1. Digestion

2. Digestive Systems Overviews
Objectives
Describe the structures and functions of the digestive system of different animals
Draw the structures of the digestive system of different animals
Label the structures of the digestive system

3. Digestion
Digestion: Breaking down large, nutrient macromolecules into simpler molecules for use by an organism.
Food enters the mouth and goes through mechanical and chemical changes as it passes through the alimentary canal.

4. Types of Stomachs Simple Stomach Man, Pig Complex Stomach
Cattle, Sheep, Goats
Simple Stomach with enlarged caecum
Horses, Rabbits, Guinea Pigs

5. Parts of Digestive Tract
Mouth: initial opening of alimentary canal
Salivary Glands
secrete juices that contain enzymes to help break up the food
Mastication
chewing, crushing, preparing food for swallowing

6. Parts of Digestive Tract
Pharynx: funnel shaped muscle between mouth and oesophagus
part of digestive and respiratory tracts
Oesophagus: muscular tube connecting pharynx to stomach
muscle contractions move food down to stomach
Achalasia?

7. Parts of Digestive Tract
Stomach: located between oesophagus and small intestine
Two basics types
Simple
Ruminant

8. Parts of Digestive Tract
Simple Stomach
Humans, swine, rabbits and horses
Divided into three regions
Cardiac
Fundus
Pylorus

9. Anatomy of the Stomach

10. Stomach Functions Absorbs Mix food Reservoir Start digestion of
Protein
Nucleic acids
Fats
Activates some enzymes
Makes intrinsic factor – B 12 absorption
Destroys some bacteria
Absorbs
Alcohol
Water
Lipophilic acid
B12

11. Simple Stomach Digestion: is mechanical, muscle contractions
is chemical, enzymes soften and break down macromolecules of food
enzymes are catalysts, they start the chemical reactions

12. Simple Stomach Enzymes that break down food
Gastric-break down proteins in stomach
Liver and pancreatic-break down fats in small intestine
Intestinal-break down carbohydrates and proteins in small intestine

13. Parts of Digestion Tract
Ruminant Stomach
Sheep, Cows and Goats
Occupies 3/4 of the abdominal cavity

14. Four Components of Ruminant Stomach
Rumen
composes 80% of ruminant stomach in mature bovine animals and 30% in young animals
Reticulum
composes about 5% of bovine stomach
prevents indigestible objects from entering the stomach

15. Four Components of Ruminant Stomach
Omasum
composes 7-8% of bovine stomach
absorbs mostly water
Abomasum
the “true” stomach
composes 7-8% of stomach in mature animals and 70% in young animals

17. Digestion in the Ruminant Stomach
Rumination: The process of regurgitation, re- mastication, re-salivation and re-swallowing of food.
Purpose: To smash and break up food which provides more surface area for bacteria to break down

18. Parts of Digestive Tract
Small Intestine: long, coiled tube connecting the stomach with the large intestine.
Is covered by villi which increases surface area to increase absorption
Food moves through by muscle contractions called peristaltic movement
Final breakdown and absorption of nutrients occurs here

19. Villus morphology

20. Parts of the Digestive Tract
Large Intestine
Includes caecum, colon and rectum
Absorbs water
Very little nutrient absorption takes place here

21. Parts of the Digestive Tract
Accessory Organs
Pancreas
secretes enzymes which breakdown fat and starches
Liver
secrets bile which emulsifies fats in preparation for digestion

22. The Digestion Process

23. The Digestion Process Food is broken down into smaller particles
Animals have digestive systems adapted to the foods that they consume
Four types of digestive systems
Ruminant (polygastric)
Simple (single) stomach (monogastric)
Avian
Equine (modified simple stomach)

24. Ruminant Digestive System
Modified to handle the breakdown of large amounts of fiber

25. Ruminant Digestive System
Mouth
no upper incisors, hard palate
molars for grinding coarse vegetation
saliva does not contain enzymes
Oesophagus
muscular tube connecting the mouth to the stomach

26. Ruminant Digestive Systems
The Four Compartmented Stomach
Rumen: storage area and fermentation vat
Reticulum: nails and wire may be found here- hardware stomach
Omasum: eliminates excess water from feed
Abomasum: true stomach, gastric juices and enzymes are secreted

27. Ruminant Digestive Systems
Stomach
Regurgitation: first step in rumination
large quantities of roughage are consumed and are chewed just enough to swallow
after swallowing, regurgitation (“cud chewing”) takes place, food is re-chewed

28. Ruminant Digestive System
Small Intestine
connects stomach to large intestine
food nutrients absorbed into blood
contains bile and pancreatic juices
pushes food through by muscle contractions

29. Ruminant Digestive System
Large Intestine
Consists of the Caecum, Colon and Rectum
Caecum: sac at junction of small intestine and large intestine
Colon and rectum: at end of system
not as long as small intestine, but larger in diameter
water and some nutrient absorption occurs here
where residue solidifies before excretion

30. Monogastric Digestive System
Characterized by inability to digest roughage efficiently

31. Objectives
Describe the structures and functions of the digestive system of non-ruminant animals
Draw the structures of the digestive system of non- ruminant animals
Label the structure of the digestive system of non- ruminant animals

32. Monogastric Digestive System
Mouth
has upper and lower incisors
digestive enzymes secreted which breaks down nutrients
Oesophagus
connects mouth to stomach

33. Monogastric Digestive System
Stomach
secretes Hydrochloric acid (HCL) to break down nutrients
enzymes such as pepsin also secreted here
churning action mixes food
small and large intestine
function just as in ruminant systems

35. Avian Digestive Systems
Characterized by several organs not found in other species that are adapted for grinding hard or encased food

36. Avian Digestive Systems
Mouth
No teeth which leads to the old adage “scarce as a hen’s teeth!!”
Saliva secretion moistens food
Oesophagus
has a modification called the “crop” which stores and moistens food
connects mouth and stomach

37. Avian Digestive Systems
Stomach
Consists of two parts
Proventriculus: same as monogastric stomach and provides digestive secretions
Gizzard: located after proventriculus, very muscular, used to grind food

38. Avian Digestive Systems
Small Intestine
Similar functions as in ruminants and monogastric systems
Large Intestine
“Cloaca”: chamber into which urinary and genital canals open
“Caeca”: aid in fiber digestion and absorption

40. Equine Digestive Systems
Characterized by non- ruminant animals that consume and digest feeds high in fiber

41. Equine Digestive Systems
Mouth
intact top and bottom incisors
molars adapted to chewing fibrous feeds
no digestive enzymes in saliva
oesophagus
not well adapted for regurgitation
connects mouth and stomach

42. Equine Digestive System
Stomach
similar to monogastric system
Small intestine
similar to monogastric and ruminant systems
no gall bladder to store bile
enlarged cecum to aid in fiber breakdown

43. Equine Digestive System
Large Intestine
similar to monogastric systems
caecum (at junction of small and large intestines) and colon take up most of the volume of the equine digestive system

45. Accessory Organs
Organs that aid in the digestive process without actually being part of the digestive system

46. Accessory Organs Pancreas produces and secretes digestive enzymes
produces insulin which regulates carbohydrate metabolism
Liver
produces bile which breaks down fatty acids
stores iron, handles fats and carbohydrates in the blood

47. The End!!

48. 1. Horse
2. Chicken
3. Cow
4. Rabbit
5. Pig
6. Ostrich