Node Of Ranvier: From 1 Different Sources
one of the gaps that occur at regular intervals in the *myelin sheath of medullated nerve fibres, between adjacent *Schwann cells.
The term node is widely used in medicine. For instance, the smaller lymphatic glands are often termed LYMPH NODES. It is also applied to a collection of nerve cells forming a subsidiary nerve centre found in various places in the sympathetic nervous system (see NERVOUS SYSTEM), such as the sinuatrial node and the atrioventricular node which control the beating of the HEART.... node
This is the natural pacemaker of the HEART, and comprises a collection of specialised muscle cells in the wall of the upper chamber (atrium) of the heart. The cells initiate electrical impulses at a rate of up to 100 a minute. These impulses stimulate the muscles of the heart to contract. The rate is altered by the effects of certain hormones and various impulses from the nervous system. Damage or disease of the node affects the regular beating of the heart. (See also CARDIAC PACEMAKER.)... sinoatrial node
A small knot of specialized muscle cells in the right atrium of the heart. Electrical impulses from the sinoatrial node pass through the atrioventricular node and along conducting fibres to the ventricles, causing them to contract.... atrioventricular node
a bony thickening arising at the proximal interphalangeal joint of a finger in osteoarthritis. It is often found together with *Heberden’s nodes. [J. C. Bouchard (1837–1915), French physician]... bouchard’s node
a bony thickening arising at the terminal joint of a finger in *osteoarthritis. It is often inherited, with women most commonly affected. [W. Heberden (1710–1801), British physician]... heberden’s node
(primitive knot) the rounded front end of the embryonic *primitive streak. [V. Hensen (1835–1924), German pathologist]... hensen’s node
the first lymph node to show evidence of metastasis (spread) of a malignant tumour (e.g. breast cancer) via the lymphatic system. Absence of cancer cells in the sentinel node indicates that more distal lymph nodes will also be free of metastasis. In breast cancer, the change in practice to perform axillary lymph node dissection only if the sentinel node contains metastatic tumour has reduced the risk of arm lymphoedema. Similarly, in head and neck squamous cell carcinomas, the sentinel lymph node procedure is used as an alternative to neck dissection.... sentinel lymph node
an enlarged lymph node that may be palpated above the left clavicle (the left supraclavicular fossa). It is strongly associated with abdominal malignancy, particularly cancer of the stomach, since the lymphatic drainage from the abdomen is channelled via the thoracic duct to the left side of the neck before it enters the left subclavian vein. Enlargement of the right supraclavicular lymph node is associated with lung and oesophageal cancer.... virchow’s node
Health Encyclopedia