Chapter Summary

I. LIPS

The lips control access to the oral cavity from the outside environment.

A. External Surface

The external surface is covered with thin skin and therefore possesses hair follicles, sebaceous glands, and sweat glands.

B. Transitional Zone

The transitional zone (vermilion zone) is the pink area of the lip. Here the connective tissue papillae extend deep into the epidermis. Hair follicles and sweat glands are absent, whereas sebaceous glands are occasionally present.

C. Mucous Membrane

The vestibular aspect of the lip is lined by a wet epithelium (stratified squamous nonkeratinized) with numerous minor mixed salivary glands in the subepithelial connective tissue.

D. Core of the Lip

The core of the lip contains skeletal muscle.

Fibers of the periodontal ligament are embedded in cementum and bone, thus suspending the tooth in its bony socket, the alveolus.

D. Pulp

The pulp is a gelatinous type of mesenchymal-appearing connective tissue that occupies the pulp chamber. It is richly supplied by nerves and blood vessels.

III. GINGIVA

The gingiva (gum) is that region of the oral mucosa that is closely applied to the neck of the tooth and is attached to the alveolar bone. It is covered by a stratified squamous partially keratinized (parakeratotic) epithelium. The underlying connective tissue is densely populated with thick bundles of collagen fibers.

IV. TONGUE

The tongue is a muscular organ whose oral region is freely moving; its root is attached to the floor of the pharynx. Skeletal muscle forms the core of the tongue,among which groups of serous and seromucous glands are interspersed.

A. Oral Region (Anterior Two-Thirds)

II. TEETH

Teeth are composed of three calcified tissues and a loose connective tissue core, the pulp.

A. Enamel

Enamel is the hardest substance in the body. It is made by ameloblasts, cells no longer present in the erupted tooth. Enamel is present only in the crown.

B. Dentin

Dentin is a calcified, collagen-based material that constitutes the bulk of the crown and root; it surrounds the pulp. Dentin is made by odontoblasts, whose long processes remain in channels, the dentinal tubules, traversing dentin. The odontoblast cell body forms the peripheral extent of the pulp.

C. Cementum

Cementum is located on the root of the tooth, surrounding dentin. Cementum is a collagen-based, calcified material manufactured by cementoblasts, which may become entrapped and then are referred to as cementocytes.

The mucosa of the dorsal surface of the anterior twothirds of the tongue is modified to form four types of lingual papillae.

1. Filiform Papillae

Filiform papillae are long and slender and are the most numerous. They form a roughened surface (especially in animals such as cats) and are distributed in parallel rows along the entire surface. They are covered by a parakeratinized stratified squamous epithelium (but bear no taste buds) over a connective tissue core.

2. Fungiform Papillae

Fungiform papillae are mushroom-shaped, are scattered among the filiform papillae, and may be recognized by their appearance as red dots. They contain taste buds along their dorsal aspect.

3. Foliate Papillae

Foliate papillae appear as longitudinal furrows along the side of the tongue near the posterior aspect of the anterior two-thirds. Their taste buds degenerate at an early

age in humans. Serous glands of von Ebner are associated with these papillae.

4. Circumvallate Papillae

Circumvallate papillae are very large and form a V-shaped row at the border of the oral and pharyngeal portions of the tongue. Circumvallate papillae are each surrounded by a moat or groove, the walls of which contain taste buds in their stratified squamous nonkeratinized epithelium. Serous glands of von Ebner open into the base of the furrow. The connective tissue core of the circumvallate papilla possesses a rich nerve and vascular supply.

B. Pharyngeal Region (Posterior One-Third)

The mucosa of the posterior one-third of the tongue presents numerous lymphatic nodules that constitute the lingual tonsils.

V. PALATE

The palate, composed of hard and soft regions, separates the oral and nasal cavities from each other. Therefore,

the palate possesses a nasal and an oral aspect. The oral aspect is covered by stratified squamous epithelium

(partially keratinized on the hard palate), whereas the nasal aspect is covered by a respiratory epithelium. The subepithelial connective tissue presents dense collagen fibers interspersed with adipose tissue and mucous glands. The core of the hard palate houses a bony shelf, whereas that of the soft palate is composed of skeletal muscle.

VI. TOOTH DEVELOPMENT

Tooth development (odontogenesis) may be divided into several stages (see Graphic 13-1). These are named according to the morphology and/or the functional state of the developing tooth. Dental lamina formation is followed by bud, cap, and bell stages. Dentin formation initiates the apposition stage, followed by root formation and eruption. These stages occur in both primary (deciduous teeth) and secondary (permanent teeth) dentition.

CHAPTER OUTLINE

Graphics

Graphic 14-1 Stomach and Small Intestine p. 336 Graphic 14-2 Large Intestine p. 337

Tables

Plates