The hiccup is perhaps the only reflex that we encounter frequently in our lives, and yet we don't know its fundamental function. In th...
The hiccup is perhaps the only reflex that we encounter frequently in our lives, and yet we don't know its fundamental function. In the search for the explanation of hiccup, we usually find the description of the process of the action, leaving unanswered or ignored the actual function of hiccup.
In physiological and medical literature, the hiccup is most often described as a malfunction, a symptom of disease, or even as an illness. However, hiccup is a fundamental and ancient reflex. We hiccup before we are born, and hiccup is a phenomenon found in many animal species. This suggests that hiccups play an important biological and physiological role. Hiccups must have a useful function necessary for the sustaining of life, meaning that hiccups are not just a malfunction, an illness, or an accompanying symptom of a disease.
What might be the role and function of hiccups in the life processes, as it is established and maintained by evolution?
The process of hiccupping is described as basically a reflexive, quick spasmodic contraction of the diaphragm muscle, which acts on the lungs and airways and causes a sudden inflow of air, which produces the characteristic sound in the vocal organs. The prerequisite for hiccups is therefore the presence of the diaphragm, and the formation of the lungs. Hiccup is therefore a reflex characteristic of animal species with a pulmonary system, which, as a physiological function, may have arisen through the evolutionary appearance of the lungs and diaphragm.
However, the majority of the causes that often lead to hiccups are not primarily related to the process of breathing, but are in some way related to the process of eating (if we exclude causes that are clearly related to a disorder or illness). Therefore, the real evolutionary function of hiccups may be related in some way to the process of nourishment, assisting the physiological process of eating. However, hiccups are not part of the normal process of eating, as the hiccup reflex is only occasional. The hiccup reflex must therefore be related to some abnormality in the eating process or to the restoration of that process.
Hiccup is an evolutionary reflex of a function to open or keep open the esophagus in an emergency or safety situation, to free up the feeding pathway from the mouth to stomach when it is blocked or obstructed during eating or because it is clogged for some other reason.
The movement of material, usually food, in the esophagus toward the stomach is normally controlled by the swallowing reflex. However, swallowing cannot always successfully move the material in the esophagus. Sometimes food or any other substance may for some reason become stuck in the esophagus, and it is becoming blocked and unable to be unblocked by the swallowing reflex.
This situation may not only be caused by an unnatural condition, there may also be completely natural causes of the dysfunction, such as air bubbles in the swallowed food which are then trapped in the esophagus, and could simply and naturally prevent successful swallowing. A capable food may also stick to the surface of the esophagus, blocking it.
However, a blocked esophagus is an emergency situation, not only because it prevents the material from reaching the stomach, but also because the blockage can lead to the blocked and accumulated material reaching the lungs. The living organism must have an evolutionary function, a physiological process, which in the case of obstruction opens and frees the path from the mouth to the stomach. This function is performed by the hiccup reflex.
Food can simply be spat out from the mouth if it is necessary, and the contents of the stomach can be emptied by vomiting in an emergency. Hiccups keep the esophagus open.
Breathing also has a similar emergency reflex to unblock and hold the airways open, which is coughing. Although hiccups use the physiological systems associated with breathing, they do not serve as a process of respiration. The hiccup is the reflex of emergency opening of the food passage, which can exert a particularly strong force in the direction of the stomach to the obstructing substance in the esophagus in the event of obstruction.
This hypothesis also implies that there must be a nerve (or a function of the vagus nerve) that specifically signals to the brain that the esophagus is blocked or that the swallowing process is not successful and there is material in the esophagus that cannot be moved by swallowing.
Hiccups can also occur as an abnormal condition, when the real intended situation that causes the hiccups does not exist. Abnormal hiccups can be caused by any abnormal functioning of the neural pathway that causes the hiccups to occur, or by several abnormal conditions or external influences. In childhood, hiccups often occur without any real cause, probably due to the natural development of the still developing central nervous system. There are also many other pathological hiccups that are not due to intended causes, which are discussed in detail in the relevant literature, listing various pathological conditions or external, extraneous causes.
Fundamentally, hiccups are essentially an evolutionary necessity, a physiological reflex whose natural function is to keep the feeding pathway open in the event of an emergency, and which can be triggered by a number of abnormal conditions and causes, also.
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