Ross & Wilson Anatomy and Physiology in Health and Illness (9 page)

BOOK: Ross & Wilson Anatomy and Physiology in Health and Illness

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In order to understand the specific diseases described in later chapters, knowledge of the relevant anatomy and physiology is necessary, as well as familiarity with the pathological processes outlined below.

There are many different illnesses, disorders and diseases, which vary from minor, but often very troublesome conditions, to the very serious. The study of abnormalities can be made much easier when a systematic approach is adopted. In order to achieve this in later chapters where specific diseases are explained, the headings shown in
Box 1.3
will be used as a guide. Causes (
aetiology
) are outlined first when there are clear links between them and the effects of the abnormality (
pathogenesis
).

Box 1.3
Suggested framework for understanding diseases

Aetiology:
cause of the disease

Pathogenesis:
the nature of the disease process and its effect on normal body functioning

Complications:
other consequences which might arise if the disease progresses

Prognosis:
the likely outcome

Aetiology

Diseases are usually caused by one or more of a limited number of mechanisms that may include:

•
genetic abnormalities, either inherited or acquired

•
infection by micro-organisms, e.g. bacteria, viruses, microbes or parasites, e.g. worms

•
chemicals

•
ionising radiation

•
physical trauma

•
degeneration, e.g. excessive use or ageing.

In some diseases more than one of the aetiological factors listed above is involved, while in others, no specific cause has been identified and these may be described as
essential
,
idiopathic
or
spontaneous
. Although the precise cause of a disease may not be known,
predisposing
(
risk
)
factors
are usually identifiable.
Iatrogenic
conditions are those that result from healthcare interventions.

Pathogenesis

The main processes causing illness or disease are out-lined below.
Box 1.4
contains a glossary of disease-associated terminology.

Box 1.4
Glossary of terminology associated with disease

Acute:
a disease with sudden onset often requiring urgent treatment (compare with chronic).

Acquired:
a disorder which develops any time after birth (compare with congenital).

Chronic:
a long-standing disorder which cannot usually be cured (compare with acute).

Congenital:
a disorder which one is born with (compare with acquired).

Sign:
an abnormality seen or measured by people other than the patient.

Symptom:
an abnormality described by the patient.

Syndrome:
a collection of signs and symptoms which tend to occur together.

Inflammation

(
p. 367
) – this is a tissue response to any kind of tissue damage such as trauma or infection. Inflammatory conditions are recognised by the suffix -itis, e.g. appendicitis.

Tumours

(
p. 49
) – these arise when abnormal cells escape body surveillance and proliferate. The rate of their production exceeds that of normal cell death causing a mass to develop. Tumours are recognised by the suffix -oma, e.g. carcinoma.

Abnormal immune mechanisms

(
p. 374
) – these are responses of the normally protective immune system that cause undesirable effects.

Thrombosis, embolism and infarction

(
p. 111
) – these are the effects and consequences of abnormal changes in the blood and/or blood vessel walls.

Degeneration

– this is often associated with normal ageing but may also arise prematurely when structures deteriorate causing impaired function.

Metabolic abnormalities

– these cause undesirable metabolic effects, e.g. diabetes mellitus,
page 227
.

Genetic abnormalities

– these may be either inherited (e.g. phenylketonuria,
p. 435
) or caused by environmental factors such as exposure to ionising radiation (
p. 49
).