In this pdf-note, we’ll start with the borders of the back:

• Superior border passes through the external occipital protuberance and the superior nuchal line

• Inferior border passes through the sacro-iliac joints, posterior segments of the ilium bones crests, coccyx

• Lateral border passes through the posterior median line

There are several anatomical regions within the back:

1. Vertebral region (regio vertebralis)

2. Scapular region (regio scapularis)

3. Infrascapular region (regio infrascapularis)

4. Lumbar region (regio lumbalis)

5. Sacral region (regio sacralis)

The muscles of the back are located within these regions. They are arranged in two layers: superficial and deep. In this pdf-note, we will learn about the superficial muscles of the back.

These include:

• Trapezius muscle (m. trapezius)

  

  

  

  Trapezius muscle
  (m. trapezius)

  Origin:

  Descending part arises from the external occipital protuberance, superior nuchal line, spinous processes of vertebrae, nuchal ligament

  Transverse part arises from the spinous processes of Th1-Th4 vertebrae

  Ascending part arises from the spinous processes of Th5-Th12 vertebrae

  Insertion:

  Descending part inserts into the external third of the clavicle

  Transverse part inserts into the acromion of the scapula, spine of the scapula

  Ascending part inserts into the spine of the scapula

  Function:

  Descending part: brings the scapula closer to the spine (superiorly and medially), helps to extend the cervical spine, helps to turn the head to the contralateral side

  Transverse part: pulls the scapula medially

  Ascending part: pulls the scapula inferiorly and medially

  Innervation:

  Motor branches: accessory nerve

  Sensory branches: cervical plexus (C3-C4)

  Blood supply: transverse cervical artery, occipital, suprascapular, posterior intercostal arteries.

• Latissimus dorsi muscle (m. latissimus dorsi)

  

  

  

  

  Latissimus dorsi muscle
  (m. latissimus dorsi)

  Origin:

  Vertebral part arises from the spinous processes of the Th7-Th12 vertebrae, thoracolumbar fascia

  Iliac part arises from the posterior third of the iliac crest

  Rib part arises from the ribs 9-12

  Scapular part arises from lower angle of the scapula

  Insertion: crest of the lesser tubercle of the humerus

  Function: arm pronation, arm adduction, arm extension; also it slightly participates in the act of breathing.

  Innervation: thoracodorsal nerve (C6-C8)

  Blood supply: thoracodorsal artery, posterior circumflex humeral artery, posterior intercostal arteries.

  The following muscles are located slightly deeper than the previous ones.

• Levator scapulae muscle (m. levator scapulae)

  

  

  Levator scapulae muscle
  (m. levator scapulae)

  Origin: transverse processes of the C1-C4 vertebrae

  Insertion: medial margin of the scapula (between the superior angle and the spine)

  Function: pulls the scapula superiorly and medially, shifts the articular cavity inferiorly, tilts the head ipsilaterally

  Innervation: anterior branches of the spinal nerves (C3-C4), posterior scapular nerve (C5)

  Blood supply: transverse cervical artery, ascending cervical artery

• Rhomboid major muscle (m. rhomboideus major)

  

  

  Rhomboid major muscle
  (m. rhomboideus major)

  Origin: spinous processes of the Th2-Th5 vertebrae

  Insertion: medial margin of the scapula (between the inferior angle and the spine)

  Function: pulls the scapula superiorly and medially, shifts the articular cavity inferiorly

  Innervation: posterior nerve of the scapula (C5)

  Blood supply: transverse cervical artery, suprascapular, posterior intercostal arteries

• Rhomboid minor muscle (m. rhomboideus minor)

  

  Rhomboid minor muscle
  (m. rhomboideus minor)

  Origin: nuchal ligament, spinous processes of the vertebrae C7-Th1

  Insertion: medial margin of the the spine of the scapula and the scapula itself

  Function: pulls the scapula superiorly and medially, shifts the articular cavity inferiorly

  Innervation: posterior nerve of the scapula (C5)

  Blood supply: transverse cervical artery, suprascapular, posterior intercostal arteries

• Serratus posterior superior muscle (m. serratus posterior superior)

  

  Serratus posterior superior muscle
  (m. serratus posterior superior)

  Origin: spinous ligament, spinous processes of the vertebrae C7-Th3

  Insertion: superior margins of the ribs 2-5

  Function: lifts the ribs, participates in the act of inhalation

  Innervation: 2nd-5th intercostal nerves

  Blood supply: posterior intercostal arteries, deep cervical artery

• Serratus posterior inferior muscle (m. serratus posterior inferior)