(meh dull´ luh) [L.: narrow] • (1) The inner, core region of an organ, as in the adrenal medulla (adrenal gland) or the renal medulla (kidneys). (2) The portion of the brain stem that connects to the spinal cord.
Core of large air-filled pockets between collapsed cells which occur in the centre of hair fibres. Fibres containing a medulla are called medullated and have a different appearance to unmedullated fibres. In kemp, the medulla forms the greatest portion of the fibre and is surrounded by a comparatively thin layer of cortex.
lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata); "the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning"
Latin = marrow; applied to part of an organ deep to its cortex, and to the spinal cord and adjoining part of brain stem, which may have been thought to be the marrow of the vertebral column, adjective - medullary pertains to the medulla of an organ or medulla oblongata.
1. A term referring to the central portion of certain organs; e.g., the medulla oblongata of the brain and the adrenal medulla, which synthesizes epinephrine and norepinephrine. 2. In more common usage, the area in the brain that regulates breathing, heartbeat, blood pressure and similar activities.
medulla - middle, innermost part]. A term used to describe the innermost part of an organ (ie. the brain, ovary or kidney). For example, in the ovary the middle portion of connective tissue that does not contain follicles.
The central portion of some animal fibres consisting of a series of cavities formed by the medullary cells which collapse during the growth process. In kemp the medulla forms the greatest portion of the fibre and is surrounded by a comparatively thin layer of cortex. In fibres from the outer coat of some breeds of sheep and certain other animals (e.g., reindeer) the inedlillaalso forms a large portion of the fibre.
Part of the hindbrain and the rearmost portion of the brain, just adjacent to the spinal cord. It is involved in the control of respiration, circulation, balance, and protective reflexes such as coughing and sneezing.
The lowest section of the brainstem, a slight enlargement of the spinal cord as it enters the skull; the point at which the major nerve tracts cross over so that the right cerebral hemisphere controls the left side of the body, and the left cerebral hemisphere controls the right side.
A central zone of cells present only in large, thick hairs. elanin: Pigmenting granules within the keratin fibers of the hair shaft that determine hair color. They usually decrease with age, resulting in gray or white hair.