Final answer:
The utricle and saccule are the two chambers in the vestibular labyrinth that are critical for maintaining static equilibrium and balance within the inner ear. They contain hair cells that respond to changes in head position due to gravity and linear accelerations, sending signals to the brain via the vestibulocochlear nerve.
Step-by-step explanation:
The two expanded chambers within the membranous labyrinth of the vestibule that function in static equilibrium are the utricle and saccule. These chambers are responsible for maintaining balance when the body is not in motion, and they respond to gravity and linear acceleration. Enclosed within the temporal bone, the labyrinth forms a crucial part of the vestibular system, which works closely with the auditory system.
The utricle and saccule house approximately 30,000 and 16,000 hair cells, respectively, which send signals to the brain via the vestibulocochlear nerve when physical movement, such as tilting of the head, occurs. These hair cells are topped with stereocilia that protrude into a gelatinous layer containing calcium carbonate crystals. When the head changes position, gravity pulls the crystals in their original direction, causing a shift in the gelatinous layer and bending the stereocilia, consequently stimulating the neurons.
This stimulus provides the brain with information on the head's position, which is crucial for maintaining balance and posture. The information received from both the vestibular and auditory parts of the inner ear is transmitted to the brain stem for processing, which can then coordinate responses to help us navigate our environment effectively.