Mouth Anatomy and Structure of the Oral Cavity

The anatomical term for mouth is the oral cavity or the buccal cavity. The oral or the buccal cavity is the orifice through which the food and air enter the body. This mouth structure is common to human mouth anatomy and any animal that consists of such an orifice. This orifice is widely used for two purposes: ingestion of food and issuing of vocal sounds. 

In human mouth anatomy, the mouth opens outside at the lips and opens up into the pharynx (or the throat) at the rear. Lips, cheeks, hard and soft palates, and glottis define the boundaries of the mouth structure in humans. The human mouth parts are divided into two sections - the vestibule, the area between the cheeks and the teeth and the true or proper oral cavity. The oral cavity comprises the tongue which is a large muscle with taste buds. 

Brief Description about Inner Mouth Structures

The vertebrates and the invertebrates have some differences in their mouth anatomy. Although both of them have similar defining characteristics of the oral cavity, there can be significant differences between the microscopic mouth inside anatomy of vertebrates and invertebrates. The similarities of a mouth diagram representation of the vertebrates and the invertebrates will show an opening with possible muscle cells to facilitate the intake of food on one end and the opening of the cavity into the pharynx at the other end for further digestion, there can be significant differences between the microscopic mouth inside anatomy of vertebrates and invertebrates.

Invertebrates: 

In some of the species of invertebrates having a hard exoskeleton, the mouth parts are also involved in feeding behaviour. Insects have diverse inner mouth anatomy suited to their modes of feeding, in some cases consisting of mandibles - the lower jaw, maxillae - the upper jaw and labium - a fused mouth part that provides support for holding food in the mouth. These internal structures are modified into suitable appendages for chewing, cutting, piercing, sponging and sucking. Interestingly, in some less advanced invertebrates such as sea anemone, the mouth structure is so designed that it even facilitates the expulsion of undigested food i.e. it functions as an anus as well. 

Vertebrates: 

The vertebrates have a complete digestive system with a mouth at one end for taking in the food and an anus at the other end for the expulsion of undigested or left-over food particles. The main parts of the mouth of a vertebrate can be divided into three parts specifically - the mandibles, the maxillae and the tongue along with the base of the oral cavity. Only the avian groups among the vertebrates lack teeth in their jaws. Instead, in the case of birds, there are beaks composed of elongated mandibles. 

Human Mouth Anatomy

As already mentioned above the human mouth anatomy is divided into two parts: the vestibule and the oral cavity. Along with that, the inner mouth anatomy of Homo sapiens is chiefly characterized by the following:

• The teeth, which tear and grind the food into digestible pieces. These teeth are held in place by the support from the gums.

• The tongue, which provides support to the chewing process by aiding in positioning and mixing food. It also has sensory receptors for taste. These taste buds or the sensory receptors are present in many small papillae on the upper surface of the tongue. The tongue and the teeth are usually found in the mouth anatomy of higher vertebrates.

• The palate, which separates the mouth from the nasal cavity. This is to allow separation between the swallowing of food into the oesophagus and intake of air into the trachea. Also, the palate provides roofing to the mouth structure providing an enclosure of the mouth anatomy.

In humans, apart from the function of intake and primary digestion of food all these human mouth parts along with the lips help in forming words and speaking. 

This combined workforce of the mouth inside anatomy initiates the digestive process by mixing the food with digestive enzymes present in the saliva of animals. The saliva not only helps in the process of digestion but also in keeping the mouth moist and clear of any debris. This saliva is a fluid that is released by three pairs of salivary glands which are present in the mucous membranes that line the oral cavity and the vestibule along with numerous other small glands. The simple mouth anatomy diagram of humans is shown below:

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Functions of the Mouth

The primary function of the mouth is, as explained above, the ingestion of food, and its primary digestion in some cases. It also helps humans in speaking. But this ability is not limited to humans. Although not understandable to humans, animals and birds have their own communication tactics and sounds. The mouth and the inner mouth anatomy helps these organisms to produce and issue vocal sounds and variations of it. A simple illustration can be the variation produced when allowing the mouth to open and close while a continuous flow of air from the trachea produces a sound.  

An important aspect of the mouth inside anatomy is thermoregulation i.e. temperature control. Some mammals use the mouth when panting or breathing heavily after intense work-out as it increases the evaporation of water from the moist surfaces of the mouth, tongue and lungs.

Fun Fact 

Even though some may state it as a function, a fun fact is that many organisms use their mouths to display fear and threat in the opponent. To do so they gape their mouths while taking an attacking position. Some birds augment the display by hissing or breathing heavily. 

Conclusion

Conclusively it becomes clear that the mouth is an important organ from the point of view of digestion and is a symbol of an advanced developed multicellular organism. The mouth structure is quite evidently used for intake and initial digestion of food. Human mouth parts in addition to the process of digestion also aid in the process of speech.