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Home , Fauces (throat), Frenulum of tongue, Hard palate, Parotid duct, Parotid gland, Soft palate

Dr. Randall E. Merchant [email protected]

THE ORAL CAVITY AND

Objectives

1. Define the limits of the oral cavity and understand the varying features of the .

2. Compare and contrast the structure of the four types of papillae over the dorsum of the .

3. Describe the basic structure of a bud.

4. Define the major subdivisions of a .

5. With the microscope, identify the three types of major salivary glands and the morphologic features that distinguish them from each other. Recognize and know the function of other structures in BOLD in the laboratory guide.

6. Describe the function of striated ducts and how they affect the consistency of the .

7. Identify the structures on the CD listed in the laboratory guide.

I. General Features of Oral Cavity

A. Definitions

1. Vestibule - internal to the and , as far back as the teeth

2. Oral Cavity Proper - behind the teeth (forward and lateral), bounded above by the hard and soft , the tongue below, ends posteriorly at the (beginning of the oropharynx)

B. Masticatory Mucosa - present on gingiva, dorsum of tongue, and

1. Stratified squamous keratinized (parakeratinized)

2. Underlying connective tissue contains Meissner's corpuscles & minor salivary glands (mostly -secreting)

Lingual Minor Salivary Glands

Submandibular

Frenulum of Tongue Sublingual

O penings of Sublingual Ducts Opening of

C. Lining Mucosa - found everywhere else except gingiva, dorsum of tongue, and hard palate

1. Stratified squamous nonkeratinized epithelium

2. Underlying connective tissue contains Meissner's corpuscles & minor salivary glands (mostly mucus-secreting and classified morphologically as compound tubuloacinar) II. Teeth

A. Overview

1. Divided into an enamel-covered crown, a -covered root, and a cervix - where the cementum and enamel meet

2. Most of tooth composed of dentin, surrounding the pulp cavity

B. Enamel

1. Hardest substance of body, 96% mineralized (calcium, hydroxyapatite)

2. Formed by amelioblasts (lost as tooth erupts)

C. Dentin - formed and maintained by odontoblasts (at pulp cavity - dentin junction)

1. Organic composition of , composed of 70% calcium hydroxyapatite and its organic component mostly collagen, proteoglycans, and glycoproteins

2. Odontoblast Processes - located within dentinal tubules throughout the dentin

3. Dentinal Tubules - S-shaped curves in dentin that extend to dentino-enamel or dentino-cementum junction

D. Pulp Cavity

1. Contains gelatinous connective tissue with blood vessels, and lymphatics

2. Odontoblasts at the periphery E. Cementum - composed of 45-50% calcium hydroxyapatite, organic component collagen, glycoproteins proteoglycans

1. Cementocytes - in lacunae, resemble osteocytes

2. Periodontal Ligament - collagen fibers, extend from the cementum to the bone, helps hold tooth in its socket

III. Tongue

A. General information

1. Dorsal Surface - anterior 2/3 and posterior 1/3 separated by the sulcus terminalis a. root of the tongue - another name for the posterior 1/3 b. covered by stratified squamous keratinized (parakeratinized) epithelium c. lingual salivary glands - some mucus- secreting others serous-secreting d. papillae found over anterior 2/3 of this surface

2. Anterior Surface - covered by stratified squamous non- keratinized epithelium

B. Papillae - only on the dorsum of the tongue

1. Filiform - most numerous of papillae a. short, tapering structures, point aimed toward the back of oral cavity b. covered by parakeratinized epithelium with a connective tissue core c. no taste buds associated with them

2. Fungiform - occur singularly over the dorsum of the tongue a. mushroom shaped, appear red due to high vascularity b. covered by non-keratinized epithelium with a connective tissue core c. taste buds located on apical surface

3. Circumvallate - 10-15 in number, located anterior to sulcus terminalis a. mushroom shaped and surrounded by a deep furrow b. taste buds along their lateral surface c. lingual glands - the serous glands of Von Ebner associated only with these papillae, their duct empty into furrows

4. Foliate - Filiform a. along lateral edge of tonPapillaegue b. poorly developed in man Fungiform c. taste buds Papilla

Skeletal Muscle of Tongue

Epithelial Cells Circumvalate Papilla Taste Cell Taste Buds Taste Pore Von Ebner’s Glands

