Olfactory bulb
Bulbus olfactorius
Definition
The olfactory bulb is a ventral structure of the cerebral hemisphere that is part of the rhinencephalon.
It receives axons from bipolar neurons of the olfactory mucosa, which pass through the cribriform plate as the olfactory nerves.
The olfactory bulb contains an olfactory ventricle filled with cerebrospinal fluid and has seven histological layers, from superficial to deep: the olfactory nerve layer, glomerular layer (where multiple olfactory axons synapse with a mitral cell), external plexiform layer, mitral cell layer, internal plexiform layer, granular layer, and periventricular layer composed of axons entering or leaving the bulb.
The axons of mitral cells form the output of the bulb to the olfactory tract, transmitting olfactory information to various regions of the rhinencephalon and the limbic brain. It plays a crucial role in odor perception and in relaying this information to limbic and emotional circuits.
The olfactory bulb is highly developed in domestic mammals (notably in cats) compared to humans, in whom it is very small.
References
Barone R, Bortolami R. Anatomie comparée des mammifères domestiques, Tome 6, Neurologie I, Vigot, Paris, 2004.
Evans HE, de Lahunta A. Miller’s anatomy of the dog, 4th edition, Elsevier Saunders, St Louis, 2012.
