Anatomy of the orbits and paranasal sinuses Flashcards
1
Q
paranasal sinuses
A
- all the paranasal cavities communicate with one another and with the nasal cavity
- lined with mucous membranes
- are not fully developed until the teenage years
2
Q
maxillary sinuses
A
- 3-4 x 2.5 x 2.5 cm but varies from person to person, and sometimes side to side in one individual
- bony walls of these sinuses are thin
- floor sits just inferior to the floor of the nasal cavity
- roots of 1st and 2nd molars are closely associated with these sinuses, so an infection in one of these roots can transfer to sinuses
3
Q
frontal sinuses
A
- located between inner table and outer table of skull, posterior to the glabella
- rarely symmetric side to side
- may be paired, singular or absent
- usually larger in men than women and rarely “aerated” before age 6
4
Q
ethmoid sinuses
A
- located in the lateral masses (labyrinths) of the ethmoid bone
- grouped anterior, middle and posterior collections
- anterior ethmoid sinuses appear in the orbital cavity on a lateral projection
5
Q
sphenoid sinuses
A
- located in the body of the sphenoid bone directly inferior to the sella turcica
- sometimes divided by a septum but not always
- CSF or blood may leak into the sphenoid sinus through a fracture in the cranial floor (basal skull fracture) causing air/fluid levels (sphenoid effusion) to appear in the sphenoid sinus
6
Q
osteomeatal complex
A
includes all the paths of communication between the frontal, ethmoid, maxillary sinuses, and the nasal cavity
7
Q
orbits
A
- each orbit is a bony-walled cone
- the rim of each orbit is known as the “base”
- the apex is the pointy end that corresponds to the location of the optic foramen, which houses the optic nerve
- the orbits project 30 degrees superiorly and 37 degrees medially when the OML is perpendicular to the IR
- the posterior openings of the orbit allow for the passage of cranial nerves
- the optic foramen houses the optic nerve which is continuous with the retina
