June 07, 2021
Each organ in our body is covered by a membrane. This membrane can vary in thickness depending on the location of the organ in the body or its function. The lining of each organ is called mucosa. In the oral cavity, three types of mucosa can be appreciated: lining mucosa, masticatory mucosa and specialized mucosa.
The lining mucosa, as the name suggests is the layer that covers a majority of the areas in the oral cavity. These are the inner surface of the cheeks, the floor of the mouth and the inner lining of the lips. The masticatory mucosa is found in regions that bare the maximum pressure and are the most functional as we chew. This mucosa is present on the tongue, the hard palate and the gingiva (gums) that attaches to the surface of the teeth. The specialized mucosa is found on the tongue, and is present mainly on the taste buds.
The most abundant cells on the outer surface of our skin are called keratinocytes. These cells are also found in the lining and masticatory mucosa. When they differentiate and proliferate from the deeper layers of the skin to the outer layer, the process is called keratinization. This process is more prominent in masticatory mucosa, but does not occur in the lining mucosa. As a result, the masticatory mucosa has a keratinized mucosa, whereas the lining mucosa has a non-keratinized mucosa.
The epithelium or the mucosa in the oral cavity when seen at a microscopic level, can be seen as four layers. The two deepest layers are constant throughout the oral cavity. The upper two layers however can be different, depending on whether the mucosa is a keratinized or not. The reason in this variation is because keratinization comes in response to the functioning of that particular site. The difference between keratinized and non-keratinized mucosa shall now be further stressed upon based on their respective internal structure.
Keratinized mucosa acts as an effective barrier because of keratinization. Its outermost layer consists of dead and hardened cells. This makes it impervious, meaning, that external agents cannot easily penetrate this mucosa. The layers of keratinized mucosa also contain certain granules, that makes it resistant to wear and tear. Keratinized mucosa also has groups or bundles of certain fibrils, that give the mucosal layer added strength to resist any forces.
Non-keratinized mucosa is comparatively a weak barrier than keratinized mucosa. Unlike keratinized mucosa, the non-keratinized mucosa consists of living cells. This mucosal lining is pervious, meaning that it is more susceptible to the attack of foreign agents. Even though the cells of non-keratinized mucosa are larger in size, they are not resistant to abrasions. The groups of fibrils in these layers of mucosa are scattered or dispersed, as a result of which they are not ideal to handle functional forces.
The keratinized and non-keratinized mucosa give us protection against the masticatory forces. Apart from chewing forces, the mucosa also helps in resisting the pressure exerted by dentures or by parafunctional habits like bruxism (clenching of teeth). The mucosa also help in facilitating the action of saliva, which helps in flushing out the noxious agents and maintaining the pH of the oral cavity. Both the types of mucosa are richly innervated. This means that they have excellent sensory perception and respond immediately to unwanted stimuli.
The skin of the oral cavity helps protects use from UV radiations, infective pathogens, temperature changes due to smoking and other detrimental habits, pH regulation, etc. The loss of keratinized or non-keratinized mucosa as a result of oral conditions and lesions can be overcome by modern techniques of tissue engineering. It involves reconstruction of the lost tissues using stem cells, grafts, scaffolds, etc. These advanced surgical techniques help in retaining the function of the oral mucosa and also establish a healthy vasculature (blood supply) in that region.
The health of the oral mucosa also gives us an indication of the health of the body in general. Inflammation, blisters, sores or any other lesions present on keratinized or non-keratinized surfaces can be an indication of bacterial, fungal, or viral infections. The oral mucosal linings thus act as very good indicators or warning signs of the health of the oral cavity and the systemic condition of the body in general.