Macula

A macula, derived from the Latin word for "spot," can refer to several distinct anatomical or pathological features depending on the context. The most common and clinically significant usage relates to the macula lutea in the eye.

In ophthalmology (macula lutea):

The macula lutea is an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye. It has a diameter of around 5.5 mm and is responsible for high-acuity, central vision, enabling tasks such as reading, driving, and recognizing faces. Within the macula is a smaller, central pit called the fovea centralis, which is approximately 1.5 mm in diameter. The fovea is densely packed with cone photoreceptor cells, specifically designed for color vision and high visual acuity. Damage to the macula, such as in age-related macular degeneration (AMD), can lead to significant vision loss and impairment of central vision while usually sparing peripheral vision.

Other uses:

In anatomy and pathology, "macula" can more generally refer to any small spot or area that is discolored or distinct from the surrounding tissue. Examples include:

• Macula densa: A specialized group of cells in the distal convoluted tubule of the kidney that monitor sodium chloride concentration in the filtrate. It plays a role in regulating glomerular filtration rate through tubuloglomerular feedback.
• Maculae of the vestibule of the inner ear: Sensory receptors located in the utricle and saccule of the vestibular system. These maculae detect linear acceleration and head position relative to gravity, contributing to balance and spatial orientation.
• Skin macules: Flat, distinct, discolored areas of skin less than 1 centimeter in diameter. They are neither raised nor depressed. Freckles are an example of skin macules.

It is crucial to consider the context when encountering the term "macula" to understand its specific meaning and significance.