The human circulatory system consists of the heart, blood vessels, and blood. The heart pumps blood through a closed system of arteries, veins, and capillaries. It has four chambers - two atria which collect blood and two ventricles which pump blood. Blood carries oxygen, nutrients, hormones and waste products as it circulates. It contains plasma, red blood cells, white blood cells and platelets. The circulatory system transports these substances between tissues and organs via a network of blood vessels, and returns waste products to the kidneys and lungs.

1. transport
in humans

2. 8.1 The Human Circulatory System

3. The human
circulatory
system consists
of three parts:
a. blood
components
b. blood vessels
c. heart
circulatorySYSTEM
heart
blood
vessels
blood

5. In multicellular organisms, cells are far
from the external environment.
Diffusion alone is too slow to:
• transport nutrients and oxygen to
the various organs
• remove waste products efficiently
Thus, a transport system is
developed to move these
substances
whyTRANSPORT?

6. 8.2 Blood Components

7. The composition of blood

9. bloodCOMPONENTS
BLOOD
plasma
red blood cells
(erythrocytes)
white blood
cells
(leukocytes)
Platelets
(thrombocytes)
PLASMA
•Pale yellowish liquid
•Contains mainly water (90%)
•Contains mainly dissolved
substances

10. Plasma transports the following
dissolved substances:
• nutrients
• hormones
• antibodies
• excretory waste products
• carbon dioxide to the lungs
(as bicarbonate ions)

11. RED BLOOD CELLS
•Produced by the bone marrow;
destroyed in the spleen
•Short lifespan of ~120 days
•Contain haemoglobin
•Transports mainly oxygen in the form
of oxyhaemoglobin.

13. RBC
adaptations
function
• Contains
haemoglobin
To bind with oxygen to form
oxyhaemoglobin and transport
oxygen around the body.
• Biconcave
and circular
shape
To increase surface area to volume
ratio for more efficient absorption &
transport of oxygen
• No nucleus Able to contain more haemoglobin
• Thin, flexible
membrane
To form bell-shaped and squeeze
through narrow blood vessels

14. WHITE BLOOD CELLS
•Much bigger in size than RBC
•Fewer in number than RBC
•Colourless (no haemoglobin)
•Contains a nucleus

15. WHITE BLOOD CELLS
•Two types:
(1) Phagocytes
• engulfs and ingests foreign particles by
phagocytosis

16. (2) Lymphocytes
• Produces antibodies that kill
pathogen such as bacteria
and viruses.
• Antibodies act by:
a) Attaching to bacteria and rupturing
bacterial surface membrane
b) Agglutinating (clumping) bacteria to
make them more easily ingested by
phagocytes
c) Neutralising toxins produced by bacteria

17. •Antibodies produced remain in the
blood long after the disease has been
overcome.
•Thus the person who has recovered
becomes immune or resistant to that
infection

18. TISSUE & ORGAN REJECTION
•After an organ transplant, the transplanted
organ may be deemed as “foreign” by the
recipient body
•The body then sends antibodies to “attack” the
“foreign organ”.
•To prevent recipient body from rejecting the
donor tissue or organ,
•the donor and recipient should be as genetically
close as possible
•‘immunosuppressant drugs’ to curb recipient’s
immune system; but recipient may become
susceptible to infection and develop lifelong
dependence on the drugs

19. bloodCOMPONENTS
PLATELETS
•Cell fragments (not complete cells)
•No nucleus
•Life span of 5-9 days
•Involved in the process of blood clotting

20. BLOOD CLOTTING
•Blood clotting helps to seal wounds, prevents
entry of foreign particles, prevents infection by
pathogens and reduces blood loss.
•People with haemophilia (genetic blood
disorder) cannot clot blood and is at risk of
bleeding to death.

