IGCSE Circulatory System

1. The Blood Circulatory System
B M Subramanya Swamy M.Sc. B.Ed.
CIE Co ordinator & Examination Officer
Kanaan Global School
Jakarta
Indonesia
subramanyaswamy1591978@gmail.com

2. The Blood Circulatory System

3. Circulatory System
• The circulatory system consist of the heart, blood
and blood vessels
• The heart pumps blood throughout the body
• Valves in the blood vessels and heart prevent the
backflow of blood
• This ensure that blood travels in only one direction
• The human circulatory system is a closed system

4. Blood circulation
Lungs
Pulmonary circulation
Body
Oxygenated
blood
Deoxygenated
blood
Heart
Systemic circulation

5. Different human circulatory systems
Mechanism
Closed system  Blood surges through the body in a closed
network of vessels
 No blood escapes into tissues or mixes
with the tissue fluid
Double
circulation
 Double circulatory system
 Both systems connected at the heart
 Circulation divided into oxygenated blood
and deoxygenated blood system
 Further division based on pulmonary
circulation and systemic circulation
 In one complete circulation, blood passes
through the heart twice

6. Comparison of the pulmonary and systemic
circulation in the body
Pulmonary circulation Systemic circulation
Pressure Low High
Main artery From heart to lungs Circulation
throughout body
except lungs
Affects Right ventricle Left ventricle

7. Blood vessels
Blood vessels consist of :
• Arteries
• Arterioles
• Capillaries
• Veins
• Venules

10. Comparison of different types of blood vessels
Characteristic Artery Vein Capillaries
Wall Thick,
muscular
elastic
Thin, less
muscular
One cell thick,
no muscles or
elastic tissue
Permeability X X 
Lumen Small Large Very small
Valve X  X
Cross section Circular Oval Circular
Colour Red Bluish red Bluish red
Pressure High Low Slow rate of
blood flow
Blood transport From heart to
organs
From organs
to heart
From arteries
to veins

11. Comparison of different types of blood vessels
Characteristic Artery Vein Capillaries
Blood type Oxygenated
blood, except
pulmonary
artery
Deoxygenated
blood except
pulmonary
vein
Oxygenated
blood at
arteriole end
and
deoxygenated
blood at
venule end
Pulse Strong X X
Location Deep in muscle Nearer to
body surface
Inside all
tissue

12. Diffusion across the capillary
• Capillary walls are one cell thick
• Great length of capillaries in a person throughout the
body
• There is an immense surface area for exchange of
materials
• This is the site of exchange of gases, nutrients and
wastes
• This exchange takes place by diffusion
• The exchange is between blood in the capillary and
the surrounding through tissue or interstitial fluids

13. Fluid exchange in Tissue
• At the arterial end, water and nutrient are
forced out of the capillaries by higher blood
pressure into the intercellular space
• At the venous end, water and dissolved waste
product returns to blood capillaries by
osmosis

14. Properties of capillaries & Tissue Fluid
Capillaries Tissue fluid
Capillary wall very permeable Source of water and nutrients to body
cells
Large variety of solutes in the blood The waste products are discharged here
Higher osmotic concentration than tissue
fluid
2/3 of plasma from capillary diffuses into
the tissue fluid and some returns to
capillaries
Blood pressure higher at artrial end than
venous end.
Other material drain into lymphatic
vessels.

15. Human Circulatory System

16. Anterior
vena cava
Head and arms Carotid artery
Pulmonary artery Lungs Pulmonary
vein
Vena cava
Heart Aorta
Hepatic vein
Liver
Hepatic artery
Small intestine
Renal vein
Kidney
Renal artery
Femoral vein
Abdomen and legs
Femoral artery

17. HEART
• A hollow muscular organ
• Situated in the left side of the chest, behind
the sternum and between the lungs
• The walls of the heart are made of cardiac
muscle

18. Structure of the heart

19. Structure and function of the heart
Structure Function
Left atrium Receives oxygenated blood from the lungs
via pulmonary vein
Left ventricle Pumps blood to all parts of the body
except the lungs via aorta
Bicuspid valve Prevents backflow of blood to left atrium
Chordae tendinae Tendons tighten to prevent valves from
flapping backward
Right atrium Receives deoxygenated blood
Right ventricle Pumps blood to the lungs via pulmonary
artery
Tricuspid valve Prevents backflow of blood to right atrium
Semi – lunar valve Prevents backflow of blood

