Do paranasal sinuses open into the oral cavity? Do they enhance the resonance of the voice and lighten the skull?
It's all yes to your questions!
Except that they open into the NASAL CAVITY
Paranasal Sinuses are air filled chambers covered with boney wall located adjacent to the nasal cavity.
Maxillary sinus and ethmoid sinus are present at birth .Frontal sinus develops the last.(approximately 10 years)
Frontal sinus opens in the anterior part of middle meatus via frontonasal ducts(frontal recess is the better term preferred by E.N.T surgeons)
Maxillary sinus opens in the infundibulum from which it connects to middle meatus via hiatus semilunaris.
Ethmoid sinus are arranged in two groups namely the anterior which opens in the middle meatus and posterior which opens in superior meatus.
Sphenoid sinus are located within sphenoid bone and drains through their osteum into the nasal cavity via sphenoethmoidal recess.
During inspiration air comes out of them into the nasal cavity to add humidity to the inspired air and during expiration air enters into them. (Paradoxical respiration of sinus)
They make the skull pneumatic thereby decreases the weight of the skull.
During speech production air vibrates in them causing resonance.
Infection of the sinus produces sinusitis,which causes severe headache and associated constitutional symptoms!
Maxillary sinusitis is the commonest of all and when all the sinuses get affected together the condition is termed as Pansinusitis