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Unit 7 – Transport in Humans 7.1 – Circulatory System

SUFEATIN SURHAN BIOLOGY MSPSBS 2010

SYLLABUS CHECKLIST

Candidates should be able to:

a) describe the circulatory system as a system of tubes with a pump and valves to ensure one-way flow of blood;

b) describe the double circulation in terms of a low pressure circulation to the lungs and a high pressure

circulation to the body tissues and relate these differences to the different functions of the two circuits;

c) name the main blood vessels that carry blood to and from the heart, lungs, liver and kidney;

d) describe the structure and function of the heart in terms of muscular contraction and the working of valves;

e) compare the structure and function of arteries, veins and capillaries;

f) investigate and state the effect of physical activity on pulse rate;

g) describe coronary heart disease in terms of the occlusion of coronary arteries and state the possible causes

(diet, stress and smoking) and preventive measures;

h) identify red and white blood cells as seen under the light microscope on prepared slides, and in diagrams

and photomicrographs;

i) list the components of blood as red blood cells, white blood cells, platelets and plasma;

j) state the functions of blood: red blood cells – haemoglobin and oxygen transport; white blood cells – phagocytosis, antibody formation and tissue rejection; platelets – fibrinogen to fibrin, causing clotting; plasma – transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins and plasma proteins;

k) describe the transfer of materials between capillaries and tissue fluid.

2 | S u f e a t i n S u r h a n / B i o l o g y / M S P S B S 2 0 1 0

The need for a transport system

Throughout an organism’s life, materials are

constantly being moved to and from all parts of the

body.

In smaller animals, internal transport is by diffusion

and active transport from cell to cell.

A complex internal transport system has evolved in

many animals, especially larger organisms.

The human body has a transport system that

consists of the heart that pumps blood around a

complex system of blood vessels.

The main function of the system is to pick up oxygen

from the lungs and transport it to every cell in the

body and to remove waste products from the cells

and transport them to organs, which remove them

from the blood and excrete them from the body.

Transport to body cells Transport away from body cells (metabolic

products) for excretion

Oxygen (from lungs) Nutrients (Digested

food products from the ileum)

Carbon dioxide (removed via lungs)

Urea (removed in urine via kidney)

The Circulatory system

The circulatory system is a system which

transports nutrients and other useful substances to

the cells of the body and removes the waste these

cells produce.

The circulatory system is made up of three

components:

1. Medium; which is the blood.

2. Blood vessels (artery, vein and capillary);

3. Pump; which is the heart.

Note: There is a second transport system known as

the lymphatic system (not included in the syllabus).

This system is different because it has different

vessels (lacteals / lymph capillaries), different

transport medium i.e. lymph and no pump.

Double circulation

Blood travels through the heart twice in one

complete circulation. Mammals have a closed double circulatory system.

Their blood circulated through two separate systems joined only at the heart.

The two systems are the Pulmonary Circulation and the Systemic Circulation.

The pulmonary circulation is responsible for

transporting:

Deoxygenated blood from the right side of the

heart to the lungs via the pulmonary artery and

Oxygenated blood from the lungs to the left side

of the heart again via the pulmonary vein.

The systemic circulation is responsible for

transporting:

Oxygenated blood from the heart to all parts of

the body via the aorta.

Deoxygenated blood back to the right side of

the heart again via the inferior and superior

vena cava.

Comparison between the systemic and pulmonary

circulation:

Circulation SYSTEMIC PULMONARY

Blood leaves the heart by

Left ventricle Right Ventricle

Artery from the heart

Aorta Pulmonary arteries

Blood pressure

Higher – due to the longer distance in which the blood has to be transported to all parts of the body

Lower – due to short distance from the lungs to the heart

Blood flows In all blood vessels of the body except those of the lungs

Only in blood vessels of the lungs

Blood in arteries is

High in oxygen, low in carbon dioxide

Low in oxygen, high in carbon dioxide

Blood in veins is

Low in oxygen, high in carbon dioxide

High in oxygen, low in carbon dioxide.

Blood returns to heart by

Superior and inferior Vena cava

Pulmonary vein

Blood enters the heart by

Right atrium Left atrium


Advantages of Pulmonary circulation:

Little force required as blood flow is not against

gravity.

Blood travels slowly in the lungs. This ensures

that the blood is well oxygenated before it is

returned to the heart.

Prevents damage to the lung capillaries.

Advantages of Systemic circulation:

To ensure that the oxygenated blood and the

nutrients are distributed to the body tissues at a

fast rate. This helps to maintain the high

metabolic rate in mammals.

