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MUSCLES OF THE SHOULDER
GIRDLE
The deltoid forms
the contour of the
shoulder.
Deep to it are : 
Supraspinatus. 
Infraspinatus. 
Subscapularis. 
Teres minor. 
Teres major. 

DELTOID
It is triangular in 
shape.
It is functionally 
divided into: anterior,
middle and posterior
parts.
Origin : 
Anterior fibers: lateral
1/3 of the anterior
border of the clavicle.

DELTOID
Middle fibers : 
lateral border of the
acromion.
Posterior fibers: 
lower border of the
spine of the scapula.
DELTOID
Insertion : 
deltoid tuberosity 
(middle of the lateral
surface of the
humerus).
DELTOID
Nerve supply : 
Axillar nerve. 
DELTOID
Action: 
1. Middle fibers: 
abduction of the arm
(helped by
supraspinatus).
2. Anterior fibers: 
flexion and medial
rotation.
3. Posterior fibers : 
extension and lateral
rotation.
AXILLARY NERVE
Origin : 
Posterior cord of the 
brachial plexus (in the
axilla).
AXILLARY NERVE
Course : 
Passes through 
the quadrangular
space.
It is closely 
related to the
inferior part of
the shoulder joint
and the surgical
neck of the
humerus.
AXILLARY NERVE
Branches : 
1. Articular : to the shoulder
joint.
2. Anterior branch : 
deltoid muscle and the skin
covering its lower half.
3. Posterior branch : 
Deltoid. 
Teres minor. 
Upper lateral cutaneous 
nerve of the arm.


QUADRANGULAR SPACE
It is an 
intermuscular
space.
Boundaries : 
Superior 
(posterior) :Teres
minor.
Superior 
(anterior):
Subscapularis 
Inferior : Teres 
major.
QUADRANGULAR SPACE
Medially : Long 
head of triceps.
Laterally : 
Surgical neck of
the humerus.
Contents : 
Axillary nerve. 
Posterior 
circumflex
humeral vessels.
ROTATOR CUFF
It is formed of (4) 
muscles
Supraspinatus. 
Infraspinatus. 
Teres minor. 
Subscapularis. 
It lies on the 
superior, posterior
and anterior aspects
of the shoulder joint.
It is deficient 
inferiorly.
ROTATOR CUFF
Function : 
The tone of the 
muscles holds the
head of the humerus
in the glenoid
cavity.
So they assist in 
stabilization of the
shoulder joint.
SUPRASPINATUS
Origin : 
Supraspinous fossa of
the scapula.

SUPRASPINATUS
Insertion : 
Upper facet of 
the greater
tuberosity of the
humerus and
The capsule of •
the shoulder
joint.
SUPRASPINATUS
Action : 
1. It initiates 
abduction of the
shoulder joint.
2. Rotator cuff. 
INFRASPINATUS
Origin : 
Infraspinous
fossa.

INFRASPINATUS
Insertion : 
Middle facet of 
the greater
tuberosity of the
humerus.
INFRASPINATUS
Action : 
1.Lateral
rotation.
2. R.C. 

NERVE SUPPLY
Suprascapular
nerve.

SUPRASCAPULAR NERVE
Origin : 
Upper trunk of the 
brachial plexus in the
posterior triangle.
SUPRASCAPULAR NERVE
Course : 
It descends behind the
suprascapular ligament
in company with the
suprascapular vessels.
Branches : 
Supraspinatus,
Infraspinatus and
Shoulder joint.

TERES MINOR
Origin : 
Upper 2/3 of the
lateral border of
the scapula.

TERES MINOR
Insertion : 
Lower facet of 
the greater
tuberosity of the
humerus.
TERES MINOR
Nerve supply :
Axillary nerve.
Action : 
1. Lateral 
rotation.
2. R.C. 


SUBSCAPULARIS
Origin : 
Subscapular
fossa.

SUBSCAPULARIS
Insertion : 
Lesser tubercle
of the humerus.

SUBSCAPULARIS
Nerve supply :
Upper & lower
subscapular
Action : 
1. Medial 
rotation.
2. R.C. 


ROTATOR CUFF TENDINITIS
Manifestations : 
Spasm 
associated with
pain in the
middle range of
abduction.
It is a common 
cause of pain in
the shoulder
region.
ROTATOR CUFF TENDINITIS
Cause : 
Excessive overhead 
activity of the upper limb
which can cause
degenerative changes in
the subacromial bursa.
This is followed by 
degenerative changes in
the supraspinatus tendon
and extend to the other
tendons of the rotator
cuff.
TERES MAJOR
Origin : 
Inferior angle 
and lower third
of lateral border
of the scapula.
TERES MAJOR
Insertion : 
Medial lip of the
bicipital groove
of the humerus.

TERES MAJOR
Nerve supply : 
Lower 
subscapular
Action : 
1. Adduction. 
2. Medial 
rotation.