20. Structure and function of the heart
Structure Function
Septum Prevents mixing of oxygenated and
deoxygenated blood
Aorta Carries oxygenated blood
Pulmonary artery Carries deoxygenated blood to the lung
Pulmonary vein Carries oxygenated blood from the lung to
the heart
Superior vena cava Returns deoxygenated blood from head
and arms to heart
Inferior vena cava Returns deoxygenated blood from lower
limbs and organs to heart

21. Heartbeat
• Heart contracts rhythmically
• Each heartbeat has two phases : diastole and systole
• During rest, a healthy adult has a heart rate of 72 beats per minute
atrial ventricular
systole systole
diastole
Events in a heartbeat

22. Summary of a heartbeat
Diastole Atrial systole Ventricular
systole
Muscles Atria and
ventricle relax
 Both atria
contract
 Both
ventricles
relax
Both
ventricles
contracts
Blood flow Into autrium Into ventricles Into
pulmonary
artery/ aorta
Bicuspid and
tricuspid
valves
Open Open Close
Atrial valves Close Close Open

23. Cardiovascular disease
Cardiovascular disease Causes
Hypertension Also known as high blood
pressure
Arteriosclerosis and
antherosclerosis
Narrowing and hardening
of arteries
Fatty deposits
(cholesterol) on the walls
of the artery (antheroma)
Coronary thrombosis Forming of blood clot
(thrombus) in the artery
Likely to occur in arrow
arteries

24. Causes and prevention of heart disease
Causes Prevention
 Unhealthy diet rich in cholesterol
and saturated fats
 Leads to high blood cholesterol level
Healthy diet and regular
exercise
 Smoking increases heart rate and
blood pressure
 Causes blood to clot more easily
 Tobacco has toxins which
reduces the blood’s ability to carry
oxygen
Stop or do not start
smoking
 Stress releases adrenaline which
increases heart rate and blood
pressure
Reduce stress

25. BLOOD
• When a sample of blood is spun in a high
speed centrifuge, blood separates into 2 layers
• The upper layer is pale coloured plasma, it
makes up 55 % of blood
• The lower layer is darker blood cells, it makes
up 45 % of blood

26. RBC WBC

27. Constituents of blood and its function
Blood Characteristic Function
Plasma 90 % of water
Plasma protein
Albumin
Globulin
Fibrinogen
 Acts as a buffer in the blood
 Maintain osmotic pressure
between blood and tissue fluid
 Medium of transport for soluble
food substances, minerals, waste
products and hormones
 Distributes heat around the body
 Maintain normal blood pressure
 Makes blood thick and viscous
 Proteins that include antibodies
 Forms blood clots

28. Constituents of blood and its function
Blood Characteristic Function
RBC  Biconcave disc, no
nucleus, elastic
membrane
 Squeeze into tiniest
capillaries
 High surface area
 Contains 95 %
haemoglobin
 Formed in bone marrow
 Survival about 120 days
 Efficient exchange of
O2 and CO2
 Contains iron,
combines reversibly
with oxygen

29. Constituents of blood and its function
Blood Characteristic Function
WBC  Larger than RBC
 Granular leucocytes
(65%)
 Produced in bone marrow
 Agranular leucocytes
(35%)
 Formed in lymph nodes
 Amoeboid movements
 Actively seeks out
and digests bacteria
 Also called phagocytes
 Produce antibodies
which destroy bacteria
and neutralise toxins
produced by bacteria
 Able to leave
capillaries to fight
infection at various
tissues

30. Constituent of blood and its function
Blood Characteristic Function
Platelets  Tiny pieces of
cytoplasm
 No nucleus
Found in bone marrow
Damaged tissues and
platelets form enzyme
thrombokinase
 Forms temporary plug for
wounds
Prothrombin  thrombin
Fibrinogen  fibrin
(meshwork that forms clot)

