ethmoid sinus

The ethmoid air cells consist of numerous thin-walled cavities in the ethmoidal labyrinthOtorhinolaryngology, Head and Neck Surgery, Anniko, Springer, 2010, page 188 that represent invaginations of the mucous membrane of the nasal wall into the ethmoid bone. They are situated between the superior parts of the nasal cavities and the orbits, and are separated from these cavities by thin bony lamellae.

There are 5-15 air cells in either ethmoid bone in the adult, with a combined volume of 2-3mL.{{Citation |last1=Cappello |first1=Zachary J. |title=Anatomy, Head and Neck, Nose Paranasal Sinuses |date=2023 |url=http://www.ncbi.nlm.nih.gov/books/NBK499826/ |work=StatPearls |access-date=2023-07-04 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29763001 |last2=Minutello |first2=Katrina |last3=Dublin |first3=Arthur B.}}

The ethmoidal cells (sinuses) and maxillary sinuses are present at birth.Moore, K.L Et al(2014). Clinically Oriented Anatomy. Baltimore: Page960 At birth, 3-4 air cells are present, with the number increasing to 5-15 by adulthood.

• The anterior ethmoidal cells drain (directly or indirectly) into the middle nasal meatus by way of the ethmoidal infundibulum.
• The middle ethmoidal cells drain directly into the middle nasal meatus.
• The posterior ethmoidal cells drain directly into the superior nasal meatus at the sphenoethmoidal recess; sometimes, one or more opens into the sphenoidal sinus.

The ethmoidal labyrinth is divided by multiple obliquely oriented, parallel lamellae. The first lamellae is equivalent to the uncinate process of ethmoid bone, the second corresponds the ethmoid bulla, and the third is the basal lamella, and the fourth is equivalent to the superior nasal concha.

The anterior and posterior ethmoid cells are separated by the basal lamella{{cite book |last1=Hechl |first1=Peter S. |title=Endoscopic Anatomy of the Paranasal Sinuses |last2=Setliff |first2=Reuben C. |last3=Tschabitscher |first3=Manfred |chapter=The ethmoid bone and middle turbinate |date=1997 |publisher=Springer Vienna |isbn=978-3-7091-7345-9 |pages=9–28 |language=en |doi=10.1007/978-3-7091-6536-2_2}} (also known as the ground lamella). It is one of the bony divisions of the ethmoid bone and is mostly contained inside the ethmoid labyrinth. The basal lamella is continuous medially with the bony middle nasal concha. Anteriorly, it vertically inserts into the ethmoid crest; the middle part attaches obliquely into the orbital lamina of ethmoid bone (lamina papyricea) while the posterior part attaches into the orbital lamina horizontally.

The ethmoidal air cells receive sensory innervation from the anterior and the posterior ethmoidal nerve (which are ultimately derived from the ophthalmic branch (CN V₁) of the trigeminal nerve (CN V)), {{Clarification needed|date=July 2023|reason=Parasympathetic mucomotor innervation only or sensory as well?|text=and the orbital branches of the pterygopalatine ganglion, which carry the postganglionic parasympathetic nerve fibers for mucous secretion from the facial nerve.}}{{Citation needed|date=July 2023}}

Haller cells are air cells situated beneath the ethmoid bulla along the roof of the maxillary sinus and the most inferior portion of the lamina papyracea, including air cells located within the ethmoid infundibulum.{{Cite journal |last1=Raina |first1=A |last2=Guledgud |first2=M V |last3=Patil |first3=K |date=May 2012 |title=Infraorbital ethmoid (Haller's) cells: a panoramic radiographic study |journal=Dentomaxillofacial Radiology |volume=41 |issue=4 |pages=305–308 |doi=10.1259/dmfr/22999207 |issn=0250-832X |pmc=3728998 |pmid=22241882}} These may arise from the anterior or posterior ethmoidal sinuses.{{Citation needed|date=July 2023}}

Also known as a sphenoethmoidal air cell, an Onodi cell is a posterior ethmoidal air cell that lies superolateral to the sphenoid sinus, often extending into the anterior clinoid process.{{Cite journal |last1=Srinivas |first1=C. V. |last2=Kauser |first2=Safina |date=October 2022 |title=Anatomy and Variations of Onodi Cells and Haller Cells: A HRCT Cum Clinical Analysis in Sinonasal Disease and Polyposis |journal=Indian Journal of Otolaryngology and Head & Neck Surgery |volume=74 |issue=Suppl 2 |pages=1683–1689 |doi=10.1007/s12070-021-02828-x |issn=2231-3796 |pmc=9702225 |pmid=36452524}} Onodi cells are clinically significant because they lie in close proximity to the optic nerve and internal carotid artery, so surgeons should be aware of their existence when performing surgery on the sphenoid sinus so as not to damage these important structures.

A central Onodi air cell is a variation in which a posterior ethmoid cell lies superior to the sphenoid sinus in a midline position with at least one optic canal bulge.{{Cite journal |last1=Cherla |first1=Deepa V. |last2=Tomovic |first2=Senja |last3=Liu |first3=James K. |last4=Eloy |first4=Jean Anderson |date=2013 |title=The central Onodi cell: A previously unreported anatomic variation |journal=Allergy & Rhinology |volume=4 |issue=1 |pages=e49–e51 |doi=10.2500/ar.2013.4.0047 |issn=2152-6575 |pmc=3679569 |pmid=23772328}}

Acute ethmoiditis in childhood and ethmoidal carcinoma may spread superiorly causing meningitis and cerebrospinal fluid leakage or it may spread laterally into the orbit causing proptosis and diplopia.Human Anatomy, Jacobs, Elsevier, 2008, page 210

File:Slide2ROMA.JPG|Ethmoid sinus. Ethmoidal air cells. Deep dissection. Superior view.

File:Diagram showing ethmoid sinus cancer that has spread to the lymph nodes CRUK 121.svg|Ethmoid sinus cancer that has spread to the lymph nodes

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Category:Bones of the head and neck

Category:Rhinology

Category:Otorhinolaryngology

Category:Sinus surgery