The circulatory system consists of three main parts:

• Heart : A muscular organ that pumps blood throughout the body. It has four chambers-two atria (upper chambers) and two ventricles (lower chambers). The heart pumps oxygenated blood to the body and deoxygenated blood to the lungs

• Blood vessels : These include arteries, veins, and capillaries.
  • Arteries carry oxygen-rich blood away from the heart to the body.
  • Veins carry deoxygenated blood back to the heart.
  • Capillaries are tiny vessels where the exchange of oxygen, nutrients, and waste occurs between blood and body cells

• Blood : The fluid that circulates through the heart and blood vessels, carrying oxygen, nutrients, and waste products. Blood is made up of plasma, red blood cells, white blood cells, and platelets

The circulatory system is divided into two main circuits:

• Pulmonary circulation : Moves deoxygenated blood from the right side of the heart to the lungs for oxygenation and returns oxygenated blood to the left side of the heart

• Systemic circulation : Delivers oxygenated blood from the left side of the heart to the rest of the body and returns deoxygenated blood back to the right side of the heart

Additionally, the lymphatic system is a related subsystem that helps return interstitial fluid to the bloodstream and supports immune function

. In summary, the key parts of the circulatory system are the heart, blood vessels (arteries, veins, capillaries), and blood, working together to transport oxygen, nutrients, and waste throughout the body via pulmonary and systemic circulation