MUSCLES OF BACK 



93 



The Muscles of the Abdomen are arranged in three directions 

 longitudinal, transverse, and oblique. The longitudinal ones 

 straight up the front, flex the trunk, helped by the oblique ones 

 when both sides act together. When the oblique muscles act 

 singly, rotation of the trunk takes place. The longitudinal 

 muscles on the posterior wall of the abdomen extend the spme~ 

 when both act together. Acting singly, they flex the spine 

 laterally. The transverse muscles of the abdominal wall are 

 mainly used to keep the contents of the abdomen in place and 

 to add to the strength of the wall, but help in flexion with the 

 others. 



Some of the muscles causing flexion and extension of the 

 cervical part of the spine are situated in the neck and attached 

 to the head ; these must not be confused with the muscles that 

 specially move the head on the spine. 



(For Flexion and Extension of Spinal Column, see pp. 94 

 and 95.) 



The movement of lateral flexion of the spinal column takes 

 place by the muscles of flexion and extension acting together 

 on one side. In the cervical region, however, there are a group 

 of muscles which cause lateral flexion of that part. 



