat digestion and absorption

22. Liver

23. Liver

24. The Large Intestine (colon)
• Much shorter than small intestine, but has
larger diameter
Functions
1. Goblet cells: create mucus that lubricates
colon and protects mucosa.
2. Absortive cells: Maintain water
balance, solidify feces, absorb vitamins
and some ions
• Prepare waste for expulsion
28

25. 29

27. Digestive System
– Ruminants –
Mouth, esophagus, liver, pancreas, gall
bladder, small intestine, and large intestine
have functions similar to monogastrics.

29. Reticulum
• Holding area for feed after it passes down esophagus.
• Provides additional area for fermentation.
• Contains microorganisms, like rumen
• Collection compartment for foreign objects.
• Helps open and close rumen.
• Minimal separation with rumen.

30. Rumen
• Largest of the four components.
• On the left side of the animal.
• Storage site and fermentation .
• Houses millions of microorganisms.
• Lined with millions of finger-like projections (papillae) that are
needed for absorption.
“paunch”

31. Omasum
• A heavy, hard organ that has many folds or leaves.
• Little, if any digestive activity.
• Grinds feed particles.
• Removes moisture.
“many piles”

32. Abomasum
• True, glandular stomach
• Functions similarly to monogastric stomach
• Secretes gastric juices which aid in digestion.
Infected with barber pole worms

33. Organs of the Digestive System
– Hind Gut Fermentors –
Mouth, esophagus, stomach, liver,
pancreas,, and small intestine have
similar functions as compared to
monogastrics.
Horse doesn’t have gall bladder

35. Digestive Tract
- Horse-
Esophagus
Stomach
Duodenum
Small
intestine
Cecum
Large
colon
Small colon
Rectum

36. Organs of the Digestive System
– Hind Gut Fermentors –
• Large Intestine
►Major difference between monogastrics
and hind gut fermentors is the large
intestine.
►Large intestine is exceptionally large
and complex compared to
monogastrics and ruminants.

37. The large intestine of hind gut fermentors is
analogous to the rumen in ruminants.
►Microbes digest structural carbohydrates
(cellulose, hemicellulose) and soluble
carbohydrates that escape digestion in
small intestine to VFA’s.
🗸 VFA’s absorbed from large intestine and
utilized by the animal.
►Microbial protein produced in large
intestine is wasted (only very limited
absorption from large intestine).

38. Avian Digestive System

39. Avian Digestive Systems
• Mouth
– no teeth
– Salivation excretion moistens food
• Esophagus
– has a modification called the “crop” which
stores and moistens food
– connects mouth and stomach

40. Avian Digestive Systems
• Stomach
– Contains two parts
•Proventriculus: same as monogastric
stomach and provides digestive
excretions
•Gizzard: located after proventriculus,
very muscular,
used to grind food

41. Avian Digestive Systems
• Small Intestine
– similar functions as in ruminants and
monogastric systems
• Large Intestine
– similar functions as in ruminants and
monogastric systems
– “cloaca”: chamber into which urinary and
genital canals open
– “ceca”: aids in fiber digestion and
absorption

43. Digestive System Comparisons
Function Monogastric Ruminants
Hind Gut
Fermentors
Digest and extract
energy from cellulose
Very limited
(large intestine)
Yes
(rumen/reticulum)
Yes
(large intestine)
Utilize dietary sugar
sources directly
Yes
(absorbed as glucose)
No
(fermented to VFA’s)
Yes
(absorbed as glucose)
Utilize protein from
feeds directly
Yes Limited
(most converted to microbial
protein)
Yes
Utilize fat from feeds
directly
Yes Some
(most fermented to VFA’s)
Yes
Utilize microbial
protein
No Yes
(60-80% of AA from microbes)
No

45. Human Cattle Bird Horses
Teeth 32 32 0 40-42

46. Organs of digestive system Comparisons
Ruminant
• Mouth
• Esophagus
• Stomach
– Reticulum
– Rumen
– Omasum
– Abomasum
• Small intestines
• Large intestines
Monogastric
• Mouth
• Esophagus
• Stomach
• Small intestines
• Large intestines
Liver
Pancreas
Liver
Pancreas

47. Thank you