1. Chapter 28
The Digestive System

2. Functions Intake and digestion of food and water
Absorption of nutrients
Elimination of solid waste

3. Terminology
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
Absorption is the process of taking digested nutrients into the circulatory system

4. Structures Mouth (teeth) Pharynx Esophagus Stomach Small intestines
Large intestines
Accessory organs of digestion

5. Teeth Carnivores Herbivores
Meat eaters - Use teeth for tearing and chewing food
Dogs and cats - long incisors (fangs)
Herbivores
Plant eaters, Grind plant materials
Horse, cow, sheep, goat

6. Teeth Omnivores Meat and plant eater Teeth adapt for variety of foods
Humans

7. Teeth Deciduous Permanent Incisors small baby teeth; curved
larger adult teeth; straight
Incisors
front teeth used to bite

8. Teeth Canines Pre-Molars Molars fangs used to tear food; longest teeth
wider teeth used to crush and grind food
Molars
rear teeth

9. Teeth Crown Root Enamel Dentin Pulp Cavity portion above the gum line
portion below the gum line
Enamel
covering of the crown
Dentin
second layer between crown and root
Pulp Cavity
where nerves, arteries, and veins enter the tooth

10. Tooth Anatomy

11. The Mouth Saliva 4 salivary glands that produce saliva
used to break down foods and line the digestive tract
Humans secret 1-2 L saliva / day
Adult cow secrets 200L of saliva / day
Tongue
skeletal muscle
obtains food and holds in mouth
forms BOLUS
Papillae- hair on tongue that acts as taste buds

12. Salivary Glands

13. Pharynx
The pharynx is the cavity in the caudal oral cavity that joins the respiratory and gastrointestinal systems
Also known as the throat
Bolus enters pharynx
Respiration is reflexively inhibited
Larynx reflexively closes and pulls up and forward
Base of tongue folds epiglottis over the laryngeal opening as it moves back
Pharynx shortens and peristaltic action of pharyngeal muscles forces bolus into esophagus

14. The Stomach Food enters stomach Monogastric Divided into 3 sections:
Single, simple stomach
Divided into 3 sections:
CARDIA (ENTRANCE)
BODY
PYLORUS (EXIT)
FUNDUS- top of the stomach at the entrance
Sphincter muscle control at entrance and exit
Peristalsis- wave like contractions to pass food

15. The Small Intestines 3 major parts
Duodenum
Jejunum
Ileum
Primary site of enzymatic digestion and absorption of nutrients

16. The Large Intestines Cecum Colon Rectum Anus
pouch that takes food from the ileum
Colon
varies among species
Absorbs water
Omnivores and herbivores: site of fermentation and microbial digestion
Rectum
caudal portion
Anus
caudal opening

17. Accessory Organs Liver Pancreas
Produces bile (salty substance) that aids in the digestion of lipids; stored in gallbladder
Pancreas
Secretion of digestive enzymes; empties into the duodenum

18. Stomach Systems 3 types of animal digestive systems: Monogastric
Ruminant
Nonruminant

19. Monogastric Systems Has only one compartment to the stomach
Process goes through the:
Mouth
Esophagus
Stomach
Small intestine: duodenum, jejunum, ileum
Large intestine: cecum, colon, rectum

20. Monogastric System

21. Monogastric Systems
Humans
Dogs
Cats
Pigs

22. Monogastric Stomach

23. The Ruminant System The Ruminant Stomach
Sheep, cows, llamas, and goats
Occupies 3/4 of the abdominal cavity
Four Components of Ruminant Stomach
Rumen
Reticulum
Omasum
Abomasum

24. The Ruminant System Rumen
composes 80% of ruminant stomach in mature bovine animals
Serves as a fermentation vat
Reticulum
composes about 5% of bovine stomach
prevents indigestible objects from entering the stomach
Most cranial
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

25. The Ruminant System
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 bacteria to break down
Eructation: belching action as gas builds up in the rumen

26. The Ruminant System Multi-compartment stomach
Ruminant animals are often called “cud chewers”
No upper front teeth in ruminant mouth

27. The Nonruminant System
System is noted in horses, rodents, and rabbits
Simple stomach with enlarged cecum
Plant fibers are broken down and digested in the cecum
Uses bacteria to break down material by process of fermentation

28. Common Digestive Conditions
Can be caused by many factors
Typical reactions: vomiting or diarrhea
Can lead to dehydration

29. Dehydration Loss of fluids in the body Skin turgor
how it can be established
area of skin at the base of neck and over the shoulders is elastic-like
skin turgor will stay “tented” or appear not to go back in its normal position

30. Dehydration Mucous membranes (mm)
hydration status can be determined by evaluating this
gums or mm can be labeled tacky or dry
Color and amount of moisture can help identify
Can be seen in eye sockets if they are sunken into head

31. Dehydration Fluid replacement Intravenous (IV) or Subcutaneous (SQ)
Fluids Lactated Ringer’s Solution (LRS)
Sodium chloride
Normal saline

32. Dehydration Percentages
Moist mm; slight skin turgor; slightly sunken eyes
8-9% Dehydration
Tacky mm; obvious sunken eyes; slow skin turgor with noted tenting
10-12% Dehydration
Dry mm; very sunken eyes; very slow and very tented skin turgor