Anatomy of the Muscles of the Abdominal Region

Muscles of the Abdominal Region - Listed Alphabetically
Muscle	Origin	Insertion	Action	Innervation		Notes
Cremaster	inguinal ligament	forms thin network of muscle fascicles around the spermatic cord and testis (or around the distal portion of the round ligament of the uterus)	elevates testis (not well developed in females)	genital branch of the genitofemoral nerve	cremasteric a., a branch of the inferior epigastric a.	Notesthe cremaster m. is internal abdominal oblique muscle's contribution to the coverings of the spermatic cord and testis; the cremasteric reflex may be elicited by stroking the medial thigh (where the femoral branch of the genitofemoral n. distributes cutaneously) (Greek, cremaster = suspender)
Dartos	subcutaneous connective tissue of the scrotum and the penis (or labium majus and clitoris)	skin of the scrotum and penis (or labium majus and clitoris)	elevates testis (tenses the skin of the pudendal region in the female)	postganglionic sympathetic nerve fibers arriving via the ilioinguinal nerve and the posterior scrotal nerve	cremasteric a., posterior scrotal (labial) a.	Notes:the dartos elevates the testis in response to cold (it is modified arrector pili fibers, or the goose-bump muscles) (Latin, dartos = leather)
External abdominal oblique	lower 8 ribs	linea alba, pubic crest & tubercle, anterior superior iliac spine & anterior half of iliac crest	flexes and laterally bends the trunk	intercostal nerves 7-11, subcostal, iliohypogastric and ilioinguinal nerves	musculophrenic a., superior epigastric a., intercostal aa. 7-11, subcostal a., lumbar aa., superficial circumflex iliac a., deep circumflex iliac a., superficial epigastric a., inferior epigastric a., superficial external pudendal a.	Notes:the inguinal ligament is a specialization of the external abdominal oblique aponeurosis; the external spermatic fascia is the external abdominal oblique muscle's contribution to the coverings of the testis and spermatic cord
Interfoveolar	transversus abdominis fibers that lie superficial to the inferior epigastric vessels	anterior lamina of femoral sheath, immediately distal to origin of inferior epigastric vessels	compresses abdominal contents	iliohypogastric and ilioinguinal nerves	inferior epigastric a.	Notes:an inconstant part of the transversus abdominis m. which may be replaced by a ligament (interfoveolar ligament)
Internal abdominal oblique	thoracolumbar fascia, anterior 2/3 of the iliac crest, lateral 2/3 of the inguinal ligament	lower 3 or 4 ribs, linea alba, pubic crest	Actionflexes and laterally bends the trunk	intercostal nerves 7-11, subcostal, iliohypogastric and ilioinguinal nerves	musculophrenic a., superior epigastric a., intercostal aa. 7-11, subcostal a., lumbar aa., superficial circumflex iliac a., deep circumflex iliac a., superficial epigastric a., inferior epigastric a., superficial external pudendal a.	Notesanterior fibres of internal abdominal oblique course up and medially, perpendicular to the fibers of external abdominal oblique; the cremaster muscle and fascia is the internal abdominal oblique muscle's contribution to the coverings of the testis and spermatic cord
Oblique, external abdominal	lower 8 ribs	linea alba, pubic crest & tubercle, anterior superior iliac spine & anterior half of iliac crest	flexes and laterally bends the trunk	intercostal nerves 7-11, subcostal, iliohypogastric and ilioinguinal nerves	musculophrenic a., superior epigastric a., intercostal aa. 7-11, subcostal a., lumbar aa., superficial circumflex iliac a., deep circumflex iliac a., superficial epigastric a., inferior epigastric a., superficial external pudendal a.	Notes:the inguinal ligament is a specialization of the external abdominal oblique aponeurosis; the external spermatic fascia is the external abdominal oblique muscle's contribution to the coverings of the testis and spermatic cord
Oblique, internal abdominal	thoracolumbar fascia, anterior 2/3 of the iliac crest, lateral 2/3 of the inguinal ligament	lower 3 or 4 ribs, linea alba, pubic crest	flexes and laterally bends the trunk	intercostal nerves 7-11, subcostal, iliohypogastric and ilioinguinal nerves	musculophrenic a., superior epigastric a., intercostal aa. 7-11, subcostal a., lumbar aa., superficial circumflex iliac a., deep circumflex iliac a., superficial epigastric a., inferior epigastric a., superficial external pudendal a.	Notesanterior fibers of internal abdominal oblique course up and medially, perpendicular to the fibers of external abdominal oblique; the cremaster muscle and fascia is the internal abdominal oblique muscle's contribution to the coverings of the testis and spermatic cord
Psoas major	bodies and transverse processes of lumbar vertebrae	lesser trochanter of femur (with iliacus) via iliopsoas tendon	flexes the thigh; flexes & laterally bends the lumbar vertebral column	branches of the ventral primary rami of spinal nerves L2-L4	subcostal a., lumbar aa.	Notesthe genitofemoral nerve pierces the anterior surface of the psoas major m. (Greek, psoas = the muscles of the loins)
Psoas minor	bodies of the T12 & L1 vertebrae	iliopubic eminence at the line of junction of the ilium and the superior pubic ramus	flexes & laterally bends the lumbar vertebral column	branches of the ventral primary rams of spinal nerves L1-L2	lumbar aa.	Notesabsent in 40% of cases (Greek, psoas = the muscles of the loins)
Pyramidalis	pubis, anterior to the rectus abdominis	linea alba	draws the linea alba inferiorly	Innervationsubcostal nerve	subcostal a., inferior epigastric a.	Notesthe pyramidalis m. is not always present
Quadratus lumborum	posterior part of the iliac crest and the iliolumbar ligament	transverse processes of lumbar vertebrae 1-4 and the 12th rib	laterally bends the trunk, fixes the 12th rib	Innervationsubcostal nerve and ventral primary rami of spinal nerves L1-L4	subcostal a., lumbar aa.	Notesthe lateral arcuate ligament of the diaphragm crosses the anterior surface of the quadratus lumborum m.
Rectus abdominis	pubis and the pubic symphysis	xiphoid process of the sternum and costal cartilages 5-7	flexes the trunk	intercostal nerves 7-11 and subcostal nerve	superior epigastric a. intercostal aa., subcostal a., inferior epigastric a.	Notesrectus sheath contains rectus abdominis and is formed by the aponeuroses of external and internal oblique and transversus abdominis mm.
Transversus abdominis	lower 6 ribs, thoracolumbar fascia, anterior 3/4 of the iliac crest, lateral 1/3 of inguinal ligament	linea alba, pubic crest and pecten of the pubis	flexes and laterally bends trunk	intercostal nerves 7-11, subcostal, iliohypogastric and ilioinguinal nerves	musculophrenic a., superior epigastric a., intercostal aa. 7-11, subcostal a., lumbar aa., superficial circumflex iliac a., deep circumflex iliac a., superficial epigastric a., inferior epigastric a., superficial external pudendal a.	Notestransversus abdominis muscle does not contribute to the coverings of the spermatic cord and testis; transversalis fascia, the deep fascia that covers the inner surface of the transversus abdominis, forms the internal spermatic fascia