Welcome to the wonderful world of histology. Histology is how we study the human body on a cellular level. This week we are going to take a look at the histology of the special sense of taste. There are four types of papillae present on our tongue. Lingual papillae are small structures on the upper surface of the tongue that give it its characteristic rough texture. Three of these contain taste buds.
Filiform are conical in shape and are the only group of papillae that do not contain taste buds.
Fungiform are blunt structures, whereas foliate are slit-like in shape and are on the margins of the tongue. The circumvallate are large and dome-shaped they are in two lines that form a ‘v’ shape towards the back of the tongue. The taste buds in these papillae are found towards the edge.
So how about taste? Taste is carried by over 3000 multicellular chemoreceptive units called taste buds. They extend the full thickness of the epithelium. Within this, there are 50 specialised cells for taste, and they circle the structure. At the surface of the tongue, there are apical taste pores.
Within the tastebuds, the special chemoreceptive units there are three different types of cells. There are taste receptor cells that have apical microvilli with chemical receptors at the pore. There are supporting cells that support the sensory cells. The basal cells act as stem cells, creating a basis for the formation of more sensory cells.
How do we taste? When we eat, a chemical is released, and it enters the taste pore. It binds its receptor and causes a release of a neurotransmitter from the sensory cell. This stimulates sensory nerve endings within the taste bud. We can interpret five different tastes – sweet, sour, salty, bitter, and umami. These different tastes allow us to enjoy food and interpret the different flavours.