Vertebrate Digestion

Vertebrates have relatively generalized digestive systems. Digestion is a multi-stage process in the digestive system. The digestion process begins from ingestion of food and ends upto egestion of wastes. All the processes in digestion involve muscle movements. Energy is required for each process to occur and the required energy is provided by the absorbed food material.

Digestion involves four main steps. They include:

  • Ingestion –

    It is the physical act of eating. It involves both mechanical and chemical processes.

  • Chemical and mechanical breakdown –

    It is the breakdown of complex food components into simpler components. Various components like acids, bile juice, acids and water present in the stomach and intestine help in mixing and masticating the food.

  • Absorption –

    The nutrients from the food particles are taken into the bloodstream and delivered to all parts of the body. Active transport, diffusion and osmosis are the processes that occur for nutrient absorption.

  • Egestion –

    The unused and waste food substances are eliminated from digestive tract.

The main and important part of digestion occurs in small intestine. In this region, the food is digested completely and the nutrients are maximum absorbed into the bloodstream. The large intestine collects the waste part of the food and reabsorbs the water. Re-absorption of water makes the waste material solid.

Among the vertebrates, in mammals the digestion process starts with cephalic stage. This is a stage where saliva is generated in the mouth and digestive juices are generated in the stomach. The two forms of digestion, mechanical and chemical digestion starts in the mouth where the food is mixed with saliva and masticated. Then the stomach continues these two forms of digestion where stomach acids and enzymes are generated. Mixing and churning of the food takes place. The process of absorption takes place in stomach and intestine. The process of digestion ends with elimination.

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