The mouth is an organ of the digestive system, and the first step to the digestion process. It contains many important things that we use daily. Without the mouth, we wouldn’t be able to communicate, let alone live because it is the main source of our body's nourishment. In the mouth we find the teeth, tongue, jaw, and many more important tissues and organs, like the outside of the mouth: the lips. All of these work together to help us eat, drink, communicate, breathe, and show emotion. The mouth is filled with a liquid called saliva that helps all of the functions mentioned above work properly. The jaw, teeth, tongue, and lips are needed to help the others function, so no matter how small of a role it plays, each part is extremely important for the functioning of the mouth itself. The mouth is one of the most complex and significant organs of the body and is one of the key components that help us live.
Teeth are multifunctional and complex structures that are located in the jaw. They are used to tear and chew the food that we eat. However, the bottom teeth are used primarily for chewing and the top teeth are used primarily for biting. In the primary state of life most people start out with twenty teeth that will eventually fall out so that the permanent ones can grow in. Teeth are classified into three groups, going from front to back, incisors, canines, and molars.
Despite what many may think, teeth are not made out of bone, they are specialized tissues, and contain many parts. The four parts of the tooth are, enamel, dentin, cementum, and pulp.
Enamel is the outside of the tooth and makes up the color we see when we look at our teeth. It is the strongest and most mineralized substance that is held in the body, and it must be supported by the dentin to make it be seen normally. With dentin the color appears to be a yellowish or white-gray tone, but without it the color turns into a slight blue. Enamel is also known as the “cap” of the tooth, in that it protects the rest of the layers from getting damaged. 
Dentin is the next layer below the enamel and is the structure that determines the size and shape of the teeth. It serves as protection for the pulp of the tooth and the support of the enamel. Dentin is also a very strong tissue but not as strong as the enamel, so it is important to take care of it because it is prone to rot and decay if not properly taken care of. 
Cementum is a special bony substance that protects the roots of the teeth. It is very thin and a lot softer then the dentin and enamel so it is a lot more susceptible to damage. Its main job in the tooth is to attach the collagen fiber to the periodontal ligament. In other words it help the root of the tooth maintain its position in the gums and keeps it from moving. 
Pulp is the last tissue layer of the tooth. It is the softest tissue of the tooth and it contains all of the tooth’s nerves, blood vessels, and connective tissue. It spreads out the entire length of the tooth all the way from the roots to the crown. In a sense, it is what keeps the tooth alive, because if the pulp is damaged it’s saying that the tooth is dead.  Pulp also is the main source of dentin development. If anything happens to the tooth, the pulp creates secondary dentin to help repair the damage. It is by far the most vital part of the tooth. 
- Main Article: Tongue
The tongue is a muscle found in the very center of the mouth and is the primary source of everything we taste. This is done by taste buds. There are four different types of taste buds that let us sense sweet, salty, bitter, and sour foods. Not only is the tongue used for taste and food digestion, but it also assists in speech. The reason why your tongue is wet is because it is covered with saliva that is secreted by salivary glands. Salivary glands are found all throughout the mouth and throat, and secrete saliva out through salivary ducts. There are also smaller glands that are located in the lips, cheeks, and the rest of the linings of the mouth and throat. The use of saliva is to moisten the mouth, initiate digestion, and protect teeth from decaying. 
The lips are located on the face and are the visible part of the mouth. The lips are filled with nerves. The infraorbital nerve is the nerve branch that supplies feeling to the upper lip and the mental nerve is the nerve branch that supplies feeling to the bottom lip. The main functions of the lips are the intake of food, erogenous zone, tactile organ, and articulation. The lips are equipped with its own muscles therefore they are able to open and close the mouth for the intake of food. Also it is the tactile organ due to how many nerves they contain. Lips are extremely sensitive to touch and temperature changes. Articulation is one of the most important functions that the lips are used for. They are able to make a large range of sounds and play a big role in speech. Last the tongue is an erogenous zone. They act as the main role in kissing and other acts of intimacy.  The lips are a way of a showing a person’s emotions. Happiness, sadness, confusion, anger, etc. can all be shown from the way the lips are positioned. 
The lower jaw, also known as the mandible, is the strongest bone of the face.  The upper part of the jaw is known as the maxilla and even though still very strong, not as strong as the mandible. The main function of the jaw itself it the manipulation of food. It is found on the inside of the mouth and it is what keeps all of the upper and lower teeth supported in the mouth.