1. Circulation
VCE BIOLOGY – UNIT 1

2. The Heart
The biological pump

3. UNoxygenated
blood enters the
atrium on the right
side of the heart.
Unoxygenated
blood comes in from
the top of the body
through the
superior vena cava.
Unoxygenated
blood comes in from
the lower body
though the inferior
vena cava.

4. While the
unoxygenated
blood is in the
right atrium, the
tricuspid valve is
closed to keep
the blood from
flowing down to
the ventricle.

5. The
atrium
contracts
and the
tricuspid
valve
opens,
forcing the
blood
down into
the
ventricle.

6. The tricuspid
valve closes
again so that
blood cannot
move back up
into the atrium.

7. The ventricle
contracts. This
forces the
unoxygenated
blood through
the pulmonary
valve and into
the pulmonary
arteries.

8. The right pulmonary
artery takes the
unoxygenated blood to
the right lung.
The left pulmonary
artery takes the
unoxygenated blood to
the left lung.
THE PULMONARY
ARTERIES ARE THE
ONLY ARTERIES THAT
CARRY
UNOXYGENEATED
BLOOD.

9. In the lungs,
the carbon
dioxide in the
blood diffuses
into the
alveoli.
The oxygen in
the lungs
diffuses into
the blood.
This is called
gas exchange. http://www.webmd.com/hw/health_guide_atoz/tp10237.asp

10. Oxygenated blood
from the lungs
enters the heart
through the left
atrium.
The mitral valve is
closed to keep the
blood from going
into the ventricle.

11. Oxygenated blood
from the right lung
returns to the heart
through the right
pulmonary vein.
Oxygenated blood
from the left lung
returns to the heart
through the left
pulmonary vein.
THE PULMONARY
VEINS ARE THE ONLY
VEINS THAT CARRY
OXYGENATED BLOOD.

12. The left atrium
contracts. This
forces the
oxygenated
blood through
the mitral valve
into the right
ventricle.

13. The mitral
valve closes
again. This
keeps the
oxygenated
blood from
moving back
up into the
atrium.

14. Oxygenated
blood is forced
into the aorta
to be carried to
the rest of the
body.

15. Oxygenated blood
is carried to all
body cells where
oxygen diffuses
into the cells and
carbon dioxide
diffuses into the
blood.
Blood carrying
carbon dioxide
then returns to the
heart.

16. And the
cycle begins
again.

17. Blood Flow: Summary

18. Blood Vessels

19. Blood Vessels: Arteries, Veins, and Capillaries
Arteries and arterioles have a
layer of smooth muscle tissue
which allows them to contract
(vasoconstrict) and expand
(vasodilate), altering their
diameter and thus blood flow.
Walls of arteries and arterioles
have many elastic fibers
enabling them to withstand
high pressures.

20. Artery and Vein
Artery
Vein
Note the much
thinner walls in
veins.

21. Components of
Blood

23. Haemoglobin
Chemical – protein
Binds to oxygen to carry
oxygen around the body.
When oxygen is bound to
it, it is called
oxyhaemoglobin.

24. Types of Circulatory
System

25. Circulatory Systems
For larger or more active animals, some form of
more efficient circulatory system is necessary for
internal transport.
• Two types of circulatory system are found:
Open Circulatory Systems
Closed Circulatory Systems

26. Open Circulatory System
• Hemolymph leaves the
heart in short, branched
arteries that open up into
large spaces called sinuses.
• Hemolymph percolates
around organs, directly
bathing the cells.
• Hemolymph then returns
to the heart directly or
through short veins.

27. Open Circulatory System
• Advantage - Exchange of materials is direct
between the hemolymph and tissues. There
is no diffusion barrier.
• Disadvantage - Little fine control over
distribution of the hemolymph to body
regions. No mechanism for reducing flow to a
specific part of an organ.

28. Open Circulatory System
• Open circulatory systems tend to be found in
more inactive animals.
• Most molluscs have an open system, but the
highly active cephalopods (squid and octopus)
have evolved a closed system.
• Insects have circumvented limitation of their
open system by their tracheal system for oxygen
supply.

29. Closed Circulatory System
• The blood is contained
within a completely
closed system of vessels.
• Vessels form a closed
loop, usually with some
sort of pumping organ like
a heart or contractile
vessels.
• Vessels branch into
smaller and smaller tubes
that penetrate among the
cells of tissues.

30. Closed Circulatory System
Advantages:
• Fine-scale control over the distribution of blood
to different body regions is possible.
• Muscular walls of vessels can constrict and dilate
to vary the amount of flow through specific
vessels.
• Blood pressures are fairly high and the circulation
can be vigorous.

31. Human Circulatory
System
A Closed Circulatory System

32. How does this system work?
pulmonary vein lungs pulmonary artery
head & arms
aorta
main vein
Right Left
liver
digestive system
kidneys
legs
Circulatory System

33. Our circulatory system is a double circulatory system.
This means it has two parts parts.
Lungs
the right side of the left side of
the system the system
deals with deals with
deoxygenated oxygenated
blood.
blood.
Body cells