Download Enumerate name of muscles of shoulder region.

Muscles Of Shoulder Region
Learning Objectives:
At the end of the lecture, the student should be able to:
 Mention the extent of shoulder region.
 Enumerate name of muscles of shoulder region.
 State the detailed structures of each muscle with
respect to
origin, insertion, nerve supply and action of muscles with any
characteristic features.
Muscles Of Shoulder Region
Lecture outline
Shoulder Region:
 Shoulder region is the proximal part of upper
limb surrounds the shoulder joint, providing
round counter at proximal end of upper
extremity.
 Bony land marks are spine of scapula,
acrominon, Inferior angle of scapula.
Muscles Of Shoulder Region:
Group of six muscles, converge from scapula
on to the humerus and surround the
shoulder joint, Includes:
 Deltoid.
 Supraspinatus.
 Infraspinatus.
 Teres Minor.
 Teres major.
 Subscapularis.
Most of part of these muscles is under the
cover of Deltoid and Trapezius.
Deltoid:
 Deltoid is a powerful muscle, has longer leaner
origin. Has three groups of muscle fibers,
anterior, middle & posterior.
 Tip: Deltoid muscle is the principle abductor of
the arm but it cannot initiate this action, it is
assisted by the supraspinatus muscles.
Greek- delta triangular shaped.
 Origin: Lateral 1/3 of clavicle, acromion
process, scapular spine.
 Insertion: deltoid tuberosity at shaft of
humerus.
 Nerve Supply: Axillary Nerve (C5-C6).
Tips:
Deltoid consists of three groups of muscle fibers:
 Anterior Fibers, arising from clavicle, fibers are parallel.
 Posterior Fibers, arising from spine of scapula, parallel fibers.
 Middle fibers, arising from the acromion, multipennate, most powerful
muscle fibers, having seven septa inside mass, make the muscle
multipennate.
Actions:
 Anterior fibers- Flexes and medially rotates shoulder.
 Middle fibers- Abducts the shoulder.
 Posterior fibers- Extends and laterally rotates the shoulder.
 Tip: Anterior & Posterior fibers act like guy ropes to steady the arm in
abducted position.
 Deltoid is common site for Intramuscular Injection (IM)
on lateral side of bulge of shoulder.
 Axillary nerve is under the cover of deltoid, it winds
around the posteriolateral aspect of shaft of humerus
below the 5-6 cm of acromion.
 If IM injection is given using wrong technique may
produce damage to axillary nerve.
Insert needle at 90° angle for
intramuscular injections.
Supraspinatus
Latin- supra above spinatus spine
Bipennate muscle, which provide great force
pull to the muscle.
 Origin: Supraspinatus fossa of the scapula.
 Insertion: Greater tubercle of the humerus.
 Nerve Supply: Suprascapular nerve (C5-C6).
 Action: initiate the abduction at shoulder joint
for first 15 degree and assists deltoid muscle
in abducting arm at shoulder, stabilizes the
head of the humerus.
 Tip: The supraspinatus is the only muscle in
the rotator cuff groups that does not actually
rotate the humerus
Infraspinatus
Latin- infra beneath spinatus spine.
Multipennate muscle, a bursa lies between the
muscle and scapula, this bursa usually
communicates with cavity of shoulder joint.
 Origin: Infrsapsinatus fossa of the scapula.
 Insertion: Greater tubercle of the humerus.
 Nerve Supply: Suprascapular nerve from the

brachial plexus (C5-C6).
Action: Lateral rotation of the shoulder, and stabilizes
the head of the humerus.
Teres Minor
Latin- teres round.




Origin: superior half of the lateral border.
Insertion: Greater tubercle of the humerus.
Nerve Supply: axillary nerve (C5 C6).
Actions: Weak adductor of humerus, laterally rotates
the shoulder and stabilizes the head of humerus on
glenoid.
Tip: It is synergist to the Infraspinatus, the teres
minor may sometimes fuse with infraspinatus.
Teres Major
Latin- teres round.
Teres major is an offspring of subscapularis; it has
migrated to the dorsal surface of Scapula.
 Origin: Inferior part of lateral border and inferior
angle of the scapula.
 Insertion: medial lip intertubercular groove of the
humerus.
 Nerve Supply: lower subscapular nerve (C5 C6).
 Action: It extends the shoulder, medially rotates the
shoulder, Adducts the shoulder.
 Tip: Its tendon can be transplanted posteriorly to provide lateral rotation.