Chapter 42: Circulatory System
Porifera: all parts of the body are close to the environment
Cnideria: Gastro vascular cavity sort of acts as a circulatory system.
In a Medusa water is sucked into the gastro vascular cavity and flowed into
canals. The cells that line the canals have cilia, which push the water in
Rotifera, Byozoa, Nematoda: fluid flows through the body cavity.
Hemolymph is the name for the interstitial fluid that is being pumped through the system.
This happens mostly in open circulatory system
When the fluid is specialized and stays inside the pumping system (blood) it is called a
closed circulatory system. (Chordata, Annelida, Phoronida)
Circulatory system plumbing:
Heart: pumps blood
Blood vessels: carry blood
• Atrium: receives blood
• Ventricle: pumps blood out of the heart
• Artery: carries blood away from the heart
• Arteriole: smaller arteries that deliver blood into capillaries
• Vein: carries blood towards the heart
• Venules: carries blood from capillaries to veins.
• Portal: carries blood from capillaries to capillaries
• Capillary: Allows gas exchange
Divisions of Chordates (crades):
Craniate, Vertebrates, Gnathostomes, Osteichthyans, Lobefin, Tetrapod, Amniotes,
Chordata circulatory system:
Pump deoxygenated blood to the gills where the gills fill it with oxygen and then pumps
it throughout the body and back to the heart.
Blood flow: Right ventricle: pumps deoxygenated blood into the pulmonary artery
Pulmonary artery: Pumps deoxygenated blood away from the heart to the lungs.
Lungs: Fill blood with
oxygen and then sends it
through into the left
Left ventricle: pumps
oxygenated blood through
the aorta through the rest
of the body
Posterior and superior
vena cava: pump the
deoxygenated blood back
into the right atrium and
then into the right
prevents the blood from
flowing back into the
ventricle from the major
prevent the blood from
flowing from the ventricle to the atria
SA node (Pacemaker): initiates the contraction by sending a wave of signals through the
heart. (Across the atria)
AV node: Takes its time to send the next impulse into the ventricles for them to contract.
When blood is flowing through the capillaries, the interstitial fluid wants to send water in
because its solute concentration is lower than blood. Becau