Introduction to the Excretory System

Describe the components of the excretory system

The daily intake recommendation for human water consumption is eight to ten glasses of water. In order to achieve a healthy balance, the human body should excrete the eight to ten glasses of water every day. This occurs via the processes of urination, defecation, sweating and, to a small extent, respiration. The organs and tissues of the human body are soaked in fluids that are maintained at constant temperature, pH, and solute concentration, all crucial elements of homeostasis. The solutes in body fluids are mainly mineral salts and sugars, and osmotic regulation is the process by which the mineral salts and water are kept in balance. Osmotic homeostasis is maintained despite the influence of external factors like temperature, diet, and weather conditions.

Photo shows two garbage trucks dumping their contents into a landfill.

Figure 1. Just as humans recycle what we can and dump the remains into landfills, our bodies use and recycle what they can and excrete the remaining waste products. Our bodies’ complex systems have developed ways to treat waste and maintain a balanced internal environment. (credit: modification of work by Redwin Law)

What You’ll Learn to Do

  • Explain why osmoregulation and osmotic balance are important body functions
  • Describe the structure of the kidneys and the functions of the parts of the kidney
  • Explain how different excretion systems function in non-vertebrates
  • Explain how hormonal cues help the kidneys synchronize the osmotic needs of the body

Learning Activities

The learning activities for this section include the following:

  • Osmoregulation and Osmotic Balance
  • The Kidneys and Osmoregulatory Organs
  • Video: The Excretory System
  • Excretion Systems
  • Hormonal Control of Osmoregulatory Functions
  • Self Check: The Excretory System