21. Blood clotting

22. BLOOD CLOTTING MECHANISM
1. Damaged tissues and platelets secrete enzyme
thrombokinase .
2. Enzyme thrombokinase converts prothrombin to
thrombin.
3. and cause the conversion of soluble fibrinogen in
the plasma into insoluble fibrin.
4. Fibrin forms a meshwork to trap RBCs and plugs up
the wound. Once the clot is formed, bleeding
stops.
Video: http://www.youtube.com/watch?v=sVoM3jAs5sc

23. Damaged tissues
& platelets
*thrombokinase
(enzyme)
release
prothrombin
(inactive plasma protein)
*thrombin
(active enzyme)Ca2+
fibrinogen
(soluble plasma protein)
fibrin threads
(insoluble mesh)
* Sci(Bio) students do
not need to know
specific enzyme names.

24. Substances in blood clotting

27. 8.3 Blood Vessels

28. Interesting Fact
 The aorta, the largest artery in
the body, is almost the
diameter of a garden hose!
 Capillaries, on the other hand,
are so small that it takes ten of
them to equal the thickness of
a human hair.

29. Prepared by, Ms Wong Fui Yen

30. • The blood vessels are a network of tubes to carry
blood around the body.
• Namely the artery, vein & capillary
bloodVESSELS

31. bloodVESSELS - artery
Structure:
•thick and elastic muscular walls to
withstand the high blood pressure
• elasticity enables artery wall to
stretch & recoil
• do not contain valves
Function:
•carry oxygeneated (except
pulmonary artery) blood away
from the heart at high pressure
Middle layer
(smooth muscle
& elastic fibres)
External layer
(connective tissue)
Small
lumen

32. bloodVESSELS - vein
Structure:
• relatively thin, less muscular
walls
• valves present to prevent
the backflow of blood
Function:
• usually carry
deoxygenated blood
(except pulmonary vein)to
the heart at lower blood
pressure

33. Blood flow in veins

35. bloodVESSELS - capillary
Structure:
•have one-cell thick walls (one
layer of partially permeable cells)
Function:
• transfer oxygen and food from
arteries to the surrounding cells
by allowing these to diffuse
across the wall
• transfer carbon dioxide and other
waste substances from cells to
veins

36. Guide to blood vessels

37. plasma
direction of
blood flow
movement of oxygen
and dissolved food
substances
movement of excretory
waste products
blood capillary wall
white blood cell squeezing
through capillary wall

38. Structure
Arteries Veins Capillaries
• _____, muscular
& elastic walls to
withstand high blood
pressure in artery.
• thin, slightly
muscular, & have
less elastic tissue
• Walls are _________
• single layer of cells,
non-muscular and elastic,
selectively permeable
• Valves are absent • ______ are present • Valves are absent
thick
Valves
very thin

39. Function of the blood vessels:
Arteries Veins Capillaries
• transport
oxygenated
blood away from
the heart, except
pulmonary artery.
• carry
deoxygenated
blood towards the
heart, except
pulmonary vein.
• Allow
exchange of
substances
between blood
and tissue fluid.

40. Arteries, capillaries and veins

41. bloodVESSELS - summary
(refer to page 160)

42. Blood pressure differences across blood vessels and
heart structures

44. 8.4 Heart

46. theHEART
RA
RV
LA
LV
• pumps blood around the
body
• made up of cardiac muscles
• comprises 4 chambers
 2 atrium
 2 ventricle
•the median septum runs down
the middle of the heart, separating
the left side from the right to
ensure oxygenated and
deoxygenated blood do not mix

47. theHEART
• right side of heart pumps deoxygenated
blood to lungs only (which are a short
distance from the heart)
• left side of heart pumps oxygenated
blood around the body (which are further
away from the heart)
• hence left ventricle has thicker muscular
walls than the right ventricle

48. RA
RV
LA
LV

49. Structure of the heart

50. Activity : Learn the Structure of Heart
http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningSimulations/CRCSC/launc
h.html

51. • Semilunar Valves prevent backflow of blood from
flowing back into the ventricles
Valves
• These prevent
backflow of blood :
• Bicuspid valves
prevent blood flowing
from left ventricle to
left atrium.
• Tricuspid valves
prevent blood flowing
from right ventricles to
right atrium.
Tricuspid
valve
Bicuspid
valve

52. theHEART
Tricuspid
valve
Bicuspid valve

53. What structure?

54. i) Why is the artery thicker than vein?
ii) Why is left ventricle wall thicker than right
ventricle?
-To withstand the high blood pressure
-To exert a greater pressure to pump oxygenated
blood around the body.

