Macula of utricle

The portion of the utricle which is lodged in the recess forms a sort of pouch or cul-de-sac, the floor and anterior wall of which are thickened, and form the macula of utricle, which receives the utricular filaments of the acoustic nerve.

Layers
The macula consists of three layers.

The bottom layer is made of sensory hair cells which are embedded in bottom of a gelatinous layer.

On top of this layer lie calcium carbonate crystals called statoconia.

The gelatinous layer and the statoconia together are referred to as the otolith. When the head is tilted such that gravity pulls on the statoconia the gelatinous layer is pulled in the same direction also causing the sensory hairs to bend.

Signals
Depending on the direction of bending, the hair cells will either be excited or inhibited resulting in either an increase or decrease in firing frequency of the hair cells.

The macula is also sensitive to linear acceleration as the inertia possessed by the statoconia can also shift the gelatinous layer during increases and decreases in linear velocity.