double circulation
What is circulation in animals?
circulation in vertebrates
The circulatory system in animals has a close relationship with other systems and does so through tubes called blood vessels. Between the vessels are veins that carry deoxygenated blood from the tissues to the heart.
For the slowest, smallest and simplest animals (poriferans, cnidarians and flatworms) their movement is enough to mix the internal fluids. Large animals need a circulatory system with a circulating fluid (transporter), conductive vessels (to carry the fluid) and a pumping system (to speed up the process)
double circulation
closed circulation
simple circulationn
open circulation
Double circulation systems occur in all vertebrates, except fish. Blood is pumped through a pulmonary circuit to the lungs, where it is oxygenated. The blood fluid then returns to the heart, which pumps oxygenated blood to the body through a systemic circuit.
Blood passes through the heart only once in each revolution of the body. It is typical of fish. They have a curved heart with a venous sinus that receives blood from the body, an atrium and a very muscular ventricle.
The heart drives the blood through the vessels but it reaches a space where it mixes with the organs and tissues, producing gas exchange.
circulatory is the closed one, in which the heart pumps blood through the vessels and never leaves those conduits.
circulation in invertebrates
Invertebrates can have two types of circulation: open, if the circulating fluid leaves the vessels that conduct it and spreads through the tissues; or closed, when the circulating liquid always moves contained in the vessels.
Blood is driven by the heart through arteries with elastic walls. These branch into others of smaller diameter, called arterioles, and these into very thin vessels with thin walls, the capillaries.