What all is there in
the chest?
S.K. Jindal,
MD (Medicine), FAMS,
FCCP, FNCCP
(Former Professor
& Head, Department of Pulmonary Medicine,
PGIMER, Chandigarh, India)
Medical Director
Jindal Clinics, SCO
21, Sector 20 D, Chandigarh, India 160020
In medical
terminology, the chest (or the thorax) comprises of a bony-cage which contains
the two lungs, the heart along with the other structures in the mediastinum,
which is the space between the two lungs.
The
bony-cage is the major part of the chest-wall.
It includes twelve ribs on each side attached to the sternum (i.e. the
breast-bone) in the front and to the spine (the vertebrae) at the back. Inferiorly, the chest is separated from the
abdomen by the two diaphragms, while superiorly, the thoracic cage is bound by
the first rib and the clavicle on each side.
The thoracic cage is supported by a number of inter-costal and vertebral
muscles. The inside of the chest wall is
lined by a smooth membrane – the parietal pleurae. Similarly, the lungs on the outside are lined
by visceral pleurae. The parietal and
visceral pleurae together form a potential space between them i.e. the pleurae
cavity.
The
mediastinum is the central part of thorax between the two lungs on each
side. Mediastinum is continuous with the
structures in the neck above and with the abdominal structures below through
different openings. Mediastinum contains
the heart along with the major vessels (aorta and main pulmonary arteries), esophagus
(food pipe), several nerves, lymphatics and lymph nodes.
The lungs
have the following important components:
1. Tracheo-bronchial
tree: The air tubes which conduct
air (from outside atmosphere) through the nose and the mouth to the interior of
the lungs – the alveoli.
2. Alveoli: These are the tiny, bubble like structures
which contain the air and constitute the main gas-exchange areas in the lungs.
3. Lung interstitium: This consists of spaces between
the alveoli, contains pulmonary capillaries, nerves, lymphatics, collagen and
loose areolar tissues,.
Involvement in diseases
Different
diseases are known to involve different parts of lungs or the respiratory
system. There however is no strict
compartmentalization. A disease which
starts in one part can also involve the other part. Based on the principal site of involvement,
the diseases are broadly classified as follows:
1. Diseases
of trachea-bronchial tree – asthma, chronic bronchitis, tracheitis and
laryngitis, chronic obstructive lung disease, bronchiectasis, bronchiolitis,
tumours.
2. Alveolar diseases: Pneumonias, alveolar proteinosis,
tuberculosis
3. Interstitial diseases: Interstitial lung
diseases e.g. pulmonary fibrosis, sarcoidosis, hypersensitive pneumonia,
tuberculosis and others
4. Pleural diseases: Pleural effusions, pneumothorax,
emphysemas; pleural tumours.
5. Mediastinal diseases: Tumours, sarcoidosis,
tuberculosis
6. Pulmonary vascular diseases – Pulmonary hypertension; vasculitis
7. Diseases of respiratory control system: Sleep apnoea
syndrome and other ventilator control diseases.
The
classification given above is meant to give a broad, general idea. A host of systemic diseases as well as the
diseases of other organs (e.g. cardiac, renal or neurological diseases) can
also involve the lungs. Moreover, the
list of diseases is not complete.
There are
many other diseases which may be relatively uncommon, but not unknown. Each disease and each patient have different
characteristics which need to be kept in mind.
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