In animals, transport of gases and nutrients is carried out by the circulatory system. Consists of several elements:
-Circulatory liquid. It transorts oxygen and nutrients to all the cells in the body. It also carries carbon dioxide and othher waste products. In annelids and vertebrates, this liquid is called blood. In molluscs and arthropods, this liquid is a colourless fluid called hemolymph. In echinoderms, it is called hydrolymph.
- Blood vessels. These tubes carry blood:
-Arteries carry blood away from the heart.
-Veins carry blood back to the heart.
-Capillaries are tiny blood vessels that exchange substances between cells and the circulatory system.
-Heart. Pump that circulates blood in the body.
Two types: open and closed.
Open circulatory system. Is typical of most arthropods and molluscs, but not cephalopods.
Closed circulatory system. Is typical of annelids, molluscs, cephalopods and vertebrates.
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