Muscles of the Deep Back, Abdominal Wall, and Pelvic Outlet

Action: extends neck and vertebral column; maintains posture Origin: tendon from posterior part of iliac creast, posterior sacrum, and lumbar spinous processes Insertion: angles of ribs; transverse processes of cervical vertebrae Innervation: cervical, thoracic, and lumbar spinal nerves

Action: extends neck and vertebral column and rotates head; maintains posture Origin: tendon from posterior part of ilac crest, posterior sacrum, and lumbar spinous processes Insertion: mastoid process of temporal bone and transverse processes of cervical and thoracic vertebrae Innervation: cervical and thoracic spinal nerves

Action: extends neck and vertebral column; maintains posture Origin: tendon from psterior part of iliac crest, posterior sacrum, and lumbar spinous processes Insertion: angles of ribs; transverse processes of cervical vertebrae Innervation: cervial, thoracic, and lumbar spinal nerves

Action: extens vertebral column; rotates vertebral column to opposite side Origin: spinous processes of each vertebra Insertion: spinous processes of more superior vertebrae Innervation: cervical, thoracic, and lumbar spinal nerves

Action: unilateral action= lateral flexion of vertebvral column; rotation of vertebral column to opposite side; bilateral action = flexes vertebral column and compresses abdominal wall Origin: external and inferior borders of the inferior 8 ribs Insertion: linea alba by a broad aponeurosis; some to iliac crest Innervation: Spinal nerves T8-T12, L1

Action: unilateral action = lateral flexion of vertebral column; rotation of vertebral column to opposite side; bilateral action = flexes vertebral column and compresses abdominal wall Origin: lumbar fascia, inguinal ligament, and ilia crest Insertion: linea alba, pubic crest, inferior rib surfaces (last 4 ribs); costal cartilages of ribs 8-10 Innervation: spinal nerves T8-T12, L1

Action: Unilateral action = lateral flexion of vertebral column; bilateral action = flexes vertebral column; compresses abdominal wall Origin: iliac creast, cartilages of inferior 6 ribs; lumbar fascia; inguinal ligament Insertion: linea alba and pubic crest Innervation: spinal nerves T8-T12, L1

Action: flexes vertebral column; compresses abdominal wall Origin: superior surface of pubis near symphyisis Insertion: xiphoid process of sternum; inferior surfaces of ribs 5-6 Innervation: spinal nerve T8-T12, L1

Group of muscles that form the anterior and lateral parts of the pelvic diaphragm

Action: forms pelvic floor and supports pelvic viscera Origin: ischial spine Insertion: lateral and inferior borders of sacrum Innervation: spinal nerve S4-S5

Action: supports pelvic organs Origin: ischial tuberosities and ischial ramus Insertion: pubic symphysis Innervation: pudendal nerve (S2-S4)

Action: narrows vaginal opening; compresses and stiffens clitoris Origin: sheath of collagen fibers at base of clitoris Insertion: perineal body Innervation: pudendal nerve (S2-S4)

Action: assists erection of penis of clitoris Origin: ischial tuberosities and ischial ramus Insertion: pubic symphysis Innervation: pudendal nerve (S2-S4)