This document describes the anatomy of several muscles around the shoulder joint, including their origins, insertions, nerve supplies, and actions. It also discusses the rotator cuff muscles, quadrangular space, triangular spaces, axillary nerve, suprascapular nerve, and arterial blood supply around the shoulder joint. Key structures mentioned include the deltoid, trapezius, latissimus dorsi, levator scapulae, rhomboid muscles, and rotator cuff muscles.

1. The Back

2. Scapula, anterior aspect

3. Scapula-Posterior Aspect

4. Trapezius
Origin
• Occipital bone(external occiptal
protuberunce),superior nuchal line,
ligamentum nuchae, spine of seventh
cervical vertebra, spines of all thoracic
vertebrae and their supraspinous ligament
Insertion
• Upper fibers into lateral third of clavicle;
middle and lower fibers into acromion and
spine of scapula
Nerve Supply
• Spinal part of accessory nerve (motor) and
C3 and 4 (sensory)
• XI cranial nerve (spinal part)
Action
• Upper fibers elevate and upwardly rotate
the scapula, extend the neck.
• middle fibers adduct(retracts) the scapula.
• lower fibers depress and help upper fibres
in rotating scapula.

5. Latissimus dorsi
Origin
• Iliac crest, lumbar fascia, spines
of lower six thoracic
vertebrae(T7-T12), lower three
or four ribs, and inferior angle of
scapula
Insertion
• Floor of bicipital groove of
humerus
Nerve Supply
• Thoracodorsal nerve(C6, 7, 8)
Action
• Extends, adducts, and medially
rotates the arm
• Its called the climbing muscle
• Raising of the trunk above the
arm
Important :As it winds around lower
border of teres major it forms
posterior fold of axilla its lateral
border forms a boundary of
lumbar triangle.

6. Levator scapulae
Origin
Transverse processes of
first fourth cervical
vertebrae
Insertion
Medial border of scapula
Nerve supply
C3 and 4 and dorsal
scapular nerve
Action
Raises medial border of
scapula
Important : Part of floor
of Posterior triangle

7. Rhomboid minor
and Major
Origin
(MInor)Ligamentum
nuchae and spines of
seventh cervical and
first thoracic vertebrae
(Major)T2-T5 spines
Insertion
Medial border of scapula
Nerve supply
• Dorsal scapular nerve
C4, 5
Action
• Raises medial border of
scapula upward and
medially

8. Deltoid
Origin
Lateral third
clavicle(Anterior)
Lateral border of
acromion(middle)
Spine of scapula(posterior)
Insertion
Middle of lateral surface of
shaft of humerus to
deltoid tuberosity
Nerve supply
Axillary nerve C5, 6
Action
Anterior fibers flex and
medially rotate arm
Middle fibers Abducts arm;
Posterior fibers extend and
laterally rotate arm
Abduction from 15-90
degrees

9. Applied anatomy
 Intramuscular injections are
given into the deltoid .
The should be given in the lower
half of the muscle to avoid
injury to axillary nerve.
 In subacromial bursitis
pressure over the deltoid
below the acromion with the
arm by the side causes pain.
However when the arm is
abducted pressure over the
same point causes no pain
because the bursa disappears
under the acromion. This is
referred to as Dawbarn’s sign.

10. Supraspinatus
Origin
Supraspinous fossa of
scapula
Insertion
Greater tuberosity of
humerus; capsule of
shoulder joint
Nerve supply
Suprascapular nerve C4, 5, 6
Action
Abducts arm and stabilizes
shoulder joint
Initiation of abduction 0-15
degrees

11. InfraspinatusOrigin
Infraspinous fossa of
scapula
Insertion
Greater tuberosity of
humerus; capsule of
shoulder joint
Nerve supply
Suprascapular nerve
C4, 5, 6
Action
Laterally rotates arm and
stabilizes shoulder
joint

12. Teres minor
Origin
Upper two thirds of lateral
border of scapula
Insertion
Greater tuberosity of
humerus; capsule of
shoulder joint
Nerve supply
Axillary nerve (C4), C5, 6
Action
Laterally rotates arm and
stabilizes shoulder joint

13. Subscapularis
Origin
Subscapular fossa
Insertion
Lesser tuberosity of humerus
Nerve supply
Upper and lower subscapular
nerves C5, 6, 7
Action
Medially rotates arm and
stabilizes shoulder joint
Important: Multipennate

