Clinical note: The oral cavity has a large and varied bacterial flora. Bacteria may accumulate and form a layer (plaque) on a tooth, releasing acids that demineralize the enamel and dentine and produce dental cavities. Other bacteria proliferating in the gingival cleft may destroy the periodontal ligament, cause resorption of alveolar bone, and loosening of teeth.

Examine a section of developing tooth in the lower jaw of the fetal skull on slide 130. The stage shown is closest to that in Fig. 15-11. Identify the dental pulp, odontoblasts, dentine, enamel (partially gone), and the (partially disrupted) layer of ameloblasts (Fig. 15-8 through 15-11).

Briefly describe how the odontoblast and ameloblast layers form the tooth.

Examine the preserved-mounted specimen of tongue and larynx,

• Note the macroscopic features (median sulcus, circumvallate papillae, filiform papillae, lingual tonsils, etc.)

What is the functional significance of these various surface structures on the tongue?

Examine sections of the tongue (slides 70 and 77) and identify filiform and fungiform papillae on the dorsal lingual surface (Figs. 15-4 and 15-5). On slide 77 look for a circumvallate papilla. (Not every slide 77 shows such a papilla, so you may have to share your neighbor's slide).

• Identify taste buds and the serous von Ebner's glands associated with circumvallate papillae (Figs. 15-5 and 15-6).

What are the chief histological differences among the different types of lingual papillae?

Let's take a look at the salivary glands.