10/19/2023 0 Comments Ethmoid bone in skull![]() At least a part of the human ethmoid bone can be seen from the outside of the skull. The human ethmoid bone is far easier to understand than the ethmoid bone of the rat. Located inside this portion of the ethmoid bone are several small, air-filled spaces that are part of the paranasal sinus system of the skull. Robert Lewis Maynard, Noel Downes, in Anatomy and Histology of the Laboratory Rat in Toxicology and Biomedical Research, 2019. The ethmoid bone is joined to the frontal bone above, the maxillae below, and the central part of the sphenoid bone behind. The lateral portions of the ethmoid bone are located between the orbit and upper nasal cavity, and thus form the lateral nasal cavity wall and a portion of the medial orbit wall. The superior and middle conchae are also parts of the ethmoid bone. The most lateral part of the ethmoid bone is this paper-thin layer, the lamina papyracea, which forms this part of the medial wall of the orbit.īetween the lamina papyracea and the upper part of the nasal cavity are the ethmoid air cells, as we’ve seen. On each side of the crista galli are the cribriform plates, which we've seen already from above, and from below. This upward projection is the beginning of the crista galli, which rises up in the floor of the anterior cranial fossa. This part, the perpendicular plate of the ethmoid, forms a large part of the bony nasal septum. The best way to see all of them is to go back to the skull that was divided in the frontal plane.Īll of this is the ethmoid bone. The ethmoid bone is a fragile coalition of parts. We’ll do that now, then we’ll come back and look at the openings of the paranasal sinuses. The posterior fontanelle usually closes first, before the anterior fontanelle, during the. It is a single bone seen in the midsection of the anterior cranial fossa. This is the junction of the 2 parietal bones and the occipital bone. The skull bones can be broadly divided into two main sections - Facial skeleton bones (14) and Cranial bones (8). We’ve encountered the various parts of the ethmoid bone, but till now we’ve put off seeing the whole of it. Normally, the human skull has twenty-two bones - fourteen facial skeleton bones and eight cranial bones. ![]() Before we go further, we need to catch up on something that we left unfinished in the previous section: understanding the ethmoid bone.
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