CHAPTER -3

SUPERFICIAL MUSCLES OF BACK

These muscles connect the upper limb and the vertebral column. They are-

Trapezius and latissimus dorsi arranged in first layer

Levator scapulae, Rhomboideus major and minor arranged in second line.

TRAPEZIUS

It is called as trapezius as the two sided muscles form the trapezoid shape.

Origin :

From the medial one third of the superior nuchal line of occipital bone.

From the entire ligamentum nuchae (attached to spinous process of cervical vertebrae)

From the spinous process and supra spinous ligaments of all twelve thoracic vertebrae.








SCAPULA


FOR OSTEOLOGY OF SCAPULA:   WATCH THIS VIDEO: https://youtu.be/apMglf2oYO8

Insertion:

Posterior border of lateral 1/3 of clavicle

Medial border of acromion and upper lip of crest of the spine of scapula.

Deltoid tubercle of scapula

Nerve supply: Spinal accessory nerve

Actions:

Upper and lower fibres : rotation of scapula

Upper fibres : elevation of scapula

Middle fibres : retraction of scapula


Position of trapezius and its parts.

  Superior fibers of the trapezius
  Middle fibers of the trapezius                 Inferior fibers of the trapezius

LATISSIMUS DORSI: ( muscle connecting upper limb with lower limb girdle)

It is called as latissimus  which means broad and is situated in the dorsum of trunk.

Origin:

From the lower six thoracic spines ( from T7) and supra spinous ligaments

From the spines and supra spinous ligaments of lumbar and sacral vertebrae

(Note: from upper spines of vertebral column, trapezius muscle and from lower, the latissimus dorsi muscle)

From the outer lip of the iliac crest

From lower three or four ribs

Insertion: Floor of inter tubular sulcus of humerus

Nerve supply: Nerve to latissimus dorsi from posterior cord

Actions:

Extension and medial rotation of shoulder joint

Along with pectoralis major, adductor of shoulder joint

In raising the arms above the head, it elevates the trunk during climbing (Climber’s muscle, swimmer’s muscle)



Two triangles are associated with latissimus dorsi :

A: Petit’s triangle (Superior lumbar triangle)

B: Triangle of auscultation (Inferior lumbar triangle)

PETIT’S TRIANGLE:

Boundaries :

In front : external oblique abdominis

Behind : latissimus dorsi

Below : iliac crest

Floor : Internal oblique abdominis.

It is a potential weak area in the posterior abdominal wall through which herniation may take place.

TRIANGLE OF AUSCULTATION:

Below: upper border of latissimus dorsi

Medially: Lateral border of trapezius

Laterally: Vertebral border of scapula

Floor: 6th and 7th ribs.

The cardiac orifice of the stomach and apex of lower lobes of both lungs lie beneath this triangle which can be auscultated.



LEVATOR SCAPULAE: Elevate the scapula with upper part of trapezius.

RHOMBOIDEUS MAJOR AND MINOR: Retract the scapula along with middle fibres of trapezius.

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