Anterior surface of the tongue.

The tongue is a mass of interlacing skeletal muscle , connective tissue with some mucous and serous glands, and pockets of adipose tissue, covered in oral mucosa.

A V-shaped line (shallow groove)- the sulcus terminalis, divides the tongue into an anterior 2/3 and a posterior 1/3.

The mucosa covering the upper surface of the tongue is thrown into numerous projections called the lingual papillae in the anterior 2/3rd of the tongue.

In the posterior 1/3rd, there are no papillae, but there are lots of lymphoid follicles present.

The three types of papillae are:

• fungiform (mushroom like)
• filiform (filum - thread like)
• circumvallate

(foliate papillae are uncommon in humans)

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Fungiform and Filiform Papillae

The slide above shows a vertical section through the tongue, taken close to its tip.

Can you identify the fungiform and filiform papillae, glands, and skeletal muscle.

Notice the type of epithelium that covers the superior surface of the tongue (including the papillae).

Use the information below, and the diagrams to help you.

Filiform papillae are the most common. They are keratinised and in the living, they look white.

Fungiform papillae are not keratinised, but are highly vascularised. In the living, they look red. most of the fungiform papillae have some taste buds.

Underneath the papillae, there are mucous and serous glands, pockets of adipose tissue, and a layer of skeletal muscle and connective tissue. The skeletal muscle is arranged in three different planes, which allows the tongue to perform a number of complex movements.

Circumvallate papillae

Now have a look at this section, a vertical section of tongue taken just anterior to the sulcus, that shows part of a circumvallate papilla . See if you can identify Von Ebner's glands, the cleft of the circumvallate papilla, the taste buds, and the muscle layer.

The papillae in this region are very large, notice the scale bar.

These papillae have taste buds in the medial walls of the cleft. These papillae are larger than the other two types of papillae. Glands, called Von-Ebner's glands (serous glands) open into the cleft.

Taste buds contain epithelially derived taste receptor cells, sustentacular cells that surround a small central cavity tat opens onto the surface as a tiny taste pore. Basal cells renew both of these types of cell. Chemicals stimulate the receptors, and initiate impulses in the afferent nerve fibres.

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