neck, a term denoting the front portion of the collum or neck (the part connecting the head and trunk) or a constricted part of an organ (for example cervix uteri). C. Of axon, a constricted part of an axon, before the myelin sheath is added. C. Columnae posterioris medullae spinalis na alternative for c. Cornus dorsalis medullae spinalis. C. Cornus dorsalis medullae spinalis, neck of dorsal horn of spinal cord: the constricted portion of the dorsal horn or column, of grey matter in the spinal cord between the base of the horn and the head, also called c. Cornus posterioris medullae spinalis (na alternative) and neck of posterior horn of spinal cord. C. Dentis, the slightly constricted region of union of the crown and the root or roots of a tooth, also called collum dentis, dental neck and neck of tooth. C. Glandis, collum glandis penis. Incompetent c., one that is abnormally prone to dilate in the second trimester of pregnancy, resulting in premature expulsion of the foetus (middle trimester abortion). C. Mallei, collum mallei. Tapiroid c., a uterine cervix with a peculiarly elongated anterior lip. C. Uteri, neck of uterus: the lower and narrow end of the uterus, between the isthmus and the ostium uteri.