Intrinsic Back Muscles - Intermediate Layer (Erector Spinae)

Question 1

Illiocostalis

Answer 1

(lumborum, thoracis, cervicis)

O:
+ broad tendon posterior part of iliac crest
+ posterior surface of the sacrum
+ sacro-iliac ligaments
+ sacral and inferior lumbar spinous processes
+ supraspinous ligaments

I: (Lumborum, thoracis, cervicis)
+ angles of lower ribs
+ cervical transverse processes

N: Posterior rami of spinal nerves

A:
Bilaterally: Extend vertebral column and head; as back is flexed, control movement by gradually lengthening their fibers

Unilaterally: Laterally flex the vertebral column

Question 2

Longissimus

Answer 2

(thoracis, cervicis, capitis)

O:
+ broad tendon posterior part of iliac crest
+ posterior surface of the sacrum
+ sacro-iliac ligaments
+ sacral and inferior lumbar spinous processes
+ supraspinous ligaments

I: (Thoracis, cervicis, capitis)
+ ribs between tubercles
+ angles to transverse processes in thoracic and cervical regions
+ mastoid process of temporal bone

N: Posterior rami of spinal nerves

A:
Bilaterally: Extend vertebral column and head; as back is flexed, control movement by gradually lengthening their fibers

Unilaterally: Laterally flex the vertebral column

Question 3

Spinalis

Answer 3

(thoracis, cervicis, capitis)
O:
+ broad tendon posterior part of iliac crest
+ posterior surface of the sacrum
+ sacro-iliac ligaments
+ sacral and inferior lumbar spinous processes
+ supraspinous ligaments

I: (Thoracis, cervicis, capitus)
+ fibers run superiorly to spinous processes in upper thoracic region
+ cranium

N: Posterior rami of spinal nerves

A:
Bilaterally: Extend vertebral column and head; as back is flexed, control movement by gradually lengthening their fibers

Unilaterally: Laterally flex the vertebral column