Provides high pressure for filtration process in

the kidneys in urine formation.

The importance of a double circulation

Repeated circulation through the heart is necessary

to maintain the blood pressure that is required to

keep the circulation of the blood around the body.

A double circulation is an efficient transport system

as:

Oxygenated blood is kept separate from

deoxygenated blood. The septum in the heart

ensures this complete separation. Oxygenated

blood flows through the left side of the heart

while deoxygenated blood flows through the

right.

The blood pressure in the systemic circulation

is kept higher than that in the pulmonary

circulation. The left ventricle, with thicker

wall, pumps blood under higher pressure to the

body and delivers oxygenated blood effectively

to all parts of the body. The right ventricle has

thinner wall and pumps blood to the lungs under

lower pressure, thereby avoiding any lung

damage.

Coronary circulation

The blood inside the heart does not serve the

cardiac or heart muscle.

Heart muscle receives its blood supply from two

coronary arteries which branch from the aorta.

Several small veins return venous blood from the

heart muscle to the right atrium.

Heart muscle differs from other muscles in at least

three important ways:

1. It is made up of branching muscle fibres

connected to each other in the form of a

network.

2. Heart muscle contracts and relaxes rhythmically

in what is termed beats.

3. Heart muscle does not fatigue despite

continuous rapid contractions over many years.

Blood

Blood is a tissue and is made up of three major

components:

1. Plasma – liquid part of the blood

2. Cells – Red blood cells (erythrocytes) and

white blood cells (leucocytes)

3. Platelets

The liquid and solid parts of the blood can be

separated by centrifugation (spinning of a sample of

blood in a test tube at high speed). The cells, which

are heavy, will settle at the bottom of the test tube

and the supernatant is the blood plasma.

Plasma

A pale yellow watery fluid, made up of 90% water

with the following substances in solution:

1. Soluble digested foods (amino acids, glucose).

2. Fat droplets (in suspension).

3. Vitamins.

4. Ions (salts) (e.g. Ca2+, Na+, Cl-).

5. Excretory materials (urea, carbon dioxide in the

form of hydrogen carbonate / bicarbonate ion –

HCO3-).

6. Hormones (e.g. insulin, adrenaline).

7. Plasma proteins (e.g. prothrombin and

fibrinogen – for blood clotting, antibodies).

Supernatant: Plasma

Solid part of the blood:

RBCs, WBCs, Platelets


Functions: As a transport medium -

1. To transport blood cells throughout the body

i.e. oxygen in red blood cells (oxyhaemoglobin)

and white blood cells.

2. To transport nutrients (soluble food

substances, ions, vitamins) to all body cells.

3. To transport hormones to target body organs

4. To transport plasma proteins to damaged sites

in the body for clotting.

5. To transport carbon dioxide (in the form of

HCO3-) from all body cells to the lungs to be

excreted.

6. To transport urea (nitrogenous waste product)

from all body cells to the kidneys to be excreted

in the urine.

7. To distribute heat uniformly through the body,

maintaining a constant body temperature

(~37°C in humans).

Plasma can be forced through blood vessel walls

under high pressure, carrying with it food and

oxygen from the blood stream.

Once it is out of the blood vessel walls, the plasma

forms a liquid called tissue fluid, which bathes

every cell in the body.

A large quantity of plasma in the form of tissue fluid

is constantly circulating among body cells supplying

food and oxygen and removing waste products.

The Red Blood Cells / Erythrocytes

Function: to carry oxygen around the body in the

form of oxyhaemoglobin.

Haemoglobin is an iron compound which readily

combines with oxygen in places where oxygen

concentration is high (air sacs in lungs) to form

oxyhaemoglobin.

Oxyhaemoglobin is unstable and easily breaks down

to release oxygen in places where oxygen

concentration is low (respiring body cells).

Hb + 4O2 HbO8

The red blood cells are adapted to perform their

function by the following ways:

The cytoplasm in red blood cells contains the

pigment haemoglobin. Haemoglobin combines

with oxygen in the lungs to become

oxyhaemoglobin. This is a reversible process.

The absence of nucleus (enucleated) means

space for more haemoglobin enabling more

oxygen to be transported increasing their

efficiency.

The cells are small (0.0072mm in diameter) and

there are many of them, so they have a very

large surface area for oxygen absorption.

They have a flat, biconcave shape making their

surface area for absorption (by diffusion) even

larger.

