Download Heart Structure and function

Features of a good transport
system
• A fluid to carry nutrients and gases
• A pump to create pressure that will push
fluid around the body
• Exchange surfaces
• Tubes or vessels – to carry fluid
(a)
Single circulation
(b)
Double circulation:
Pulmonary cirulation – carries
blood to the lungs to pick up
oxygen
Systemic circulation – carries
the oxygen and nutrients
around the body to tissues.
© Pearson Education Ltd 2008
This document may have been altered from the original
Advantages of a Double Circulation
• Heart increases the pressure on blood
after it has passed through the lungs so
blood flows more quickly to the body
tissues.
• Systemic circulation can be at a higher
pressure than the pulmonary circulation
• Blood pressure in pulmonary system
cannot be too high as it could damage
lungs.
AORTA
VENA CAVA
RIGHT
ATRIUM
PULMONARY
ARTERY
PULMONARY
VEIN
SEMI LUNAR
VALVE
LEFT
ATRIUM
LEFT
VENTRICLE
ATRIOVENTRICULAR
VALVES
RIGHT
VENTRICLE
Valves in the heart prevent
the backflow of blood
The internal structure of the heart
© Pearson Education Ltd 2008
This document may have been altered from the original
Structure of the Heart
Why is a mammalian heart is
divided into a right and left side?
• Keeps oxygenated and deoxygenated
blood separate
• Allows as much oxygen as possible to be
carried to the tissues
• Allows different pressures to exist – left
more pressure required to force blood to
body
whereas right side requires less as forcing
blood a shorter distance to lungs
Main adaptations of the heart
• Composed of cardiac muscle
A specialised tissue that can contract automatically,
powerfully and without fatigue.
All cells in cardiac muscle are connected by specialised
junctions called intercalated discs.
This allows the rapid spread of impulses through the muscle
ensuring that all cells contract at the same time
Main adaptations of the heart
• Thickness of the walls
The thickness of the walls in the different heart
chambers reflects their function.
Atria: thin muscle as only pumps blood a short distance
Right Ventricle: thicker muscle than atria – forcing blood a
further distance to lungs.
Left Ventricle: thickest walls – has to force blood all the
way round body
Main adaptations of the heart
• Valves
Ensure unidirectional flow through the heart
and prevent backflow.
The AV valves
Location: between atria and ventricle
Function: to prevent blood flowing back into atria when
ventricles contract
The Semilunar valves
Location: found at the openings of the aorta and
pulmonary artery
Function: prevent backflow of blood into ventricles during
diastole
Valve structures
The cardiac cycle
© Pearson Education Ltd 2008
This document may have been altered from the original
Atrial Systole
AV valves open
semi-lunar valves
closed
Filling of
ventricles
atrial systole
Ventricular Diastole
Ventricle
muscles
contract
Pressure
increases
Ventricular Systole
Semi-lunar valves
close
Ventricles relax
Pressure in the
ventricles falls
AV valves open
AV valves close
Semi-lunar
valves open
Blood enters
arteries
Action of the atrioventricular valves
© Pearson Education Ltd 2008
This document may have been altered from the original
Describe the sequence of events involved
in one heart beat
1. atrial systole / atria contract ;
2. blood passes into ventricles ;
3. atrioventricular / AV valves open ;
4. ventricular systole / ventricles contract ;
5. blood to, the arteries /Aorta and Pulmonary Artery;
6. via open, semilunar valves ;
7. Atrioventricular (AV) valves shut to stop backflow ;
8. relaxation / diastole, of ventricles (and atria) ;
9. semilunar, valves shut to stop backflow ;
Pressures changes in the aorta, left ventricle and left atrium during one
heartbeat
© Pearson Education Ltd 2008
This document may have been altered from the original
Week 8
• Describe how heart action is coordinated with reference to the sinoatrial
node, the atrioventricular node and the Purkyne tissue.
• Interpret and explain electrocardiogram (ECG) traces with reference to
normal and abnormal heart activity.
© Pearson Education Ltd 2008
This document may have been altered from the original
The pathway followed by the wave of excitation
© Pearson Education Ltd 2008
This document may have been altered from the original
Week 8
A normal ECG trace compared with others indicating an unhealthy heart
© Pearson Education Ltd 2008
This document may have been altered from the original