Site author Richard Steane
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Common defects of the circulatory system

Cholesterol is a substance which is suspected of causing problems in the heart and circulatory system.
What sort of substance is it (chemically)?
>fat (lipid)
Some people (but not all) are at risk because their bodies build up cholesterol as a result of foods they eat. This may be one cause of hardening of the arteries.
What categories of food provide the most risk?
>animal fat/ dairy produce
If all the arteries in the body become narrower, the resistance to flow increases.
What effect do you think this increased resistance will have on the heart?
> strain - more effort required to pump
How do you think a doctor will be able to measure this?
> measure blood pressure - using sphygmomanometer

Similarly, some people (but not all) are at risk of developing high blood pressure because of the effect of salt in foods that they eat. This is especially true for prepared foods.
What category of nutritional information on food packaging will provide information about this risk?
> sodium content (/100g)
A thrombosis is a blockage in a blood vessel, usually an artery.
Why are arteries more likely to get blocked than other blood vessels?
> narrower internal diameter - and getting narrower as they branch into arterioles, etc.
What in general is likely to happen as a result of stopping the blood flow to a particular organ? (several stages)
> less oxygen, less glucose/ reduced activity / death

What is the name for a condition due to a blockage in a blood vessel in part of the brain, and what symptoms does it cause?
> stroke > lack of some function,
e.g. paralysis, sensory input, processing e.g.speech

What may result due to a blockage in a blood vessel supplying the retina, in the back of the eye?
> death of (part of) retina, blindness

Heart showing coronary arteries The coronary arteries are fairly small blood vessels on the outside of the heart, receiving oxygenated blood directly from the aorta (main artery).
What (symptoms, name) may be felt as a result of a partially blocked coronary artery?
> chest pains, angina
What (event) may happen as a result of a deterioration in the situation?
> heart attack, death of part of heart muscle (myocardial infarction), strain on heart, death of individual

Heart surgery

If surgery is possible, the chest may be opened and a section of another blood vessel may be inserted to replace the damaged and blocked section of the coronary blood vessel - this is called a coronary by-pass. There are several branches of these blood vessels, so different sections may need to be replaced.
Another technique involves the insertion of a special flexible probe (from the groin!) into the blood vessel, which is then expanded to stretch the blood vessel slightly, or the insertion of a tube to keep the blood vessels from constricting. This "keyhole surgery" has several advantages, involving less trauma to the patient, and after-care is also much cheaper.
The main artery (aorta), being nearest to the heart, may become stretched due to the blood pressure, resulting in an aortic aneurism. Reinforcement of damaged blood vessels with synthetic material may be possible.

Lifestyle effects

With increased age, blood pressure may rise. This may be the cause of a variety of other ill effects on the body. There are various types of drugs available which may be used to reduce the strain on the system - by reducing the effects of the nervous stimulation on the heart, or by reducing the body's fluid content, or by generally opening up blood vessels (vasodilation).

As well as having a number of bad effects on the lungs, smoking has several effects on the heart and blood.
How much greater is the risk of heart disease to a smoker?
> 3 times
Tobacco smoke contains small quantities of carbon monoxide, which combines irreversibly with haemoglobin in the red blood cells.
Normally haemoglobin carries out this function:
oxygen + haemoglobin (reversible reaction) oxy-haemoglobin

However when carbon monoxide is inhaled, the following occurs:
carbon monoxide + haemoglobin (IRREVERSIBLE reaction) carboxy-haemoglobin

What effect will this have on the functioning of the blood system?
> reduces oxygen carrying capacity
On average, our heart beats (pulse rate) 72 times per minute.
How many times is this per day?
> 103,680
Assuming this rate is constant, how many times does the heart beat in a lifetime of, say, 70 years?
> 2.65 x 109

Why is this rate not constant over the years?
> faster when young, slower when old> depends on activity

If we are fit, our heart beats faster when we exercise ourselves.
In what other way can our heart also increase the flow of blood?
> pump greater volume per beat (increased "stroke volume")

List 4 functions performed by our blood under these conditions (exertion).
> provide more oxygen > remove carbon dioxide
> provide more glucose/"food" > remove heat
carry adrenalin to muscles etc
Can you think of any reasons why it has long been thought that the heart is central to a person's emotions, and character?
> speeds up when you get excited
stops when you die!
in middle of chest?

