Back Muscles

Question 1

what is the action of the superficial muscles of the back?

Answer 1

to act on pectoral girdle on humerus

Question 2

what muscles are part of the superficial layer of the back, which act on pectoral girdle on humerus?

Answer 2

trapezius, latissimus dorsi, levator scapulae, rhombodideus major, rhomboideus minor

Question 3

what is the action and innervation of the trapezius?

Answer 3

superior fibers elevate the scapula and rotate it upwards
middle fibers retract the scapula
inferior fibers depress the scapula and rotate it upwards

accessory nerve (CN XI)

Question 4

what is the action and innervation of the latissimus dorsi?

Answer 4

powerful adduction, extension, and medial rotation of the arm

thoracodorsal nerve (from C6-C8)

Question 5

what is the action and innervation of the levator scapulae?

Answer 5

elevation and downward rotation of scapula

dorsal scapular (C5)

Question 6

what is the action and innervation of the rhomboideus major?

Answer 6

scapula retraction

dorsal scapular (C5)

Question 7

what is the action and innervation of the rhomboideus minor?

Answer 7

scapula retraction

dorsal scapular (C5)

Question 8

what is the action of the intermediate muscles of the back?

Answer 8

act as accessory muscles of respiration (attach to ribs and vertebrae)

Question 9

what are the muscles of the intermediate layer of the back that act as accessory muscles to respiration? what innervates them?

Answer 9

serratus posterior superior, serratus posterior inferior, levatores costarum (12 pairs)

ventral rami of spinal nerves

Question 10

what is the action of the muscles of the deep layer of the back?

Answer 10

act on vertebral column (attach to transverse and spinous processes of vertebrae and act at intervertebral joints)

Question 11

what muscles are in the deep layer of the back and act on the vertebral column? what are they innervated by?

Answer 11

splenius capitus, splenius cervicis, erector spinae, transversospinalis

dorsal rami of spinal nerve

Question 12

what is the action the splenius capitus?

Answer 12

extends the head

Question 13

what is the action of the splenius cervicis?

Answer 13

rotates the head

Question 14

if both the splenius capitus and splenius cervicis act unilaterally, what action do they produce?

Answer 14

lateral bending of the cervical vertebrae

Question 15

what are the muscles of the erector spinae? what are their positions in relation to one another?

Answer 15

from lateral to medial: iliocostalis, longissimus, spinalis

*I Love Spaghetti

Question 16

when the erector spinae muscles act bilaterally what action is produced? unilaterally?

Answer 16

bilaterally: extend vertebral column at intervertebral joints
unilaterally: lateral bending of the vertebral column at the intervertebral joints

Question 17

what are the muscles of the transversospinalis? what are their positions in relation to one another?

Answer 17

from superficial to deep: semispinalis, multifidus, rotatores

Question 18

when the muscles of the transversospinalis act bilaterally what action is produced? unilaterally?

Answer 18

bilaterally: extend the vertebral column
unilaterally: rotation of the vertebral column

Question 19

what is the order of the deep layer muscles of the back?

Answer 19

most superficial: splenius capitus, splenius cervicis
between: erector spinae (with iliocostalis, longissimus, spinalis form lateral to medial)
most deep: transversospinalis (with semispinalis, multifudus, and rotatores from superficial to deep)

Question 20

what is the action of the suboccipital muscles?

Answer 20

act on atlas and axis for extension at atlanto-occiptal joint (YES) and rotation at atlantoaxial joint (NO)

Question 21

what are the muscles of suboccipital region? what is their innervation?

Answer 21

rectus capitis posterior minor, rectus capitis posterior major, inferior oblique capitis, superior oblique capitis

dorsal ramus of C1 (suboccipital nerve)

Question 22

what are the muscles of the rotator cuff?

Answer 22

supraspinatus, infraspinatus, teres minor, subscapularis

*(SITS)

Question 23

what is the function of the rotator cuff muscles?

Answer 23

rotating the arm at the shoulder and maintaining integrity of the shoulder joint (keep head of humerus closely opposed to the glenoid fossa of the scapula during full range of arm motion)

**see specific actions and innervations in the arm muscle set