What are the three main components of the circulatory system?

The circulatory system is primarily composed of the heart, arteries, and veins, which play essential roles in transporting blood throughout the body. The heart acts as the muscular pump that propels blood, ensuring that oxygen and nutrients are delivered to cells while waste products are removed.

Arteries are the vessels that carry oxygen-rich blood away from the heart to various tissues and organs, where it can deliver essential resources. Conversely, veins are responsible for returning oxygen-poor blood back to the heart after the oxygen has been utilized by the body’s cells. This system is crucial for maintaining homeostasis and supporting cellular function.

The other options refer to components that do not constitute the circulatory system. For instance, while the lungs are related to the respiratory system and have a critical function in gas exchange, they are not a direct part of the circulatory system itself. Similarly, the stomach, liver, and kidneys are involved in digestion and metabolism but do not function as direct components of blood circulation. Nerves and muscles, while important for movement and signaling in the body, do not form part of the circulatory system's structure.