Anatomy of the Oral Cavity

Superior Aspect

• Roof of the oral cavity which comprises the hard palate anteriorly and soft palate posteriorly.

Tongue

• Forms the floor and base of the mouth, crucial for manipulating food during chewing and assisting in swallowing.

• Boundaries:

  • Posteriorly bounded by fauces and tonsils; anteriorly encompasses the tip.

• Contains various folds:

  • Palatoglossal fold: connects the soft palate to the tongue.

  • Palatopharyngeal fold: connects the soft palate to the pharynx.

• Medial and posterior structures: Includes the uvula, which is important for preventing food from entering the nasal cavity during swallowing.

Types of Oral Mucosa

General Overview

• Oral mucosa is divided into three types:

  1. Masticatory Mucosa: Found in areas subjected to friction, such as the hard palate and gingiva.

  2. Lining Mucosa: Found in the soft palate, cheeks, and floor of the mouth, provides flexibility.

  3. Tongue Mucosa (Specialized Mucosa): Contains specialized taste buds for gustation.

Function of Oral Mucosa

• Separation into three layers:

  1. Epithelial Layer: Rapid turnover of cells for protection against irritants and pathogens. Predominantly consists of stratified squamous epithelium, either keratinized or nonkeratinized depending on location.

  2. Lamina Propria: A layer of connective tissue below the epithelium, provides structural support and is rich in nerves and blood vessels, including fibroblasts and immune cells (e.g., macrophages).

  3. Submucosa: The deepest layer of oral mucosa, consisting of loose connective tissue that contains glands, adipose tissue, large nerves, and blood vessels, allowing flexibility and movement of the oral mucosa.

Types of Epithelium

Keratinized vs Nonkeratinized Epithelium

• Keratinized Epithelium: Found in areas like the hard palate and gingiva; characterized by thick layers of keratin, with no nuclei in the outer layers; offers greater protection and waterproofing.

• Nonkeratinized Epithelium: Present in buccal and sublingual areas; contains nuclei in outer layers, providing less protection than keratinized epithelium and allowing for flexibility.

Innervation and Vascular Supply

• Innervation:

  • Anterior two-thirds of the tongue: Lingual nerve (CN V3).

  • Posterior tongue: Lingual branch of the glossopharyngeal nerve (CN IX).

  • Epiglottis sensation: Internal laryngeal branch of the vagus nerve (CN X).

• Vascular Supply:

  • Major contribution from the lingual artery, which facilitates nourishment of the tongue and oral tissues.

  • Venous drainage through deep and dorsal lingual veins; facial artery branches also supply the cheeks.

Changes with Aging

Oral Mucosa Aging Effects

• Epithelium: Becomes thinner and less keratinized, increasing susceptibility to injury.

• Lamina Propria and Submucosa: Lose elasticity and flexibility, impacting mobility of the oral mucosa.

• Decreased Saliva Production: Increases the risk of dry mouth (xerostomia), complicating oral hygiene and increasing the risk of dental caries.

• Taste Perception: Decline in taste sensitivity can lead to nutritional deficiencies, as older adults may neglect necessary dietary components due to a diminished sense of taste.

Tooth Development and Eruption

Stages of Tooth Eruption

1. Pre-eruptive Phase: Involves the movement of teeth before they emerge into the oral cavity; significant root development occurs.

2. Pre-functional Phase: The crowns of the teeth begin to appear, with adjustments taking place to accommodate neighboring teeth; important for alignment and spacing.

3. Eruptive Phase: Involves the formation of roots and alignment into the occlusal plane; this stage initiates functional interactions with opposing teeth.

Movements

• Bodily Movement: Whole tooth germ moves towards the oral cavity.

• Eccentric Growth: Part of the tooth undergoes directional growth, affecting positioning relative to opposing teeth.

Tooth Positioning

• Primary (deciduous) teeth erupt first, typically within the first year of life, followed by permanent teeth, which begin to replace primary teeth around age six.

Summary of Age-Related Changes in Oral Health

• Teeth undergo enamel wear leading to increased sensitivity and risk of caries.

• Changes in oral microbiome composition may also affect oral health.

• General sensation may decline, impacting the oral-digestive function and increasing vulnerability to infections and periodontal disease due to reduced saliva production.