Shoulder Girdle

Trapezius / Levator Scapulae / Rhomboids / Pectoralis Minor / Serratus Anterior /
Sternocleidomastoid
Trapezius
The Trapezius is part of the group of muscles which control the shoulder girdle and is divided into
parts; upper, middle and lower.

Part 1: Upper fibres of the cervical vertebrae. This is the weakest part of the muscle and only
provides minor elevation of the clavicle

Part 2: The area commonly known as upper trapz. This is a strong elevator, rotator and
retractor of the scapula

Part 3: The mid-portion of the Trapzius. These fibres are mainly responsible for scapula
retraction

Part 4: The lower fibres of Trapezius. This part of the muscle assists in retraction and
rotation.
When all parts of the muscle work together they have the effect of simultaneously elevating and
retracting the scapula. The Trapezius is used most commonly to fix the scapula to allow the Deltoid
to move the Humerus.
Origin

Base of skull

Ligaments cervical (upper) spine

Spinous processes of Cervical 7 to Thoracic 12 vertibrae
Insertion

Posterior outer 1/3 of the clavicle

Acromion process

Spine of the scapula
Actions

Elevate the Scapula

Retract the Scapula

Upward rotation of the scapula
Which nerve supplies the muscle?

Cranial nerve
Daily uses

Shrugging the shoulders

Overhead movements or the arm
Levator Scapulae
Shrugging the shoulders (scapula elevation) requires the use of levator scapulae and Trapezius.
Fixation of the scapula by other muscles, allows the levator scapulae muscles to work together to aid
cervical extension, or independently to laterally flex (side bend) the neck towards the side of the
working muscle.
Origin

Transverse processes of C1-4
Insertion

Medial border of the scapula above the level of the scapula spine
Actions

Scapula elevation

Lateral flexion of the cervical spine (each side independently)

Extension of the cervical spine (each side independently)
Which nerves supply this muscle?

Cervical nerve

Dorsal scapular nerve
Daily uses

Shrugging shoulders

Carrying a heavy shopping bag
Rhomboids
There are two rhomboid muscles - Rhomboid major is larger and positioned below rhomboid minor.
Both muscles work together to retract the scapula (bring the shoulder blades together) and rotate
the scapula.
Chins and dips are excellent activities for developing these muscles.
Origin

Spinous processes of C7-T5
Insertion

Medial border of the scapula, below the level of the spine of the scapula
Actions

Scapula retraction

Rotation of the scapula downwards
Which nerve makes it move?

Dorsal scapular nerve
Daily uses

Pulling a draw open
Pectoralis Minor
The Pectoralis Minor muscle is the smallest of the two pectoral (chest) muscles. It works together
with Serratus anterior which protracts and rotates upwards. When the two work together, pure
protraction (without rotation) is produced.
Origin

Outer surface of ribs 3-5
Insertion

Coracoid process of the scapula
Actions

Scapula protraction

Rotation of the scapula downwards
Innervation

Medial pectoral nerve
Daily uses

Pushing a door open
Serratus Anterior
The Serratus anterior muscle is used in activities which draw the scapula forwards. It is used strongly
in push-ups and bench presses. Winged scapula are an indicator of having a weak Serratus anterior.
Origin

Upper nine ribs at the side of the chest
Insertion

Costal aspect (side articulating with the ribs) of the medial border of the scapula
Actions

Scapula protraction

Rotation of the scapula upwards
Innervation

Long thoracic nerve
Daily uses

Reaching up to open a high window
Sternocleidomastoid Muscle
The Sternocleidomastoid muscle is the big thick muscle in the neck and is easily seen at the front of
the neck when rotating the head the other way.
Origin

Anterior surface of the upper sternum

Inner part of the clavicle
Insertion

Mastoid process (behind the ear)
Actions

Contraction on both sides: Flexes the neck

Contraction on one side only: Laterally flexes (side bends) to the same side and rotates to
the other side
Innervation

Acessory XI nerve
Daily uses

Looking at the floor

Looking over your shoulder

Holding the phone between your ear and shoulder