Oral mucosa

Definition

The oral mucosa is the mucous membrane lining the inside of the oral cavity. It consists of stratified squamous epithelium and an underlying connective tissue called the lamina propria. In certain areas, it is supported by a deeper submucosa.

The oral mucosa serves as a primary barrier against mechanical trauma, microorganisms, and toxic substances, while also providing sensory information (touch, temperature, and taste).

Classification by Function

The oral cavity is not uniform; the mucosa is specialized based on the mechanical stress it endures:

1. Masticatory Mucosa

This mucosa is designed to withstand the forces of mastication (chewing). It is typically keratinized or parakeratinized.

Locations: Hard palate and Attached gingiva.
Characteristics: Firmly bound to the underlying bone (mucoperiosteum); lacks a submucosa in most areas.

2. Lining Mucosa

The most common type, providing flexibility for speech and swallowing. It is non-keratinized.

Locations: Buccal mucosa (cheeks), labial mucosa (lips), floor of the mouth, ventral surface of the tongue, and soft palate.
Characteristics: Soft, moist, and elastic; usually has a well-developed submucosa containing minor salivary glands.

3. Specialized Mucosa

Found specifically on the dorsal (top) surface of the tongue.

Characteristics: Contains both keratinized and non-keratinized areas and is characterized by the presence of lingual papillae and taste buds.

Microscopic Structure

The oral mucosa is composed of several distinct layers:

Epithelium: Stratified squamous type. It can be orthokeratinized (no nuclei in the top layer), parakeratinized (shrunken nuclei present), or non-keratinized.
Basement Membrane: The interface between the epithelium and connective tissue.
Lamina Propria: A layer of connective tissue containing blood vessels, nerves, and collagen fibers. It is divided into the papillary layer and the reticular layer.
Submucosa (where present): Contains larger blood vessels, nerves, and adipose tissue or salivary glands.

Clinical Significance

Permeability: The lining mucosa (especially under the tongue) is highly permeable, allowing for sublingual administration of medications (e.g., nitroglycerin).
Fordyce granules: Ectopic sebaceous glands commonly found in the buccal mucosa; considered a variation of normal.
Lineal alba: A white line on the buccal mucosa caused by frictional keratinization from the teeth.
Oral Lichen Planus: A common chronic inflammatory condition affecting the oral mucosa.