Back Myology Flashcards
What is the relation of Six Layer model of back muscles to Extrinsic/Intrinsic catergories?
- The superficial 3 layers are extrinsic (innervated by a branch of an Anterior Ramus or Cranial nerve)
- The deep 3 layers are intrinsic (innervated by Posterior Rami)
What are the muscles present in layer 1 of the back?
- Trapezius M.
- Latissimus Dorsi M.
What muscle is this?

Trapezius M.
What muscle is this?

Lattisimus Dorsi M.
Trapezius M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous processes of C7-T12, Ligamentum Nuchae, External Occipital Protuberance and medial 1/3 of Superior Nuchael Line of Occipital B.
Insertion: Lateral 1/3 of the Clavicle, Acromion and Scapular Spine
Action: Whole muscle (rotate point of the Glenoid Clavity superiorly, retract the Scapula); upper fibers (elevate Scapula); lower fibers (depress Scapula); with the Scapula fixed the upper fibers with extend the Neck working bilaterally, laterally flex the Neck and rotate the Face away when working unilaterally
Innervation: Motor: Spinal Accessory N. (CN XI); Sensory: C3,4
Lattisimus Dorsi M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous Processes of T6-12, Ribs 9-12, Iliac Crest and Spinous Processes of L1-5, and Median Sacral Crest via Thoracolumbar Fascia
Insertion: Floor of the Humeral Intertubercular Groove
Action: extend, abduct, and medially rorate the Humerus; rotate the Glenoid Cavity inferiorly
Innervation: Thoracodorsal N. (C6-8)
What muscles are present in layer 2 of the back?
- Rhomboid Major M.
- Rhomboid Minor M.
- Levator Sapulae M.
What muscle is this?

Rhomboid Major M.
What muscle is this?

Rhomboid Minor M.
What muscle is this?

Levator Scapulae M.
Rhomboid Major M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous Processes of T2-5
Insertion: Medial border of Scapula (inferior to Scapular Spine)
Action: Retract and elevate Scapula, rotate the Glenoid Cavity inferiorly
Innervation: Doral Scapular N. (C4, 5)
Rhomboid Minor M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous Processes of C7-T1, lower part of the Ligamentum Nuchae
Insertion: Medial border of Scapula (at Scapular Spine)
Action: Retract and elevate Scapula, rotate the Glenoid Cavity inferiorly
Innervation: Dorsal Scapular N. (C4, 5)
Levator Scapulae M.
Origin:
Insertion:
Action:
Innervation:
Origin: Posterior Tubercles of Transverse Processes C1-4
Insertion: Medial border of Scapula (superior to Scapular Spine)
Action: Elevate Scapula, rotate the Glenoid Cavity inferiorly; when the Scapula is fixed, extend and laterally flex the Neck
Innervation: C3, 4, Dorsal Scapular N. (C5)
What muscles are present in layer 3 of the back?
- Serratus Posterior Superior M.
- Serratus Posterior Inferior M.
What muscle is this?

Serratus Posterior Superior M.
What muscle is this?

Serratus Posterior Inferior M.
Serratus Posterior Superior M.
Origin:
Insertion:
Action:
Innervation:
Origin: Nuchal L. and Spinous Processes C7-T3
Insertion: Superior surfaces of Ribs 2-4
Action: Elevate Ribs with forced inspiration (primarily proprioceptive)
Innervation: Intercostal N. (2-5)
Serratus Posterior Inferior M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous Processes T11-L2
Insertion: Inferior surface of Ribs 8-12
Action: Depress Ribs with forced expiration (primarily proprioceptive)
Innervation: Anterior Rami T9-12
What muscles are present in layer 4 of the back?
- Splenius Capitis M.
- Splenius Cervicis M.
What muscle is this?

Splenius Capitis M.
What muscle is this?

Splenius Cervicis M.
Splenius Capitis M.
Origin:
Insertion:
Action:
Innervation:
Origin: Lower 1/2 Nuchal L., Spinous Processes C7-T3(4)
Insertion: Mastoid Process of Temporal B., lateral 1/3 Superior Nuchal Line of the Occipital B.
Action: Extend the Neck when working bilaterally; laterally flex the Neck and rotate Face toward when working unilaterally
Innervation: Posterior Rami C3-5
Splenius Cervicis M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous Processes T3-6
Insertion: Transverse Processes C1-3(4)
Action: Extend the Neck when working bilaterally; laterally flex the Neck and rotate Face toward when working unilaterally
Innervation: Posterior Rami C5-7
What muscles are present in layer 5 of the back?
(intrinsic, largest layer)
- Iliocostalis (lateral group): Iliocostalis Lumborum M., Iliocostalis Thoracis M., Iliocostalis Cervicis M.
- Longissimus (intermediate group): Longissimus Thoracis M., Longissinus Cervicis M., Longissimus Capitis M.
- Spinalis (medial group): Spinalis Thoracis M. (often blends with Longissimus Thoracis M.), Spinal Cervicis M. (usually absent), Spinalis Capitis M. (usually absent or blended with Semispinalis Capitis M.)
What is the action and innvervation of the Erector Spinae Group (layer 5) of the back?
- Action: maintain erect posture and extend the Vertebral Column and Head when working bilaterally; laterally flex the Vertebral Column when working unilaterally
- Innervation: segmentally innervated by Posterior Rami of Spinal Nerves
What muscle is this?