55. 8.6 The Main Arteries & Veins of
the Human Circulatory System

56. Animation: How does Heart Works?

58. Blood flow through the heart

59.  In mammals, blood flows through the heart TWICE
in one complete circuit.
Aorta distributes oxygenated blood to different
parts of the body. For example, it supplies blood
through :
• Hepatic artery to the liver.
• Renal artery to kidneys.
• Pulmonary vein to lung
• Coronary artery to heart
 Coronary artery (supplies blood to the heart ) lie
on the outside of the heart and supply
oxygenated blood to the muscles in the wall of
the heart.

60. Animation: Blood Pressure

61. 8.7 Cardiac Cycle

62. Cardiac Cycle

63. The cardiac cycle

64. Interactive heart

65. Ventricular
diastole
Ventricular
systole
aorta
atrium
ventricle
Pressure/kPa
Time /s
4. semilunar
valves close
3. semilunar
valves open
1. atrioventricular
valves close
4. atrioventricular
valves open
One heartbeat = one cardiac cycle

66. The Cardiac Cycle
1
The atria contracts, forcing blood into the
relaxed . This causes a slight
increase in both the atrial pressure and
ventricular pressure
1
ventricles.

67. 2
2
The ventricles contract. This is called
ventricle systole. The ventricle pressure
increases. This causes the
atrioventricular valves to close,
producing a loud “lub” sound and
prevents the backflow of blood into the
atria.

68. 3
3
The pressure in the ventricles becomes
higher than that of the aorta and
pulmonary artery. The semi-lunar valves
open and blood flows into the aorta and
pulmonary artery.

69. 4
4
The ventricles relax. This
is called ventricular
diastole. The drop in
pressure in the ventricles
causes the semi-lunar
valves to close, producing
a soft “dub” sound. This
prevents the backflow of
blood into the ventricles.

70. The Cardiac Cycle
5
5
The pressure in the
ventricle continues to
decrease as they relax.
6
6
The atrioventricular
valves opens as
pressure in the ventricle
becomes lower than
that in the atria.
7
7
The pressure in the
ventricles gradually
increases as blood
continues to enter the
ventricle from the atria

71. 8.8 Heart Disease

72. heartDISEASE
Coronary arteries lie on the outside of
the heart and supply blood to the
muscles in the wall of the heart.

73. heartDISEASE

74. • This is the condition when fatty
substances such as cholesterol and
polysaturated fats deposit on the inner
surface of the coronary arteries.
• This results in the blockage of the
coronary arteries, reducing the supply of
oxygenated blood and nutrients to the
heart muscles.
•Heart muscle eventually die and leading
to failure for heart to pump blood around
the body.
• A heart attack results.

75. Arteriosclerosis

76. Effect of tobacco smoke
Substance Effect
nicotine increases blood pressure and the
risk of blood clotting in the
coronary arteries.
carbon
monoxide
increase the risk of fatty deposits
(atherosclerosis) on the inner
surfaces of arteries.

