- - AGRICULTURE CORE CURRICULUM - - (CLF3000) Advanced Core Cluster: ANIMAL SCIENCE (CLF3200) Unit Title: ANIMAL PHYSIOLOGY ____________________________________________________________________________ (CLF3201) Topic: THE DIGESTIVE Time Year(s) PROCESS 3 hours 3 / 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: Learning Outcome #: (C-1) - Demonstrate an understanding of the structure and function of the digestive system by tracing the pathways of food through the four types of livestock digestive systems, with emphasis on function of organs in the digestive process. Special Materials and Equipment: Diagrams of the ruminant, non- ruminant, and avian digestive systems. Actual digestive organs may be obtained from slaughter plants or local butchers. References: Bundy and Diggins (1968). LIVESTOCK AND POULTRY PRODUCTION. Cole, H. H., and Ronning, Magnar. (1974). ANIMAL AGRICULTURE. California Vocational Agriculture Curriculum Guidelines, AG PRODUCTION, "Anatomy and Physiology of Farm Animals", (Diagrams are available). Evaluation: Quiz by instructor and completion of Supplemental Worksheet #1. TOPIC PRESENTATION: THE DIGESTIVE PROCESS Review the Basic Core Curriculum CLF242, C-1&2, "Digestive Systems". A. Digestion 1. The process of digestion in all animals is fundamentally the same. a. Food is broken down mechanically and chemically so it can be utilized by body cells. b. Different species of animals consume different types of feeds. Their digestive systems are adapted to break down different feed stuffs depending on the species in question. 2. Types of digestive systems: a. polygastric or ruminant, b. monogastric or simple stomach, c. avian, and d. equine or modified simple stomach (sometimes referred to as "cecal fermenters -- i.e., non ruminant). B. Ruminant Digestive System 1. May be the most complex because their digestive system is modified to handle the breakdown of large amounts of more highly lignified fiber. 2. Parts of the ruminant digestive tract: a. The Mouth - 1) has no upper incisors in ruminants, just a hard palate. 2) contains molars that are adapted for grinding coarse vegetation. 3) secretes large amounts of saliva which does not contain any enzymes (unlike human saliva). b. The Esophagus - 1) serves as a muscular tube connecting the mouth to the stomach. c. The Stomach - 1) The ruminant stomach is divided into 4 compartments: a) the rumen - (paunch) is the largest compartment which serves as a storage area and fermentation vat. This is where millions of bacteria help break down fiber and synthesize vitamins and amino acids. b) the reticulum - (honeycomb) is closely associated with the rumen. Many foreign bodies such as nails and wire may be retained here. (Hence the nickname of "hardware stomach".) c) the omasum - (many plies) helps eliminate excess water from the feed before it enters the "true-stomach". d) the abomasum - (true-stomach) is where gastric juices and enzymes are secreted. 2) Regurgitation (First step in rumination, see basic core): a) A phenomena in ruminants where large quantities of roughage are consumed and are chewed just enough to make swallowing possible. b) After they consume the food, regurgitation or "cud" chewing takes place and the food is re-chewed, so it can be further digested in the omasum and abomasum. d. The Small Intestine - 1) is a long coiled tube connecting the stomach to the large intestine. 2) has been called the most important digestive organ because many food nutrients are absorbed into the blood at this point in the system. 3) contains digestive juices such as bile and pancreatic juice that are secreted into the duodenum, which is located at the beginning of the small intestine near the stomach. 4) pushes food through it by waves of muscular contractions called.peristalsis. e. The Large Intestine - 1) consists of a cecum, colon, and rectum. a) The cecum is a blind sac at the junction of the small and large intestines. b) The colon and rectum are at the end of the system. 2) is a coiled tube that is not as long as the small intestine, but larger in diameter. 3) is where water and some nutrient absorption occurs. 4) is where the residue becomes solid before being excreted. C. The Monogastric Digestive System (Swine) 1. Is characterized by the inability to digest roughages efficiently. 2. Parts of the monogastric's digestive system: a. The Mouth - 1) has both upper and lower incisors. 2) has a digestive enzyme called "ptylan", which is secreted in the saliva which helps breakdown certain nutrients (carbohydrates). b. The Esophagus - connects the mouth to the stomach. c. The Stomach - 1) has a strong acid (hydrochloric acid) that is secreted to break down other nutrients. 2) contains enzymes such as pepsin which are also secreted into the digestia in the stomach. 