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A sinus is a sac or cavity in any organ or tissue, or an abnormal cavity or passage. In common usage, "sinus" usually refers to the paranasal sinuses, which are air cavities in the cranial bones, especially those near the nose and connecting to it. Most individuals have four paired cavities located in the cranial bone or skull.
Anatomy figure: 28:03-06 at Human Anatomy Online, SUNY Downstate Medical Center – "Venous dural sinuses." Cavernous+Sinus at the U.S. National Library of Medicine Medical Subject Headings (MeSH) lesson2 at The Anatomy Lesson by Wesley Norman (Georgetown University) Atlas image: n3a8p1 at the University of Michigan Health System
Recent studies have classified two types of maxillary sinus septa: primary and secondary. Primary septa are those initially described by Underwood and that form as a result of the floor of the sinus sinking along with the roots of erupting teeth; these primary septa are thus generally found in the sinus corresponding to the space between teeth, as explained by Underwood.
The, paranasal sinuses are joined to the nasal cavity via small orifices called ostia. These become blocked easily by allergic inflammation, or by swelling in the nasal lining that occurs with a cold. If this happens, normal drainage of mucus within the sinuses is disrupted, and sinusitis may occur. Because the maxillary posterior teeth are ...
Frontal sinus. Each frontal sinus is situated between the external and internal plates of the frontal bone. [1] [2] Their average measurements are as follows: height 28 mm, breadth 24 mm, depth 20 mm, creating a space of 6-7 ml. [3]
The frontonasal duct is a duct through which either frontal sinus drains into the nasal cavity. [2] [3] Each frontal sinus opens into the frontonasal duct by an opening (the opening of frontal sinus or frontal sinus aperture [4]) on the inferomedial part [3] of the floor of the sinus. [4]
These sinuses play a crucial role in cerebral venous drainage. A dural venous sinus, in human anatomy, is any of the channels of a branching complex sinus network that lies between layers of the dura mater, the outermost covering of the brain, and functions to collect oxygen-depleted blood. Unlike veins, these sinuses possess no muscular coat.
The transverse sinuses are frequently of unequal size, with the one formed by the superior sagittal sinus being the larger; they increase in size as they proceed, from back to center. On transverse section, the horizontal portion exhibits a prismatic form, the curved portion has a semicylindrical form.