7c682e55_RSES__abnormal_uterine_actions__CONSTRICTION_RING
[0] Uterus [RETRACTION RING] Upper segment is tonically contracted with no relaxation The wall becomes thicker, lower segment becomes distended and thinned out [CONSTRICTION RING] 
Upper segment contracts and retracts with relaxation in between lower segment remains thick and loose.
A GUIDE FOR NURSES: abnormal uterine actions
CONSTRICTION RING