An acid (from the Latin acidus/acÄre meaning sour) is a chemical substance whose aqueous solutions are characterized by a sour taste, the ability to turn blue litmus red, and the ability to react with bases and certain metals (like calcium) to form salts.he Swedish chemist Svante Arrhenius attributed the properties of acidity to hydrogen ions (H +) or protons in 1884. An Arrhenius acid is a substance that, when added to water, increases the concentration of H + ions in the water.
The surface of the inner wall of all of the body cavities is lined by a serous membrane which consists of a single layer of flat epithelium with a thin underlying propria (connective tissue). Within the thoracic cavity, this is known as the pleura. The visceral pleura which coats the outer surface of the lung is derived from the splanchnic mesoderm.
The lining on the surface of the heart and the pericardial sac that surrounds the heart. Serous membranes consist of a simple squamous epithelium called mesothelium and a thin underlying layer of areolar connective tissue. The thinness of serous membranes allow fluid to seep through and form a transudate.