Swallow

Pied-winged swallow (Hirundo leucosoma)

Riparia riparia

Hirundo abyssinica

Adult Northern Rough-winged Swallow (Stelgidopteryx serripennis) in Waterville, Maine

Tachycineta bicolor 18319

File:Nesting Swallows at Skomer Island, Wales.webm Swallowing is a complex process that involves the coordinated action of several muscles and nervous system pathways. It is essential for the intake of food and liquid, enabling them to move from the mouth through the pharynx and esophagus into the stomach. Swallowing occurs in three main stages: the oral phase, the pharyngeal phase, and the esophageal phase, each involving specific mechanisms and reflexes.

Oral Phase

The oral phase is the voluntary part of swallowing. It begins with the preparation of food in the mouth. Chewing mixes the food with saliva, forming a bolus. The tongue then pushes the bolus to the back of the mouth, initiating the swallowing reflex.

Pharyngeal Phase

The pharyngeal phase is an involuntary process that begins when the bolus enters the pharynx. This triggers a series of reflex actions: the soft palate rises to close off the nasopharynx, preventing food from entering the nasal passages; the larynx moves upward and forward, and the epiglottis closes over the trachea, preventing food from entering the respiratory system. These actions ensure that the bolus is directed towards the esophagus.

Esophageal Phase

The esophageal phase is also involuntary. It involves the relaxation of the upper esophageal sphincter, allowing the bolus to enter the esophagus. Peristaltic waves then move the bolus down the esophagus and into the stomach. The lower esophageal sphincter relaxes to allow the bolus to enter the stomach and then contracts to prevent stomach contents from refluxing into the esophagus.

Disorders of Swallowing

Swallowing disorders, or dysphagia, can occur at any stage of the swallowing process. Causes of dysphagia include neurological disorders (such as stroke, Parkinson's disease, or multiple sclerosis), structural abnormalities (such as esophageal stricture or cancer), and infections (like esophagitis). Symptoms may include difficulty swallowing, pain while swallowing, coughing or choking during or after eating, and recurrent pneumonia due to aspiration of food particles into the lungs.

Diagnosis and Treatment

Diagnosis of swallowing disorders typically involves a thorough history and physical examination, followed by specific tests such as a barium swallow, endoscopy, and manometry. Treatment depends on the underlying cause and may include dietary modifications, swallowing therapy, medications, or surgery.

Conclusion

Swallowing is a critical function for nutrition and hydration. Understanding the complex mechanisms involved in this process is essential for diagnosing and treating swallowing disorders, ensuring that individuals can continue to eat and drink safely.