Oral Cavity | histology – University of Michigan

1. Lining Mucosa

Slide 114R (lip, human, H&E) View Virtual Slide Slide 114 triC (lip, human, trichrome) View Virtual SlideSlide 114M (lip, monkey, H&E) View Virtual Slide

A stratified squamous non-keratinized epithelium lines the oral surface of the lips, cheeks, floor of mouth, and covers the ventral surface of the tongue In slide 114 (human) and 114M (monkey) of the lip, note that skin (stratified, keratinized squamous epithelium with hair follicles) covers the external surface View Image, skeletal muscle (orbicularis oris muscle) forms the core View Image, and a mucosal epithelium(stratified, non-keratinizing squamous epithelium) covers the internal surface View Image. A lamina propria underlies the mucosa and small salivary glands (labial salivary glands) View Image are present in the submucosa. Note the transition zone between the keratinized epithelium of the skin and the nonkeratinized epithelium of the mucosa. This transition zone is called the vermillion zone(present only in humans) View Image. In the transition zone, long connective tissue papillae extend deep into the epithelium. Capillaries are carried close to the surface in these papillae. Because the epithelium is very thin in this region, the lips appear red (this arrangement may or may not be apparent in your glass slides). Salivary glands are lacking in the vermillion zone, therefore, the lips must be continuously moistened (by the tongue) to prevent drying out.

Slide 115 (fetal palate, H&E) View Virtual SlideSlide 115 (fetal palate, trichrome) View Virtual Slide

A stratified squamous keratinized epithelium is found on surfaces subject to the abrasion that occurs with mastication, e.g., the roof of the mouth (palate) and gums (gingiva). Slide 115, which you used to study bone and the respiratory system, is a longitudinal section through the palate and includes the lip, gingiva, hard palate, and a portion of the soft palate [orientation]. This tissue is from a term fetus (with unerrupted teeth) and the epithelium over the hard palate is not yet fully differentiated (i.e. not fully keratinized). The slide is, however, a good overall orientation to the histology of the hard and soft palate. In the adult the epithelium of the hard palate is keratinized. Identify respiratory epithelium, bone (hard palate), forming tooth View Image, and skeletal muscle in the lipView Image and the soft palate View Image. Some slides show mucous salivary glands View Image in the submucosa.

Slide 116 40x (tongue, H&E) View Virtual SlideSlide 117 20x (tongue, H&E) View Virtual SlideSlide 117 40x (tongue, H&E) View Virtual SlideSlide 117N 40x (tongue, rabbit, H&E) View Virtual Slide

The dorsal surface and lateral borders of the tongue are covered by a mucous membrane that contains nerve endings for general sensory reception and taste perception. In slide 116, the dorsal surface of the tongue is covered with tiny projections called papillae View Image, which are lacking on the ventral surface. The body of the tongue is composed of interlacing bundles of skeletal muscle View Image that cross one another at right angles. The dense lamina propria of the mucosa is continuous with the connective tissue of the muscle, tightly binding the mucous membrane to the muscle. Some glass slides in our collection show mucous glands in the submucosa, which are found only on the ventral side of the tongue. These glands are not present in the digital slides, but their ducts may be seen View Image.

In slide 116 there are two types of papillae on the tongue. Locate the numerous filiform papillae View Image, that appear as conical structures with a core of lamina propria covered by a keratinized epithelium. Fungiform papillae View Image are scattered among the filiform papillae. They have expanded smooth round tops and narrower bases. In young children, the fungiform papillae can be seen with the naked eye as red spots on the dorsum of the tongue (because the non-keratinized epithelium is relatively translucent). These papillae are less readily observed in adults, because of slight keratinization of the epithelium.

Slide 117 and especially slide 117N contain examples of circumvallate papillaeView Image. These are large circular papillae surrounded by a deep trench. The covering epithelium is non-keratinized. Taste budsView Image, the chemoreceptors for the sense of taste, are located on the lateral borders. Each taste bud contains about 50 spindle shaped cells that are classically described based on their appearance as light (receptor) cells, dark (supporting) cells, and basal (stem) cells, although these distinctions are difficult to see in your slides so we do not require you to identify the cell types. Non-myelinated nerves from cranial nerves VII, IX, or X (depending on the location of the taste bud) synapse with the receptor and, to some extent, supporting cells of the taste bud. Some slides show serous glands (of von Ebner) View Image in the lamina propria and interspersed between the bundles of muscle beneath the papillae. These glands drain into the base of the trench around the circumvallate papillae.

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Oral Cavity | histology - University of Michigan