They are flexible, allowing them to be pushed

easily through the small blood vessels i.e.

capillaries whereby they become bell-shaped.

The White Blood Cells / Leucocytes

These cells are much bigger and less numerous

(about 5 000 in 1mm3 blood) than red blood cells.

Each is colourless, contains a nucleus, can move

about and change its shape.

White blood cells are also able to move in and out

of capillaries.

White blood cells can only live for a few days.

There are several types of white blood cells, but the

two main kinds are:

1. Lymphocytes – produced in lymph glands and

nodes.

2. Phagocytes – produced in bone marrow.

Low O2 concentration

High O2 concentration

Haemoglobin

(purplish red)

Oxyaemoglobin

(bright red)


Phagocytes

Structure:

Multi-lobed nucleus.

Made in the bone marrow.

Capable of movement and can squeeze out of

capillaries (formation of pseudopodia into

spaces among body cells).

Function:

They carry out phagocytosis i.e. engulf and

ingest potential harmful bacteria to prevent or

to overcome infection.

In the process of fighting with the bacteria at

the site of wound, some of the phagocytes are

killed. These dead cells, together with the dead

bacteria, form pus.

Lymphocyte

Structure:

A large round nucleus occupying almost the

whole cell

Made in the lymph nodes

Function:

They produce antibodies which bind to the

antigens (large, organic molecules made of

protein/polysaccharides) on the surface of the

bacteria and clump the bacteria together

(agglutination) for ingestion by phagocytes.

Antibodies are specific to the organism against

which they are produced. They may also directly

kill the bacteria.

Some antibodies are in the form of antitoxins

i.e. neutralise poisons (toxins) in the blood

which have been released by invading bacteria.

Plays an important role in tissue rejection

during organ transplant.

Organ transplant and tissue rejection

Organ or tissue transplant is when a person’s

damaged or diseased organ or tissue is replaced by a

healthy one.

The organ or tissue to be transplanted must not be

rejected by the recipient’s immune system (must be

compatible).

Any incompatible organ or tissue will be identified

as a foreign body by the recipient’s immune system.

His lymphocytes may respond by producing

antibodies to destroy the transplanted organ.

Prevention of Tissue Rejection:

Before transplantation can take place, the organ

or tissue must be checked for compatibility, a

procedure known as tissue matching. The tissue

of both donor and recipient must be as

genetically similar as possible, as in the case of

sisters, brothers, parents and close relatives.

This problem will not arise if the organ or tissue

comes from the recipient’s body itself.

Use of immunosuppressive drugs to inhibit the

activity of the recipient’s immune system.

Plateletes

Structure:

Fragments of some cells in the bone marrow.

They are about 3µm in diameter.

Consists of cytoplasm surrounded by a cell

membrane.

No nucleus.

Lifespan of only ~ 6 days


Function:

Platelets play a part in blood clotting, forming

a temporary plug at wound or cut.

Clotting is important because:

o It prevents excessive loss of blood from

the body through a wound or cut.

o It enables tissue repair to take place under

the dried clot.

o It prevents the entry of bacteria into the

body.

Clotting

Damaged cells and platelets release an enzyme

called thrombokinase into the blood.

Thrombokinase acts on prothrombin (a plasma

protein) which is converted into thrombin, an

activated enzyme.

Thrombin acts on another plasma protein,

fibrinogen, which is converted into an insoluble

stringy protein called fibrin, in the presence of

calcium ions and vitamin K.

Fibrin forms a mesh which traps blood cells and

becomes a clot to prevent the entry of bacteria.

The clot dries and hardens to form a scab.


Haemophilia

Haemophilia is a genetic disease that is inherited

and only affects the males in a family. The females

may have the haemophilia allele but will not be

affected, acting only as a carrier passing on this

allele to their male children.

A haemophiliac does not have blood clotting ability

(absence of a clotting factor) so a minor wound may

result in fatal bleeding.

Body’s line of defence against pathogens

(disease-causing organisms)

In general, the skin provides sufficient protection

against the entry of bacteria into the body as it has

adaptations for this purpose (solid physical barrier

separating the internal environment from the

external and the slightly acidic nature of sweat.

However, if the skin is damaged such as by a wound,

blood clotting prevents the bacteria from entering

the body.

If the first two defences are not sufficient and the

pathogen manages to enter the body, white blood

cells act as the last line of defence. Phagocytes

remove the pathogen via phagocytosis, helped by

the antibodies produced by lymphocytes.

