Introduction:
- Olfactory nerve is first cranial nerve.
- Both olfactory and optic nerve attaches to forebrain.
- No nuclei present, Olfactory nerve responsible for smell.
- Purely sensory.
- Each olfactory nerve consists of 20 minute bundle of non-myelinated nerve fibre.
FEATURES:
Primary sensory neuron:
- Present in epithelial lining of the nasal cavity.
- undergo continuous turnover.
👉Functional component- special sensory afferent fibres.
They carry sensation of smell from olfactory region of nasal cavity.
↓
Terminate in olfactory bulb.
Course:
✹Distributes the olfactory region of nasal cavity.
Why infection from nose can spread into brain?
- Bundles of olfactory nerve surrounded by 3 meninges near cribriform plate- piamater ,arachnoid mater, duramater.
- Thus, provide communication between subarachnoid space & lymphatics of nasal mucosa.
Clinical anatomy:
Anosmia:
- loss of olfactory fibers with aging.
- caused by abscess of frontal lobe of brain or pressure created on olfactory bulb or tract by meningioma in anterior cranial fossa, atrophic rhinitis, ethmoid fracture.
Head injury:
- If cribriform plate of ethmoid fractured, olfactory bulbs may be torn away from olfactory nerves as it passes through, which leads to anosmia.
- It also called CSF rhinorrhea.
Allergic rhinitis:
temporary olfactory impairment.
Unicate fits(Temporal lobe epilepsy):
caused by lesion of lateral olfactory area. it is imaginary disagreeable odors with involvment of tongue and lips.
Clinical testing of olfactory nerve:
By asking the patient to smell common odors- peppermint, garlic or cloves from each side of his nostril separately with eye closed.
(The above content is retrieved from multiple anatomy books, if you found any mistakes let me know in the comment box.)
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