Sensory - Smell Development
Embryology - 27 Jun 2024 Expand to Translate |
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Introduction
These notes introduce the development of the sense of smell or olfaction: nasal placode, olfactory epithelium, olfactory bulb, vomeronasal organ. Recent research has shown a relationship between what the receptive epithelium is exposed too and how the central neural pathway develops, similar to that shown earlier for the visual system.
A French research group has recently been investigating the development of smell in the fetus and in neonates. The nasal epithelium has also been a researh "hot topic" as it is one of the few easily accessible sites of adult neural stem cells.
Note the different spellings "odour" (UK) or "odor" (USA). Anosmia is the term used to describe having no sense of smell. Anosmia/hyposmia is related to the absence or hypoplasia of the olfactory bulbs and tracts.
Smell Links: Introduction | placode | Rhinencephalon | head | respiratory | Student project | taste | sensory | Category:Smell | ||
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Senses Links: Introduction | placode | Hearing and Balance hearing | balance | vision | smell | taste | touch | Stage 22 | Category:Sensory |
Some Recent Findings
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More recent papers |
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This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.
More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Smell Development <pubmed limit=5>Smell Development</pubmed> |
Olfactory Epithelium
Adult - pseudostratified columnar epithelium overlying a lamina propria
Five basic cell types:
- horizonatal basal cells - not present embryonically.
- globose basal cells - transit amplifying progenitors of the olfactory epithelium.
- sustentacular cells - aligned on the surface with thin cytoplasmic projections terminating at the basal lamina.
- olfactory receptor neurons - located in an intermediate zone between basal and apical layers, form the bulk of the epithelium.
- olfactory gland cells (Bowman's gland/duct complex) - extend from the glands in the lamina propria to the ducts within the epithelium. Function to carry secretions to the apical epithelial surface.
Olfactory ensheathing cells
- neural crest in origin.[2]
- accompany and ensheath the small olfactory axons of the nonmyelinated olfactory nerves.
- compartmentalize the small olfactory axons into fascicles.
- allow regenerating olfactory nerves to cross the peripheral/central nerve threshold.
Olfactory Receptors
Odours bind to and activate olfactory receptors located on the dendrites of sensory neurons in the nose and how the mitral cells of the olfactory bulb (OB) process olfactory information. What has yet to be thoroughly described is how the piriform cortex receives and transforms information arriving from the OB via the lateral olfactory tract (LOT). Although the cell types present in the piriform cortex are known (Shepherd, 2004), previous work has failed to differentiate between disparate electrophysiological profiles and synaptic contacts made between principal cells.
Embryonic
Week 5 to 8 - Stage 15, 17, 20
Development of the Human Olfactory System (Carnegie Stage 15, 17 and 20)[6]
Abbreviations: (cal) calretinin immunostaining, (CS) Carnegie stage, (HE) hematoxylin-eosin staining, (MZ) marginal zone, (OB) olfactory bulb, (OP) olfactory placode, (Tel) telencephalon.
Week 8 - Stage 22
Olfactory Pathway
Olfactory receptor neurons (ORNs) - odours bind and activate olfactory receptors located on dendrites of sensory neurons in the nose.
Olfactory bulb (OB) - Mitral cells process olfactory information (encoded in a chemotopic map).
Lateral olfactory tract (LOT) - pathway to cortex.
Primary olfactory cortex (= Piriform cortex) - receives and transforms information.
Vomeronasal Accessory Olfactory System
Adult Mouse VMO anatomical position and showing also solitary chemosensory cells[8]
The vomeronasal accessory olfactory system (vomeronasal organ, VNO) is involved in detecting and transfering pheromone information through the vomeronasal nerve (nervus vomeronasalis) to the neuroendocrine hypothalamus. This signaling pathway can be used for mating and as olfactory cues for nocturnal animals. There are two families of receptors located in the vomeronasal organ the V1Rs and the V2Rs, are thought to detect pheromonal signals. [9]
Human embryos also have a vomeronasal organ, though later many structures such as the vomeronasal nerve, accessory olfactory bulb and chemoreceptor cells within the organ are lost. Therefore it is not clear whether there is any postnatal neuroendocrine role for this structure.[10]
Grueneberg Ganglion
The Grueneberg ganglion[11] "Within the nasal epithelium of mammals, there are several compartments which are populated with neuronal cells. One of them - the so-called Grueneberg ganglion - is composed of ciliated neurons residing in the anterior region of the nose."
