Sensory epithelium

The sensory epithelium represents a specialized form of epithelium that is able to react to stimuli from the external environment. It occurs as squamous epithelium in two forms.

Primary sensory epithelium
It originates from neuroectoderm. It is characterized by the presence of both types of nerve processes - dendrites and axon. The olfactory epithelium, retina is of neuroectoderm origin.

Secondary sensory epithelium
They differ in their origins. It comes directly from the germ sheet - ectoderm. It does not contain a conducting process (axon). Such an epithelium is capable of responding to a stimulus, but without the presence of a nerve fiber the signal could not be further sent to higher centers; eg taste cup.