Once the infection has been cleared, some of the

antibodies against this particular pathogen will

remain within the circulatory system providing

immunity against this pathogen in the future.

Summary – Main functions of Blood

A. Blood as a transport system:

o Transport of oxygen from lungs to body tissues

in the form of oxyhaemoglobin.

o Transport of carbon dioxide from body tissues to

lungs.

o To transport digested food from the villi to the

liver and the body tissues.

o To transport nitrogenous waste or urine from

the cells to the kidneys for removal.

o To transport vitamins and hormones, which are,

required by the body for growth and other cell

activities.

B. Blood as a means to prevent infection:

o To protect or defend the body against harmful

bacteria and germs by phagocytosis.

o To protect the body against harmful toxins

discharged by bacteria by the production of

antitoxins and antibodies by leucocytes.

C. Formation of clots:

o To prevent the body from losing too much blood

through a wound.

o To prevent the entry of bacteria and other

harmful substances into the body.

D. Maintaining a constant body temperature:

o To maintain a constant body temperature

(about 370C in humans).

o To distribute heat uniformly throughout the

body.

Summary – Transport function of blood

SUBSTANCES TRANSPORTED

BY FROM TO

Oxygen Red blood cells

lungs All body cells

Carbon dioxide (as hydrogen carbonate ions)

Plasma All body cells

Lungs

Urea (Nitrogenous waste)

Plasma liver Kidneys

Digested food Plasma intestine Body cells

Hormones Plasma Endocrine glands

Target cells

Heat Plasma Liver and muscles

All body cells (excess to skin)

Blood Vessels

There are three types of blood vessels:

1. Arteries

2. Veins

3. Capillaries

*The flow of blood:

Arteries Arterioles Capillaries Venules Veins

Arteries carry blood away from the heart.

Arteries will form smaller branches called

arterioles.

Capillaries are made up of microscopic vessels

linking an arteriole and a venule. Capillaries take

nutrients, oxygen and other useful substances to the

cells and remove waste products produced in these

cells.

Veins carry blood towards the heart. Veins will

form smaller branches called venules.

The following are simplified diagrams showing a

capillary network:


The table below shows the differences between an

artery, a vein and a capillary:

Feature Arteries Veins Capillaries

Function

To transport oxygenated blood away from the heart except pulmonary artery

To transport deoxygenated blood towards the heart except pulmonary vein

To transport blood from arteries to veins *To allow exchange of substances (nutrients, waste products, gases) between blood and tissue fluid (fluid bathing cells)

Wall Thick muscular walls (impermeable)

Thin muscular walls (impermeable)

One cell thick walls (endothelium); Fenestrated (have gaps between the endothelial cells of the walls)

Lumen size

Smaller than veins but bigger than capillaries

Largest

Smallest Just enough for the diameter of one red blood cell Red blood cells travel in a single file

Valves Absent

Present (Semi-lunar valves: to prevent backflow of blood as blood is flowing at low pressure)

Absent

Blood flow

In pulses (rapid flow, in high pressure). Flow is maintained by the contraction of heart muscle.

No pulse (slow flow but faster than in capillaries). Blood flow is maintained by contraction of skeletal muscles, which squeeze the veins between them.

Pulse gradually disappears (slow flow). Flow is along the gradient of blood pressure.


The diagram below shows the major blood vessels in

humans:

Differences between arteries and veins:

ARTERIES VEINS

Transport blood away from the heart to body tissues.

Transport blood from body tissues towards the heart.

Have strong thick muscular elastic walls.

Have thin muscular walls.

Transport oxygenated blood except the pulmonary artery.

Transport deoxygenated blood except the pulmonary vein.

Valves are not present. Valves are present to prevent the back flow of blood.

Blood is generally under higher pressure.

Blood is generally under lower pressure.

Lumen is small. Lumen is large.

Usually is deep seated except the artery in the neck.

Usually superficial (found close to the surface of the skin)

How valves work to prevent the backflow

of blood

Transfer of materials between capillaries,

tissue fluids and body cells

Capillaries are adapted to allow the exchange of

materials between the blood and the cells.

Adaptations of capillaries include:

1. Capillaries have very thin, permeable walls,

only one-cell thick to ensure rapid diffusion of

materials.

2. Capillaries are abundant which provides a huge

surface area for:

Nutrients and oxygen to diffuse from blood

to tissues.

Waste materials and carbon dioxide diffuse

from tissues into blood.

