Figure 20.20b
• Why do we need a circulatory system?– supplies in
• fuel (sugars)– digestive system
• oxygen– respiratory system
– waste out• CO2
– respiratory system
– need to pick up & deliver the supplies & wastes around the body
• circulatory system
Feeding Energy Needs
Simple organisms
When your body is only 2-cell layers thick, you can get supplies in and waste out just through diffusion
– all cells within easy reach of fluid
HydraJellyfish
Complex organisms• Circulatory system
– made up of 3 parts• organ
– heart
• tissues & cells– blood vessels
» arteries» veins» capillaries
– blood» red blood cells» plasma
Vertebrate Heart• 4-Chambered heart
– atria (atrium)• thin wall• collection chamber• receive blood
– ventricles • thick wall pump• pump blood out right
atrium
leftatrium
rightventricle
leftventricle
Evolution of circulatory system
fish amphibian reptiles birds & mammals
A A
VV V VV
A AAAA
V
2 chamber 3 chamber 3 chamber 4 chamber
Not everyone has a 4-chambered heart
AV
SL
AV
Lub-dub, lub-dub• 4 valves in the heart
– flaps of connective tissue– prevent backflow
• Heart sounds – closing of valves– “Lub”
• force blood against closed AV valves
– “Dub”• force of blood against
semilunar valves
• Heart murmur– leaking valve causes hissing sound – blood squirts backward through valve
Major arteries
pulmonaryartery
pulmonaryartery =to lungs
aorta carotid = to headto brain & left arm to right arm
coronary arteries
to body
Electrical signals
allows atria to empty completely before ventricles contract
stimulates ventricles to contract from bottom to top, driving
blood into arteries
• heart pumping controlled by electrical impulses • signal also transmitted to skin = EKG
Structure-function relationship• Capillaries
– very thin walls – allows diffusion of
materials across capillary
• O2, CO2, H2O, food, waste
body cell
O2
food
waste
CO2
Cardiovascular healthbypass surgery
• Risk Factors– genetics– diet
• high animal fat
– exercise & lifestyle• smoking• lack of exercise
Figure 21.14
Figure 21.14 Homeostatic Adjustments that Compensate for
a Reduction in Blood Pressure and Blood Flow
Figure 21.14
Figure 21.14 Homeostatic Adjustments that Compensate for
a Reduction in Blood Pressure and Blood Flow