Iliocostalis Lumborum M.
What muscle is this?

Iliocostalis Thoracis M.
What muscle is this?

Iliocostalis Cervicis M.
What muscle is this?

Longissimus Thoracis M.
What muscle is this?

Longissimus Cervicis M.
What muscle is this?

Longissimus Capitis M.
What muscle is this?

Spinalis Thoracis M.
What muscle is this?

Spinalis Cervicis M.
What muscle is this?

Spinalis Capitis M.
Iliocostalis Lumborum M.
Origin:
Insertion:
Origin: Posteromedial Iliac Crest, Spinous Processes T11-L5, median Sacral Crest, lateral Sacral Crest, Sacrotuberous L., and Long Posterior Sacroiliac L.
Insertion: Costal Angles of Ribs 6-12
Iliocostalis Thoracis M.
Origin:
Insertion:
Origin: Costal Angles of Ribs 6-12
Insertion: Costal Angles of Ribs 1-6 and Transverse Process C7
Iliocostalis Cervicis M.
Origin:
Insertion:
Origin: Costal Angles of Ribs 3-6
Insertion: Posterior Tubercles of Transverse Processes C4-6
Longissimus Thoracis M.
Origin:
Insertion:
Origin: common origin with Iliocostalis Lumborum, Transverse and Accessory Processes L1-5
Insertion: Transverse Processes T1-L2, Ribs 3-12 between the Costal Tubercle and Costal Angle
Longissimus Cervicis M.
Origin:
Insertion:
Origin: Transverse Processes T1-5
Insertion: Posterior Tubercles of Transverse Processes and Articular Processes of C2-6
Longissimus Capitis M.
Origin:
Insertion:
Action:
Origin: Transverse Processes T1-5, Articular Processes C4-7
Insertion: Mastoid Process of the Temporal B.
Action: Extend Neck working bilaterally; laterally flex Neck and rotate Face toward working unilaterally
Spinalis Thoracis M.
Origin:
Insertion:
Origin: Spinous Processes T11-12
Insertion: Spinous Processes T1-4
Spinalis Cervicis M.
Origin:
Insertion:
Origin: Spinous Processes T1-6
Insertion: Spinous Processes C2 (3, 4)
What is the difference between back sprain and back strain?
- A back sprain is an injury to the ligamentous attachments between bone, usually the result of inadequate stretching before activity
- A back strain involves excessive stretching and sometimes tearing of muscle fibers produced by an overly strong muscular contraction
(muscle tissue will spasm, or involuntarily contract, in response to injury and inflammation as a protective measure)
What muscles are present in layer 6 of the back?
Intrinsic, Transversosplinalis Group
- Semispinalis Thoracis M.
- Semispinalis Cervicis M.
- Semispinalis Capitis M.
- Multifidus M.
- Rotatores Longus M.
- Rotatores Brevis M.
What muscle is this?

Semispinalis Thoracis M. (thin muscular fasciculi)
What muscle is this?

Semispinalis Cervicis M.
What muscle is this?

Semispinalis Capitis M.
What muscle is this?

Multifidus M. (extends 3-4 spinal segments, best developed in lumbar region)
What muscle is this?

Rotatores Longus M. (extends 2 spinal segments)
What muscle is this?

Rotatores Brevis M. (extends to adjacent spinal segment)
Semispinalis Thoracis M. (thin muscular fasciculi)
Origin:
Insertion:
Action:
Innervation:
Origin: Transverse Processes T6-12
Insertion: Spinous Processes C6-T4
Action: Extend Spine and rotate Spine away
Innervation: Posterior Rami

Semispinalis Cervicis M.
Origin:
Insertion:
Action:
Innervation:
Origin: Transverse Processes T1-6
Insertion: Spinous Processes C2-5
Action: Extend Spine and rotate Spine away
Innervation: Posterior Rami

