drugs which dissolve
clots associated with
and can prevent damage
to the heart following
such an event. Are best
used within one hour of
THE RESPIRATORY SYSTEM 235
The key symptom of angina is similar to that of an MI. It is a central chest
pain that may radiate to the left shoulder, jaw, arm or other areas of the
chest. Some patients may confuse arm or shoulder pain with arthritis or
indigestion pain. It is a temporary condition, which occurs when the heart
muscle needs more oxygen than can be provided by the heart arteries. It
is frequently precipitated by exertion or stress. It may result from three
- atheromatous lesions of the coronary arteries, reducing their diameter and
limiting the blood flow through them;
- vasospasm of the coronary arteries, resulting in a temporary reduction in
- a combination of 1. and 2.
Classic angina is associated with high levels of atheroma in the coronary
arteries and occurs when blood flow does not meet the needs of the heart
muscle. Physical exertion, emotional stress and exposure to cold are among
the triggers for this type of angina. A second type of angina, known as variant
angina, results from the coronary arteries going into spasm. This results
in significant reductions in the diameter of the arteries and reduced blood
flow through them. This effect may be exacerbated by the reductions in the
normal diameter of the arteries as a result of atheroma. Unlike classic angina,
variant angina typically occurs during rest and may occur at night. What
causes the coronary arteries to go into spasm is not fully understood. It may
involve sympathetic nervous system activity or problems in the calcium
processes involved in the firing of neurons.
The respiratory system
The respiratory system delivers oxygen to and removes carbon dioxide from
the blood. The exchange of oxygen and carbon dioxide occurs in the lungs.
The system comprises:
n the upper respiratory tract, including the nose, mouth, larynx and trachea;
n the lower respiratory tract, including the lungs, bronchi, bronchioles
and alveoli. Each lung is divided into upper and lower lobes – the upper
lobe of the right lung contains a third subdivision known as the right
The bronchi carry air from the mouth to the lungs. As they enter the lungs,
they divide into smaller bronchi, then into smaller tubes called bronchioles
(see Figure 8.9). The bronchioles contain minute hairs called cilia, which beat
rhythmically to sweep debris out of the lungs towards the pharynx for expulsion
and thus form part of the mechanical element of the immune system –
see earlier in the chapter. Bronchioles end in air sacs called alveoli – small,
thin-walled ‘balloons’, which are surrounded by tiny blood capillaries. As we
breathe in, the concentration of oxygen is greater in the alveoli than in the
severe pain in the
chest associated with
a temporary insufficient
supply of blood to the
a situation in which the
muscles of artery walls
in the heart contract and
relax rapidly, resulting in
a reduction of the flow of
blood through the artery.
236 CHAPTER 8 • THE BODY IN HEALTH AND ILLNESS
haemoglobin in the blood travelling through the capillaries. As a result,
oxygen diffuses across the alveolar walls into the haemoglobin. As we
breathe out, carbon dioxide concentration in the blood is greater than that in
the alveoli, so it passes from the blood into the alveoli and is then exhaled.
Respiration is the act of breathing:
n Inspiration: two sets of muscles are involved in inhalation. The main
muscle involved is the diaphragm. This is a sheet of muscle that divides the
abdomen and is found immediately below the lungs. Contraction of this
muscle pulls the lungs down and sucks air into them. The second set of
muscles is known as the intercostal muscles. These are found between the
ribs and can expand the chest – again pulling air into the lungs.
n Expiration: relaxation of the diaphragm and intercostal muscles allows
the lungs to contract, decreases lung volume, and pushes air out of them.
The air then passively flows out.
The rate of breathing is controlled by respiratory centres in the brainstem.
These respond to:
n the concentration of carbon dioxide in the blood (high carbon dioxide
concentrations initiate deeper, more rapid breathing);
n air pressure in lung tissue. Expansion of the lungs stimulates nerve receptors
to signal the brain to ‘turn off’ inspiration. When the lungs collapse,
the receptors give the ‘turn on’ signal, known as the Hering-Breuer
Other automatic regulators include increases in blood pressure, which slows
down respiration, a fall in blood acidity, which stimulates respiration, and
a sudden drop in blood pressure, which increases the rate and depth of
Figure 8.9 Diagram of the lungs, showing the bronchi, bronchioles and alveoli.
THE RESPIRATORY SYSTEM 237
Matthews, K.A., Katholi, C.R., McCreath, H., Whoolry, M.A., Williamson, D.R., Zhu, S. and
Markovitz, J.H. (2004). Blood pressure reactivity to psychological stress predicts hypertension in the
CARDIA study. Circulation, 110: 74–8.
This paper considered whether blood pressure reactivity predicted long-term hypertension.
The team used a longitudinal method, measuring blood pressure reactivity at one point in
time and hypertension up to 13 years later to see whether these initial measures were predictive
of later levels of blood pressure. They hypothesised that high levels of blood pressure
increases in response to psychological stress measured at baseline would be predictive of
resting blood pressure when measured later.
The CARDIA study is a longitudinal study, initially, of 5,115 black and white men and
women recruited in various parts of the USA. They were aged between 18 and 30 at baseline.
Two years into the study, their blood pressure reactivity was measured by comparing blood
pressure at rest and during ‘stressful’ tasks. At this time, 4,624 participants were still in the
study. Of these, 422 participants did not take part in the reactivity study. Accordingly, the
study sample comprised 4,202 people, all of whom had normal blood pressures at baseline.
