Ross & Wilson Anatomy and Physiology in Health and Illness (117 page)

Learning outcomes

After studying this section, you should be able to:

describe the main inflammatory and infectious disorders of the upper respiratory tract

outline the main tumours of the upper respiratory tract.

Infectious and inflammatory disorders

Inflammation of the upper respiratory tract can be caused by inhaling irritants, such as cigarette smoke or air pollutants, but is commonly due to infection. Such infections are usually caused by viruses that lower the resistance of the respiratory tract to other infections. This allows bacteria to invade the tissues. Such infections are a threat to life only if they spread to the lungs or other organs, or if inflammatory swelling and exudate block the airway.

Pathogens are usually spread by droplet infection, in dust or by contaminated equipment and dressings. If not completely resolved, acute infection may become chronic.

Viral infections cause acute inflammation of mucous membrane, leading to tissue congestion and profuse exudate of watery fluid. Secondary infection by bacteria usually results in purulent discharge.

Viral infections commonly cause severe illness and sometimes death in infants, young children and the elderly.

Common cold and influenza

The common cold (coryza) is usually caused by the rhinoviruses and is a highly infectious, normally mild illness characterised mainly by a runny nose (rhinorrhoea), sneezing, sore throat and sometimes slight fever. Normally a cold runs its course over a few days. Influenza is caused by a different group of viruses and produces far more severe symptoms than a cold, including very high temperatures and muscle pains; complete recovery can take weeks and secondary bacterial infections are more common than with a simple cold. In adults, most strains of influenza are incapacitating but rarely fatal unless infection spreads to the lungs.

Sinusitis

This is usually caused by spread of microbes from the nose and pharynx to the mucous membrane lining the paranasal sinuses. The primary viral infection is usually followed by bacterial infection. The congested mucosa may block the openings between the nose and the sinuses, preventing drainage of mucopurulent discharge. Symptoms include facial pain and headache. If there are repeated attacks or if recovery is not complete, the infection may become chronic.

Tonsillitis

Viruses and
Streptococcus pyogenes
are common causes of inflammation of the palatine tonsils, palatine arches and walls of the pharynx. Severe infection may lead to suppuration and abscess formation (
quinsy
). Occasionally the infection spreads into the neck causing cellulitis. Following acute tonsillitis, swelling subsides and the tonsil returns to normal but repeated infection may lead to chronic inflammation, fibrosis and permanent enlargement. Endotoxins from tonsillitis caused by
Streptococcus pyogenes
are associated with the development of rheumatic fever (
p. 121
) and glomerulonephritis (
p. 343
). Repeated infection of the nasopharyngeal tonsil (adenoids,
Fig. 10.3
) can leave them enlarged and fibrotic, and can cause airway obstruction, especially in children.

Pharyngitis, laryngitis and tracheitis

The pharynx, larynx and trachea may become infected secondary to other upper respiratory tract infections, e.g. the common cold or tonsillitis

Laryngotracheobronchitis
(croup in children) is a rare but serious complication of upper respiratory tract infections. The airway is obstructed by marked swelling around the larynx and epiglottis, accompanied by wheeze and breathlessness (dyspnoea).

Diphtheria

This is a bacterial infection of the pharynx, caused by
Corynebacterium diphtheriae
, which may extend to the nasopharynx and trachea. A thick fibrous membrane forms over the area and may obstruct the airway. Powerful exotoxins may severely damage cardiac and skeletal muscle, the liver, kidneys and adrenal glands. Where immunisation is widespread, diphtheria is rare.

Hay fever (allergic rhinitis)

In this condition,
atopic
(‘immediate’) hypersensitivity (
p. 374
) develops to foreign proteins (antigens), e.g. pollen, mites in pillow feathers, animal dander. The acute inflammation of nasal mucosa and conjunctiva causes
rhinorrhoea
(excessive watery exudate from the nose), redness of the eyes and excessive secretion of tears. Atopic hypersensitivity tends to run in families, but no genetic factor has yet been identified. Other forms of atopic hypersensitivity include:

•
childhood onset asthma (see below)

•
eczema (
p. 362
) in infants and young children

•
food allergies.

Tumours

Malignant disease of the nose, sinuses, nasopharynx and larynx is relatively rare.

Benign (haemangiomata)

These occur in the nasal septum. They consist of abnormal proliferations of blood vessels interspersed with collagen fibres of irregular size and arrangement. The blood vessels tend to rupture and cause persistent bleeding (epistaxis).

Obstructive lung disorders

Learning outcomes

After studying this section, you should be able to:

compare the causes and pathology of chronic and acute bronchitis

discuss the pathologies of the main forms of emphysema

discuss the causes and disordered physiology of asthma

explain the main physiological abnormality in bronchiectasis

describe the effect of cystic fibrosis on lung function.