up:: [[List of Systems of the Human Body]] tags:: #on/physiology #on/anatomy # Circulatory System > The human body has over 100,000 km of blood vessels. The circulatory system, encompassing the heart, blood vessels, and blood, serves as a vital organ network in humans and vertebrates, facilitating the *circulation of oxygen, nutrients, and waste materials throughout the body*. Comprising both the cardiovascular and [[Immune System|Lymphatic System]], it ensures the body's homeostasis and immune defense mechanisms. The cardiovascular system is divided into systemic and pulmonary circuits, with arteries carrying oxygenated blood away from the heart, while veins return deoxygenated blood back to the heart. Blood, consisting of plasma, red and white blood cells, and platelets, acts as the carrier medium for these essential substances. Additionally, the lymphatic system complements the circulatory system by draining excess fluid from tissues and supporting immune functions. The heart, a muscular organ with four chambers, pumps *oxygenated blood to the body via the systemic circulation and deoxygenated blood to the lungs via the pulmonary circulation*. The arterial system branches out from the heart into smaller arterioles, eventually leading to *capillaries where nutrient exchange occurs*, and then merges into veins for return to the heart. Specialized circulatory routes include coronary circulation for the heart itself, cerebral circulation for the brain, and renal circulation for the kidneys. Developmentally, the circulatory system originates during embryogenesis through vasculogenesis, with the arterial and venous systems developing separately. Fetal circulation initially bypasses the lungs, obtaining oxygen and nutrients from the placenta. **Key points:** - The circulatory system includes the cardiovascular and lymphatic systems, facilitating the transport of essential substances and immune functions. - The cardiovascular system comprises systemic and pulmonary circuits, with the heart pumping blood through arteries, capillaries, and veins. - Specialized circulatory routes include coronary, cerebral, and renal circulations. ### Pathologies Clinical significance of the circulatory system encompasses various diseases, including cardiovascular diseases like [[Atherosclerosis]] and [[Thrombosis]], as well as congenital anomalies. Cardiologists, cardiothoracic surgeons, and vascular surgeons specialize in treating these conditions through medical management and surgical interventions. ### Function The circulatory system plays a vital role in transporting oxygen, nutrients, and waste products throughout the body. In humans and other vertebrates, including annelids and cephalopods, the *circulatory system is closed, meaning that blood circulates within vessels and is pumped by the heart*. In contrast, some invertebrates like arthropods have an open circulatory system, where a fluid called hemolymph bathes the organs directly. Additionally, some animals like flatworms lack a circulatory system altogether, relying on direct diffusion for nutrient exchange. In the open circulatory system of arthropods, hemolymph fills the body cavity and surrounds cells, delivering nutrients and oxygen. Muscular movements aid in hemolymph circulation, but flow diversion is limited. This system contrasts with the closed circulatory systems found in vertebrates, which maintain blood within vessels. Vertebrates exhibit various levels of circulatory system complexity, from fish with single pump hearts to mammals with double circulatory systems featuring four chambers. Modern advancements, including Nobel Prize-winning research on heart catheterization in the 20th century, have furthered our understanding of the circulatory system. Computer-based imaging systems developed in the 1970s have enabled non-invasive visualization of the circulatory system. These advancements continue to enhance our knowledge of cardiovascular health and disease. **Key Points:** - Circulatory systems vary among animals, with vertebrates featuring closed systems and some invertebrates possessing open or no circulatory system. - Arthropods have an open circulatory system where hemolymph bathes organs directly, while vertebrates have closed circulatory systems with blood confined to vessels. - Modern advancements, including Nobel Prize-winning research, have improved our understanding of cardiovascular physiology and pathology. > Circulatory system. (2023, December 3). In _Wikipedia_. https://en.wikipedia.org/wiki/Circulatory_system