Download Muscles of the shoulder region

Muscles of the shoulder
region
Muscles of the shoulder region:
Are divided into
1. Superficial muscles (Trapezius and Latissimus dorsi),
that cover most of the other muscles on the back.
2. Deep extrinsic muscles: arise from the axial skeleton
( Levator scapulae, Rhomboideus major and minor,
and the serratus anterior).
3. Intrinsic muscles arising from the scapula and passing
to the humerus (arising and inserted on the skeleton of
the limb): Deltoid, supraspinatus, infraspinatus, teres
major and minor, and the subscapularis.
Muscles of the shoulder region
Trapezius muscle: it is
somewhat triangular in
shape,
arises
from
occipital bone, ligamentum
nuchae, spine of 7th
cervical vertebra, spines of
all thoracic vertebrae.
Insertion: Upper fibers
into lateral third of
clavicle; middle and lower
fibers into acromion and
spine of scapula.
Muscles of the shoulder region
Trapezius muscle
Muscles of the shoulder region
Trapezius muscle:
Nerve supply: spinal part of accessory nerve (XI cranial
nerve).
Function: Upper fibers elevate the scapula; middle fibers
pull scapula medially; lower fibers pull medial border of
scapula downward
Muscles of the shoulder region:
Latissimus dorsi muscle: it
arises from Iliac crest, lumbar
fascia, spines of lower six
thoracic vertebrae, lower three
or four ribs, and inferior angle
of scapula.
Muscles of the shoulder region:
Latissimus dorsi muscle:
Insertion: Floor of bicipital
groove of humerus.
Nerve supply: Thoracodorsal
nerve.
Function: Extends, adducts,
and medially rotates the arm
Muscles of the shoulder region:
Levator scapulae muscle: it
arises from Transverse processes
of 1st four cervical vertebrae. It
inserts into the medial border of
scapula. Nerve supply: dorsal
scapular nerve
Function: Raises medial border
of scapula.
Levator scapulae muscle
Muscles of the shoulder region:
Rhomboid major: it is flat
muscle arises from second to
5th thoracic spines. It is
inserted on medial border of
scapula.
Nerve supply: Dorsal scapular
nerve.
Function: Raises medial
border of scapula upward and
medially.
Rhomboid major
Muscles of the shoulder region:
Rhomboid minor: it is flat
muscle lies deep to the
trapezius muscle. It arises
from Transverse processes of
1st four cervical vertebrae. It
inserts into medial border of
scapula.
Nerve supply: dorsal scapular
nerve.
Function:
Raises
medial
border of scapula
Rhomboid minor
Muscles of the shoulder region:
Serratus anterior : it covers
much of the lateral aspect of the
thorax. It arises from Upper
eight ribs. It inserts into medial
border and inferior angle of
scapula.
Nerve supply: Long thoracic
nerve.
Function:
Draws
forward
(protracts) the scapula, hold the
medial border of scapula firmly
against the thoracic wall, and
rotates scapula.
Serratus anterior :
Muscles of the shoulder region:
Deltoideus (Deltoid muscle):
is a large, thick, triangular
muscle, which covers the
shoulder joint in front, behind,
and laterally.
It arises from the lateral third
of clavicle, acromion and spine
of scapula.
Muscles of the shoulder region:
Deltoideus (Deltoid muscle):
Insertion: deltoid tuberosity on
the middle of lateral surface of
shaft of humerus.
Nerve supply: axillary nerve.
Function: abducts arm; anterior
fibers flex and medially rotate
arm; posterior fibers extend and
laterally rotate arm.
Muscles of the shoulder region:
Supraspinatus: occupies the
whole of the supraspinous fossa
of the scapula.
It arises from the supraspinous
fossa. It inserts into the greater
tuberosity of humerus and
capsule of the shoulder joint.
Nerve supply: suprascapular
nerve.
Function: abducts the arm and
stabilizes the shoulder joint.
Supraspinatus muscle
Muscles of the shoulder region:
Infraspinatus: is a thick triangular
muscle, occupies most of the
infraspinous fossa of scapula. It
arises from the infraspinous fossa.
