Digestive Systems: Monogastric, Avian, Ruminant & Pseudo-Ruminant Systems

Digestive systems Digestion Digestion is: The breakdown of food into smaller nutrients for absorption and use by the body A similar process across all species The four different types of digestive systems are: Monogastric (humans and many mammals) Avian (chickens and other birds) Rumin...

Digestive systems Digestion Digestion is: The breakdown of food into smaller nutrients for absorption and use by the body A similar process across all species The four different types of digestive systems are: Monogastric (humans and many mammals) Avian (chickens and other birds) Ruminant (cows and goats) Pseudo-ruminant (horses and rabbits) Monogastric digestive system Both carnivores and omnivores may have monogastric digestive systems. (e.g., humans, swine, dogs, and cats) Monogastric systems have a simple stomach structure (one compartment) Digestive tract of the monogastric mammal large intestine anus jejunum ileum pancreas rectum duodenum esophagu s mouth tongue teeth cecum gall bladder liver salivary glands stomach small intestine Monogastric parts and functions Mouth Mastication occurs here—teeth grind food Addition of saliva from salivary glands Tongue helps move food and allows for taste and repares food for swallowing Prehension: method in which animals “grasp” their food Monogastric parts and functions Epiglottis Flap or valve that closes windpipe (trachea) while swallowing Monogastric parts and functions Esophagus Muscular tube for passage of food from the mouth to the stomach Smooth muscle lining Peristalsis carries food to the stomach Monogastric parts and functions Stomach Storage/additional breakdown of food Food digested by HCl (hydrochloric acid): pH between 3–4 Secretes pepsin (enzyme that breaks down protein) Pyloric valve (smooth muscle sphincter): Ring of muscle surrounding and serving to guard or close an opening or tube Monogastric parts and functions Liver Controls storage and concentration of nutrients such as proteins, fats, carbohydrates, vitamins, and minerals Make proteins Make clotting factors Produces bile, a digestive compound. Monogastric parts and functions Gall bladder Where bile is stored Bile can be concentrated here Released from here into the small intestine Structure and location around liver can vary greatly between species Monogastric parts and functions Pancreas Regulate blood sugar by producing insulin in endocrine system Also produces pancreatic juice in exocrine system Enzyme that breaks down carbs, fats, and proteins Secreted through the pancreatic Monogastric parts and functions Small intestine Enzymatic digestion and absorption Functions of the small intestine: digestion of proteins, carbohydrates, and fats; absorption of the end products of digestion Divided into three sections: Duodenum: Most digestion occurs here Jejunum: Some digestion and absorption occur Ileum: Mostly absorption Monogastric parts and functions Villi: Finger-like projections in lining of small intestine that contain blood vessels for nutrient transfer Monogastric parts and functions Duodenum First section of the small intestine Connects stomach to the small intestine Where bile and pancreatic juices are added Monogastric parts and functions Jejunum Middle section Makes up about two-fifths of the small intestine Absorbs fully-digested carbohydrates, proteins, sugars, fatty acids, and amino acids Nutrients enter the bloodstream, where they can then be distributed to the organs of the body Monogastric parts and functions Ileum Means “twisted intestine” Final section of small intestine Longest section Absorbs any nutrients that got past the jejunum, mainly vitamin B12 and bile acids Bile salts are reabsorbed by active transport in the ileum and returned by the blood to the liver Monogastric parts and functions Enzymes Proteins that help to break down nutrients within digestive systems Biochemically function to break down specific nutrients Different digestive systems have different enzymes and some systems use bacteria or other microbes to help break down specific food stuffs. Enzymes in the small intestine Enzyme Function Source trypsin chymotrypsin digest proteins carboxypeptides secreted from pancreas pancreatic amylase digest carbohydrates lipases digest lipids disaccharidase digest carbohydrates secreted dipeptidases digest peptides from small intestine Monogastric parts and functions Ileocecal valve Smooth muscle sphincter Where the ileum joins the large intestine Monogastric parts and functions Large intestine Also referred to as the colon Much shorter than the small intestine in length, but larger in diameter Three main things happen here: Bacterial activity: continuation of breakdown of the more indigestible food Lots of water absorption, creating solid waste Avian digestive system Avian parts and functions Beak No teeth Prehensile action: pecking food with their beak/bill Secretes saliva to soften food and aid in swallowing Houses the tongue which manipulates food and aids in swallowing food whole Avian parts and functions Esophagus Connects the mouth to the stomach Moves food from the mouth to the stomach using wave- like muscle contractions (peristalsis) Often deposits food in the crop of many types of birds before going to the stomach Avian parts and functions Crop (part of the