Moodle Book 4: Important Terms

Absorption

Process where nutrients pass from the GI tract into the blood (water soluble nutrients) or lymph (fat soluble nutrients)

Chemical Digestion

Process where enzymes or catalysts (at body temperature) speed up the breakdown of large food molecules into smaller ones

Digestion

Chemical and physical (mechanical) breakdown of the feed for absorption

Mechanical Digestion

Chewing and muscular contractions (e.g., stomach churning)

Pretension

The act of bringing food into the mouth

Mastication

The act of chewing

Deglutition

The act or process of swallowing the bolus

Pharynx

the throat, or a cone-shaped passageway leading from the head to the esophagus and larynx; the pharynx chamber serves both respiratory and digestive functions

Esophagus

a muscular tube used for the passage of food from the pharynx to the stomach; peristalsis transports bolus to the stomach, but reverse peristalsis is undesirable in monogastric animals because it results in vomiting

• The esophagus transports feed from the mouth to the rumen. The swallowed feed is called a "bolus". In ruminants, digesta also comes up from the rumen to the mouth. However, this is a natural process and is not considered vomiting. The regurgitation of feed is called rumination.

Stomach

an enlarged, sac-like portion of the alimentary canal and one of the principal organs of digestion

• In monogastric animals, the stomach is located between the esophagus and the small intestine.

• In most ruminants, the stomach is composed of three - four chambers: rumen, reticulum, omasum and abomasum. However, in monogastrics, the stomach is a single chamber and is not the major site of digestion.

• Stomach contents are constantly mixed and churned, since the stomach is a muscular organ.

Rumen

the first large compartment of the stomach in ruminants; cellulose is broken down by the action of symbiotic microorganisms

• The ruminal environment is warm, moist, and is constantly receiving nutrients through feed. This is an ideal environment for anaerobic microbes! The ruminant does not secrete anything into the rumen.

• There are three types of microbes that live in the rumen: bacteria, protozoa, and fungi. These microbes (especially the bacteria) are responsible for the digestion of dietary fiber. No animal enzymes can digest fiber! The microbial waste products are the main source of energy for ruminants.