Knowra Circulatory system Circulatory system An organ system that moves blood or another circulating fluid through the body, transporting substances between tissues and supporting functions such as gas exchange and waste removal.
Heart : A muscular organ that pumps blood through the circulatory system. Its rhythmic contractions generate the pressure that drives blood flow.
Blood : A fluid connective tissue composed of plasma, cells, and cell fragments. It is the circulating fluid that carries gases, nutrients, wastes, and signals.
Open circulatory system : A transport system in which circulating fluid leaves vessels and directly bathes organs. It contrasts with the enclosed vessel network found in humans and many other animals.
Gas exchange : The exchange of oxygen and carbon dioxide between an organism and its environment. Circulation connects lung gas exchange with oxygen use in distant tissues.
Evolution of the circulatory system : The evolutionary history of fluid-transport systems in animals. Comparative anatomy reveals how circulation diversified across animal lineages.
Blood vessel : A tube that carries blood through the body, including arteries, veins, and capillaries. Different vessel types distribute blood, return it, and exchange substances with tissues.
Plasma : The liquid component of blood, containing water, dissolved substances, and proteins. It carries cells and transports many dissolved materials through the body.
Closed circulatory system : A transport system in which blood remains within vessels as it circulates. This is the vessel-contained arrangement characteristic of vertebrate circulation.
Lymphatic system : A network that returns excess tissue fluid to the bloodstream and supports immune defense. It complements blood circulation by recovering fluid that leaves capillaries.
William Harvey : An English physician who demonstrated that blood circulates continuously through the body, published in 1628. His account established the heart's pumping role and circulation's closed loop.
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