Seröse

Seröse, or serous, refers to tissues, membranes, and fluids associated with serous membranes. In anatomy, serosa are thin membranes that line closed body cavities and cover the surfaces of many organs. The major serous membranes are the pleura (lungs), pericardium (heart), and peritoneum (abdominal organs). Each serous membrane consists of a mesothelial cell layer supported by connective tissue and is divided into a parietal portion lining the cavity and a visceral portion covering the organ. Between the two layers is a small amount of serous fluid.

Serous fluid is a clear, pale yellow, relatively low-viscosity secretion that provides lubrication to reduce friction during organ movement. It is normally produced in small amounts by the serous membranes and is derived from capillary filtration and the secretory activity of mesothelial cells. The fluid is typically reabsorbed by nearby lymphatics, maintaining a balance under normal conditions.

Clinical relevance lies in the accumulation of serous fluid within a cavity, known as a serous effusion. Such effusions can arise from systemic conditions that alter hydrostatic or oncotic pressures, such as heart failure, liver cirrhosis, nephrotic syndrome, or hypoalbuminemia, producing transudative effusions. Inflammation can also affect serous membranes and produce a serous exudate, which may become more protein-rich or contaminated if infection occurs. In pleural effusions, serous fluid is sometimes classified as transudate or exudate based on biochemical criteria, including protein and LDH levels. Treatment targets the underlying cause and may involve drainage in symptomatic cases.