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Digestive Systems Digestive Systems Overviews Objectives •Describe the structures and functions of the digestive system of ruminant animals •Draw the structures of the digestive system of ruminant animals •Label the structures of the digestive system of ruminant animals 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. Types of Stomachs • Simple Stomach – Man, Pig • Complex Stomach – Cattle, Sheep, Goats • Simple Stomach with enlarged ceacum – Horses, Rabbits, Guinea Pigs 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 Parts of Digestive Tract • Pharynx: funnel shaped muscle between mouth and esophagus – part of digestive and respiratory tracts • Esophagus: muscular tube connecting pharnyx to stomach – muscle contractions move food down to stomach Parts of Digestive Tract • Stomach: located between esophagus and small intestine – Two basics types • Simple • Ruminant Parts of Digestive Tract Simple Stomach • Humans, swine, rabbits and horses – Divided into three regions • cardiac • fundus • pylorus 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 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 Parts of Digestion Tract Ruminant Stomach • Sheep, Cows and Goats • Occupies 3/4 of the abdominal cavity 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 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 Digestion in the Ruminant Stomach • Rumination: The process of regurgitation, re-mastication, re-salivation and reswallowing of food. • Purpose: To smash and break up food which provides more surface area bacteria to break down 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 Parts of the Digestive Tract • Large Intestine – Includes cecum, colon and rectum – Absorbs water – Very little nutrient absorption takes place here Parts of the Digestive Tract Accessory Organs • Pancreas – secretes enzymes which breakdown fat and starches • Liver – secrets bile which digest fats The Digestion Process The Digestion Process • Food is broken down • Animals have digestive systems adapted to the foods that they consume • Four types of digestive systems – – – – Ruminant(polygstric) Simple Stomach(monogastric) Avian Equine-modified simple stomach Ruminant Digestive System Modified to handle the breakdown of large amounts of fiber Ruminant Digestive System • Mouth – no upper incisors, hard palate – molars for grinding coarse vegetation – saliva does not contain enzymes • Esophagus – muscular tube connecting the mouth to the stomach 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 Ruminant Digestive Systems Stomach (cont.) • 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 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 Ruminant Digestive System • Large Intestine – Contains Cecum, Colon and Rectum • Cecum: 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 Monogastric Digestive System Characterized by inability to digest roughage efficiently Objectives • Describe the structures and functions of the digestive system of non-ruminant animas • Draw the structures of the digestive system of non-ruminant animals • Label the structure of the digestive system of non-ruminant animals Monogastric Digestive System • Mouth – has upper and lower incisors – digestive enzymes secreted which breaks down nutrients • Esophagus – connects mouth to stomach Monogastric Digestive System • Stomach – secretes Hydrochloric Acid 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 Avian Digestive Systems Characterized by several organs not found in other species that are adapted for grinding hard or encased food Avian Digestive Systems • Mouth – no teeth which leads to the saying “scarce as a hen’s teeth!!” – Salivation excretion moistens food • Esophagus – has a modification called the “crop” which stores and moistens food – connects mouth and stomach 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 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 Equine Digestive Systems Characterized by non-ruminant animals that consume and digest feeds high in fiber Equine Digestive Systems • Mouth – intact top and bottom incisors – molars adapted to chewing fibrous feeds – no digestive enzymes in saliva • Esophagus – not well adapted for regurgitation – connects mouth and stomach 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 Equine Digestive System • Large Intestine – similar to monogastric systems – cecum (at junction of small and large intestines) and colon take up most of the volume of the equine digestive system Accessory Organs Organs that aid in the digestive process without actually being part of the digestive system Accessory Organs • Pancreas – produces and secretes digestive enzymes – produces insulin which regulates carbohydrate metabolism • Liver – produces bile-breaks down fatty acids – stores iron, handles fats and carbohydrates in the blood The End!!