EFFECT OF DRUGS AND CHEMICALS ON SALIVARY SECRETION
Substances
which increase salivary secretion
1. Sympathomimetic drugs like
adrenaline and ephedrine.
2. Parasympathomimetic drugs like
acetylcholine, pilocarpine, muscarine and physostigmine.
3. Histamine.
Substances
which decrease salivary secretion
1. Sympathetic depressants like
ergotamine and dibenamine.
2. Parasympathetic depressants like
atropine and scopolamine.
3. Anesthetics such as chloroform and
ether stimulate the secretion of saliva. However, deep anesthesia
decreases the secretion due to central
inhibition.
HYPOSALIVATION
Reduction in the secretion of saliva
is called hyposalivation. It is of two types, namely temporary
hyposalivation and permanent
hyposalivation.
1. Temporary hyposalivation occurs in:
i. Emotional conditions like fear.
ii. Fever.
iii. Dehydration.
2. Permanent hyposalivation occurs in:
i. Sialolithiasis (obstruction of
salivary duct).
ii. Congenital absence or hypoplasia
of salivary glands.
iii. Bell palsy (paralysis of facial
nerve).
HYPERSALIVATION
Excess secretion of saliva is known as
hypersalivation. Physiological condition when hypersalivation occurs is pregnancy.
Hypersalivation in pathological conditions is called ptyalism, sialorrhea,
sialism or sialosis. Hypersalivation occurs in the following pathological conditions:
1. Decay of tooth or neoplasm
(abnormal new growth or tumor) in mouth or tongue due to continuous
irritation of nerve endings in the
mouth.
2. Disease of esophagus, stomach and
intestine.
3. Neurological disorders such as
cerebral palsy, mental retardation, cerebral stroke and parkinsonism.
4. Some psychological and psychiatric
conditions.
5. Nausea and vomiting
OTHER DISORDERS
In addition to hyposalivation and
hypersalivation, salivary secretion is affected by other disorders also,
which include:
1. Xerostomia
2. Drooling
3. Chorda tympani syndrome
4. Paralytic secretion of saliva
5. Augmented secretion of saliva
6. Mumps
7. Sjögren syndrome.
1. Xerostomia
Xerostomia means dry mouth. It is also
called pasties or cottonmouth. It is due to hyposalivation or absence of salivary
secretion (aptyalism).
Causes
i. Dehydration or renal failure.
ii. Sjögren syndrome (see below).
iii. Radiotherapy.
iv. Trauma to salivary gland or their
ducts.
v. Side effect of some drugs like
antihistamines, antidepressants, monoamine oxidase inhibitors,
antiparkinsonian drugs and
antimuscarinic drugs.
vi. Shock.
vii. After smoking marijuana
(psychoactive compound from the plant Cannabis).
Xerostomia causes
difficulties in mastication, swallow ing and speech. It also causes halitosis
(bad breath; exhalation of unpleasant odors).
2. Drooling
Uncontrolled flow of
saliva outside the mouth is called drooling. It is often called ptyalism.
Causes
Drooling occurs because of excess
production of saliva, in association with inability to retain saliva within the
mouth.
Drooling occurs in the following
conditions:
i. During teeth eruption in children.
ii. Upper respiratory tract infection
or nasal allergies
in children.
iii. Difficulty in
swallowing.
iv. Tonsillitis.
v. Peritonsillar abscess.
3. Chorda Tympani
Syndrome
Chorda tympani syndrome is the
condition characterized by sweating while eating. During trauma or surgical procedure,
some of the parasympathetic nerve fibers to salivary glands may be severed. During the
regeneration, some of these nerve fibers, which run along with
chorda tympani
branch of facial nerve may deviate and join with the nerve fibers
supplying sweat glands. When the food is placed in the mouth, salivary secretion
is associated with sweat secretion.
4. Paralytic
Secretion of Saliva
When the parasympathetic nerve to
salivary gland is cut in experimental animals, salivary secretion
increases for first three
weeks and later diminishes; finally it stops at about sixth week. The increased
secretion of saliva after cutting the
parasympathetic nerve fibers is called paralytic secretion. It is
because
of hyperactivity of
sympathetic nerve fibers to salivary glands after cutting the parasympathetic
fibers. These hyperactive sympathetic fibers release large amount of catecholamines,
which induce paralytic secretion. Moreover, the acinar
cells of the salivary glands become hypersensitive to
catecholamines after denervation. The paralytic secretion
does not occur after the sympathetic nerve fibers to salivary
glands are cut.
5. Augmented
Secretion of Saliva
If the nerves supplying salivary
glands are stimulated twice, the amount of saliva secreted by the second
stimulus is more than
the amount secreted by the first stimulus. It is because, the first stimulus
increa ses
excitability of acinar cells, so that
when the second stimulus is applied, the salivary secretion is augmented.
6. Mumps
Mumps is the acute viral infection
affecting the parotid glands. The virus causing this disease is paramyxovirus. It
is common in children who are not immunized. It occurs in adults also.
Features of mumps are puffiness of cheeks (due to swelling of parotid glands), fever,
sore throat and weakness. Mumps affects meninges, gonads and pancreas also.
7. Sjögren
Syndrome
Sjögren syndrome is an autoimmune
disorder in which the immune cells destroy exocrine glands such as
lacrimal glands and salivary glands.
It is named after Henrik Sjögren who discovered it. Common symptoms of this
syndrome are dryness of the mouth due to lack of saliva (xerostomia),
persistent cough and dryness of eyes. In some cases, it causes dryness of skin,
nose and vagina. In severe conditions, the organs like kidneys, lungs, liver,
pancreas, thyroid, blood vessels and brain
are affected.
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