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

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