The digestive tract tends to be more complex in omnivores, which feed on both plants and animals, and most complex in herbivores, which feed principally on the fibrous portions of plants. Carnivores, which feed exclusively on other animals, and species that feed on plant concentrates (seeds, fruit, nectar, and pollen) tend to have the shortest and simplest digestive tract. In other aspects, the digestive systems of vertebrates show numerous structural and functional adaptations to their diet, habitat, and other physiological characteristics ( Fig. Some characteristics of the vertebrate digestive system are common to all classes of vertebrates and appear to have been conserved in their evolution. Enzymes produced by the host animal and microbes indigenous to the digestive tract destroy harmful agents and convert food into a limited number of nutrients, which are selectively absorbed. Food is ingested, reduced to particles, mixed with digestive fluids and enzymes, and propelled through the digestive tract. The vertebrate digestive system consists of the digestive tract (alimentary canal) and ancillary organs that serve for the acquisition of food and the assimilation of nutrients required for energy, growth, maintenance, and reproduction. Proper digestion could not take place without substantial numbers of indigenous bacteria, which are found throughout the digestive tract.Ī set of structures and organs in which food substances are digested. The major physiological activities of the digestive system are motility, secretion, digestion, and absorption. The nervous and endocrine systems control the activities of the digestive system. The gastrointestinal (digestive) tract of most vertebrates includes the headgut (mouthparts and pharynx), foregut (esophagus and stomach), midgut (small intestine), pancreas, biliary system (liver and gallblader), and hindgut (large intestine, cecum, colon, and rectum or cloaca). The digestive system is the organ system in which food substances are broken down in the body.
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