What is one of the main functions of the excretory system?

The excretory system plays a crucial role in maintaining homeostasis within the body primarily by filtering waste from the blood. This system, which includes organs such as the kidneys, ureters, bladder, and urethra, is responsible for removing metabolic waste products, toxins, and excess substances, such as salts and water, from the bloodstream. The kidneys filter the blood and create urine, which carries these waste products out of the body, thus preventing the accumulation of harmful substances.

By effectively filtering waste, the excretory system helps to regulate various physiological parameters, including blood pH, volume, and electrolyte levels, contributing to overall health. This function is vital, as the buildup of waste products can lead to serious health issues. In contrast, the other functions mentioned in the options relate to different systems: blood circulation is regulated by the cardiovascular system; oxygen transport is a function of the respiratory system and the blood; and hormone production for growth is primarily associated with the endocrine system. Therefore, the primary function of the excretory system is best described as filtering waste from the blood.