The Epiglottis and How It Helps Maintain Homeostasis
The epiglottis is a leaf-like flap of cartilage and membrane. It is made up of connective tissue and elastic cartilage and is located at the base of the tongue. Homeostasis is defined as a state of equilibrium or stability.
The digestive system is the primary system that comes into play with regard to the epiglottis. The digestive process comprises three primary phases: the oral phase, pharyngeal phase and the esophageal phase. The role of the epiglottis in the pharyngeal phase is crucial.
During the process of swallowing food certain steps are initiated. Once the pharyngeal phase is in progress the food must be stopped from entering the nasal cavity or windpipe (trachea). A coordinated connection of movements occurs to prevent this from happening. Firstly the tongue throws the rounded mass of food that has been mixed with saliva (commonly known as a bolus) back into the pharynx. In an automatic movement the soft palate rises and closes off the nasopharynx, which protects the nasal cavity. Immediately the epiglottis moves to shut the passage to the trachea.
The actual coordination is complex and involves interconnected actions involving the larynx, vocal cords and epiglottis. The larynx is pulled both upward and forward. The vocal cords are drawn together accordingly. The tongue moves backward to accommodate this. The epiglottis is thus pushed into a horizontal position, when ordinarily it points upwards.
The epiglottis performs the shutting function by changing position. It folds over the glottis and closes the opening of the trachea. This temporary closure is crucial to ensure that food does not enter the lungs. The passageway of air is blocked by the action, preventing food from traveling into the nasal cavity or windpipe.
The movements of the epiglottis as it changes position to one of blocking are involuntary and reflexive. The functions performed have multiple effects. By blocking the passageway, especially with the vocal cords compacting together, food cannot pass through the larynx. The food is deflected to either side of the epiglottis, rather than sliding over its edge to move into the pharynx. Furthermore, respiration is temporarily inhibited. Thus the digestive system and respiratory system work in harmony, alongside the central nervous and endocrine systems.
If the passage of food was not blocked and the epiglottis did not function properly, a person would choke. The epiglottis acts as a guard to the respiratory system, preventing entry into the nasal cavity and trachea. In this way the respiratory system functions in a mode of stability as does the digestive system. When, for some reason, the food “goes down the wrong way” into the windpipe, the result is choking and coughing in an attempt to dispel the food and to restore equilibrium. This can happen when a person talks or laughs while eating. The food inadvertently ends up in the upper part of the respiratory tract, causing the above discomfort. There is a further concern if food were to pass into the lung area, as this could cause irritation and inflammation or infection.
Once the food is swallowed, the epiglottis can return to its normal relaxed position. This opens the passageway to the trachea and regular breathing is initiated once more. The open position of the epiglottis, allowing the free passage of air, returns the bodily systems to a state of renewed homeostasis. It is this automatic and essential mechanism of being open, then closing and re-opening, that creates the flow of systems so that homeostasis is maintained at all times. It is only when one of the parts malfunctions that homeostasis is adversely affected.
The digestive system can also return to its process of digesting the food, allowing the esophageal phase to take place. As the food moves through the esophagus it does so by a series of involuntary contractions created as muscle waves. This movement is referred to as peristalsis.
The brain triggers in the medulla send messages to the parts of the body that are required to move or be still. From blockages, to temporary respiratory inhibition, to peristalsis, all are aspects of a system that maintains equilibrium by the appropriate functioning of body organs and parts at appropriate times. The epiglottis serves to play its part in this maintenance of homeostasis.
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