View source for 1. Disorders of chewing, swallowing and esophagus functions – the gastro-esophageal reflux disease.

== Salivation and chewing ==
Food is processed in the oral cavity by breaking it into smaller pieces by chewing and by mixing it with saliva and digestive enzymes. This forms a ''bolus'' which then gets into the stomach by swallowing. Proper oral preparation of food is essential also for digestion and absorption of food in the intestines.

We produce around 1.5L of saliva every day. Carbohydrate digestion begins already in the oral cavity with the amylase enzyme that is found in the saliva. Some heavy metals and urea are excreted through the saliva.

The saliva contains antibodies and anti-microbial molecules that contribute to the prevention of dental caries and oral infection.

Dry mouth (Xerostomy) may develop in

* in Sjögren syndrome – where salivary glands are destroyed by autoimmunity
* in vitamin A deficiency
* Sialadenitis, Sialolithiasis
* Increased sympathetic tone (During a stressfull oral exam)
* Patients who breath exclusively through the mouth

Problems with salivation impair bolus formation and makes swallowing more difficult. It also causes dry oral mucosa, which is easily damaged, and increased risk for infection.

Hypersalivation can either be caused by increased production or decreased clearance of saliva.

Salivation is under control of the autonomic nervous system, so increased parasympathetic tone, as seen in for example organophosphate poisoning or parasympathomimetic administration will increase production. Increased production also occurs in local inflammatory processes like oral ulcers and oral infections. Any condition that makes it hard or painful to swallow will cause hypersalivation by decreased clearance, like tonsillitis, epiglottitis, problems with the jaw or neurological problems like Parkinson’s, ALS or stroke.

Chewing is more essential for proper preparation of food. Without proper mastication will it be impossible to swallow many foods. Problems with chewing can therefore elicit a state that corresponds to starvation.

''Trismus'', also called lockjaw, is the condition where there the masseteric muscles spasm so that the jaw can’t open properly. It can occur in epilepsy, rabies, tetanus but most frequently in pharyngitis or tonsillitis.

Other causes of impaired chewing include jaw trauma, aphthous stomatitis, tumors and dental disorders like imperfect dentures. These conditions may cause problems with maintaining proper oral hygiene resulting in changes of oral bacterium flora and increased risk of various infections.

=== Swallowing ===
Swallowing is a coordinated function of the pharynx, larynx and oesophagus. The oesophagus moves the food into the stomach with peristaltic movements. Dysphagia (impaired swallowing) doesn’t just cause a starvation-like state but also may cause aspiration of food. It can also cause oesophagitis which can spread to the mediastinum, causing acute mediastinitis. We divide dysphagias into two types: organic dysphagia and functional dysphagia.

Organic dysphagia may be caused by oesophageal ulcers, strictures, scars, scleroderma or tumors. This type of dysphagia mainly affects swallowing of solid food, because the problem mainly occurs from obstruction in the oesophagus upon swallowing.

Functional dysphagia affects both solid and fluid food and occurs because swallowing is difficult or painful. Painful swallowing is called ''odynophagia''. It can be caused by:

* Achalasia, a disorder of the oesophageal motility where the peristaltic movements is impaired, and the lower oesophageal sphincter can’t relax properly. The stagnating food remains in the oesophagus, causing inflammation and pain
* Diffuse oesophageal spasm is a condition where the oesophageal contractions are uncoordinated
* Nutcracker oesophagus, also called hypertensive peristalsis, is a condition where the oesophageal contractions are coordinated but have excessive amplitude
* Gastro-oesophageal reflux disease
* Diaphragmatic hernia in cases where the lower oesophageal sphincter, which is usually situated below the diaphragm, is dislocated into the thoracic cavity

== Gastro-oesophageal reflux disease ==
Gastro-oesophageal reflux disease, also called GERD, is a condition where excessive amounts of gastric juice refluxes into the oesophagus because the lower oesophageal sphincter doesn’t close properly. This causes a burning sensation in the chest called heart burn and dysphagia. Oesophagitis may occur.

Some reflux is normal even in healthy people, and the oesophagus has defence mechanisms against the acid. GERD occurs only when these defence mechanisms are overloaded, so that the oesophagus is exposed to acid reflux over prolonged periods and may be damaged.

GERD predisposes to metaplasia in the oesophagus, so-called Barrett’s oesophagus. If acid reaches the upper parts of the oesophagus can chronic laryngitis and tracheobronchitis occur.
[[Category:Pathophysiology 2]]