Muscles of the abdomen
Intercostal muscles (muscles between the ribs)
Connects the ribs. There is an inner layer (mm. intercostalis interni) and an outer layer (mm. intercostalis externi).
Interni: These muscles run from the lower edge of the upper rib and attach obliquely downward and dorsally. They lower the ribs. They are active during exhalation. Externi:
The muscles run from the lower edge of the ribs and extend diagonally forward and downward. They lift the ribs and are active during inhalation. (Image on the right)
M. Rectus abdominis (straight abdominal muscle)
Origin: cartilago costa 5–7 (rib cage)
Insertion: os pubis, symphysis
Function: flexes the trunk, lowers the chest, raises the anterior part of the pelvis
M. Transversus abdominis (transverse abdominal muscle)
Origin: thoracolumbar fascia , ribs 7–12, iliac crest, inguinal ligament
Insertion: rectus sheath
Function: exhalation and abdominal contraction (image below right)
M. Obliquus externus abdominis (external oblique muscle)
Origin: costa 5–12
Insertion: rectus sheath, crista iliaca, inguinal ligament
Function: lateral flexion and rotation of the spine; contributes to abdominal contraction
M. Obliquus internus abdominis (internal oblique muscle)
Origin: thoracolumbar fascia , iliac crest, inguinal ligament
Insertion: ribs 10–12, rectus sheath
Function: lateral flexion, rotation, and flexion of the spine; contributes to abdominal pressure
Back muscles
M. Erector spinae (deep back muscles)
Origin: sacrum, ilium, ribs, and the transverse and spinous processes of the vertebrae.
Insertion: ribs, and the transverse and spinous processes of the vertebrae.
Function: lateral flexion , extension, and rotation of the head, trunk, and spine.
Trapezius (trapezius muscle)
Origin: superior nuchal line , spinous processes of C7–T12
Insertion: clavicle, acromion, and scapular spine
Function: elevates , adducts, and rotates the scapula; rotates the neck/head.
M. Latissimus dorsi (broad back muscle)
Origin: spinous processes of T7–L5 via the thoracolumbar fascia, sacrum, and ilium
Insertion: crista tuberculi minoris humeri
Function: extension , adduction, and internal rotation of the shoulder joint
