Digestive System

1. Digestive System

2. Path of Digestion • Food is grasped and collected into the oral cavity • This is called prehension • Mastication (chewing) breaks food into smaller pieces • Deglutition moves chewed food into the pharynx and on into the esophagus • The epiglottis closes off the entrance to the trachea • Food moves down the esophagus by gravity and peristalsis • Peristalsis is a series of wavelike contractions of smooth muscle • -stalsis means contraction

3. 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-to- side mixing of ingesta

4. Structures and Functions • The organs of the gastrointestinal tract (GI) form a tubelike passage through the body cavaties. • From the mouth to the anus by way of the pharynx, esophagus, stomach, and intestines • The main functions of this system is • Prehension • Transport • Breakdown of food • Absorption of nutrients • Eliminate waste

5. Structures and Functions • Food moves through the digestive system aided by peristalsis, an involuntary, wavelike movement. • The digestive tract in all mammals generally has the same parts • Mouth • Teeth • Tongue • Pharynx • Esophagus • Stomach • Small intestine • Large intestine

6. The Mouth • 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.

7. Teeth • 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 • Ruminants do not have upper incisors, just a pad.

9. Salivary Glands • Saliva is produced in 4 salivary glands • Parotid • Sublingual • Mandibular • Zygomatic • Referred to as exocrine glands • Saliva begins the breakdown of some foods (carbohydrates) in the mouth. • Moistens food, lubricant for the bolus.

11. 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 • Meta- means change or beyond • Anabolism is building up of body cells • Catabolism is breakdown of body cells

12. Absorption • Absorption is the process of taking digested nutrients into the circulatory system • also called assimilation • Absorption occurs in the small intestine • Villi are tiny hairlike projections that help increase the surface area of the small intestine allowing more nutrients to be absorbed • Vill/i means tuft of hair • The valleys that result from the projections of the small intestine are called crypts

13. 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

14. 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

16. Ruminant Digestive System

17. Digestive System • 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) • 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

18. Digestive System • Accessory organs: • Pancreas secretes enzymes to break down fat • Liver (largest internal organ) secretes bile, which digests fats • also stores iron

19. 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__________

20. Digestive System • Mouth: “Prehension” tool (grasps food) • ___________________secrete juices containing enzymes (digest food) • Chewing food breaks down • ____________: muscular tube that connects mouth to stomach • Peristaltic Movement: sequential contraction of ring like___________ • Reverse ___________= blowing chunks

21. Simple Stomach • Muscular contractions break down food • Enzymes break down food: • Gastric: ___________ • Liver and ____________: fats

22. Ruminant Digestive System

23. I thought Dumbo was an elephant 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 • Symbiotic relationship with bacteria • Produces 13 gallons of gas/hour • Produces 40 liters of saliva/day

24. Ruminant Stomach • Stomach occupies 3/4 of abdominal cavity, mostly on the left side • Rumen (paunch): 80% of stomach, lighter food collects here • microbes digest cellulose • lots of water • Reticulum (hardware stomach): 5% of stomach, heavy foreign items are trapped here

25. Ruminant Stomach • Omasum (many plies): 8% of stomach, absorbs water • Abomasum (true stomach): 8% of stomach, typical enzyme activity • Rumination: regurgitation, rechewing of food

26. 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)

27. 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

28. Omasum • Third compartment • Globe-shaped • Lining called “many plies” • Reduces feed particle size • Absorbs water and dries out ingesta • Absorbs volatile fatty acids

29. 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

30. Ruminant Digestion

31. Rumination Ruminant Digestion • Intake • Mastication (chewing) • Swallowing • Regurgitation • Remastication • Fermentation • Eructation • Absorption • Digestion

32. 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

33. 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: • Mouth, esophagus, stomach, intestines, anus, liver, teeth, pancreas, and salivary glands

34. Equine Digestive System • Mouth • Lips, pharynx, soft palate • Lips pick up loose feed which is then passed into the mouth by the tongue • Pharynx • Short, funnel shaped tube between the mouth and the esophagus • Food and water cannot return through the mouth after passing through • Horse that chokes has food pass through nose

35. Digestive System • 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.

36. 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

37. 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.

38. Large Intestine, Horses 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 Kicking at abdomen, rolling, lying down and standing up repeatedly, restlessness .