Four pair of muscles of the abdomen protect the
abdominal organs. They include the rectus abdominis,
external oblique, internal oblique, and transverse abdomi-
nis. Figure 6.18 illustrates and describes these muscles.
M uscles o f th e ab d o m e n th a t p ro te c t th e abdom inal o rg an s • Figure 6.18
Anterior superficial view
Anterior deep view
Internal oblique
Rectus abdominis
External oblique (cut)
Rectus abdominis
External oblique
Transverse abdominis
Muscle
Origin
Insertion
Action
Muscles of the abdomen that protect the abdominal organs
Rectus abdominis
(REK-tus ab-DOM-in-is)
Pubis and pubic
symphysis
Cartilage of fifth to seventh ribs
and xiphoid process of sternum
Flexes vertebral column and compresses
abdomen to aid in defecation, urination,
forced exhalation, and childbirth
External oblique
Lower eight ribs
Crest of ilium and linea alba (a
tough connective tissue band
that runs from xiphoid process
to pubic symphysis)
Contraction of both external obliques
compresses abdomen and flexes vertebral
column; contraction of one side alone bends
vertebral column laterally and rotates it
Internal oblique
Ilium, inguinal ligament,
and thoracolumbar
fascia
Cartilage of last three or four
ribs and linea alba
Contraction of both internal obliques
compresses abdomen and flexes vertebral
column; contraction of one side alone bends
vertebral column laterally and rotates it
Transverse abdominis
Ilium, inguinal ligament,
lumbar fascia, and
cartilages of last six ribs
Xiphoid process, linea alba,
and pubis
Compresses abdomen
Skeletal Muscles Are Grouped Based on Location and Action 177
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