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| a nerve fiber bundle that emerges from of the spinal cord and joins with another bundle to form each spinal nerve in the series of spinal nerves |
| one of the two organs in the back of the abdominal cavity that excrete urine, regulate fluid and electrolytes, and act as endocrine glands |
| circulatory system | |
| —n | |
| anatomy, zoology the system concerned with the transport of blood and lymph, consisting of the heart, blood vessels, lymph vessels, etc | |
circulatory system n.
The system of structures, consisting of the heart, blood vessels, and lymphatics, by which blood and lymph are circulated throughout the body. Also called vascular system.
circulatory system (sûr'kyə-lə-tôr'ē) Pronunciation Key
(click for larger image in new window) The system that circulates blood through the body, consisting of the heart and blood vessels. In all vertebrates and certain invertebrates, the circulatory system is completely contained within a network of vessels (known as a closed circulatory system). In arthropods and many other invertebrates, a substance analogous to blood (known as hemolymph) is pumped through vessels that open into the intercellular spaces (in what is known as an open circulatory system). In vertebrates, the lymphatic system is also considered part of the circulatory system. |
The system in the body by which blood and lymph are circulated. The parts of the circulatory system include the heart, along with all the arteries, veins, and capillaries. The organs of the lymphatic system are also considered to be part of the circulatory system. Nutrients, oxygen, and other vital substances are carried throughout the body by the blood, which is pumped by rhythmic contractions of the heart. Blood is pumped from the heart to the arteries, which branch into smaller and smaller vessels as they move away from the heart. The blood passes oxygen and nutrients to the cells and picks up waste in the capillaries, then returns to the heart via a system of veins.