Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Sense Organs. Analyzers
Organs of Taste and Smell
The Organ of Smell and its Analyzer

The Organ of Smell is located in the olfactory region of the nasal mucosa, which encompasses the superior nasal concha and the corresponding area of the nasal septum, where the mucosa is covered by olfactory epithelium. Humans have approximately 40 million olfactory receptor Cells. The peripheral process, or dendrite, of an olfactory Cell terminates in a Swelling known as the olfactory club. At the tip of this club lie 10–12 motile olfactory hairs (cilia) that interact with odorants. After dissolving in the secretion of mucous glands, odorant molecules bind to receptor Proteins on the cilia, generating a Nerve Impulse. A single odor molecule is sufficient to stimulate one olfactory (sensory) cell. The central processes, or axons, of the olfactory cells pass between supporting cells and converge to form 20–40 olfactory nerves. These nerves enter the cranial cavity through the cribriform plate of the Ethmoid bone and project to the olfactory bulb. The olfactory bulb houses the secondary Neurons of the olfactory pathway. The axons of these cells form the olfactory tract, the fibers of which then pass through the anterior perforated substance and the olfactory trigone. Subsequently, these fibers follow a complex pathway through the fornix of the Brain and around the corpus callosum, ultimately reaching the mamillary bodies and the cortical center of the olfactory analyzer, located in the uncus of the parahippocampal gyrus. Olfactory impulses are also projected to the Hypothalamus, hippocampus, and amygdala—Key Components of the limbic system, which plays a vital role in mediating emotional responses.