What is the main function of the animal circulatory system?

The main function of the animal circulatory system is to transport nutrients, oxygen, and waste products throughout the body. This system is essential for maintaining cellular homeostasis and ensuring that tissues receive adequate oxygen and nutrients while removing metabolic waste products, such as carbon dioxide and urea, from cellular metabolism.

Throughout the body, blood flows through a network of vessels, including arteries, veins, and capillaries, facilitating the exchange of substances between the blood and tissues. For example, oxygen is taken up by the blood in the lungs and then transported to tissues where it is released for cellular respiration. Similarly, nutrients absorbed from the digestive system enter the bloodstream and are distributed to cells for energy production and growth.

While protecting against infections, facilitating digestion, and regulating body temperature are important functions in their own right, they are not the primary role of the circulatory system. Immune responses involve white blood cells and antibodies that are transported by the circulatory system but are not its main function. Digestion is primarily a process that occurs in the gastrointestinal tract, and temperature regulation is influenced by various systems, including the integumentary system and mechanisms such as vasodilation and vasoconstriction to adjust blood flow. Thus, while these functions are interrelated with