Subsequent measures of blood pressure were taken three, five, eight and thirteen years
following these initial measures. The study investigated whether levels of blood pressure and
the development of hypertension over the period of the study could be predicted by the level
of blood pressure reactivity at baseline.
Resting blood pressure on each occasion was measured using a mercury sphygmomanometer.
Three measurements were taken at one-minute intervals, and the last two were averaged to
form the reported resting blood pressure.
At baseline, this measure was added to by blood pressure readings during three stress tests.
The testing period involved an eight-minute baseline period during which the participants sat
quietly, followed by three tasks:
- a three-minute video game (Atari’s Breakout – a state-of-the-art game when the baseline
data were gathered);
- a three-minute star-tracing task – participants had to trace the image of a star while
looking at their drawing through a mirror;
- a cold pressor task – involved placing a hand in cold water for 45 seconds.
The tasks appeared in a random order. Blood pressure was measured using an automated
blood pressure machine at one-minute intervals during the baseline period and the first two
tasks and was measured once during the cold pressor task (the paper does not specify when).
Blood pressure reactivity was calculated by subtracting the average of the final three baseline
readings from the average pressure during each task.
Participants averaged 27 years of age at the time of testing. The results were considered in
terms of ethnic group and gender:
n Blacks had greater increases in DBP during the video game and cold pressor tasks than whites.
n Men had greater increases in DBP than women during the cold pressor and star-tracing
task and larger increases in SBP during the video game and star-tracing task.
238 CHAPTER 8 • THE BODY IN HEALTH AND ILLNESS
Diseases of the respiratory system
n Chronic obstructive airways disease
Chronic obstructive airways disease (COAD) is a group of lung diseases
characterised by limited airflow through the airways resulting from damage
to the alveoli. Its most common manifestations are emphysema and chronic
bronchitis. The leading cause of both conditions is smoking. Prolonged
tobacco use causes lung inflammation and variable degrees of destruction of
the alveloli. Chronic bronchitis results from inflammation and a consequent
narrowing of the airways. Emphysema results from the destruction of the
alveoli, resulting in reduced lung elasticity and reductions in the surface area
on which the exchange of oxygen and carbon dioxide can occur. Both result
in significant and long-term shortness of breath, an unproductive cough
(which produces no phlegm), and a marked reduction in exercise capacity.
Severe cases of each condition may require the affected individual to be on a
constant supply of oxygen.
The conditions result from exposing the alveoli to irritants, whether as
a result of direct or passive smoking or living or working in a polluted
environment. About 15 percent of long-term smokers will develop COAD
(Mannino 2003). More rarely, an enzyme deficiency called alpha-1 antitrypsin
deficiency can cause emphysema in non-smokers.
n Lung cancer
Lung cancer is the second most common cancer affecting both sexes. As
women have taken up smoking following the Second World War, rates of
n When risk for hypertension over time was assessed, the main predictors were being older
at the time of testing, being less well educated, having a higher body mass index and higher
resting SBP or DBP. However, greater changes in SBP and DBP during all tasks added
significantly to the regression equations used to predict whether or not participants were
hypertensive at each subsequent assessment time.
n The relationship between reactivity and subsequent measures of blood pressure differed
according to race, gender and task.
n Reactivity to the cold pressor tasks predicted earlier raised SBP most strongly in white
n Reactivity to the video game predicted earlier raised DBP in both black and white men, but
These data suggest that blood pressure reactivity during a stressful task increases risk for the
development of hypertension. However, the authors note that the mechanism through which
this process occurs is not understood. It should also be noted that the effects were quite small
and specific. The effect of blood pressure reactivity on subsequent levels of blood pressure
may be significant, but among all the other potential influences on blood pressure such as
smoking and salt intake, it cannot be considered a strong effect.
a persistent airway
with combinations of
chronic bronchitis, small
airways disease, asthma
a late effect of chronic
infection or irritation
of the bronchial tubes.
When the bronchi
become irritated, some
of the airways may be
obstructed or the walls
of the tiny air spaces
may tear, trapping air in
the lung beyond them.
As a result, the lungs
may become enlarged,
at the same time
efficient in exchanging
oxygen for carbon
THE RESPIRATORY SYSTEM 239
lung cancer among this group have risen, while those among men have fallen
(Tyczynski, Bray, Aareleid et al. 2004). Key risk factors for lung cancer
n exposure to carcinogens, including asbestos and radon.
Two different types of lung cancer have been identified:
- Small cell cancer. The main treatment is chemotherapy. The overall
survival depends on the stage of the disease. For limited-stage small cell
cancer, cure rates may be as high as 25 percent, while cure rates for
extensive-stage disease are less than 5 percent.
- Non-small cell cancer (between 70 and 80 percent of cases). The main
treatment for this type of cancer involves removal of the cancer through
surgery. Where the tumour is small and has not spread, up to 50 percent
of people with the condition may survive. The prognosis is worse the
larger the tumour. Where the tumour has spread and lymph nodes are
involved, the disease is almost never cured, and the goals of therapy are to
extend life and improve quality of life (Beadsmoore and Screaton 2003).
IN THE SPOTLIGHT
Snoring – a health warning