macula
1. A patch of sensory hair cells in the utriculus and sacculus of the inner ear that provides information about the position of the body in relation to gravity. The hairs of the cells are embedded in an otolith, a gelatinous cap containing particles of calcium carbonate. Movement of the particles in response to gravity pulls the gelatinous mass downwards, which bends the hairs and triggers a nerve impulse to the brain (see illustration).

2. An area of the retina of the vertebrate eye with increased visual acuity. Maculae occur in some animals that lack foveae and often surround foveae in those animals that possess them.

macula In the retina of many vertebrates that lack a fovea, an area of relatively acute sensitivity to light stimulation and so of relatively acute vision. In the human retina the macula lutea is a similarly sensitive area, containing a yellow pigment, that surrounds the fovea.

macula (mak-yoo-lă) n. (pl. maculae) a small anatomical area that is distinguishable from the surrounding tissue. m. lutea the yellow spot on the retina at the back of the eye, which surrounds the greatest concentration of cones (see fovea).
—macular (mak-yoo-ler) adj.