Transcript Ch428thed
CIRCULATION AND GAS
EXCHANGE
Chapter 42
GAS EXCHANGE
The exchange of Oxygen and Carbon dioxide
What characteristic do all respiratory surfaces
have in common?
They must be moist
Respiratory surfaces in different animals are
adapted for maximal gas exchange capacity
GILLS
Ventilation – increasing flow over the respiratory
surface
What is the advantage of countercurrent
exchange?
How can insects meet their high metabolic
demands for oxygen with an open circulatory
system?
LUNGS
Connects to circulatory system
Located in thoracic cavity, near the heart
Describe the pathway of oxygen to the lungs.
What is the passage of oxygen as it enters your nasal
passageway and is used by tissues in your big toe?
How do mammals ventilate their lungs?
What is so special about the avian respiratory
system?
Control of
Breathing
INTERNAL TRANSPORT
Gastrovascular
cavity makes circulatory
system unnecessary
Open and closed circulatory systems
What are the limits an open circulatory
system places on an organism?
What is the difference between an artery
and a vein?
Arteries carry blood away from the heart
Veins bring blood back to the heart
Why do veins have valves and arteries do not?
Veins move blood against gravity without benefit of
the heart contraction
Blood flow:
Heart arteries arterioles capillaries venules
veins heart
Which chamber of the heart receives the blood?
Which chamber pumps the blood?
VERTEBRATE CIRCULATORY EVOLUTION
Fish have 2 chambered heart, one beat circuit:
1 atrium
1 ventricle
Amphibians have 3 chambered heart:
2 atria
1 ventricle
Reptiles have 3 – 4 chambered heart:
Septum keeps 2 parts of ventricles separate
Mammals and birds have 4 chambered heart!
THE HEART
Cardiac muscle
Atria have thin walls
Ventricles have thick and powerful walls
Systole = ventricular contraction blood is pumped
Diastole = ventricular filling
Lub dub = heart sounds opening and closing of
the valves
Lub = contraction of ventricles (AV closing)
Dub = blood recoiling against Semi Lunar valves
Heart murmur = valve defect
CO = cardiac output ;
Volume of blood pumped/ minute
SV = stroke volume:
Amount of blood pumped by L ventricle/contraction
CO is effected by heart rate and SV
Myogenic heart can regulate its own rhythm
SA node is the pacemaker of the heart
ARTERIES AND VEINS
How do differences between arteries and veins
reflect their different functions?
Artery wall is very thick to absorb pulsation from
heart
Veins are wider in diameter and are not as
muscular
Veins have valves
Capillaries have only single layer of endothelium
BLOOD PRESSURE
The force that blood exerts against vessel walls
BP is greater in arteries than veins
Pulse is measure of BP
Exact BP is measured as systolic/diastolic
pressures
Constricted blood vessels have higher BP than
dilated vessels
In veins heart has little effect on BP
How, then does blood move in veins?
Blood
Flow
Velocity
Blood Flow
Through
Capillary
Beds
Capillary Movement of Fluids
LYMPHATIC SYSTEM
Lymphatic system returns lost blood to
circulatory system
Lymph nodes filter the lymph
Help fight infection
How can 1
heartbeat
circulate
blood through
2 capillary
beds?
What are the advantages and disadvantages of
the amphibian circulatory system?
Why do endotherms have the greatest need for a 4
chambered heart?
Birds and mammals show convergent evolution of 4 chambered heart!