Types of Circulation in Animals

Types of Circulation in Animals
Objective: Introduce the types of circulatory systems that we can find in organisms.
There are two main types of circulatory systems and there are some animals who can
live without circulatory systems. We'll talk about the ones without circulatory systems
first then we'll talk about what's called an open circulatory system, where we have open-
ended vessels that both the tissues
directly in the circulatory fluid . Then, we'll talk about close circulatory systems, which is
what we observe and ask.
Circulation
- The first thing we are going to discuss are the different types of circulatory systems
organisms utilize:
 None
 Open
 Closed




 Some animals have no circulatory system because their size and surface area allow
for the diffusion of gases and key solutes.
 These organisms also live in aqueous solutions.




 For example, natural animals rely on a circulatory system because very small or flat
animals can just rely strictly on diffusion to get in key nutrients that they are bad,
very small organisms.
 Like on the far left, we have a rotifer, in the middle, this is a tapeworm, and then on
the right is a jellyfish. Rotifers are very small, tapeworms are thin and flat, and with
the jellyfish, what we see is that they put their active tissues outside of their body,
allowing them to directly interact with the surrounding water.
 However, this would not work in larger animals.
 As a result, they have circulatory systems that contains a transport tissue that
comes in close contact with every cell of the body.




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, But we know that this doesn't work in large animals, because remember that you can
only be a few cell layers thick for diffusion to really be an effective means of getting
oxygen or nutrients to all of your body cells and so what we see is the evolution of
circulatory systems that contain some sort of transport tissue, so blood and hemolymph,
which we'll be talking about are technically considered connective tissues in the body,
and they are going to reach every single cell of the body, either by directly bathing those
cells in open circulatory systems or by vessels branching to the point of such a fine
point, that they come into contact with every cell like we see in closed circulatory
systems.
 Open circulatory systems, found in insects and many mollusks, have a fluid
connective tissue known as hemolymph that is pumped throughout the body but
does not stay confined to vessels.
 This hemolymph comes in direct contact with the tissues.

Circulatory systems
can be found in
insects and in
mollusks, such as
clams and their fluid
connective tissue, is
called pamelin. Now,
what's interesting
about hemolymph, is that it doesn't stay confined to vessels. If we look at the diagram,
we will see that there is a heart and we do not have vessels, but the vessels are open-
ended, and so what happens is that the fluid gets drawn in and the heart pumps it, and
the fluid goes out, and bath take the tissues directly with the hemoline. It's good to
mention here that for some of these organisms, such as mollusks, they do have gills
that the hemolymph will pass over to help pick up oxygen, and then we'll move into the
vessel to be pumped out again, and directly over the tissues.
 Muscular movement or simple hearts pump to help to circulate the hemolymph and
move it into vessels that empty into an open, fluid-filled space.

So what we see is that organisms
with simple hearts helping them
to pump and circulate the
hemolymph. Sometimes
muscular movement is also
adequate enough to help move
the hemolymph around. Once
again, you know these are open
spaces where cells in the
hemolymph, are bought that
helps in carrying nutrients and oxygen.




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