77. Prepared by, Ms Wong Fui Yen
Examples of Famous People with Heart Disease
 Bill Clinton –
quadruple bypass
surgery in 2004
 David Letterman -
quadruple bypass
surgery in 2000
 Larry King - heart
attack and bypass
surgery in 1987
 Michael Jackson –
died of cardiac arrest
2009

78. heartDISEASE - causes
Atherosclerosis and coronary heart
disease can be caused by
diet rich in cholesterol & saturated
animal fats
emotional stress
smoking

79. heartDISEASE - prevention
Atherosclerosis and coronary heart
disease can be prevented by
healthy diet with little saturated
fats
proper stress management
avoid smoking
regular exercise

80. Coronary Bypass Surgery
to replace the blocked coronary arteries.

81. 8.9 Blood Groups
(Pure Biology)

82. • There are 4 human blood groups:
 A, B, AB and O
• Classification is based on the types of antigens
and antibodies present in the blood:
 Antigens represented by capital letters A & B
 Antibodies represented by small letters a & b

86. • Antibody a reacts with antigen A
and agglutination (clumping) occurs.
• So a person with blood group A, has
antibodies that react against antigen B, so
this person cannot have antigen B in his
blood, and only has antigen A.
• During blood transfusions, it is vital to know
the donor’s and recipient’s blood types in
order to avoid tissue mismatch.
• Transfusing the wrong type of blood can
cause agglutination of blood cells, which
can become fatal if the blood clumps
block up blood vessels in vital organs.

88. • Blood group O donors do not have any
antigens so their blood can be accepted
by recipients of any blood group. They are
known as universal donors.
• Blood group AB recipients do not have
any antibodies so they can receive blood
from any donor. They are known as
universal recipient.

89. Are ‘blood agglutination’ and ‘blood clotting’
similar?
Blood clotting is the formation of an enmeshed
network of fibrin that traps RBCs and seal the wound
from further blood loss.
Blood agglutination is the clumping of RBC when
natural antibodies in the recipient’s body react with
the antigens on the donor’s red blood cells.

90. microQuestion (p145 of textbook)

91. Answers (p145):
(a) X : Blood group B
Y : Blood group AB
Z : Blood group O
(b) Antibody b in the serum reacts with antigen B on the red
blood cells, causing clumping of the red blood cells from X.
(c) Blood group O
(d) Blood groups A and AB
(e) Such a person’s red blood cells do not contain any
antigens, so this person’s blood can be donated to any blood
group without causing clumping of the recipient’s red blood
cells.

92. 8.10 Tissue Fluid
(Pure Biology)

93. Formation of tissue fluid

94. tissueFLUID (pure)
plasma
direction of
blood flow
movement of oxygen
and dissolved food
substances
movement of excretory
waste products
blood capillary wall
white blood cell squeezing
through capillary wall

95. • Tissue cells are bathed in tissue fluid (interstitial
fluid)
• Tissue fluid allows the diffusion of dissolved
substances between the tissue cells and the blood
capillaries.
• Dissolved food substances and oxygen diffuse
out from the blood capillaries into the tissue fluid
then into the cells
• Excretory products diffuse out from the cells into
the tissue fluid and then through the capillary walls
into the blood.

96. Circulatory
System
HeartBlood vessels Blood Components
4 chambers 4 valves
Left
Atrium
Right
Atrium
Left
Ventricle
Right
Ventricle
Tricuspid Bicuspid 2 Semilunar
valves
consist of
has
called known as
Septum

97. Glossary

98. 1. Arteries contain valves.
2. Capillaries have a one-cell thick muscular wall.
3. White blood cells fight bacteria.
4. Carbon dioxide is transported in the red blood cell.
5. There are only 2 chambers in the heart.
6. Coronary arteries are vessels carrying blood away from the heart to the rest
of the body.
7. The left ventricle walls are thicker to withstand the higher pressure.
8. All arteries transport oxygenated blood.
9. Consuming too much fatty foods will encourage fatty acids to build up in the

99. 1. Arteries contain valves.
2. Capillaries have a one-cell thick muscular wall.
3. White blood cells fight bacteria. (overgeneralisation)
4. Carbon dioxide is transported in the red blood cell.
5. There are only 2 chambers in the heart.
6. Coronary arteries are vessels carrying blood away from the heart to the rest
of the body.
7. The left ventricle walls are thicker to withstand the higher pressure.
8. All arteries transport oxygenated blood.
9. Consuming too much fatty foods will encourage fatty acids to build up in the