| Lower's ring | One of four fibrous rings that surround atrioventricular and arterial orifices of the heart, providing attachment for the valve leaflets and maintaining patency of the orifice. As part of the fibrous skeleton of the heart, the fibrous rings also provide origin and insertion for the myocardium. Synonym: annulus fibrosus cordis, annulus fibrosus, coronary tendon, fibrous ring, Lower's ring. (05 Mar 2000) |
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| Lower's tubercle | The slight projection on the wall of the right atrium between the orifices of the venae cavae. Synonym: tuberculum intervenosum, Lower's tubercle. (05 Mar 2000) |
| lower uterine segment | The inferior portion or isthmus of the uterus, the lower extremity of which joins with the cervical canal and, during pregnancy, expands to become the lower part of the uterine cavity. (05 Mar 2000) |
| lower uterine segment cesarean section | A cesarean section in which the uterus is entered in its lower segment by a transperitoneal approach. (05 Mar 2000) |