Soft Tissues of the Back - Superficial

Superficial Tissues

Triangles and fascia

1. Triangle of auscultation

• Is bounded by the upper border of the latissimus dorsi , the lateral border of the trapezius , and the medial border of the scapula .
• Has a floor formed by the rhomboid major.
• Is the site where breathing sounds can be heard most clearly using a stethoscope.

2. Lumbar triangle (of Petit)

• Is formed by the iliac crest, latissimus dorsi, and posterior free border of the external oblique abdominal muscle; its floor is formed by the internal oblique abdominal muscle.

3.Thoracolumbar (lumbodorsal) fascia

• Invests the deep muscles of the back.
• Has an anterior layer that lies anterior to the erector spinae and attaches to the vertebral transverse process.
• Has a posterior layer that lies posterior to the erector spinae and attaches to the spinous processes.
• Provides the origins for the latissimus dorsi and the internal oblique and transverse abdominis muscles.
  

Blood vessels

Occipital artery

• Arises from the external carotid artery, runs deep to the sternocleidomastoid muscle, and lies on the obliquus capitis superior and the semispinalis capitis.
• Pierces the trapezius, is accompanied by the greater occipital nerve (C2) , and supplies the scalp in the occipital region.

Transverse cervical artery

• Arises from the thyrocervical trunk of the subclavian artery and divides into the superficial and deep branches.
• Has a superficial branch (supe rficial cervical artery), which divides into an ascending branch that supplies the upper part of the trapezius and adjacent muscles and a descending branch that accompanies the spinal accessory nerve on the deep surface of the trapezius.
• Has a deep branch (dorsal scapular or descending scapular artery) that accompanies the dorsal scapular nerve (C5) deep to the levator scapulae and the rhomboids along the medial side of the scapula.

Nerves

Accessory nerve

• Consists of a cranial portion, which joins the vagus nerve, and a spinal portion, which runs deep to the sternocleidomastoid, lies on the levator scapulae, and passes deep to the trapezius.
• Supplies the sternocleidomastoid and trapezius muscles.

Dorsal scapular nerve (C5)

• Is derived from the ventral primary ramus of the fifth cervical spinal nerve, runs along with the deep branch of the transverse cervical artery, and supplies the rhomboid major and minor and levator scapulae muscles.

Greater occipital nerve (C2)

• Is derived as a medial branch of the dorsal primary ramus , the second cervical spinal nerve.
• Crosses obliquely between the obliquus inferior and the semispinalis capitis, pierces the semispinalis capitis and the trapezius, and supplies cutaneous innervation in the occipital region.
• May innervate the semispinalis capitis and communicates with the suboccipital and third occipital nerves.

Third (least) occipital nerve (C3)

• Is derived from the dorsal primary ramus of the third cervical spinal nerve.
• Ascends across the suboccipital region, pierces the trapezius, and supplies cutaneous innervation in the occipital region.

Lesser occipital nerve (C2)

• Is derived from the ventral primary ramus of the second cervical spinal nerve.
• Is a cutaneous branch of the cervical plexus and ascends along the posterior border of the sternocleidomastoid to the scalp behind the auricle.

Superficial or extrinsic muscles

Superficial Muscles of the Back

Muscle Origin Insertion Nerve Action

Trapezius
External occipital protuberance, superior nuchal line, ligamentum nuchae, spines of C7 T12
Spine of scapula, acromion, and lateral third of clavicle
Spinal accessory nerve; C3 C4
Adducts, rotates, elevates, and depresses scapula
Levator scapulae
Transverse processes of C1 C4
Medial border of scapula
C4 C5; dorsal scapular nerve
Elevates scapula; rotates glenoid cavity
Rhomboid minor
Spines of C7 T1
Root of spine of scapula
Dorsal scapular nerve (C5)
Adducts scapula
Rhomboid major
Spines of T2 T5
Medial border of scapula
Dorsal scapular nerve (C5)
Adducts scapula
Latissimus dorsi
Spines of T7 T12, thoracodorsal fascia, iliac crest, ribs 9 12
Floor of bicipital groove of humerus
Thoracodorsal nerve
Adducts, extends, and rotates arm medially; depresses scapula
Serratus posterior-superior
Ligamentum nuchae, supraspinal ligament, and spines of C7 T3
Upper border of ribs 2 5
Intercostal nerve (T1 T4)
Elevates ribs
Serratus posterior-inferior
Supraspinous ligament and spines of T11 L3
Lower border of ribs 9 12
Intercostal nerve (T9 T12)
Depresses ribs




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