Digestion

Digestive Systems Overviews Objectives Describe the structures and functions of the digestive system of different animals Draw the structures of the digestive system of different animals Label the structures of the digestive system

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 caecum 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 oesophagus part of digestive and respiratory tracts Oesophagus: muscular tube connecting pharynx to stomach muscle contractions move food down to stomach Achalasia?

Parts of Digestive Tract Stomach: located between oesophagus 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

Anatomy of the Stomach

Stomach Functions Absorbs Mix food Reservoir Start digestion of Protein Nucleic acids Fats Activates some enzymes Makes intrinsic factor – B 12 absorption Destroys some bacteria Absorbs Alcohol Water Lipophilic acid B12

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 re-swallowing of food. Purpose: To smash and break up food which provides more surface area for 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

Villus morphology

Parts of the Digestive Tract Large Intestine Includes caecum, 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 emulsifies fats in preparation for digestion

The Digestion Process

The Digestion Process Food is broken down into smaller particles Animals have digestive systems adapted to the foods that they consume Four types of digestive systems Ruminant (polygastric) Simple (single) 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 Oesophagus 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 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 Consists of the Caecum, Colon and Rectum Caecum: 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 animals 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 Oesophagus connects mouth to stomach

Monogastric Digestive System Stomach secretes Hydrochloric acid (HCL) 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 old adage “scarce as a hen’s teeth!!” Saliva secretion moistens food Oesophagus has a modification called the “crop” which stores and moistens food connects mouth and stomach

Avian Digestive Systems Stomach Consists of two parts Proventriculus: same as monogastric stomach and provides digestive secretions 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 “Cloaca”: chamber into which urinary and genital canals open “Caeca”: aid 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 oesophagus 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 caecum (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 which breaks down fatty acids stores iron, handles fats and carbohydrates in the blood

The End!!

1. Horse 2. Chicken 3. Cow 4. Rabbit 5. Pig 6. Ostrich