 Dear students, in this topic we shall discuss chemoreceptors which include the receptors for taste and smell. The chemoreceptors are the cells which are specialized to acquire information about the chemical environment. There are two categories of chemoreceptors. First are the gastatory receptors, that is, taste receptors, and the second category includes the olfactory receptors, that is, the smell receptors. First, we shall discuss the gastatory or taste receptors in detail. The taste receptors respond to the dissolved molecules that come in direct contact with the receptor cells. Taste receptors are widely found in animal kingdom. First, we shall discuss the taste receptors in insects. The organs of taste in insects are called sensory sensilla. These sensory sensilla are located on their feet and mouth parts. A sensilla consists of many receptor cells. Each receptor cell is sensitive to a particular chemical. Insects can respond to water, cations, anions, and carbohydrates. The receptor cells of insects have hair-like appearance due to their longer dendrites. The dendrites are sent to the cuticle, that is, they come out of the cuticle and can be seen from outside. The cuticle around the sensilla has minute pores. There are small pores in the cuticle where stimulant molecules enter the sensilla and direct contact with dendrites. This stimulus is converted into electrical signals by the underlying soma of sensory cells. These students, fish's sensory receptors for taste are located on different parts. Some fish have pectoral fins that are modified into the organs of taste. They keep receptors with them. The taste receptors in all other vertebrates are located at their interior and inside their buccal cavity. For example, on the tongue, on their epiglottis, on the back of mouth and pharynx and upper esophageal area. These gastatory organs of vertebrates are called taste buds. We shall discuss this structure of taste bud. A taste bud is composed of about 50 types of modified epithelial cells. The most important of these epithelial cells are the sporting cells called sustenticular cells, basal cells, and taste receptor cells. Among these, basal cells are progenitor cells in which continuous cell division is carried and as a result, they produce new taste receptor cells. Because the life of taste receptor cells is not too long and they are replaced after Now we shall see the structure of taste receptor cells. The outer types of taste receptor cells have a minute pore which is called taste pore. Out of this taste pore, several microvilli protrude out. These microvilli protrude out of this taste pore. Actually, these receptors provide surface for taste and molecules. When taste and molecules are received through contact through these microvilli, then these taste cells generate this signal. This signal is a terminal, a network of neurons which receives these signals. Dear students, now we shall discuss the receptors for alfaction or smell. The alfactory receptors respond to airborne molecules which can stimulate the receptors from distance. These alfactory receptors can detect the odorants and pheromones. In insects, the alfactory sensilla are present on their antennae. On the antennae, they have alfactory receptors of insects and they smell from there. Whereas, vertebrates' alfactory receptors are present in the nasal cavity. Dear students, vertebrates' alfactory system contains two different types of organs. First is called the main alfactory epithelium that detects odorants. Second to hear that is called the meronazel organ that detects pheromones.