Veterinary Technology The Digestive System Veterinary Technology Chapter 7

Objectives •Describe the basic function of the primary components of the digestive system. • Compare the function and location of the digestive organs to those in the monogastric, modified monogastric and ruminant digestive systems. • Explain the difference between and identify diagrams of the different types of digestive systems of various animals.

What is Digestion? The process by which food is taken into the body and broken down into smaller molecules. Digestion must happen before absorption The remnants on non-nutritional portions are eliminated.

Digestive System Structures Teeth are used to gather, cut and grind the food. Page #92 Differences between: Carnivore Herbivore Omnivore Parts of the tooth: Crown vs. Root Enamel: hardest substance in body! Dentin: majority

Digestive System Structures “Baby” teeth = AKA: deciduous teeth Teeth are classified by function: Incisor: foremost – used to bite the food Canine: longest teeth – used for tearing food Premolars: used for crushing and grinding food Molar: used for crushing and grinding food Equine Teeth Floating/Aging System

Digestive System Structures In all types of digestive systems, digestion begins in the mouth. Saliva is produced by 4 salivary glands (page 94) The tongue (skeletal muscle) Esophagus = food pipe, 4 layers 1. Epithelial lining AKA mucosa 2. & 3. two layers of smooth muscle 4. Connective tissue covering AKA serosa Pharynx = posterior portion of throat Larynx = voice box Trachea = wind pipe Epiglottis = flap that protects larynx/trachea/esophagus

Digestive System Structures Peristalsis = process that moves food bolus through the esophagus. All of these are common to all types of digestive systems. The four main types are 1. Monogastric 2. Ruminant 3. Avian 4. Pesudo-Ruminant

Monogastric Digestion Humans, swine, dogs and cats all have a simple stomach, which is also known as a monogastric digestive system. Theses animals are designed to consume concentrates. The simple, one chambered stomach is divided into 3 regions.

Digestive Tract of the Monogastric Mammal

Parts and functions of the monogastric mammal digestive system •Mouth -gather and chew feed using tongue and teeth -salivary glands moisten feed to aid in swallowing -saliva begins the carbohydrate breakdown with salivary amylase • Esophagus -tube from mouth to stomach that is open at the mouth end -separated from stomach by the esophageal sphincter • Stomach -muscular gland lined sac that receives ingesta from the esophagus and conducts both physical and chemical digestion -primary secretions: pepsin - enzyme that digests protein; hydrochlorides - acids that aid in protein digestion

Parts and functions of the monogastric mammal digestive system continued… •Small Intestine -enzymatic digestion and absorption -Functions of the small intestine: digestion of proteins, carbohydrates, and fats; absorption of the end products of digestion 1. duodenum - most digestion occurs here 2. jejunum - some digestion and some absorption occur 3. ileum - mostly absorption -Bile - made in liver, stored in gall bladder, active in the small intestine, emulsifies fat to aid in digestion

Parts and functions of the monogastric mammal digestive system continued… Enzymes in the small intestine

Parts and functions of the monogastric mammal digestive system continued… •Cecum - essentially non functioning in many monogastrics. Rabbits and horses have an enlarged cecum that acts like a rumen and is involved with microbial digestion (fermentation) • Large Intestine -bacterial activity -water absorption -waste storage

Digestive Tract of the Avian Known as a modified monogastric system

Parts and functions of the avian digestive system •Mouth/Beak - gather and break down feed • Esophagus - tube from mouth to stomach that is open at the mouth end • Crop - feed storage and moistening • Proventriculus - glandular stomach (HCI and gastric juices); enzymatic • Gizzard - muscular stomach; mechanical breakdown

Parts and functions of the avian digestive system continued… •Small Intestine - enzymatic digestion and absorption -Functions of the small intestine: digestion of proteins, carbohydrates, and fats; absorption of the end products of digestion -Enzymes in the small intestine • Large Intestine -bacterial activity -water absorption -waste storage • Cloaca - common chamber for GI and urinary tracts • Vent - common exit for GI and urinary tracts

Ruminant Digestive System Sheep, cows, and goats are examples of animals with complex stomachs, which are also known as ruminant digestive systems

Parts and functions of the ruminant digestive system Ruminants are characterized by having a stomach with four compartments Rumination - the regurgitation, rechewing and reswallowing of ingested food Cud - mass of regurgitated ingesta; bolus Process of rumination 1. regurgitate bolus from rumen 2. rechew and reinsalivate 3. reswallow 4. repeat with another bolus Anus 7. Reticulum Rectum 8. Esophagus Cecum 9. Abomasum Colon 10. Omasum Duodenum 11. Small Intestine Rumen

Parts and functions of the ruminant digestive system continued… • Mouth -contains dental pad, teeth, tongue and saliva -saliva contains no salivary amylase • Esophagus -tube from mouth to stomach -tube from stomach to mouth

Parts and functions of the ruminant digestive system continued… • Rumen - large fermentation vat; also called the "paunch" -anaerobic -Temperature = 39oC (103oF) -saturated with gasses -constant motion Lining of the rumen

Parts and functions of the ruminant digestive system continued… • Functions of Microorganisms -digest roughages to make Volatile Fatty Acids -make protein -make vitamins K and B complex (Very similar to cecum of rabbit and horse) The function of the rumen is to house microorganisms.

Parts and functions of the ruminant digestive system continued… • Reticulum - "honeycomb" -houses microorganisms -catches hardware (ingested by animal) -houses the opening to the omasum • Omasum - "manyplies“ or “book” -full of folded tissue -water absorption • Abomasum - true stomach -pepsin -HCl

Parts and functions of the ruminant digestive system continued… Small Intestine -enzymatic digestion and absorption -Functions of the small intestine: digestion of proteins, carbohydrates, and fats; absorption of the end products of digestion duodenum jejunum ileum Cecum - some microbial fermentation Large Intestine -water absorption -waste storage

Review Pigs, Rabbits, Horses, Chickens, and Humans have a simple stomach or a monogastric digestive system Cows, Sheep and Goats have a complex stomach or a ruminant digestive system

What type of digestive system is this? Ruminant

What type of digestive system is this? Avian Monogastric System (modified monogastric)

What type of system is this? Monogastric

How does that compare to you?