The effects of exercise

People who are physically fit have a lower rate of heart beat than those who are unfit, and although it also speeds up by less under exertion, it also returns more quickly to normal.
Fit people also have a steadier heartbeat than unfit ones.

Use the information above to draw 2 lines, one for a fit and one for an unfit person, to show how their heartbeat is likely to vary minute by minute before, during and after a period of exertion:
Include a key:

fit person

unfit person

blank exercise graph
In what ways does exercise improve the body?

> strengthens heart muscle

> makes heart bigger!

> makes body muscles more efficient

Exercise and oxygen debt

The function of the circulatory system is to provide oxygen for, and to remove carbon dioxide resulting from, respiration inside cells of the body, so the circulating blood contains a certain amount of oxygen, in combination with haemoglobin inside the red cells.
Transfer of this oxygen to the tissues relies on diffusion via tissue fluid, which may be too slow for some activities, such as sprinting. If the (muscle) tissues use up oxygen faster than it can be supplied by the blood, then they may respire anaerobically and a condition known as oxygen debt is built up. The anaerobic respiration is inefficient and results in the production of lactic acid, which must then be transported (in the blood) to the liver for reprocessing. The accumulation of this acid may be the cause of muscle fatigue, and exercise may increase the efficiency of the body in dealing with this.

It is fairly obvious that exertion causes increased breathing, for example when running for a bus.
Why do you continue to breathe deeply and be out of breath even though the activity has ceased?
> oxygen debt must be "repaid" - restoring blood to normal level of oxygenation

Our heart normally varies its output automatically according to our body's requirements. However, it may stop beating, or its rhythm may become erratic if it is damaged, for instance due to a heart attack.
The heart's natural beating may be restarted within a few seconds as a result of cardiac massage, or external blows to the chest, or strong electrical impulses (several hundred volts), perhaps in combination with powerful stimulatory drugs.

Why are these drastic actions performed with such priority, but abandoned so quickly if there is no immediate response?

> it is no use if the brain is dead due to lack of oxygen

If the heart's own speed controlling centre ("pacemaker") is damaged, an artificial electronic pacemaker device may be substituted, but this is unlikely to be able to respond flexibly to increased demands by the body when exercising, for example.


Like other organs, a heart may be removed from the body of a person who has recently died (the donor), and transplanted into somebody whose own heart is failing (the recipient).

However, it is not a simple operation surgically, and there are a number of problems, apart from expense, which is an important consideration in the National Health Service today. It should be realised that a heart transplant is not a large scale life saving operation, as it relies on the death of one person for each operation, and it may merely improve the quality of life for one other, rather ill, person.

Why is it a simpler process to transplant a heart and lungs in combination, than to transplant a heart alone?

> fewer connections - trachea , aorta, venae cavae

In the case of people suffering from cystic fibrosis, the lungs are sometimes damaged due to buildup of thick mucus secretions and a heart+lung transplant may be a possible solution. Surprisingly, the heart of such individuals are often extremely healthy, and may be transplanted on to other individuals!

If the body's defence mechanisms recognise the transplanted organ as "foreign", then it may undergo rejection. In order to counteract this, immunosuppressive drugs may be used.

Tissue typing (like blood groups, but more complex) is carried out to attempt to match up as closely as possible the donor and recipient, but there are many different factors which may cause incompatibility.

What is meant by "the body's defence mechanisms"?

> white cells, etc.

Why are kidney transplants between members of the same family often quite successful?

> shared genes mean less tissue incompatibility

Why are kidney transplants between identical twins usually the most successful?

> identical genes mean no tissue incompatibility

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