Tongue and epiglottis
Learning objectives
After completing this study unit you will be able to:
- Describe the structure of the tongue and identify the structures in histological images.
- Explain the structure and function of the epiglottis and name its various epithelia.
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The tongue is a muscular organ with intrinsic and extrinsic muscles. The tongue has keratinized squamous epithelium on its dorsal surface, specifically the fungiform/filiform papillae, while its ventral surface is largely lined with multi-layered, nonkeratinized squamous epithelium and characterized by numerous papillae that house taste buds to facilitate gustation as well as sensory detection of touch and temperature.
About three quarters of all taste buds are found on the dorsal surface of the tongue in small raised structures called papillae, of which there are four different types:
- Filiform papillae are thread-like and serve the sense of touch. They do not contain taste buds and are thus not involved in taste sensation.
- Fungiform papillae are mushroom-shaped and contain numerous taste buds on their surface.
- Foliate papillae are leaf-shaped and also contain taste buds.
- Circumvallate papillae are flat and surrounded by a moat. Surrounding each papilla is a depression in which gustatory glands (of Von Ebner) empty a serous secretion to remove food residues. They contain about 50% of all taste buds.
The lamina propria of the tongue is interspersed with numerous glands, blood vessels and nerve fibers, while the deeper muscular coat consists of striated muscle fibers that give the tongue its high mobility.
The epiglottis is located at the entrance to the larynx and is made of elastic cartilage. It closes the laryngeal inlet during swallowing to prevent the passage of food and liquid into the lungs via the trachea.
The lingual surface of the epiglottis faces the tongue and the laryngeal surface faces the larynx. Both sides have a different epithelial lining. The lingual surface is covered with thick, stratified, nonkeratinized squamous epithelium, while the laryngeal surface is lined with respiratory ciliated epithelium. There are many seromucous glands in the lamina propria that keep the epithelium moist.
Watch the following video to learn more about the histology of the tongue and epiglottis:
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Tongue
Time to review the histological appearance of the above structures in the image gallery below:
Epiglottis
Time to review the histological appearance of the above structures in the image gallery below:
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