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The Blood Circulatory System
B M Subramanya Swamy M.Sc. B.Ed. CIE Co ordinator & Examination Officer
Kanaan Global School Jakarta
Indonesia [email protected]
The Blood Circulatory System
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 thebackflow of blood
• This ensure that blood travels in only one direction
• The human circulatory system is a closed system
Blood circulation
Lungs
Body
Oxygenated blood
Deoxygenated blood
Heart
Pulmonary circulation
Systemic circulation
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
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
Blood vessels
Blood vessels consist of :
• Arteries
• Arterioles
• Capillaries
• Veins
• Venules
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
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
Diffusion across the capillary
• Capillary walls are one cell thick
• Great length of capillaries in a person throughout thebody
• There is an immense surface area for exchange ofmaterials
• This is the site of exchange of gases, nutrients andwastes
• This exchange takes place by diffusion
• The exchange is between blood in the capillary andthe surrounding through tissue or interstitial fluids
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
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 lymphaticvessels.
Human Circulatory System
Anterior
vena cavaHead and arms Carotid artery
Pulmonary artery Lungs Pulmonary
vein
Vena cava
Heart Aorta
Hepatic vein
Liver Hepatic artery
Small intestine
Renal vein
KidneyRenal artery
Femoral vein
Abdomen and legs
Femoral artery
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
Structure of the heart
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
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
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
Summary of a heartbeatDiastole 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
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
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
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, itmakes up 55 % of blood
• The lower layer is darker blood cells, it makesup 45 % of blood
RBC WBC
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
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
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
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)
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
Carbon dioxide transport in blood
Function of blood
Function Mode of actionDissolved 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
Antibodies and Immunity
• All cells have surface markers called antigens
• Lymphocytes produces proteins called antibodies
• Each antibody is very specific
Cells of the Immune System
White Blood Cells
• Phagocytes - Neutrophils
- Macrophages
can engulf and then digest micro
organisms, called phagocytosis
• Lymphocytes
produce antibodies
Phagocytes
• Monocytes and macrophages• Provide a non-specific response to infection
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
Phagocytosis
Microbes
MACROPHAGE
Vacuole Lysosomecontainingenzymes
Microbesare engulfedinto cell.
Pseudopodiasurroundmicrobes.
Vacuolecontainingmicrobesforms
Vacuoleand lysosome
fuse.Toxiccompoundsand lysosomalenzymesDestroy microbes.
Microbial debris is released byexocytosis.
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
Lymphocyte
Lymphocytes
Provide a specific immune response to
infectious diseases.
There are 2 types: -
- T-cells - B-cells
Lymphocytes• Produce antibodies
• B-cells mature in bone marrow thenconcentrate in lymph nodes and spleen
• T-cells mature in thymus
• B and T cells mature then circulate in theblood and lymph
• Circulation ensures they come into contactwith pathogens and each other
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.
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.
Active and Passive Immunity
Artificial passive immunity
Used when a very rapid immune response is needede.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.
Active and Passive Immunity
Natural passive immunity
A mother’s antibodies pass across the placenta to thefoetus and remain for several months.
Colostrum (the first breast milk) contains lots ofImmunoglobulin A which remain on surface of thebaby’s gut wall and pass into blood
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
Antigens and antibodies