Circulation and gas exchange:
Basic function - to provide the body with oxygen, nutrients, remove wastes and CO
(lungs/gills generally don’t do much with nutrients and wastes, but, as usual, there are
Reason for having a circulatory system:
all cells in the body need access to oxygen, etc.
Methods of granting access to oxygen/nutrients
[Fig., similar to 23.1, p. 468]
- open circulatory system - some blood vessels may be present, but no capillaries.
In other words, heart beats, fluid moves into some large vessels, and from there
into the body.
All parts of the body are therefore “bathed” in this fluid [e.g.,
insects, many arthropods].
- closed circulatory system - blood is always confined to blood vessels.
blood vessels are present throughout the tissues and thus insure that blood can get
to all parts of the body [e.g., cephalopods, earthworms, vertebrates].
Vertebrate cardiovascular systems:
- heart is composed of at least two parts:
an atrium and a ventricle.
vertebrates may add to this (e.g., two atria).
- atrium receives blood from the body, then moves blood to ventricle, ventricle
pumps blood out of heart.
- arteries -> arterioles -> capillaries (&capillary beds) -> venules -> veins
(NOTE that this says nothing about what parts of the body the blood is going to,
just the names of the blood vessels)
The flow of blood in mammals
[Fig. 23.2, p. 469]
- compared to other animals, all parts of the body get newly oxygenated
blood under high pressure.
right ventricle -> lungs -> left atrium -> left ventricle -> body ->
right atrium -> right ventricle.