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 re-swallowing 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!!