cortex

The cortex is the outermost layer of an organ or structure in the body, most notably referring to the cerebral cortex of the brain. The cerebral cortex is a thin, highly folded sheet of neural tissue that covers the cerebrum and plays a key role in many higher brain functions. It is involved in sensory perception, voluntary motor activities, language, decision-making, and complex thought processes.

The cerebral cortex is divided into two hemispheres, each comprising four main lobes: the frontal, parietal, temporal, and occipital lobes. These lobes are responsible for specific functions such as reasoning, sensory processing, auditory perception, and visual processing, respectively. The cortex consists primarily of grey matter, which contains neuron cell bodies, dendrites, and synapses, and beneath it lies white matter composed of myelinated nerve fibers that facilitate communication between different brain regions.

Structurally, the cortex is characterized by numerous folds called gyri and grooves called sulci, which increase its surface area and enhance neural connectivity. The thickness of the cortex varies across regions but generally ranges from 2 to 4 millimeters. In addition to the brain, the term "cortex" is also used in other organ systems, such as the adrenal cortex, which secretes hormones like cortisol and androgens, and the renal cortex in the kidneys, involved in filtration and urine formation.

Overall, the cortex's layered organization and complex architecture support its critical role in integrating sensory information and orchestrating complex behaviors. Its study provides insights into brain function, development, and disorders, making it a central focus in neuroscience research.