Semispinalis Capitis M. (best developed Semispinalis)
Origin:
Insertion:
Action:
Innervation:
Origin: Transverse Processes C7-T6
Insertion: Between Superior and Inferior Nuchal Lines of the Occipital B.
Action: Extend Head, rotate Face away
Innervation: Posterior Rami

Multifidus M. (extends 3-4 Spinal segments, best developed in lumbar region)
Origin:
Insertion:
Action:
Innervation:
Origin: Mamillary Processes of Lumbar Vertebrae, Transverse Processes of Thoracic Vertebrae, and Articular Processes of C4-7
Insertion: Spinous Processes three numeric segments superior, does not insert onto the Atlas
Action: Extend Spine, rotate Spine away
Innervation: Posterior Rami

Rotatores Longus M. (extends 2 spinal segments)
Origin:
Insertion:
Action:
Innervation:
Origin: Transverse Processes
Insertion: Roots of Spinous Processes 2 numeric segments superior
Action: Extend Spine, rotate Spine away (primarily proprioceptive)
Innervation: Posterior Rami

Rotatores Brevis M. (extends to adjacent spinal segment)
Origin:
Insertion:
Action:
Innervation:
Origin: Transverse Processes
Insertion: Roots of Spinous Processes 1 numeric segment superior
Action: Extend Spine, rotate Spine away (primarily proprioceptive)
Innervation: Posterior Rami

What are the other Deep Back muscles that are not considered a part of a “layer”?
- Interspinalis M. (best developed in Cervical and Lumbar regions)
- Intertransverarii M. (best developed in Cervical and Lumbar regions)
- Levator Costarum Longus M.
- Levator Costarum Brevis M.
What muscles are these?

- (top): Levator Costarum Brevis M.
- (bottom): Levator Costarum Longus M.
Interspinalis M. (best developed in Cervical and Lumbar regions)
- Origin:
- Insertion:
- Action:
- Innervation:
- Origin: Spinous Process
- Insertion: Adjacent Spinous Process
- Action: Extend Spine
- Innervation: Posterior Rami

Intertransversarii M. (best developed in Cervical and Lumbar regions)
- Origin:
- Insertion:
- Action:
- Innervation:
- Origin: Transverse Process
- Insertion: Adjacent Tranverse Process
- Action: Laterally flex Spine
- Innervation: Posterior portion (Posterior Rami), anterior portion (Anterior Rami)

Levator Costarum Longus M.
- Origin:
- Insertion:
- Action:
- Innervation:
- Origin: Transverse Processes C7-T11
- Insertion: 2nd Rib inferior to origin
- Action: Elevate Ribs
- Innervation: Posterior Rami
Levator Costarum Brevis M.
- Origin:
- Insertion:
- Action:
- Innervation:
- Origin: Transverse Processes C7-T11
- Insertion: Adjacent Rib inferior to origin
- Action: Elevate Ribs
- Innervation: Posterior Rami
What are the muscles present in the Suboccipital Region?
- Rectus Capitis Posterior Major M. (medial border Suboccipital Triangle)
- Rectus Capitis Posterior Minor M.
- Obliquus Capitis Inferior M. (inferior border Suboccipital Triangle)
- Obliquus Capitis Superior M. (lateral border Suboccipital Triangle)
What muscle is this?

Rectus Capitis Posterior Major M.
What muscle is this?

Rectus Capitis Posterior Minor M.
What muscle is this?

Obliquus Capitis Inferior M.
What muscle is this?

Obliquus Capitis Superior M.
Rectus Capitis Posterior Major M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous Process C2
Insertion: Lateral portion Inferior Nuchal Line
Action: Extend Head, rotate Face toward
Innervation: Suboccipital N.
Rectus Capitis Posterior Minor M.
Origin:
Insertion:
Action:
Innervation:
Origin: Posterior Tubercle C1
Insertion: Below Inferior Nuchal Line
Action: Extend Head
Innervation: Suboccipital N.
Obliquus Capitis Inferior M.
Origin:
Insertion:
Action:
Innervation:
Origin: Spinous Process C2
Insertion: Transverse Process C1
Action: Rotate Face toward
Innervation: Suboccipital N.
Obliquus Capitis Superior M.
Origin:
Insertion:
Action:
Innervation:
Origin: Transverse Process C1
Insertion: Between Superior and Inferior Nuchal Lines
Action: Extend and laterally flex Head
Innervation: Suboccipital N.
What are the borders and the contents of the suboccipital triangle?
- boundaries: Rectus Capitis Posterior Major M., Obliquus Capitis Inferior M., and Obliquus Capitis Superior M.
- contents: Vertebral A. travels through the floor of the triangle, and Suboccipital N. (of the posterior ramus of 1st Cervical Spinal N. and innervates musculature of Suboccipital Region)