Insertion: greater tuberosity of
humerus and the capsule of the
shoulder joint.
Nerve supply: Suprascapular nerve.
Function: laterally rotates arm and
stabilizes shoulder joint.
Infraspinatus
Muscles of the shoulder region:
Teres minor: is a narrow,
elongated muscle.
Origin: upper two thirds of
lateral border of scapula. It is
inserted on greater tuberosity of
humerus and capsule of the
shoulder joint.
Nerve supply: axillary nerve.
Function: laterally rotates arm
and stabilizes shoulder joint.
Teres minor
Muscles of the shoulder region:
Teres major: is a thick but
somewhat flattened muscle.
It arises from lower third of
lateral border of scapula and
inserts into medial lip of bicipital
groove of humerus.
Nerve supply: lower subscapular
nerve.
Function: medially rotates and
adducts arm and stabilizes
shoulder joint.
Teres major
Muscles of the shoulder region:
Subscapularis: is a large
triangular muscle which fills the
subscapular fossa of scapula.
Origin:
Subscapular
fossa.
Insertion: lesser tuberosity of
humerus.
Nerve supply: upper and lower
subscapular nerves.
Function: medially rotates and
stabilizes shoulder joint.
Muscles of the shoulder region:
The position and stability of the
scapula on the posterior wall of
the thorax is maintained by the
tone and balance of the muscles
attached to it. If one of these
muscles is paralyzed, the balance
is disturbed, as in dropped
shoulder, caused by paralysis of
the trapezius, or winged scapula,
caused by paralysis of the
serratus anterior.
Rotator Cuff
The rotator cuff is the name given to the tendons of the
subscapularis, supraspinatus, infraspinatus, and teres
minor muscles, which are fused to the underlying capsule
of the shoulder joint.
This cuff plays a very important role in stabilizing the
shoulder joint. The tone of these muscles assists in holding
the head of the humerus in the glenoid cavity of the
scapula during movements at the shoulder joint.
Rotator Cuff
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.
Arterial
Anastomosis
Shoulder Joint
around
the
The extreme mobility of the shoulder joint may result in
kinking of the axillary artery and a temporary occlusion of
its lumen. To compensate for this, an important arterial
anastomosis exists between the branches of the subclavian
artery and the axillary artery, thus ensuring that an
adequate blood flow takes place into the upper limb
irrespective of the position of the arm.
Arterial Anastomosis around the Shoulder Joint
Branches from the Subclavian Artery:
■ Suprascapular artery: distributed to the supraspinous and
infraspinous fossae.
■ Superficial cervical artery: gives off a deep branch that runs
down the medial border of the scapula
Arterial Anastomosis around the Shoulder Joint
Branches from the Axillary Artery:
■ Subscapular artery: and its circumflex scapular branch
supply the subscapular and infraspinous fossae, respectively.
■ Anterior and posterior circumflex humeral artery. Both the
circumflex arteries form an anastomosing circle around the
surgical neck of the humerus.
Joints of the Pectoral and Shoulder
Region
Acromioclavicular Joint
It is an articulation between the acromion process of the scapula
and the lateral end of the clavicle. It is synovial plane joint. There
is capsule surrounds the joint and is attached to the margins of the
articular surfaces.
Acromioclavicular Joint
The capsule is lined by the synovial membrane. The capsule is
reinforced by Superior and inferior acromioclavicular
ligaments. From the capsule, a wedge-shaped fibrocartilaginous
disc projects into the joint cavity from above.
Acromioclavicular Joint
Coracoclavicular ligament:
is an accessory ligament, it is
very strong ligament extends
from the coracoid process to
the undersurface of the
clavicle.
It
is
largely
responsible for stability of the
clavicle and AC joint.
Nerve supply: suprascapular
nerve.
Acromioclavicular Joint
Movements:
A gliding movement takes place when the scapula rotates or
when the clavicle is elevated or depressed. Although it is small
movement, but it is necessary to movement of the shoulder.