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Oral Cavity

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Microscopic image of oral mucosa, stained pink. Top of the view shows the stratified squamous epithelium with characteristic polygonal cells and visible nuclei, transitioning to the underlying lamina propria with collagen fibers. Texture varies between dense cellular regions and fibrous areas. Composition from upper left to lower right.
Figure 1: Oral mucosa microscopic view. Layered tissue with cells stained pink.

The oral cavity, also known as the mouth, is the first part of the digestive system. It is where food enters the body. Food undergoes initial mechanical and chemical digestion there. 

Mucosa

The epithelium lining the oral cavity is composed of multiple layers of flat, stratified squamous epithelial cells. This type of epithelium provides protection against mechanical abrasion and chemical damage from food, as well as from microorganisms. In areas subject to greater mechanical stress, such as the gingiva (gums) and hard palate, the epithelium may be keratinized. It contains layers of keratin protein. These layers provide additional protection and resistance to wear and tear. In areas such as the buccal mucosa (inner lining of the cheeks), the epithelium is non-keratinized. The ventral surface of the tongue also has non-keratinized epithelium. These areas are not subject to as much mechanical stress.

Submucosa

Beneath the mucosa is the submucosa, a layer of loose connective tissue containing blood vessels, lymphatic vessels, and nerves. The submucosa provides support to the mucosa. It serves as a conduit for blood vessels and nerves entering the oral cavity.

Muscularis Externa

The muscular layer of the oral cavity consists of skeletal muscle. It is responsible for the movements involved in chewing (mastication), swallowing (deglutition), and speaking (articulation). The muscles of the tongue, cheeks, and lips are particularly important for these functions.

Serosa

The hard palate forms the anterior portion of the roof of the mouth and consists of bone covered by mucosa. It provides a rigid surface for the tongue to push against during chewing and swallowing.
The soft palate is the back part of the roof of the mouth. It has a muscular structure covered by mucosa. It helps to close off the nasal cavity during swallowing. This prevents food and fluids from entering the nasal passages.

Photomicrograph of oral mucosa at high magnification: Layer of polygonal cells with dark edges and light interiors, stained reddish-brown, sits atop a layer of irregular fibrous connective tissue stained blue. The brown cellular layer undulates with cells decreasing in size.
Figure 2: Microscopic view of oral mucosa showing cell structure in brown with blue connective issue.
Micrograph of oral mucosa, stained. High magnification reveals a stratified squamous epithelium (pink), connective tissue (blue), and striated muscle (red). Epithelial surface shows irregular ridging. Connective tissue contains collagen fibers, fibroblasts, and circular blood vessels appear as small circles with dark borders. Bundles of striated muscle fibers appear below, forming a woven like pattern. Some dark spots in the connective tissue are possibly glands. The colors of the tissue are probably due to trichrome stain. The image is shot in a high angle.
Figure 3: Microscopic view of oral mucosa tissue. Shows layers of epithelium, connective tissue, and underlying muscle with blood vessels.
A photomicrograph of oral mucosa tissue, stained with Masson's trichrome. The reddish-brown epidermis forms a distinct layer at the top. A blue-stained collagen-rich dermis can be seen below, containing interspersed blood vessels appearing as white or lightly stained circles. Fibroblasts and extracellular matrix contribute to the textured appearance. The image showcases cellular structure and tissue composition under magnification.
Figure 4: This is a microscopic view of oral mucosa tissue. It shows layers of epidermis and connective tissue. They are stained in reddish and bluish hues.

Functions

Mechanical digestion via mastication.

Specializations

The oral cavity is specialized for mastication with teeth.  The tongue also participates in forming the bolus or moist ball of food that will be swallowed.

Figure 1: Oral pharynx, H&E, 40X Slide 152
Figure 2: Oral pharynx, Masson trichrome stain, 40X Slide 152AF
All by University of Michigan Histology, licensed under CC BY-NC-SA 3.0.

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