This chapter, the first of the book, focuses on the human cardiovascular system, described as a rapid transport network through which blood carries red blood cells, white blood cells, platelets, oxygen, nutrients, carbon dioxide, waste products, hormones, heat, antibodies, and many other substances. The three key components of the cardiovascular system-the heart, blood, and blood vessels-are examined in detail. A dedicated section covers blood, its components, and its functions. Following this, the structure of the human heart is explored, along with an in-depth study of the cardiac cycle. The final section focuses on blood vessels, beginning with an overview of the circulatory routes. Each type of vessel is then examined in detail, starting with arteries, followed by veins, and concluding with capillaries in the microvasculature. Throughout, the chapter introduces the fundamental concepts of human cardiovascular anatomy and physiology while also considering the broader context of fluid physiology and mathematical modelling. The chapter concludes with a summary and recommendations for further reading.