Define nadir. nadir synonyms, nadir pronunciation, nadir translation, English dictionary definition of nadir. n. 1. Astronomy A point on the celestial sphere directly below the observer, diametrically opposite the zenith. 2. The lowest point: the nadir of their...
Annular tear â definition and causes. By Michael Perry, M.D. An annular tear is one of the most common degenerative spine conditions that develop with the natural aging process of the spine. In fact, many people over the age of 50 have an annular tear and never know it.
Background. Calcification of various cardiovascular structures is associated with aging. Mitral annular calcification (MAC) is a chronic degenerative process of the mitral valve ring; it was first described in 1908 by Bonninger as associated with complete heart block.aseous calcification of the mitral valve is a rare form of MAC that typically affects the posterior annulus. The contents of the cavity are composed of a mixture of calcium, fatty acid, and cholesterol, with a ââtoothpaste-likeââ texture, and may present as an intracardiac mass or cavity.