3. Blood flows through them slowly.

4. Body cells are never far from a capillary.

The capillary walls act as a filter. Substances such

as water with dissolved oxygen, glucose, fatty acids,

glycerol, amino acids, vitamins, minerals and

hormones are very tiny and so are able to pass


through the capillary walls and enter the tissue

fluid.

Larger ones such as red blood cells, most of the

white blood cells and large protein molecules are

held back.

Tissue fluid

Body cells are bathed in tissue or intercellular fluid.

This fluid is actually dilute plasma (usually without

plasma proteins).

The fluid is formed continuously as plasma filters

out between the cells in the capillary walls into the

intercellular spaces.

This occurs at the arteriole end of the capillary

network due to the high pressure here.

Tissue fluid seeps back into capillaries at the venule

end of the capillary network.

Some tissue fluid drains into the lymph vessels.

This in turn, empty into the blood vessels.

Blood capillary


EXTENSION MATERIAL…

What is lymph?

A colourless, alkaline fluid similar in composition to

blood except it contains less protein and lacks red

blood cells.

It contains fats absorbed by the lacteals of the small

intestines.

How is lymph formed?

Not all tissue fluid returns to the blood capillaries.

One-tenth enters a separate system of capillaries

called lymph capillaries. Lymph capillaries are part

of the lymph system.

What is the difference between tissue fluid and

lymph?

They have similar composition but tissue fluid

surrounds the tissues. Lymph is found in the lymph

system.

What are lymph nodes?

Lymph nodes are swellings found along the lymph

vessel.

There are large lymph nodes in the groin, under

the arms and in the neck.

Lymph nodes often swell up if you have an

infection.

Functions:

1. Remove particles of debris.

2. Manufacture of lymphocyte.

3. Ingestion of bacteria. (Large phagocytes

are attached to the walls of these nodes)

What are lymphatic ducts?

There are two lymphatic ducts:

The thoracic duct collects lymph from the left

side of the body and empties it into the left

subclavian vein.

The right lymphatic duct collects lymph from

the right side of the body and empties it into

the right subclavian vein.

What are functions of the lymph?

Transport digested fat into the circulatory system.

Oxygen from red blood cells diffuses into lymph and

is conveyed to the respiring cells.

Carbon dioxide and waste substances from the cells

are transported by the lymph to the blood stream.

Most of the hormones reach the blood system via

the lymph.

The lymph nodes filter out the dust particles and

bacteria thus preventing their entry into the

bloodstream.


The Heart


It is a muscular pump, made up of special muscle

known as cardiac muscle, which has the ability to

contract rhythmically even without stimulation

(myogenic).

It never tires or suffers from cramp and beats about

70 times per minute in the average adult at rest.

It has four chambers, all with similar volumes when

full: The top two chambers are the atria (s - atrium)

and the bottom two are the ventricles (s - ventricle)

Feature Atria (also known as auricles)

Ventricles

Wall

Thin walls Less force is required for contraction to transport blood in a short distance

Thick walls particularly left ventricle as blood is travelling at long distances. This requires a very strong contraction force

Blood flow

Right atrium receives blood from the superior and inferior vena cavae. Left atrium receives blood from the pulmonary veins.

The right ventricles receive blood from the right atrium. The left ventricle receives blood from the left atrium.

Prevention of blood flow

By closing valves in the vena cava and the pulmonary veins.

By closing of tricuspid calve on the right side of the heart and bicuspid valve on the left side of the heart.

On contraction blood is pumped

Blood flows from atria to ventricles.

Blood flows into the pulmonary artery and aorta

The heart is protected by the vertebral column at

the back, sternum and the rib cage in front. The

heart lies in a fluid filled cavity called the

pericardial cavity. This acts as a lubricant.

The right and left side of the heart is separated by

septum (separates the oxygenated and

deoxygenated blood)

Heart muscles receive their oxygen and nutrient

supply from two coronary arteries, which branch

from the aorta.

A system of valves ensures one-way flow of blood

through the heart.

Between the right atrium and right ventricle is the

tricuspid valve (three pockets / flaps).

Between the left atrium and left ventricle is the

bicuspid or mitral valve (two pockets / flaps).

Between the arteries leading away from the heart

and the ventricles are the semi-lunar valves (three

pockets / flaps)

Note: The valves between the atria and the

ventricles are also known in general as

atrioventricular valves.

The main blood vessels of the heart and its function:

MAIN BLOOD VESSELS

FUNCTION

Superior vena cava

Transports deoxygenated blood from the upper parts of the body to the right atrium.

Inferior vena cava Transports deoxygenated blood from the lower parts of the body to the right atrium.