14. Teres major
Origin
Lower third of lateral border of
scapula
Insertion
Medial lip of bicipital groove of
humerus
Nerve supply
Lower subscapular nerve C6, 7
Action
Medially rotates and adducts arm
and stabilizes shoulder joint
Important : Considered
continuation of subscapularis

15. Rotator Cuff
• The rotator cuff is the
name given to the tendons
of the subscapularis,
supraspinatus,
infraspinatus, and teres
minor muscles
• Fused to the underlying
capsule of the shoulder
joint
• The cuff lies on the
anterior, superior, and
posterior aspects of the
joint
• The cuff is deficient
inferiorly, and this is a site
of potential weakness.

16. Quadrangular Space
 Superiorly by the
subscapularis and capsule
of the shoulder joint
 Inferiorly by the teres
major muscle
 Medially by the long
head of the triceps
 laterally by the surgical
neck of the humerus.
Contents
 The axillary nerve and
the posterior circumflex
humeral vessels

17. Upper & Lower
Triangular spaces
Upper
 Superiorly subscapularis
and teres minor
 Inferiorly teres major
 Laterally the long head of
the triceps
• Contains circumflex
scapular vessels.
Lower
 superiorly the teres
major
 medially long head of the
triceps brachii
 laterally Medial head of
triceps
• Contains radial nerve and
profunda brachii artery.

18. The triangle of auscultation
• It is the site where breathing
sounds can be heard most
clearly, using a stethoscope.
 Is formed by the vertebral or
medial border of the scapula,
superior border of latissimus
dorsi
the lateral border of the trapezius.
 It has a floor formed by
rhomboid major.
 It covers the intercostal space
between ribs 6 and 7 and rib 7.
 It lies superficial to the cardiac
orifice of the stomach on the
left side, where splash of
swallowed liquids was timed in
cases of esophageal
obstruction.
It is the site where breathing sounds can be
heard most clearly, using a stethoscope.

19. The lumbar triangle
Is formed by
the posterior free border of
the external oblique,
the superior border of the
iliac crest and
the lateral border of the
latissimus dorsi.
• Its floor if formed by
internal oblique
abdominal muscle.
• It may be site of an
abdominal hernia.

20. Axillary Nerve
 Arises from the posterior
cord of the brachial plexus
(C5 and 6) in the axilla
 Passes backward ,through
quadrangular space with
the posterior circumflex
humeral artery
 In close association with
surgical neck of humerus
and capsule of shoulder
joint
 It terminates by dividing
into anterior and posterior
branches

21. Branches
 Articular branch to the
shoulder joint
 Anterior terminal branch
supplies the deltoid and
the skin that covers its
lower part.
 Posterior terminal
branch supplies teres
minor muscle and
deltoid, then emerges
as the upper lateral
cutaneous nerve of the
arm

22. Applied Aspect
• The axillary nerve may be damaged by
dislocation of shoulder or by fracture of
surgical neck of humerus.
• The patient presents with loss of abduction of
shoulder upto 90 degrees (as deltoid is
paralysed), loss of rounded countour of
shoulder and sensory loss over lower deltoid.

23. Suprascapular nerve The suprascapular nerve
originates from Upper trunk
of the brachial plexus
 It passes through
suprascapular foramen to
reach the posterior scapular
region
 innervates the supraspinatus
muscle
 then passes through the
greater scapular
(spinoglenoid) notch
 Terminate in and innervate
the infraspinatus muscle.
 Mnemonic(“Army over and
navy under the bridge”)

24. Arterial Anastomosis Around the
Shoulder Joint
Branches from the
subclavian artery
1. The suprascapular artery
is a branch of
thyrocervical trunk of
subclavian artery.
Supplies the supraspinous
and infraspinous fossae,
and their contents .
2. Deep branch of
transverse cervical artery
supplies the rhomboidei
and the medial border of
the scapula, running deep
to levator scapulae.

25. Branch from the axillary artery
3. The circumflex scapular artery, a
branch of the subscapular artery
which arises from the third part of
axillary artery
Applied aspect
• Scapular anastomoses is an
anastomoses between the first
part of subclavian and third part
of axillary artery. So it provides a
collateral circulation through
which blood can flow to the limb
in case of blockage of distal part
of subclavian artery or proximal
part of axillary artery.