Introduction to the Digestive System

Describe the components of the digestive system

Photo shows a variety of fresh vegetables being sold at a market.

Figure 1. For humans, fruits and vegetables are important in maintaining a balanced diet. (credit: modification of work by Julie Rybarczyk)

All living organisms need nutrients to survive. While plants can obtain the molecules required for cellular function through the process of photosynthesis, most animals obtain their nutrients by the consumption of other organisms. At the cellular level, the biological molecules necessary for animal function are amino acids, lipid molecules, nucleotides, and simple sugars. However, the food consumed consists of protein, fat, and complex carbohydrates. Animals must convert these macromolecules into the simple molecules required for maintaining cellular functions, such as assembling new molecules, cells, and tissues. The conversion of the food consumed to the nutrients required is a multi-step process involving digestion and absorption. During digestion, food particles are broken down to smaller components, and later, they are absorbed by the body.

One of the challenges in human nutrition is maintaining a balance between food intake, storage, and energy expenditure. Imbalances can have serious health consequences. For example, eating too much food while not expending much energy leads to obesity, which in turn will increase the risk of developing illnesses such as type-2 diabetes and cardiovascular disease. The recent rise in obesity and related diseases makes understanding the role of diet and nutrition in maintaining good health all the more important.

What You’ll Learn to Do

  • Compare and contrast different types of digestive systems
  • Explain how energy is produced through diet and digestion
  • Detail the steps involved in digestion and absorption
  • Discuss the role of neural regulation in digestive processes
  • Explain the processes of digestion and absorption

Learning Activities

The learning activities for this section include the following:

  • Digestive Systems
  • Nutrition and Energy Production
  • Digestive System Processes
  • The Digestive System
  • Digestive System Regulation
  • Self Check: The Digestive System