Muscles of the Back

By- Dr. Avi Sharma

Ph.D.(Sch.),M.D.(Hom.),B.H.M.S.
www.homoeopathy.care
Dr.avisharma@live.com
+91-9958687544
Trapezius
The right and left muscle together form
Trepezium that covers the upper half of the
back.

Origin- Insertion-
1. Medial 1/3rd of superior nuchal 1. Upper fibres, into posterior
line. border of lateral 1/3 of clavicle
2. External Occipital protuberance 2. Middle fibres, into the medial
3. Ligamentum Nuchae margin of the acromion and the
4. C7 Spine upper lip of the crest of the spine
5. T1-T12 Spines of the scapula.
6. Corresponding supraspinous 3. Lower Fibres, on the apex of the
ligaments triangle at the end of the spine,
with a bursa intervening.
Trapezius muscle- Origin and Insertion
Various ligaments of vertebrae
 Nerve supply and action of Trapezius
Nerve Supply Action

Spinal part of accessory nerve is motor Upper fibers act with levator scapulae,
and elevate the scapula: as in shrugging.

Branches from C3 and C4 are Middle fibers act with rhomboids, and
proprioceptive. retract the scapula.

Upper and lower fibers act with serratus

anterior, and rotate the scapula forward
round the chest wall thus playing an
important role in abduction of the arm
beyond 90 degree.

Steadies the scapula

• Developmentally the trapezius is related to
the sternomastoid. Both of them develop
from branchial arch mesoderm and are
supplied by the spinal accessory nerve.
• The principal action of the trapezius is to
rotate the scapula during abduction of the
arm beyond 90 degree. Clinically the muscle is
tested by asking the patient to shrug his
shoulder against resistance.
Structures under cover of the Trapezius:
A large number of structures lie immediately under cover
of the trapezius.
A. Muscles-
1. Semispinalis capitis (The semispinalis capitis is a long,
thin muscle located in both sides of the back of your
neck. Interestingly, this muscle is one that can
become painful from whiplash or from sitting too long
with poor posture.)
2. Splenius capitis
3. Levator scapulae
4. Inferior belly of omohyoid
5. Rhomboideus minor
6. Rhomboideus major
7. Supraspinatus
8. Infraspinatus
9. Latissimus dorsi
10. Serratus posterior superior

B. Vessels-
1. Suprascapular artery and vein
2. Superficial branch of the transverse cervical
artery and accompanying veins.
3. Deep branch of transverse cervical artery and
accompanying veins.
C. Nerves-
1. Spinal part of accessory nerve.
2. Suprascapular nerve.
3. C3 and C4 nerve.
4. Posterior primary rami of C2-C6 and T1-T12
pierce the muscle to become cutaneous
nerves.
D. Bursa-
A bursa lies over the smooth triangular area at
the root of the spine of the scapula.
Latissimus dorsi
• Develops in the extensor compartment of the
limb. Thereafter it migrates to its wide
attachment on the trunk, taking its nerve
supply (thoracodorsal nerve) along with it.
• It is developed in the animals that suspend
themselves by their arms (Brachiators like
apes, monkeys etc.). The complexity of the
muscle is indicated by the occasional presence
in man of the axillary arch and dorso-
epitrochlearis brachii normally present in
apes.
Latissimus dorsi-Origin and Insertion
• The axillary arch is muscular slip which arises
from the edge of the latissimus dorsi in the
posterior fold of the axilla. It crosses the axilla
in front of the vessels and the nerves of the
region and joins the tendon of the pectoralis
major, of the coracobrachialis or of biceps. It is
present in about 7% of subjects.
• A fibrous or muscular slip may connect the
lower border of the latissimus dorsi to the
long head of the triceps. When muscular, it is
called the Dorsoepitrochlear brachii.
Dorso-Epithrochlearis brachii- Muscular
• The latissimus dorsi is tested clinically by
asking the patient to cough, and feeling the
contracting muscle in the posterior fold of the
axilla.
Muscle Origin from Insertion into
Latissimus dorsi Posterior 1/3 of the outer The muscle winds round
lip of iliac crest the lower border of the
It covers a large area of the teres major, and forms the
lower back, and is posterior fold of the axilla
overlapped by the
trapezius

Posterior layer of lumbar The tendon is twisted

fascia; thus attaching the upside down and is
muscle to the lumbar and inserted into the floor of
sacral spines the intertubercula sulcus.
Spine of T7-12

Lower 4 ribs

Inferior angle of the

scapula
Nerve supply and action of Latissimus Dorsi

Nerve Supply Action

Thoracodorsal nerve (C6,7,8) Adduction, extension and medial rotation
of the shoulder as in swimming, rowing,
climbing, pulling, folding the arm behind
the back, and scratching the opposite
scapula
(N. to latissimus dorsi) Helps in voilent expiratory effort
coughing, sneezing etc.
Essentially a climbing muscle
Holds inferior angle of the scapula in
place.
Levator Scapula
Origin from Insertion into Nerve Supply Action

Transverse process Superior angle and Branch from dorsal Helps in elevation
of C1 and C2 upper part of scapular nerve (C5) of scapula
medial border (up
to triangular area)
of scapula
Posterior tubercles C3 and C4 Steadies the
of the transverse scapula during
process of C3 and movements of the
C4 arm
Rhomboideus Major
Origin from Insertion into Nerve supply Action
Lower part of Base of the Dorsal scapular Help in retraction of
ligamentum nuchae triangular area at nerve (C5) the scapula and
the root of the steading it
spine of the scapula
Spines of C7 and T1
Rhomboidus Major
Origin from Insertion into Nerve Supply Actions
Spines of T2, 3,4,5 Medial borders of Dorsal scapular Helps in retraction
the scapula below nerve (C5) of the scapula and
the root of the also in steading it
spine
Supraspinous
Liagemnts
Triangle of Auscultation
• This is a small triangular interval bounded
medially by the lateral border of the trapezius,
laterally by the medial border of scapula and
inferiorly by the upper border of the
latissimus dorsi. The floor of the triangle is
formed by the 7th rib, 6th and 7th intercostal
spaces, and the rhomboideus major. This is
the only part of the back which is not covered
by muscles. Respiratory sounds (heard on
auscultation) are said to be better heard over
this triangle that elsewhere on the back.
On the left side, the cardiac orifice of the
stomach lies deep to the triangle, and in days
before X-rays were discovered the sound of
swallowed liquid were auscultated over this
triangle.
Lumbar Triangle (Of Petit)
This is another small triangle surrounded by
muscles. It is bounded medially by the lateral
border of latissimus dorsi, laterally by the
posterior border of external oblique muscle of
the abdomen and inferiorly by the iliac crest
(which forms the base). The occasional hernia at
this site is called lumbar hernia.
END.