31. Function of blood
Function Mode of action
Transport
 Oxygen
 Carbon dioxide
 Haemoglobin combines reversibly
with oxygen
 Hb + 4O2
 Hb(O2)4
 Release oxygen to cells lacking in
oxygen
 Picks up CO2, combines with water
in a series of reactions
 CO2 + H2O  H2CO3
 H2CO3
 H+ + HCO3
–
 70 % of ions remain in plasma
 H+ + HCO3
-  H2CO3
 H2CO3
 CO2 + H2O
 Carbon dioxide is breathed out

32. Carbon dioxide transport in blood

33. Function of blood
Function Mode of action
Dissolved food substances,
hormones, antibody, water
Found in plasma
Protection  From invading bacteria by
phagocytes and antibodies
 Neutralise toxins
 Form blood clots
Regulation  Body temperature by
distribution of heat
 Metabolism
 Maintains concentration of
tissue fluid

34. Antibodies and Immunity
• All cells have surface markers
called antigens
• Lymphocytes produces
proteins called antibodies
• Each antibody is very specific

35. Cells of the Immune System
White Blood Cells
• Phagocytes - Neutrophils
- Macrophages
can engulf and then digest micro
organisms, called phagocytosis
• Lymphocytes
produce antibodies

36. Phagocytes
• Monocytes and macrophages
• Provide a non-specific response to infection

37. Phagocytosis
• Phagocytes are white blood cells with lobed nuclei
• They are capable of amoeboid movements
• Steps in phagocytosis
Step Mode of action
1 Phagocytes at the site of infection
2 Forms pseudopodia (false feet)
3 Engulfs bacteria
4 Site of infection becomes inflamed
5 Dead tissue, dead and living bacteria and
phagocytes form pus
6 Leaves body as harmless pus

38. Phagocytosis
Microbes
MACROPHAGE
Vacuole Lysosome
containing
enzymes
Pseudopodia
surround
microbes.
Microbes
are engulfed
into cell.
Vacuole
containing
microbes
forms
Vacuole
and lysosome
fuse.
Toxic
compounds
and lysosomal
enzymes
Destroy microbes.
Microbial debris is
released by
exocytosis.

39. Steps in phagocytosis
Steps Mode of action
1 Phagocytes at the site of infection
2 Forms pseudopodia (false feet)
3 Engulfs bacteria
4 Site of infection become inflamed
5 Dead tissue, dead and living bacteria and
phagocytes form pus
6 Leaves body as harmless pus

40. Lymphocyte

41. Lymphocytes
Provide a specific immune response to
infectious diseases.
There are 2 types: -
- T-cells
- B-cells

42. Lymphocytes
• Produce antibodies
• B-cells mature in bone marrow then
concentrate in lymph nodes and spleen
• T-cells mature in thymus
• B and T cells mature then circulate in the
blood and lymph
• Circulation ensures they come into contact
with pathogens and each other

43. Active and Passive Immunity
Active immunity
Lymphocytes are activated by antigens on the
surface of pathogens
Natural active immunity - acquired due to infection
Artificial active immunity – vaccination
Takes time for enough B and T cells to be produced
to mount an effective response.

44. Active and Passive Immunity
Passive immunity
B and T cells are not activated and plasma cells have
not produced antibodies.
The antigen doesn’t have to be encountered for the
body to make the antibodies.
Antibodies appear immediately in blood but protection
is only temporary.

45. Active and Passive Immunity
Artificial passive immunity
Used when a very rapid immune response is needed
e.g. after infection with tetanus.
Human antibodies are injected. In the case of
tetanus these are antitoxin antibodies.
Antibodies come from blood donors who have
recently had the tetanus vaccination.
Only provides short term protection as antibodies
destroyed by phagocytes in spleen and liver.

46. Active and Passive Immunity
Natural passive immunity
A mother’s antibodies pass across the placenta to the
foetus and remain for several months.
Colostrum (the first breast milk) contains lots of
Immunoglobulin A which remain on surface of the
baby’s gut wall and pass into blood

47. Transfusions
• Blood transfusions :
- injury
- surgical operation
- blood type of donor = blood type of patient
- blood group type A, B, AB, O
Blood
group
Can donate blood to Can receive blood from
A A and AB A and O
B B and AB B and O
AB AB All groups
O All groups O

48. Antigens and antibodies