Olfactory nerve (olfactory organ and bulb) (English)

Microscopic view of the olfactory organ (olfactory part of nasal mucosa) and neural pathways of the olfactory bulb. The olfactory epithelium contains olfactory sensory neurons (olfactory receptor cells) that are wedged between supporting and basal epithelial cells. The peripheral processes (dendrites) of each neuron bears dendritic bulbs (sometimes known as olfactory vesicles), with cilia protruding above the epithelial surface which react to odiferous stimuli dissolved with the nasal mucus. The central processes(axons) of each olfactory neuron collect into olfactory fiber bundles that pass through the cribriform plate and project into the olfactory bulb. Underlying the olfactory epithelium is the lamina propria which contains olfactory glands (of Bowman) that span the olfactory epithelium and secrete mucus. The olfactory bulb contains about 2000 olfactory glomeruli formed by synapses between terminal ends of the olfactory fiber bundles and the primary dendrites of projection neurons (mitral and tufted cells) as well as periglomerular cells, which are involved in odor discrimination. The projection neurons in turn project their axons (afferent fibers) posteriorly/caudally to form the olfactory tract. Additionally, the olfactory bulb contains [amacrine] granular cells which receive efferent fibers from central brain areas (as well as other mitral/tufted cells) and modulates the afferent signals from mitral/tufted cells.