n, often cap E  :  a mass of lymphoid tissue at the pharyngeal opening of the eustachian tube
 
Eu•sta•chio, Bartolomeo (ca 1520-1574), Italian anatomist. Eustachio served as a professor of anatomy at a school of medicine in Rome. Between 1562 and 1563 he produced a remarkable series of treatises on the kidney, the ear, the nervous system, and the teeth. His treatise on the kidney was the first work specifically concerned with that organ. It revealed a knowledge of the kidney that exceeded previous works, and it contained the first account of the adrenal glands. The treatise on the ear contains the classic description of the Eustachian tube. Eustachio is known for an extraordinary series of 47 anatomical drawings. The set included an illustration of the sympathetic nervous system that is generally considered to be one of the best ever produced. One plate illustrated the valve in the right atrium of the fetal heart that is now known as the Eustachian valve.
 
 also   
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.