Pulmonary artery Transports deoxygenated blood from the lungs to the left atrium.

Pulmonary vein Transports oxygenated blood from lungs to the left atrium

Aorta Transports oxygenated blood from the left ventricle to all parts of the body.

Renal artery Transports oxygenated blood from the heart to the kidneys.

Renal vein Transports deoxygenated blood from the kidney to the heart.

Hepatic artery Transports oxygenated blood from the heart to the liver.

Hepatic vein Transports deoxygenated blood from the liver to the heart.

Hepatic portal vein

Transports blood rich in digested food from villi of small intestine to the liver.


The Cardiac Cycle

The rhythmic contraction and relaxation of the

heart to produce one heartbeat (‘lub-dub’ sound).

Systole: cardiac muscles contraction.

Diastole: cardiac muscles relaxation.

There are three main stages in a single cardiac

cycle:

1. Atrial systole

Both atria contract (ventricles relax).

Blood in atria pushed into the ventricles.

Blood at high pressure pushing the bicuspid

and tricuspid valves open.

2. Ventricular systole

Both ventricles contract (atria relax).

Blood in ventricles pushed into the arteries

(pulmonary artery and aorta).

Blood at high pressure pushing the semi-

lunar valves open.

Simultaneously, bicuspid and tricuspid

valves close (to prevent backflow into atria)

to produce ‘lub’ sound.

3. Diastole (pause between ‘lub-dub’ sound)

Both atria and ventricles relax.

Blood in aorta and pulmonary artery under

high pressure causing the semi-lunar valves

to close producing the ‘dub’ sound (prevents

blood from flowing back into the ventricles).

Blood from the veins (vena cava and

pulmonary veins) flow into atria.

The whole cycle is then repeated

A graph showing the changes in blood pressure in

one cardiac cycle.

QUESTION 1: MATCH THE LETTERS ON THE GRAPH WITH

THE FOLLOWING EVENTS:

Semi – lunar valves open: _____

Semi – lunar valves closes: _____

Atrioventricular valves open: _____

Atrioventricular valves closes: _____

QUESTION 2: HOW MANY HEARTBEATS WOULD THERE BE

IN 1 MINUTE?


Blood Pressure and Pulse

Blood pressure is the force exerted by blood on the

walls of the arteries as a result of the contraction

and relaxation of the heart.

This succession surge or wave of pressure can be

felt as a pulse.

The pulse beat in an artery can be located by gently

pressing on the wrist at the base of the thumb using

your middle and index fingers (radial pulse) or at

the neck (carotid pulse).

The pulse rate is the same as the number of

heartbeats per minute.

There is no such surge in the veins where blood

flows smoothly under much lower pressure.

Veins, however, have semi-lunar valves which

ensure that blood continues to flow towards the

heart.

Otherwise, veins rely on the movement of the

nearby skeletal muscles to massage the blood from

one set of semi-lunar valves to the next.

Coronary Heart disease

Diet is important for a healthy heart but like all

muscles, the heart benefits from exercise.

Fat deposits (atherosclerosis) and blood clots

(thrombosis) on the inner walls of the coronary

arteries can partially block their lumen, obstructing

blood flow to the heart muscles.

The

heart muscles will not get enough nutrients and

oxygen.

This will lead to their degeneration, resulting in a

severe heart pain – a heart attack.

Other than high animal fats diet, drinking alcohol

also increases atheroma formation.


The heart is also affected by cigarette smoking.

Carbon monoxide in cigarette smoke encourages

the build-up of atheroma.

Nicotine triggers the release of adrenaline,

which increases rate of heartbeat and constricts

the blood vessels. Nicotine also increases the

tendency for blood to clot.

If these (atheroma, thrombosis) happen in the

coronary arteries causing an occlusion of these

arteries, they may therefore not supply enough

blood (oxygen and nutrients) to the heart

muscle causing heart attack (myocardial

infarction – severe damage or death of heart

muscles)

People who lead stressful lives are also at risk of

heart disease.

Stress increases the release of adrenaline, which

constricts artery walls.

In this way, stress adds to existing problems of

partially blocked arteries.

One of the early symptoms of a heart disease is

angina (pain in the centre of the chest during

exercise and disappears at rest).

To decrease the risk of heart disease:

Restrict the intake of animal fats and

cholesterol.

Avoid obesity (control weight).

Do not smoke and do not comsume alcoholic

drinks.

Settle for a less stressful lifestyle.

Take regular exercise.

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