Swallowing consists of a voluntary preparatory phase, the swallowing reflex, and the oral, pharyngeal, and esophageal transport phases. Thus, the swallowing process is only partially controllable by volition. Swallowing disorders are dysphagias and may be neurological, psychological, or due to diseases of the structures involved.
What is swallowing?
Swallowing is a complex sequence of movements. More specifically, the process corresponds to a perfectly coordinated contraction of certain muscles of the mouth, throat and neck. Swallowing is a complex sequence of movements. More precisely, the process corresponds to a perfectly coordinated contraction of certain muscles of the mouth, throat and neck. In addition to transporting food toward the stomach, swallowing also results in the removal of saliva. The swallowing process also cleanses the esophagus and removes residual stomach acid from the sensitive area. Humans experience up to 3000 swallows per day. When asleep, he swallows significantly less than when awake. The act of swallowing consists of a voluntary preparatory part and the involuntary swallowing reflex. The irritation of individual areas at the base of the tongue counts as voluntary preparation. The subsequent processes cannot be influenced. Only the oral preparation phase and the oral transport phase can be influenced voluntarily. The pharyngeal and esophageal transport phases belong to the involuntary swallowing reflex.
Function and task
The swallowing process involves the participation of various anatomic structures. In addition to the oral cavity and its boundary structures, the pharynx, larynx, esophagus, and stomach are involved in swallowing. More than 20 pairs of muscles interact in the act of swallowing. The coordination of these muscle pairs is subject to control by the so-called swallowing center, which is located primarily in the brainstem and higher suprabulbar and cortical centers. Several pairs of cranial nerves are relevant to the swallowing act. In addition to the trigeminal nerve, the facial nerve, glossopharyngeal nerve, vagus nerve, and hypoglossal nerve have important functions in swallowing. Humans need three cervical nerves to swallow. All three originate from spinal cord segments C1 to C3. The swallowing reflex is a mandatory part of the swallowing process. The innate foreign reflex protects the respiratory tract and only makes the harmless intake of food possible. The mucous membrane at the base of the tongue, the pharyngeal groove, or the posterior pharyngeal wall is irritated during the preparatory phase, and the mechanoreceptors located there transmit the stimulus via afferent fibers of the glossopharyngeal and vagus nerves to the medulla oblongata of the brainstem, which in turn responds to the stimulus information by contacting the swallowing muscles. Interestingly, swallow size varies markedly from swallow to swallow and also depends on the particular type of food. 20 grams of watery porridge or 40 milliliters of liquid is the maximum per swallow. The duration of swallowing can also vary greatly and depends primarily on the consistency of the morsels and their mixing with saliva. The journey of a bite through the esophagus takes 20 seconds at most. Each swallowing act consists of three different transport phases and a preparatory phase, which is mainly relevant for the absorption of solid food. In the oral preparation phase, the bite of food is sufficiently chewed. The chewed food is then infused with saliva to make it slippery. In addition to the lips, teeth, temporomandibular joint and masticatory muscles, the tongue and oral salivary glands are involved in the preparatory phase. Only when the preparatory phase is complete is the act of swallowing possible at all. In the subsequent oral transport phase, the lips close completely. This prevents saliva loss. In addition, no air is to be swallowed. The cheek muscles contract and the tongue moves to the hard palate, which assumes an abutment function. The bolus performs a wave-like movement directed backwards and is supported by the styloglossus and hyoglossus muscles. Thus, the tongue pulls backward in a plunger-like manner and pushes into the pharynx. The swallowing reflex is only triggered when the base of the tongue is touched by the bite. The process can only be partially influenced from the swallowing reflex.
Diseases and complaints
Medicine refers to any disorders of the swallowing act as dysphagia.The structures involved in the act are either impaired in their function or their interaction does not function sufficiently. All diseases of the oral cavity, its boundaries, diseases of the pharynx, those of the esophagus and those of the entrance to the stomach can be associated with swallowing disorders. In addition, neurological problems are often associated with problems with swallowing. An example of this is the disease ALS. Due to the decomposition of the motor 8s9brain nerve nuclei, ALS gradually paralyzes the muscles of the body. This is how dysphagia and bulbar symptoms develop. Patients regularly choke on their own saliva and are often treated with salivary medications. Patients with the autoimmune disease multiple sclerosis also frequently suffer from neurologically related dysphagia caused by autoimmune inflammation in the swallowing center of the brain. Dysphagia is sometimes also due to psychological disorders. If the dysphagia additionally causes pain symptoms, it is called odynophagia. Possible symptoms are a feeling of pressure in the throat, a gag reflex during the swallowing act, coughing during meals, aspiration of food particles and an overproduction of saliva. Accompanying symptoms, patients with dysphagia often complain of nasal speech and general hoarseness. When food is aspirated, pneumonia with fever is common. Dysphagia can be an age-related condition and, in this case, manifests most commonly in those over 75 years of age. This type of dysphagia is usually due to neurological, to psychiatric or generally chronic conditions in old age. Not every patient needs to be aware of dysphagia.
