Muscles 2 - the trunk

Erector spinae group - extends into vertebral column and flexes it laterally, contains three separate muscle groups, the iliocostalis, longissimus and spinalis

all

iliocostalis - part of Erector spinae group - extend vertebral column, maintain posture, laterally bend column when contracted on one side only

Red

Longissimus - part of Erector spinae group, extend vertebral column, keep posture, minor roll, extending and rotating head to same side, lat bend vertebral column on one side

yellow

Spinalis - part of Erector spinae group

Extends vertebral column, minor role in extending head

blue

External intercostal muscles -

elevates rib cage, spreading ribs and assisting in inspiration

green

Internal intercostal muscles -

depresses the rib cage, pulling ribs closer together, assisting an expiration

yellow

Diaphragm -

flattens to lower the floor of the thoracic cavity and increasing volume and decreasing pressure causing inspiration

Rectus Abdominis - Flexes the trunk with the vertebral column fixed, compresses abdominal cavity

O: Superior aspect of pubic bones

I: intercostal cartilages of lower ribs

Highlighted

 external oblique - flexes and laterally bends the trunk with the vertebral column fixed, compresses abdominal cavity

Left

Internal oblique - flexes and laterally bends the trunk compresses abdominal cavity

right

Transversus abdominis - Compresses abdominal cavity

 Trapezius - middle and inferior fibers - retracts (via middle fibers) and depresses (via inferior fibers) The scapula, rotates Scapula upward in collaboration with upper fibers

all

Trapezius Middle fibers - Scapular retraction 

Red

trapezius inferior fibers - Depresses outwardly rotates and stabilizes scapula 

Magenta

Levator scapulae - elevates scapula

pectoralis minor - protracts and depresses scapula

red

Serratus anterior - Prime mover of scapula in protraction assists in upward rotation of scapula

blue

 rhomboid major - retracts scapula

rhomboid minor - retracts scapula