C. Taste Buds - associated with fungiform, circumvallate, and foliate papillae

1. Basic Structure - oval structure, apex reaches surface having access to the oral cavity through a taste pore

2. Component Cells - neuroepithelial cells and supportive cells

Stratified Squamous Epithelium

Neuroepithelial Cell Taste Pore

3. Innervation - fibers penetrate basement membrane to contact neuroepithelial cells a. Cranial Nerve V () - general sensation b. Cranial Nerve VII () - taste to anterior 2/3 of tongue c. Cranial Nerve IX (Glossopharyngeal Nerve) - taste to posterior 1/3 of tongue

D. Muscles of the tongue

1. Striated muscle in three planes at 90o to each other

2. Innervated by Cranial Nerve XII (Hypoglossal Nerve)

IV. Major Salivary Glands - Parotid, Submandibular, and Sublingual

A. General Features

1. Basic Structural Features - compound acinar (Parotid Glands) or compound tubuloacinar glands (Submandibular and Sublingual Glands)

2. Salivon - minimal physiological parenchymal unit ( + its duct that modifies the product)

Parotid Duct

Tongue

Openings of Sublingual Ducts

Opening of Submandibular Duct

Sublingual Gland Ducts of & Submandibular Duct

Submandibular Gland B. Component cells - forms acini and/or tubular glands

1. Serous Cells - only parenchymal cells of Parotid Glands and a portion of the population in the Submandibular and Sublingual Glands a. display apical eosinophilic apical secretory granules and basal RER b. joined tightly together by cell junctions c. release their granules in response to parasympathetic nervous stimulation d. can form serous demilumes in the Submandibular and Sublingual Glands

2. Mucus Cells - only found in the Submandibular and Sublingual Glands a. show mucinogen granules in apical cytoplasm as well a prominent Golgi apparatus b. if serous demilunes present, canaliculi extend between the mucus cells to allow secretions of serous cells to reach the lumen of the duct

3. Myoepithelial Cells - found in all three types of major salivary glands a. contractile cells with processes embracing secretory cells of acini b. also found around cells of intercalated ducts

C. The Duct System

1. Intercalated Ducts (always an Intralobular Duct) a. formed of a simple cuboidal epithelium b. in all major salivary glands but most prominent in Parotid Glands c. cells add bicarbonate ions to saliva

2. Striated Ducts (can be an Intralobular or Interlobular) a. formed of a simple columnar epithelium b. are intensely eosinophilic because of high numbers of mitochondria in basal striations c. their cell junctions are extensive d. account for approximately 75% of the volume of saliva e. remove sodium and chloride from saliva

3. Interlobular and Excretory Ducts a. may be pseudostratified or stratified columnar epithelium b. largest excretory ducts are lined by stratified squamous epithelium

D. Diagnostic Features

1. Parotid Gland - compound acinar gland a. serous acini only b. striated ducts prominent

2. - compound tubuloacinar gland a. serous and mucous acini - serous acini dominant b. striated ducts prominent

3. Sublingual Gland - compound tubuloacinar gland a. serous and mucus acini - mucus acini dominant b. striated ducts poorly developed

E. Saliva

1. Produces 1.0 - 1.2 liters/day

2. Composed chiefly of water, proteins, electrolytes, and IgA

3. Is hypotonic because sodium is resorbed by striated ducts

4. Parasympathetic stimulation of glands produces watery saliva, while sympathetic stimulation yields thicker saliva with relatively more mucus

5. Functions - protects oral cavity, limits bacterial growth, solubilizes food for taste, contains enzymes (amylases, peroxidases) that begin digestion, buffers against noxious ingested agents, and helps maintain the teeth

Oral Cavity - Laboratory List Find the following among the images on the CD

Lip keratinized stratified squamous epithelium Submandibular Gland hairs compound tubuloacinar gland sebaceous glands mucus- and serous-secreting cells the vermillion zone acini moist stratified squamous epithelium mucous tubules accessory (minor) salivary glands serous demilunes serous- and mucus-secreting cells intercalated ducts orbicularis (skeletal) muscle striated ducts interlobular ducts Tooth enamel Sublingual Gland dentin mixed compound tubuloacinar gland dentine tubules mucous acini & mucus-secreting cells pulp cavity mucus tubules cementum serous-secreting cells cementocyte lacunae serous demilunes interlobular ducts Tongue filiform papillae parakeratinized, stratified squamous epithelium moist stratified squamous epithelium taste buds circumvallate papillae glands of Von Ebner serous- and mucus-secreting cells accessory salivary glands

Parotid Gland compound, acinar gland serous acini and acinar cells intralobular ducts intercalated ducts striated ducts simple columnar epithelium interlobular ducts stratified columnar epithelium