Ross & Wilson Anatomy and Physiology in Health and Illness (146 page)

•
the urine (ketonuria)

•
the lungs, giving the breath a characteristic sweet smell of acetone or ‘pear drops’.

In ketosis, compensation is required to maintain acid– base balance. This is achieved by buffer systems that excrete excess acid (hydrogen ions) by the lungs, through hyperventilation, or kidneys. In health, ketosis is self-limiting and ketone body production stops when fasting or exercise ceases. Ketoacidosis is associated with uncontrolled type 1 diabetes mellitus (
p. 227
).

Glycerol and energy release (
Fig. 12.44
)

The body converts glycerol from the degradation of fats into one of the intermediary compounds produced during glycolysis, and in this form it enters the central metabolic pathways.

Diseases of the mouth

Learning outcomes

After studying this section, you should be able to:

discuss the main inflammatory and infectious conditions of the mouth

outline the sites and effects of oral squamous cell carcinoma

distinguish between cleft lip and cleft palate, including describing the anatomical abnormalities involved.

Inflammatory and infectious conditions

Injury may be caused to tissues in and around the mouth by food and other ingested substances, if they are corrosive, abrasive or excessively hot or cold. Corrosive chemicals are the most likely to cause serious tissue damage and acute inflammation. The mouth contains a large number and variety of micro-organisms. The antibacterial action of saliva helps to limit their growth, but the presence of plaque and residual foodstuffs, especially sugars, in the mouth can promote infection. Inflammation of the mouth is known as
stomatitis
, and inflammation of the gums as
gingivitis
.

Thrush (oral candidiasis)

This acute fungal infection of the epithelium of the mouth is caused by the yeast
Candida albicans
, which grows in white patches on the tongue and oral mucosa. In adults it causes opportunistic infection mainly in debilitated people and in those whose immunity is lowered by, e.g., steroids, antibiotics or cytotoxic drugs. In babies it may be a severe infection, sometimes causing epidemics in nurseries by cross-infection. It occurs most commonly in bottle-fed babies.
Chronic thrush
may develop, affecting the roof of the mouth in people who wear dentures. The fungus survives in fine grooves on the upper surface of the denture and repeatedly reinfects the oral mucosa.

Angular cheilitis

Painful cracks develop in folds of tissue at the corners of the mouth, usually in elderly debilitated people, especially if they do not wear their dentures and the folds remain moist. Common causal organisms are
Candida albicans
and
Staphylococcus aureus
.

Dietary deficiency of iron and B group vitamins predispose to this condition.

Gingivitis

This is inflammation of the gums, which may be acute or chronic.

Acute gingivitis

This is a rare condition previously known as Vincent’s infection, in which there is severe inflammation that mainly affects the gums. It is caused by two commensal organisms acting together,
Borrelia vincenti
and a fusiform bacillus. Both organisms may be present in the mouth but only cause the condition in the presence of malnutrition, debilitating disease, poor oral hygiene or injury caused by previous infection.

Chronic gingivitis

This common inflammatory condition occurs in response to accumulation of bacterial plaque around the teeth. It causes bleeding gums and gradually destroys the tissues that support the teeth, which eventually loosen and may fall out.

Aphthous stomatitis (recurrent oral ulceration)

This common condition features extremely painful ulcers that occur singly or in crops inside the mouth. The cause is unknown.

Viral infections

Acute herpetic gingivostomatitis

Inflammation of the mouth and gums is caused by
Herpes simplex
virus and is the most common oral virus infection. It is characterised by extensive and very painful ulceration.

Secondary or recurrent herpes lesions (cold sores)

Lesions, caused by
Herpes simplex
virus, occur round the nose and on the lips. After an outbreak the viruses remain dormant within the cells. Later outbreaks, usually at the same site, are precipitated by a variety of stimuli including exposure to UV rays (strong sunlight) and impaired immune response in, for example, old age.

Tumours of the mouth

Squamous cell carcinoma

This is the most common type of malignant tumour in the mouth. It affects mainly elderly people and carries a poor prognosis. The usual sites are the lower lip and the edge of the tongue. Ulceration occurs frequently and there is early spread to surrounding tissues and cervical lymph nodes.

Congenital disorders

Cleft palate and cleft lip (harelip)

During embryonic development, the roof of the mouth (hard palate) develops as two separate (right and left) halves; this occurs from the lips anteriorly to the uvula posteriorly. Before birth, these two halves normally fuse along the midline. If fusion is incomplete, a cleft (division) occurs, which may be very minor, or it may be substantial.
Cleft lip
(
Fig. 12.45B
) ranges from a minor notch in the upper lip to a more extensive condition when the lip is completely split in one or two places and the nose is involved. In
cleft palate
, there is a gap between the two halves of the palate, which creates a channel of communication between the mouth and the nasal cavity (
Fig. 12.45C
). Factors believed to play a causative part in these conditions include genetic abnormalities, and fetal exposure to factors such as hypoxia, certain drugs or poor nutrition, between weeks 7 and 10 of pregnancy.

Figure 12.45 
Cleft lip and cleft palate: A.
Normal hard palate.
B.
Cleft lip.
C.
Cleft palate.

Drinking, eating and development of speech cannot take place normally until the defect has been surgically repaired.

Dental caries

Tooth decay starts with discolouration and then formation of cavities (caries). It arises when bacteria present in plaque on the teeth act on sugars forming acid, which may eventually destroy the hard parts of the teeth. The condition can be prevented by good oral hygiene.

Diseases of the pharynx

See tonsillitis and diphtheria (
p. 254
).

Diseases of salivary glands