Digestive System II ppt.

Department of Anatomy &Histology Dr.Raja Ali

Digestive System:
Taste buds: are present on fungiform, foliate, and circumvallate papillae.
In histologic sections, taste buds appear as oval, pale-staining bodies that extend through the thickness of the epithelium . A small opening onto the epithelial surface at the apex of the taste bud is called the taste pore, Fig.( 1 ).
Three principal cell types are found in taste buds:
• Neuroepithelial (sensory) cells are the most numerous cells in the taste bud. These elongated cells extend from the basal lamina of the epithelium to the taste pore, through which the tapered apical surface of each cell extends microvilli . Near their apical surface they are connected to neighboring neuroepithelial or supporting cells by tight junctions. At their base they form a synapse with the processes of afferent sensory neurons of the facial (cranial nerve VII), glossopharyngeal (cranial nerve IX), or vagus (cranial nerve X) nerves.
• Supporting cells are less numerous. They are also elongated cells that extend from the basal lamina to the taste pore. Like neuroepithelial cells, they contain microvilli on their apical surface and possess tight junctions, but they do not synapse with the nerve cells.
• Basal cells are small cells located in the basal portion of the taste bud, near the basal lamina. They are the stem cells for the two other cell types. Taste buds are also present on the glossopalatine arch, the soft palate, the posterior surface of the epiglottis, and the posterior wall of the pharynx down to the level of the cricoid cartilage.
Fig.( 1 ):schematic &histological section of taste buds