Chewing & Swallowing

SWALLOWING

• There are three stages

• Oral

• Pharyngeal

• Oesophageal

Assessing the Oral cavity

cavities

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Salivary Glands FUNCTIONS Lubrication •Thins and dilutes food for swallowing •Anti acid function, buffers and neutralises acids, particularly important when there are acids of bacterial origin present •Bacteriostatic Bacteriolytic action on endogenous bacteria •Digestive: Amylase (Lipase)

Mucous cellsgastric acid can cause chronic cellular damage and eventually

gastric erosions or ulcers.

• Mucous provides a protective mucosal barrier against the acid content of gastric juice and the proteolytic enzymes in gastric juice. The surface epithelium of the stomach has tight junctions which, with the addition of the thick mucous layer, prevents damage to the mucosa.

• The secretion of mucous is regulated by the actions of local hormones such as prostaglandin. If the mucous layer is damaged or reduced cellular damage can occur.

• Aspirin, alcohol and an excess of gastric acid can cause chronic cellular damage and eventually gastric erosions or ulcers

Cranial Nerves in Chewing & Swallowing

CN V -- Trigeminal - sensory and motor fibres that innervate the face - important in chewing located at the level of the pons

CN VII -- Facial - sensory and motor fibres important for sensation of oropharynx & taste to anterior 2/3 of tongue

CN IX -- Glossopharyngeal

- sensory and motor fibres important for taste to posterior tongue, sensory and motor functions of the pharynx

CN X -- Vagus - sensory and motor fibres important for taste to oropharynx, and sensation and motor function to larynx and laryngopharynx. - important for airway protection

• CN XII -- Hypoglossal - motor fibres that primarily innervate the tongue

Swallowing

3. Throat muscles squeeze food down

2. Soft palate seals Nose

4. Vocal cords close

5. Oesophagus opens

Vocal cords

• Airway function requires that the vocal cords move away from each other when air is flowing into the lungs, while voice production requires the vocal cords to move toward each other when air is flowing out of the lung.

• The intact vocal cords can perform these dual functions of airway and voice production because they can automatically open and close the airway as needed.

• If the vocal cords cannot move away, the patient will have difficulty breathing but can speak. On the other hand, if the vocal cord(s) cannot come together, the patient can breathe but may not be able to speak.

Oesophagus

• The oesophagus is a muscular tube that carries the food from the back of the throat to the stomach. It must contract in a very co-ordinated fashion so we don't regurgitate our food or feel that our meals are sticking as we swallow.

• It is inflammation within the oesophagus that gives the sensation of heartburn.

© UWCM/SONMS/nutrition/MJohn

Food chunks up here and amylase continues to work until food drops into the stomach

The swallowing centre controls the contraction of several muscles

• The soft palate closes off the nasopharynx (levator & tensor palati muscles- interestingly, these muscles also open the Eustachian tube which helps to relieve discomfort in the ears when swallowing)

• The vocal cords of the larynx are moved up and forward to causing the epiglottis to close over the glottis (to protect the respiratory tract)

• This also widens to space available for the bolus• Pharyngeal muscles also produce peristaltic action.• It takes around 4-8 seconds for food to enter the upper

oesophagus. Reflexes then conveyed by the vagus and myenteric nerves produce peristaltic action in skeletal and smooth muscle. These contractions propel the bolus towards the stomach

Stage 1- to chew – to masticate• The is triggered by both the presence of food in the mouth & by

voluntary control

• Contraction of a group of muscles allows us to masticate food. These include muscles of the lips, lower jaw, cheek and the tongue. These muscles create exceptional pressure forces: this can rise to as much as 75 mmhg or 10kPa (Rutishauser 1996)

• The aim of chewing is to mix food with saliva and to make a bolus. This helps both digestion of food and swallowing.

• The stimulus for saliva secretion comes from the saliva centre (located between the medulla and the pons). Parasympathetic nerves increase the activity of the centre; while sympathetic nerves decrease the firing rate of this centre. Higher brain centres such as smell, vision, hearing and thought also bring about saliva release. Reflexes from the stomach and the small intestine also increase salivation (part of the Gastro-colic reflex).

Stage 2 and stage 3–Deglutition• First the pharyngeal stage

• This is a reflex action

• What is a reflex action

• When food is swallowed, it enters the throat (oropharynx) and then the laryngopharynx.

Swallowing starts off as a voluntary action. This involves pushing the food to the back of the mouth into the oropharynx. The tongue is used to move the food backwards. The swallowing reflex starts as food enters the back of the mouth. This stimulates receptors situated around the pharynx, the soft palate, the tonsils, the epiglottis and the base of the tongue. These receptors further stimulate cells of the medulla (swallowing centre).

COMMON SWALLOWING PROBLEMS

Pocketing or pooling of food in the oral cavity

Poor tongue control or tongue thrusting

Coughing before or after swallowing Choking

Excessive secretions, drooling or food lost from mouth

Wet-sounding or gurgly voice after eating or drinking

Pneumonia or elevated temperature

Regurgitation of material through nose, mouth or tracheotomy tube

Inadequate intake of food or fluid; weight loss

Excessive eating time, Mealtime resistance—clenching of teeth, pushing away of food, clutching throat, etc.

Dysphagia• Emotional tension can cause the cricopharyngeal

muscle may go into spasm. This gives the sensation of a lump in the throat even though the swallow reflex if intact.

• Oesophageal cancer or peptic ulcer may cause obstruction, through growths or inflammation. This can cause both increased peristalsis (leading to chest pain) and obstruction to the bolus - dysphagia.

• Disruption of cranial nerve activity through brain haemorrhage, or trauma such as head injury or stroke may disrupt the co-ordination of the reflex.

Oral PhaseProblems of weakness of the lips, tongue and cheeks due to stroke, or degenerative neurological conditions can cause problems keeping food in the mouth.

• Disorders prevent an individual from organising the food into a well-formed bolus and moving it posteriorly in the mouth.

•If there is specific unilateral cheek (buccal) weakness, food can enter a pocket in one cheek making eating unsafe.

•Problems with xerostomia (dry mouth) such as after radiation therapy can result in difficulty breaking down solids and difficulty swallowing them smoothly through the hypopharynx.

Pharyngeal PhaseThe most common problems that occur in the

pharyngeal phase can be categorized into problems of timing and weakness.

Problems with timing usually occur in patients with neurological deficits. In such persons, the swallow reflex does not trigger effectively enough for the larynx to be protected beneath the epiglottis.

= penetration or aspiration of food or liquids.

Aspiration of foodsWhen the food passes through the vocal folds the patient

may cough in an attempt to expel the dangerous food particles from the airway.

If the cough response is diminished, aspiration may occur without warning. This is referred to as "silent aspiration".

Silent aspiration is very dangerous & may result in aspiration pneumonia or even death.

A trained swallowing specialist does not rely on the presence of coughing alone when assessing the patient’s swallowing function & further diagnostic testing, such as Video Fluoroscopy (a modified barium swallow) may be needed

Oesophageal PhaseDifficulties due to problems with oesophageal

peristalsis -tumour, or stricture.

A tumour in the oesophagus or a stricture from reflux or chemical injury can cause a mechanical obstruction with difficulty passing food. Surgically removing the tumour or dilation of the stricture will relieve the dysphagia in most cases.