What are open cavities in the skull called? What is the name of the sacs surrounding the body's movable joints?
1 Answer
Mar 21, 2016
Sinuses.
Bursa.
Explanation:
Sinus or antrum is a cavity within a bone. Para-nasal sinuses are a connected system of hollow cavities in the bones of the skull and face (frontal, ethmoid, sphenoid and maxillary bone).
Diagrams below show the Sinuses :
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The sacs surrounding the body's movable joints are called Bursae (bursa in singular). They prevent friction during joint movements.
Following diagram is showing a bursa around a joint :
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Several bursae around shoulder : 
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