3) has a churning action that to mix the food and enzymes. d. The small intestine - functions in a similar way to the small intestine of the ruminant. e. The large intestine - functions in a similar way to the large intestine of the ruminant. __________________________________________________________ ACTIVITY: 1. Using diagrams of the swine and ruminant digestive systems, identify organs and compare the 2 types of digestive systems. __________________________________________________________ D. Avian Digestive System 1. Is characterized by several organs not found in other species. This digestive system is adapted for grinding hard or encased (shells of seeds) food. 2. Parts of the avian digestive system: a. The Mouth - 1) has the saying, "Scarce as hen's teeth", which is correct since birds do not have teeth. 2) has saliva secretion to moisten food and to aid in swallowing. b. The Esophagus - 1) has a modification which is called the "crop" where food is stored and further moistened. 2) connects the mouth to the stomach. c. The Stomach - 1) consists of two parts. a) The "proventriculus" which is completely analogous to the monogastric stomach and provides digestive secretions. b) The "gizzard" which is located after the proventriculus and is specialized and very muscular and is used for grinding food. d. The Small Intestine - 1) varies in length depending on the diet. It is longer in herbivores (plant eating birds) and shorter in carnivores (flesh eating birds). 2) functions similar to the small intestine of ruminants and monogastrics. e. The Large Intestine - 1) functions similar to the small intestine of ruminants and monogastrics. 2) has the "cloaca" at the terminal end of the large intestine, which is a chamber into which the urinary and genital canals open. 3) has at the junction of the small and large intestine, two "ceca" which are pouches which further contribute to aiding in fiber digestion and absorption. __________________________________________________________ ACTIVITY: 1. Go over the parts of the poultry digestive system using a diagram. 2. If possible, obtain chickens, pigeons, or other fowl to dissect and examine the digestive system. __________________________________________________________ E. Equine Digestive System (Modified simple digestive system) 1. Is characterized by non-ruminant animals that consume and digest feeds high in fiber. Rabbits and Guinea Pigs are other examples. 2. Parts of the Equine Digestive System: a. The Mouth - 1) has intact top and bottom incisors and the molars are adapted for chewing fibrous feeds. 2) has no digestive enzymes in the saliva. b. The Esophagus - 1) is similar to the monogastric system and is not well adapted for regurgitation. 2) connects the mouth to the stomach. c. The Stomach - is similar to the monogastric system. d. The Small Intestine - 1) functions similarly to that of the monogastric and ruminant. 2) has no gall bladder attached to it to store bile. The liver still produces and secretes bile to break down fats as with all species discussed so far. 3) has an enlarged "cecum" at the junction of the small intestine and large intestine, which aids in fiber breakdown. Microbial action takes place here which is similar to that in ruminants (vitamins and amino acids are synthesized here through microbial action). e. The Large Intestine - 1) is similar in function to that of the large intestine of the monogastric. 2) has the cecum and colon which takes up the majority of the volume of the horse's digestive system. __________________________________________________________ ACTIVITY: 1. Observe parts of the equine digestive system using a diagram to compare it to other systems studied. __________________________________________________________ F. Accessory Organs 1. Definition: Organs that aid in the digestive process without actually being a part of the actual digestive tract. 2. Examples: a. Pancreas - Functions to produce and secrete digestive enzymes. This organ produces a hormone called insulin which regulates carbohydrate metabolism. b. Liver - 1) Functions to produce bile which emulsifies (breaks down) fatty acids. 2) The liver is a very complex organ with many other functions including storing iron, handling fats and carbohydrates in the blood, etc. __________________________________________________________ ACTIVITY: 1. Complete Supplemental Worksheet #1."The Digestive Process". __________________________________________________________ Supplemental Worksheet #1 THE DIGESTIVE PROCESS Name_____________________________________ Date_____________________________________ Per._____________________________________ 1. What are the 4 types of digestive systems discussed in lecture? __________________________________, ___________________________________, __________________________________, and _______________________________ 2. Draw a diagram for each type of digestive systems listed above and label each diagram: 3. Describe the function of the following organs: Esophagus - Crop - Stomach - Rumen - Proventriculus - Small intestine - Cecum - Large intestine - Cloaca - Gizzard - 4. What is meant by "accessory organs"? List two."accessory organs": __________________________ and _______________________________ 5/2/90 sg #%&C