Anatomy & Physiology: The Unity of Form and Function, 7th Edition

Published by McGraw-Hill Education
ISBN 10: 0073403717
ISBN 13: 978-0-07340-371-7

Chapter 8 - Section 8.2 - Study Guide - Assess Your Learning Outcomes - Page 271: 11

Answer

The Ethmoid bone is a cranial bone situated between the eyes. It is a part of the medial wall of the orbit, and helps to form the roof and walls of the nasal cavity ; it also and contributes to the structure of the nasal septum. The ethmoid bone is porous and delicate in structure, and is easily compressed and damaged. The major parts of the ethmoid bone are the perpendicular plate, the the horizontal cribriform plate and the labyrinth. The perpendicular (vertical) plate is a thin plate of bone that forms two-thirds of the nasal septum--the vomer forms the lower one third. This septum divides the nasal cavity into right and left halves--fossae or air spaces. In some individuals the septum is curved toward one fossa or the other. This is a called deviated septum. A patient with this diagnosis may have some difficulty in breathing freely, and an ENT specialist may advise surgical correction. The second part of the ethmoid is the cribriform plate. This structure forms the roof of the nasal cavity. A median section of this roof area is called the crista galli; it is one of the points of attachment of the dura mater. Holes (olfactory foramina) are found in two longitudinal depressions on either side of the crista galli. The olfactory bulbs are located in the longitudinal grooves and the foramina permit the entrance of the olfactory nerves from the nasal cavity to the olfactory bulbs. The labyrinth, the third part of the ethmoid bone, is a large mass on each side of the perpendicular plate. . It contains a large number of air spaces (ethmoid cells) which constitute the ethmoid sinus. The orbital plate is a smooth concave area on the lateral surface of the labyrinth. On its medial wall the labyrinth gives rise to two other structures; these are the scroll-like superior and middle nasal conche --there is also a inferior nasal conchae (turbinate bone). The three conchae occupy most of the nasal cavity. Their function is to cause turbulence in the inspired air; this has the effect of causing the air to contact the mucous membranes over the bones and promote cleansing, humidification and warming of the air before it reaches the lungs.

Work Step by Step

The superior conchae, and the nasal septum also assist in the function of smelling.
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