commissure
noun
com·mis·sure ˈkä-mə-ˌshu̇r 
1
: a point or line of union or junction especially between two anatomical parts (such as adjacent heart valves)
2
: a connecting band of nerve tissue in the brain or spinal cord
commissural
ˌkä-mə-ˈshu̇r-əl
adjective 
Word History
Etymology
Middle English, "suture, seam," borrowed from Middle French & Latin; Middle French, borrowed from Latin commissūra "joint, juncture, seam," from commissus (past participle of committere "to join together") + -ūra -ure — more at commit
First Known Use
15th century, in the meaning defined at sense 1
Medical Definition
commissure
noun
com·mis·sure ˈkäm-ə-ˌshu̇(ə)r
1
: a point or line of union or junction between two anatomical parts (as the lips at their angles or adjacent heart valves)
2
: a connecting band of nerve tissue in the brain or spinal cord see anterior commissure, corpus callosum, gray commissure, habenular commissure, hippocampal commissure, posterior commissure compare massa intermedia