Histology
Animal Models
Mouse
The nasal mucosa features four separate olfactory areas:
- main olfactory epithelium (MOE)
- septal organ (SO)
- ganglion of Grüneberg (GG)
- vomeronasal sensory epithelium (VNsE) forms a part of the vomeronasal organ (VNO)
- Links: Mouse Development
Abnormalities
Anosmia
Term used to describe having no sense of smell. Anosmia/hyposmia is related to the absence or hypoplasia of the olfactory bulbs and tracts.
Kallmann Syndrome
- A developmental disease affecting both the hormonal reproductive axis and the sense of smell.
- Affected individuals have mutations in either of two different genes KAL1 and FGFR1 (20%) and prokineticin receptor-2 (PROKR2) or prokineticin-2 (PROK2) genes (10%).
Choanal Atresia
- Choanal atresia is the most common form of congenital nasal obstruction, usually diagnosed at birth.[12]
- failure of the posterior nasal cavity (choanae) to communicate with the nasopharynx.
- unilateral or bilateral bony membranous septum located between the nose and the pharynx.
- occurs in approximately 1 in 5000 to 7000 live births.
- Thought to be secondary to an abnormality during the rupture of the buccopharyngeal membrane in the embryological period.
Additional Images
Historic
Keith, A. (1902) Human Embryology and Morphology. London: Edward Arnold.
References
- ↑ <pubmed>24440370</pubmed>
- ↑ 2.0 2.1 <pubmed>21943152</pubmed>
- ↑ <pubmed>21441906</pubmed>
- ↑ <pubmed>21041441</pubmed>| J Cell Biol.
- ↑ <pubmed>20624980</pubmed>
- ↑ <pubmed>26270645</pubmed>
- ↑ <pubmed>20723208</pubmed>| Neural Dev.
- ↑ <pubmed>20689832</pubmed>| PLoS One.
- ↑ <pubmed>20844586</pubmed>| PLoS One
- ↑ <pubmed>16487792</pubmed>
- ↑ <pubmed>20503179</pubmed>
- ↑ 12.0 12.1 <pubmed>21772853</pubmed>
Articles
<pubmed>7469043</pubmed> <pubmed></pubmed>
Reviews
<pubmed>21041441</pubmed>| JCB <pubmed>20502748</pubmed> <pubmed>20387075</pubmed> <pubmed>19172161</pubmed> <pubmed>18808328</pubmed> <pubmed>18809492</pubmed>
Search PubMed
Search Pubmed: Smell Development | olfactory receptors | Olfactory bulb development | anosmia
External Links
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Terms
- glomerulus - the functional unit of the olfactory bulb.
- odorant - a compound that elicits the perception of smell.
- odorant receptor - (OR) a receptor expressed by an olfactory sensory neuron. Receptor belongs to the G protein–coupled receptors (GPCR) superfamily. There are multiple families of odorant receptors, which include the OR (the largest family), TAAR, V1R, V2R, and formyl peptide-like receptors.
- olfactory cortex - refers to the brain regions that receive direct input from the olfactory bulb are responsible for the perception of smell and for generating odor-evoked behaviours. The five brain regions are the: piriform cortex, anterior olfactory nucleus, olfactory tubercle, entorhinal cortex, and amygdala.
- olfactory glomeruli - spherically shaped regions of neuropil where information is passed from sensory neurons to postsynaptic neurons.
Glossary Links
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Cite this page: Hill, M.A. (2024, June 27) Embryology Sensory - Smell Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Sensory_-_Smell_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G