Digestion 7.02

Digestive Terminology  Digestion- the process of breaking feed down into simple substances that can be absorbed by the body.  Digestive System- the parts of the body involved in chewing and digesting feed.  Absorption- the process of taking digested parts of feed into the bloodstream.

 Ruminants- animal that have a stomach that is divided into several parts.  Cattle, goats and sheep are examples of ruminant animals.  Ruminant animals can digest larger amounts of roughage material compared to nonruminants.  Ruminants do not chew their food completely. Some food is swallowed and then rechewed later through a process known as “chewing the cud.” This process is also called rumination.

 Nonruminant- animals that have a monogastric or single compartment stomach.  Horses, pigs, dogs, cats, and poultry are examples of monogastric animals.  Non-ruminants cannot eat and digest as much roughage as ruminants.

Ruminant Digestion

 Mouth  Function: Bites and chews food. Breaks food into smaller particles. Saliva present in mouth contains enzymes which speed up the digestive process.  Description: Beginning of digestive tract. Includes teeth and tongue.  Esophagus  Function: Guides food from mouth to stomach with involuntary muscular contractions.  Description: pinkish grey colored muscular tube next to trachea. Guides food from mouth to the stomach.

 Rumen  Function: Bacteria change large amounts of roughages into amino acids.  Description: Large white/grey colored sac on the left side of the animal. Largest section of the stomach. Interior lining resembles carpet. The rumen and reticulum make up 85% of stomach capacity.

 Reticulum  Function: Take in liquids that soak food for microbial digestion.  Description: White/grey colored sac connected to the rumen on the left side of the animal. Interior lining resembles a honeycomb pattern.  Omasum  Function: Contains papillae responsible for grinding roughage.  Description: Round, muscular part of stomach with many layers of tissue that squeezes feed and removes some liquid.

 Abomasum  Function: Enzymes and gastric juices act on feed. The abomasums is the only functional portion of the ruminant’s stomach when animals are born.  Description: Elongated sac at the base of the stomach. Interior lining is the smoothest of all stomach parts.  Small Intestine  Function: Partially digested feed is mixed with bile, pancreatic juice and intestinal juice. Most food nutrients are absorbed from the villi (small hairlike projections) in the small intestine.  Description: Long coiled tube.

 Cecum  Function: Serves little to no function for most animals. Horses and rabbits and guinea pigs have an enlarged cecum that uses microbial action to break down roughages.  Description: A blind pouch located between small and large intestine.

 Large Intestine  Function: Absorbs water and adds mucus to the undigested feed to form feces.  Description: Coiled tube shorter in length, but larger in diameter than the small intestine.  Anus  Function: Excrete waste.  Description: End of digestive tract.

Nonruminant Digestive System Parts and Functions

 Mouth  Function: Bites and chews food. Breaks food into smaller particles. Saliva present in mouth contains enzymes which speed up the digestive process.  Description: Beginning of digestive tract. Includes teeth and tongue.  Esophagus  Function: Guides food from mouth to stomach with involuntary muscular contractions.  Description: Pinkish grey colored muscular tube next to trachea. Guides food from mouth to the stomach. 

 Stomach  Function: Enzymes act on feed, churns, and mixes feed.  Description: A “U” shaped pinkish/white colored sac connected to the esophagus.  Small Intestine  Function: Partially digested feed is mixed with bile, pancreatic juice and intestinal juice. Most food nutrients are absorbed from the villi (small hairlike projections) in the small intestine.  Description: Long coiled tube.

 Cecum  Function: Serves little to no function for most animals. Horses, rabbits and guinea pigs have an enlarged cecum that uses microbial action to break down roughages.  Description: A blind pouch located between small and large intestine.

 Large Intestine  Function: Absorbs water and adds mucus to the undigested feed to form feces.  Description: Coiled tube shorter in length, but larger in diameter than the small intestine.  Anus  Function: Excrete waste.  Description: End of digestive tract.

Ruminant and Nonruminant Digestive System Accessory Organs

 Liver  Function: Produces bile that acts on fats.  Description: Dark brown structure made of several lobes. Largest gland in the body, located under the stomach.  Pancreas  Function: Produces digestive enzymes.  Description: Elongated reddish colored organ that lies against the stomach.  Gall Bladder  Function: Produces bile that aids in digestive process.  Description: Sac like structure filled with greenish fluid. Located on the liver.

Poultry Digestive System Parts and Functions

 Mouth  Function: Pecks and takes in feed. Poultry do not have teeth.  Description: Yellow pointed structure.  Esophagus  Function: Guides food from beak to crop.  Description: Muscular tube shaped structure.

 Crop  Function: Stores and softens feed from saliva secretions.  Description: Oval sac-like structure between esophagus and proventriculus.  Proventriculus  Function: True stomach of chicken, but serves no true function.  Description: A wider section of the digestive system compared to esophagus.

 Gizzard  Function: Feed is crushed and mixed with digestive juices. Contains grit and gravel to assist in crushing feed particles.  Description: Oval shaped muscular that is purplish in color. Located between the proventriculus and small intestine.  Liver  Function: Accessory organ that produces bile that acts on fats.  Description: Dark red colored organ made up of several lobes.

 Small Intestine  Function: Mixes juices, most food nutrient absorption occurs in small intestine.  Description: Long tube like structure.  Ceca  Function: Contain soft, undigested feed, but function is unknown.  Description: Unlike other animals, poultry have two ceca. Located between small and large intestine and are “blind” pouches, each are approximately 7 inches in length.

 Large Intestine  Function: Absorbs water and adds mucus to undigested feed, which becomes feces.  Description: Tube-like structure large in diameter when compared to small intestine. Filled with digested feed.  Cloaca  Function: Digestive and reproductive tracts combine and prepare for excretion of waste or eggs.  Description: Enlarged part of digestive tract located just before the vent.

 Vent  Function: Excrete solid (feces) and liquid (urine) waste.  Description: External opening and the end of the digestive tract.