[Fascicular structure of the middle trunk of the brachial plexus in human post-fetal life].

Thickness of the middle trunk of the brachial plexus, size of cross-section area of its fascicles, number of fascicles and size of index of the fascicle's area has been examined bilaterally on bodies of 34 males and 34 females who died at the age between the 11th and 86th year of life. The middle trunk was present in all the cases and it always made continuation of the root of the brachial plexus coming from C7. The internal structure of the middle trunk is characterized by a great individual variability and asymmetry. The examined features of the middle trunk underwent big changes in postnatal life, mostly up to 22nd year of life. The thickness of the trunk increased 3.5 times, the size of the cross-section area of fascicles--3.2 times, and the number of fascicles by 59%, but the index of fascicle's area decreased by over 11%. The participation of fascicles of different thickness in the structure of the trunk also changed.