Oral Vestibule (Lips, Cheeks, Teeth, Gums) - Oral Cavity Anatomy

The digestive system begins with the oral cavity, where food enters and salivation starts. From there, it moves through the pharynx to the esophagus and into the stomach for processing by hydrochloric acid. The journey continues in the small intestine (duodenum, jejunum, ileum) before reaching large intestine sections like caecum and colon until waste exits via rectum. Accessory structures such as teeth, tongue, salivary glands along with liver, gallbladder and pancreas aid digestion.

The external mouth consists of the upper and lower lips, which meet at their lateral ends forming the oral angle or labial commissure. Above these are two grooves called nasolabial sulci, with a central depression known as the philtrum. Below the lips lies another groove termed mentolabial sulcus or fold. The orbicularis oris muscle within regulates mouth opening through an aperture referred to as either oral fissure or rima oris.

The oral cavity, as the starting point of our digestive system, is divided into two main parts: the Oral Vestibule and the Oral Cavity Proper. The vestibule refers to the area between lips or cheeks and teeth, while everything inside this boundary forms part of what we call "proper." This division helps in understanding its structure and function within digestion.

The oral vestibule is defined by its external and internal borders, separated by teeth and gums. The external boundaries consist of lips and cheeks, while the internal ones are formed by teeth and gums. This area serves as a key structural component in understanding oral anatomy.

The lips are characterized by distinct inner and outer sides, each covered with different types of epithelium. A transitional zone exists between these two areas. The upper lip connects to the gums via the Frenulum of the upper lip, while a similar structure links the lower lip to its corresponding gum. Within their mucosa lie labial glands that produce saliva for lubrication.

The cheeks, or Buccae, are shaped by the buccinator muscle. Covering this muscle is the buccopharyngeal fascia, which extends behind the pharynx. Above it lies Bichat’s fat pad (buccal fat pad), combined with subcutaneous connective tissue to define cheek appearance. Externally there are skin layers; internally resides mucous membrane (tunica mucosa). The tunica mucosa houses openings for parotid ducts surrounded by small elevations called papillae.

Anatomy and Structure of Teeth Teeth are divided into three main regions: the crown (visible part), root (embedded in dental alveolus), and neck (transition covered by gums). The root is fixed via periodontium, forming a strong dentoalveolar joint. Inside, teeth contain pulp cavities with neurovascular structures extending through the apical foramen at the base. Surrounding layers include dentine as the core substance, enamel covering crowns, cementum around roots/necks, and periodontal ligaments encasing it all.

Developmental Stages of Human Teeth Humans have two sets of teeth during their lifetime: milk teeth and permanent teeth. Milk teeth emerge around 6 months old; there are typically 20 that fully develop by age two before gradually falling out between ages 6-12 years to make way for permanent ones. Permanent adult sets consist of 32 total—including wisdom molars appearing later from ages17–24—marking full maturity.

Teeth are categorized into four quadrants starting from the midline, with each quadrant containing eight teeth. The first two teeth near the midline are incisors (1 and 2), followed by canines (3), premolars (4 and 5), molars (6, 7) including wisdom tooth as number 8. Permanent teeth total to 32 across all quadrants while milk teeth lack premolars but include two incisors, one canine, and two molar teeth per quadrant. Incisors and canines typically have a single root; however, premolars and molars may possess multiple roots.

The gums, or gingiva, are mucous membranes covering the alveolar processes of the maxilla and mandible where teeth are rooted. They consist mainly of dense fibrous tissue with varying consistency depending on their region. Clinically, they divide into two parts: alveolar mucosa (mobile due to submucosal connective tissue) at tooth roots and gum proper (immobile as it attaches to periosteum) near necks and crowns. Key anatomical features include gingival papillae between teeth necks, elevated gingival margins around teeth, and grooves called gingival sulci between these margins.