esophagus) Temporary food storage pouch Located just outside the body cavity in the neck region An evolutionary adaptation that allows birds that need to eat in the open to consume large amounts of food for digestion later Swallowed feed and water are stored in the crop until they are passed to the rest of the digestive tract Very little digestion takes place here Avian parts and functions Stomach Divided into two parts Proventriculus Glandular part of the stomach where food is partially digested Hydrochloric acid and digestive enzymes, such as pepsin are added Ventriculus/gizzard Part of the digestive tract of birds, reptiles, earthworms, and fish Muscular portion of the stomach which grinds food, often with the help of ingested stones or grit (a supplement given to chickens that eat whole grains) Avian parts and functions Small intestine Made up of the duodenum, jejunum, and ileum Duodenal Loop: surrounds pancreas Varies in length depending on diet Longer in carnivorous (meat eater) birds Shorter in herbivorous (plant eater) birds Remainder of digestion takes place here Main place of absorption of nutrients Bile aids in absorption of fat-soluble vitamins (A, D, E, and K) Avian parts and functions Ceca Plural form of cecum Two pouches located where the small and large intestines meet Remaining water is absorbed here Fermentation of any remaining coarse materials Avian parts and functions Large intestine Also known as the colon Absorbs water, dries out indigestible items, and eliminates waste products Contains bacteria which allow birds to metabolize remaining nutrients Connects to the cloaca Avian parts and functions Intestinal microflora Both the small and large intestines contain beneficial organisms Microflora: ‘micro’ meaning “small” and ‘flora’ meaning “plants” Aid in digestion Born with sterile digestive tracts and need to consume the microflora Mother’s fecal material Probiotics in feed Avian parts and functions Cloaca/vent Location where digestive wastes mix with wastes from the urinary system Chickens usually void fecal material as digestive waste with uric acid crystals on the outer surface Therefore, chickens do not urinate! Eggs come out of this chute Ruminant digestive system What is a ruminant? Animals that acquire nutrients from plant- based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. Ruminant parts and functions Mouth Where food is moistened to aid in chewing by teeth Lips, tongue, teeth, and saliva start the digestion process Ruminants only have front teeth in the lower jaw, which cut grass against the dental pad Upper and lower molars used for grinding food Ruminant parts and functions The esophagus Transports food to and from the mouth and stomach Food can make multiple trips Ruminants can regurgitate, re- masticate, and re-swallow their food (“chewing their cud”) May do this for up to 8 hours a day Ruminant parts and functions The stomach One stomach; four parts Each compartment has a specific function The first and third are considered forestomachs Aid digestion through microbial fermentation Microbes help break down fibrous material Ruminant parts and functions The stomach Rumen a.k.a. “the paunch” Largest compartment Can hold up to 40 gallons in a cow Makes up 80% of the stomach Top third is gas, middle third is solid feedstuffs, and the bottom third is digested feedstuffs Contains a large population of microorganisms Help digest feed and provide energy for the animal Produce the majority of amino acids Ruminant parts and functions The stomach Papille Finger-like structures that texture the inner lining Provides more surface area Ruminant parts and functions The stomach Reticulum a.k.a. honeycomb or “hardware” stomach Relatively small 2 gallons in a cow Makes up 5% of the stomach Contractions cause movement for the rumen to mix feed Pumps food back up the esophagus for rumination Acts as a sieve Ruminant parts and functions The stomach Omasum a.k.a. “the butcher’s Bible” Round, muscular section has many folds to grind and squeeze the feed Holds 4 gallons in a cow Makes up 8% of the stomach Many folds in the interior walls’ structure—looks like a book Absorbs water Ruminant parts and functions The stomach Abomasum The “true stomach” Functions are similar to the monogastric stomach Bile added to help the breakdown of proteins and lipids Only compartment that produces enzymes and mucous Ruminant parts and functions Small intestine Where most nutrients are absorbed into the bloodstream Is about 20 times the length of the animal! 6-foot long cow = 120 feet Three main parts: Duodenum Jejunum Ileum Ruminant parts and functions Large intestine Unused food material is prepared for removal from the body Three main parts: Cecum: minor role in further breakdown of roughages Colon: absorbs water and forms undigested wastes into feces Rectum: stores feces until it is passed out of the body Anus Opening in which waste exits the body Feeds that aren’t Pseudo-ruminants An animal that eats large amounts of roughage Does not have a stomach with several compartments Digestive system performs some of the same functions as those of ruminants (i.e., in horses, the cecum ferments forages) Can digest large amounts of roughage because of a greatly enlarged cecum and large intestine (many areas for microbial digestion of fiber) Pseudo-ruminants often eat forages