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!