The gums, known scientifically as the gingiva, are the specialized soft tissues that surround and support the teeth. These tissues cover the alveolar processes, which are the parts of the jawbone that hold the tooth sockets, and terminate at the neck of each tooth. The primary function of the gingiva is to act as a robust, biological barrier, protecting the delicate underlying bone and the root structures of the teeth from the constant exposure to the oral environment. This protective shield is composed of two distinct layers of tissue, forming a secure and resilient environment.
The Outer Protective Layer
The visible surface of the gums is covered by stratified squamous epithelium, composed of multiple layers of cells. This outer layer is the first line of defense against the mechanical stress of chewing and the constant presence of oral bacteria. The epithelial tissue is categorized based on keratinization, a process that dictates its toughness and location within the mouth.
The gingiva firmly attached to the bone, known as the attached gingiva, is composed of keratinized epithelium, making it resilient and tough. Keratinization is the process where epithelial cells produce and accumulate keratin, a fibrous protective protein. This results in a dense, waterproofing layer on the surface, helping the attached gingiva withstand abrasive forces.
Conversely, the marginal gingiva, which forms the collar around the tooth, and the tissue lining the gingival crevice are non-keratinized. This non-keratinized tissue is softer and more permeable, allowing for a constant outward flow of fluid and defensive cells, assisting in immune surveillance. The cells in this outer layer also have a rapid turnover rate, continuously shedding and replacing themselves to physically remove attached bacteria and toxins.
The Inner Support Structure
Beneath the epithelial outer layer lies a dense connective tissue called the lamina propria, which provides the structural foundation and nourishment for the gingiva. This support structure is highly fibrous, with collagen fibers making up approximately 60 to 65% of its composition, giving the tissue strength and resilience. These collagen bundles are organized into specific groups that anchor the gingiva firmly to the tooth and the underlying alveolar bone.
The lamina propria is rich in fibroblasts, the primary cells responsible for synthesizing the collagen fibers and other components of the surrounding matrix. This matrix is composed of a gel-like ground substance that fills the spaces between the cells and fibers. Within this supportive framework, a dense network of blood vessels, known as the dentogingival plexus, delivers oxygen and nutrients to the overlying epithelial layer.
This inner tissue layer also contains nerve endings, providing the sensation and feedback that helps protect the mouth from injury. Immune cells are housed within the lamina propria, ready to initiate an inflammatory response if bacteria breach the outer epithelial barrier.
How Gums Form a Seal Around the Tooth
The specialized attachment between the gingiva and the tooth is achieved by the junctional epithelium (JE). The JE is a non-keratinized band of cells that forms a collar around the tooth and creates a tight biological seal, preventing microorganisms from entering the deeper periodontal tissues. This epithelial attachment is secured to the tooth surface by tiny adhesion complexes called hemidesmosomes.
The JE is positioned at the bottom of the gingival sulcus, the shallow, V-shaped space between the free gingiva and the tooth surface. In a healthy mouth, this sulcus typically measures 3 millimeters or less in depth. The integrity of the junctional epithelium is maintained by its rapid turnover of cells, which constantly migrate toward the surface and are shed into the sulcus, carrying bacteria with them.
This area is also protected by gingival crevicular fluid, a serum-like fluid that flows out of the sulcus and contains various antimicrobial components and immune cells. The tight seal created by the JE defends against infection, but it is also a vulnerable point where periodontal disease can begin if the attachment is compromised by bacterial plaque accumulation. Maintaining this specific biological connection is crucial for the overall health of the tooth and its supporting structures.