The document describes the process of deglutition (swallowing), which involves both voluntary and involuntary phases, starting in the mouth and moving through the pharynx to the esophagus, coordinated by the swallowing center in the medulla. It outlines the roles of various physiological components and the reflex actions that prevent food from entering the respiratory tract. Additionally, it discusses disorders related to swallowing, including dysphagia, aerophagia, and gastroesophageal reflux disease (GERD).

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DEGLUTITION
▪ Initiated voluntarily in mouth, involuntary Thereafter
o Pharynx has three parts
▫ Nasopharynx
▫ Oropharynx
▫ Throat
Swallowing reflex
▪ Somatosensory receptors near pharynx → detect sensory information (e.g. food
in mouth) → travel via vagus and glossopharyngeal nerves → swallowing center
in medulla → sends efferent, motor information via glossopharyngeal, vagus
nerves → directs coordinated movement of pharyngeal striated muscle, upper
esophagus
ORAL (VOLUNTARY)
▫ Tongue presses against hard palate → forces bolus towards oropharynx →
pharynx contains high density of somatosensory receptors → activation →
swallowing reflex initiation in medulla
PHARYNGEAL
▫ Soft palate, uvula moves upwards → creates narrow passage → prevents
food reflux into nasopharynx → epiglottis closes down over laryngeal opening
→ larynx moves upwards against epiglottis → act as seal to prevent food entering
trachea → upper esophageal sphincter relaxes → food passes from pharynx to
upper esophagus → peristaltic wave initiation → food propelled through open
upper esophageal sphincter
▫ Breathing inhibited during this phase
Control of the pharyngeal stage of swallowing -swallowing reflex: Swallowing
center – in the medulla and lower pons Afferent nerves – Vth, VIIth, IXth,
Xth Coordination of the swallowing with respiration
ESOPHAGEAL
▫ Swallowing reflex closes upper esophageal sphincter → food cannot reflux back
into pharynx → primary peristaltic wave (coordinated by swallowing reflex) →
propels food along esophagus → if all food not cleared → distended esophagus
→ secondary peristaltic wave is initiated by enteric nervous system
DISORDERS OF SWALLOWING
1. Abolition of deglutition reflex: Abolition of deglutition reflex causes regurgitation of
food into the nose or aspiration into the larynx and trachea 2. Aerophagia: Aerophagia
refers to the unavoidable swallowing of air along with the swallowing of food bolus and
liquids. 3. Dysphagia :Dysphagia is a term used to denote difficulty in swallowing 4.
Cardiac achalasia :_ Cardiac achalasia is a neuromuscular disorder of the lower two-
thirds of oesophagus, characterized by absence of oesophageal peristalsis and failure of the
LES to relax during swallowing. 5. GERD:Gastroesophageal reflux disease refers to a
condition in which incompetence of the LES causes reflux of acidic gastric contents into
the oesophagus. Reflux of stomach acid causes oesophageal pain (heartburn) and may lead
to irritation of oesophagus or bronchioles (due to aspiration).