The mouth

Oral cavity

The mouth, also called the (oral cavity) or buccal cavity is the entranceway into the digestive system containing both primary and accessory organs of digestion.

The mouth is designed to support chewing, (mastication) and swallowing, (deglutition), and speech (phonation).

Two rows of teeth are supported by facial bones of the skull, the maxilla above and the mandible below.

Teeth are surrounded by gingiva, or gums, part of the periodontium, support tissue of oral cavity protection.

In addition to the teeth, other structures that aid chewing are the lips, cheeks, tongue, hard palate, soft palate, and floor of the mouth.

Teeth

Humans normally will produce two sets of teeth called primary dentition, or deciduous teeth, and secondary dentition, or permanent teeth.

A tooth is the toughest known substance in the body exceeding bones in density and strength. Tooth enamel lends great strength to the tooth structure. The formation of a developing tooth includes the process of dentin formation, (see: Dentinogenesis) and enamel formation, (see: amelogenesis). As the tooth breaks through the gum into the mouth, the process is called eruption. The formation of teeth begins in early fetal development and goes through six stages:

* (1) initiation stage, 6th - 7th week
* (2) bud stage, 8th wk
* (3) cap stage, 9th-10 wk
* (4) bell stage, 11th-12th wk
* (5) apposition
* (6) maturation stage

Tooth enamel is white initially but is susceptible to stains from coffee and cigarette usage. A tooth sits in a specialized socket called gomphosis. The tooth is held in location by a periodontal ligament, with the assistance of cementum.

The white visible part of a tooth is called the crown. The rounded upper projections of the back teeth are cusps. The hard white exterior covering of the tooth is the enamel. As the tooth tapers below the gumline, the neck is formed. Below the neck, holding the tooth into the bone, is the root of the tooth. The inner portions of the tooth consist of the dentin, a bonelike tissue, and the pulp. The pulp is a soft tissue area containing the nerve and blood vessels to nourish and protect the tooth, located within the pulp cavity.

There are various tooth shapes for different jobs. For example, when chewing, the upper teeth work together with the lower teeth of the same shape to bite, chew, and tear food. The names of these teeth are:

* (1) Incisors, there are eight incisors located in the front of the mouth (four on the top and four on the bottom). They have sharp, chisel-shaped crowns that cut food.
* (2) Cuspids (or canine tooth), the four cuspids are next to each incisor. Cuspids have a pointed edge to tear food.
* (3) Premolars (or bicuspids), the four pairs of molars are located next to the cuspids. They crush and tear food.
* (4) Molars, there are twelve molars, in sets of three, at the back of the mouth. They have wide surfaces that help to grind food.

Adults have 32 permanent teeth, and children have 20 deciduous teeth.

Salivary glands

There are three sets of salivary glands: the parotid, the submandibular and the sublingual glands. The (exocrine) glands secrete saliva for proper mixing of food and provides enzymes to start chemical digestion.

Saliva also helps to hold together the formed bolus which is swallowed after chewing.

Saliva is composed of primarily of water, ions, salivary amylase, lysozymes, and trace amounts of urea.

Periodontium

The periodontium includes all of the support membranes of the dental structures surround and support the teeth such as the gums and the attachment surfaces and membranes.

This includes epithelial tissues (epithelium), connective tissues, (ligaments and bone), muscle tissue and nervous tissue.

Tongue

The tongue is a specialized skeletal muscle that is specially adapted for the activities of speech, chewing, developing gustatory sense (taste) and swallowing.

It is attached to the hyoid bone.

Terms meaning tongue include "glosso" and "lingual."

Mucosa

The protective tissues of the oral cavity are continuous with the digestive tract are called mucosa or mucous membranes.

They line the oral, nasal, and external auditory meatus, (ear), providing lubrication and protection against pathogens.

This is a stratified squamous epithelium containing about three layers of cells.

The lips are also protected by specialized sensory cells called Meissner's corpuscles.

The cells of the inner oral cavity are called the buccal mucosa.