3. Lung
All other parts
of the body
The mammalianThe mammalian
circulation plancirculation plan
Double circulation in mammals
Heart Blood
Blood
vessels
Circulatory
system
pulmonary
circulation
systemic
circulation
As blood
passes
through
heart twice,
this also
known as
double
circulation
4. The human circulatory systemThe human circulatory system
The pulmonary circulationThe pulmonary circulation
2 The blood is
pumped
through
pulmonary
artery into lungs
for gas
exchange
3 The blood
becomes
oxygenated
4 The blood
flows through
pulmonary
veins to left
atrium
1 Deoxygenated
blood in right
ventricle
5. The human circulatory systemThe human circulatory system
The systemic circulationThe systemic circulation
1 Oxygenated
blood in left
ventricle
2 The blood is
pumped
through aorta
to all parts of
the body
except lungs
3 O2 and
nutrients
diffuse into
cells while CO2
and wastes
diffuse out
4 The blood
flows through
inferior/
superior vena
cava to right
atrium
8. External Structure of heartExternal Structure of heart
Heart consists of 4 chambers
2 atria (right atrium and left
atrium)
– smaller
– on the
upper part
2 ventricles
– larger
– below atria
(plural)
left
atrium
right
atrium
right
ventricle
left
ventricle
9. Internal Structure of heartInternal Structure of heart
Heart consists of 4 chambers
2 atriums
– smaller
– on the
upper part
2 ventricles
– larger
– below
atriums
left
atrium
right
atrium
right
ventricle
left
ventricle
10. Atriums and ventricles are separated by valves to
prevent backflow of blood
bicuspid
valve
Septum
prevents mixing
of blood in both
sides of the heart
chordae tendineae
holds valves in position
and avoids them to turn
inside-out
tricuspid
valve
semi-lunar
valves
11. Blood flow and blood vessels
aorta
pulmonary artery
superior
vena cava
inferior
vena cava
pulmonary
veins
from body
from
body
to lung
from lung
deoxygenated
blood
oxygenated
blood
to body
19. Label the external parts of the
heart:
1. superior vena cava
2. aorta
3. pulmonary arteries
4. left atrium
5. right atrium
6. right ventricle
7. left ventricle
8. right coronary vein
9. right coronary artery
10. apex
20. Label the internal parts of the
heart:
1. superior vena cava
2. right atrium
3. tricuspid valve
4. right ventricle
5. papillary muscle
6. aorta
7. pulmonary artery
8. left atrium
9. bicuspid valve
10. median septum
22. Mode of action
right atrium left atrium
right ventricle
contract simultaneously
left ventricle
pulmonary arch
contract simultaneously
aortic arch
Backflow
prevented
by
tricuspid
valve
Backflow
prevented
by bicuspid
valve
(atria contracts) (atria relaxes)
23. Mode of action
• closing of tricuspid & bicuspid ‘ valves
produce loud ‘lub’ sound (ventricular
contraction/systole)
• closure of semilunar valves produce ’dub’
sound (ventricular relaxation/diastole)
• one systole + one diastole = one
heartbeat
• atria and ventricle work alternately
25. Blood pressure
• Force of blood exerted on blood vessel walls
• Highest during ventricular systole, when blood is forced
into arteries
• Decreases during ventricular diastole
• Varies in different parts of the body (arteries near heart
→ high; veins (far from heart → low)
• Varies with individuals
Normal person:
systolic pressure = 120-140mm of mercury
diastolic pressure = 75-90mm of mercury
• Blood pressure is given as the systolic pressure being
the first number than diastolic pressure being the second
number e.g. 120/80 (120 over 80)
• High blood pressure when blood pressure is 140/90 or
higher
26. High blood pressure
• High blood pressure when blood pressure
is 140/90 or higher
• May occur temporarily after heavy
exercise or when a person is angry
• Persistent high blood pressure (in middle-
aged or elderly people) is a dangerous
medical condition
• Can be easily controlled if they see a
doctor in time and follow the medical
advice given
27. ***Pressure changes in the heart
(Refer to pg 161 Biology Textbook)
Recall
• one systole + one diastole = one heartbeat
• atria and ventricle work alternately (ventricular systole + atrial
diastole occur simultaneously and atrial systole + ventricular
diastole occur simultaneously)
28. Increase in pressure
due to blood flowing
into the ventricle when
the atrium contracts
Increase in pressure
due to blood flowing
into the aorta when
the ventricle contracts
Pressure in the aorta
follows that of the
pressure in the
ventricle (pressure is
slightly lower)
Pressure in the aorta
rises due to backflow
of blood in the aorta
29. ‘O’ Level Bio P1 Nov 2008
( D )
For bicuspid valve to open, pressure in the left
atrium must be high and vice versa
30. ‘O’ Level Bio P1 Nov 2006
( B )
Atrio-ventricular valve = bicuspid or tricupid
valves
Semi-lunar valve = valve in aorta
Between W and X, ventricular pressure is
increasing hence atrio ventricular valves
would be closed and semi lunar valve
would open as blood is pushed through the
aorta
31. ‘O’ Level Bio P1 Nov 2006
( C )
0.6 s = one heartbeat
60/0.6 = 100 heartbeats per min
33. Pulse (produced after every ventricular contraction)
ventricular contraction
aortic arch
blood is pumped into
arteries
blood is pumped into
arteries dilate
increased pressure causes
walls of arteries recoil
Blood forced along in series of waves
[Imagine a fireman’s hose]
35. Demonstrating the presence of
valves
Procedure:
• Bandage the upper arm (valves in veins appear as small
swellings) [see above]
• Place 2 fingers at point Y
• Using one finger push blood to point X
• Blood flowed back to from X to b and no further
38. Coronary Heart Disease
• Coronary arteries lie on the outside of the heart
and carry blood to the muscles in the walls of the
heart
• Blood supply to the heart can be greatly reduced
if the coronary arteries become blocked or
narrowed
Narrowing/ blocking
of coronary arteries
1) Angina
(chest pains)
2) Heart attack
41. 2) Heart Attack!!!
• Fatty substances (cholesterol and
polysaturated fats) may be deposited on the
inner surfaces of the coronary arteries
(atherosclerosis);
• This narrows the lumen of these arteries +
increases blood pressure;
• Such an affected artery develops rough inner
surfaces, which increases the risk of a blood
clot being trapped in the artery (thrombosis);
• If it occurs in the coronary arteries, the supply
of blood and oxygen to the heart muscles may
be completely cut off. The heart muscle cells
may be damaged and die, triggering a heart
attack.
43. Atheroma formation
A thrombus is an aggregate of a network of fibrin, platelets,
and blood elements trapped by the fibrin net
44. Factors that increase the risk of
atherosclerosis and coronary heart
disease
1. A diet rich in cholesterol and
saturated animal fats
2. Emotional stress
3. Smoking
45. Preventive measures against
coronary heart disease
• Proper diet
– rich in dietary fibres; substitute animal fats with
polyunsaturated plant fats
• Proper stress management
• Avoid smoking
- Nicotine increases blood pressure
- CO increases risk of fatty deposits on inner surfaces of
arteries
• Regular physical exercise
- strengthens the heart and maintains elasticity of arterial
walls
