Shoulder Girdle
Muscles connecting the upper limb to the vertebral column
They are arranged into two layers, as follows:
1) First layer:
1)Trapezius.
2 )Latissimus dorsi.
2) Second layer:
1 ) Levator scapulae.
2 ) Rhomboid minor.
3 ) Rhomboid major.
1) First layer:
1)Trapezius.
2 )Latissimus dorsi.
2) Second layer:
1 ) Levator scapulae.
2 ) Rhomboid minor.
3 ) Rhomboid major.
Trapezius
Origin
1 ) The superior nuchal line
2 ) External occipital proturberance.
3 ) Ligamentum nuchae.
4) Spine of the 7th cervical vertebra.
5) Spines of all thoracic vertebrae.
Insertion
1) The upper fibres are inserted into the posterior border of the lateral third of the clavicle.
2) The middle and lower fibres are inserted into the medial border of the acromion and the upper border of the spine of the scapula.
Nerve supply
Spinal accessory.
Actions
1) The upper fibres elevate the scapula (shrugging).
2 ) The middle fibres pull the scapula medially (retraction).
3 ) The lower fibres pull the medial border downward.
1 ) The superior nuchal line
2 ) External occipital proturberance.
3 ) Ligamentum nuchae.
4) Spine of the 7th cervical vertebra.
5) Spines of all thoracic vertebrae.
Insertion
1) The upper fibres are inserted into the posterior border of the lateral third of the clavicle.
2) The middle and lower fibres are inserted into the medial border of the acromion and the upper border of the spine of the scapula.
Nerve supply
Spinal accessory.
Actions
1) The upper fibres elevate the scapula (shrugging).
2 ) The middle fibres pull the scapula medially (retraction).
3 ) The lower fibres pull the medial border downward.
Figure1: Trapezius.
Latissimus dorsi
Origin
1) Lower six thoracic spines and related interspinous ligaments,
2) Lumbar fascia,
3) Iliac crest, and
4) Lower three or four ribs.
Insertion
Its tendon is inserted into the floor of the bicipital groove of the humerus.
Nerve supply
Thoracodorsal nerve.
Actions
Adduction, extension and medial rotation of the shoulder.
1) Lower six thoracic spines and related interspinous ligaments,
2) Lumbar fascia,
3) Iliac crest, and
4) Lower three or four ribs.
Insertion
Its tendon is inserted into the floor of the bicipital groove of the humerus.
Nerve supply
Thoracodorsal nerve.
Actions
Adduction, extension and medial rotation of the shoulder.
Figure2: Latissimus dorsi.
Levator Scapulae
Origin
From the transverse processes of the upper four cervical vertebrae.
Insertion
At the dorsal surface of the medial border of the scapula from the superior angle to the root of the spine.
Nerve supply
1) Dorsal scapular nerve.
2) Anterior rami of the C3 and C4 spinal nerves.
Actions
Elevation of the scapula.
From the transverse processes of the upper four cervical vertebrae.
Insertion
At the dorsal surface of the medial border of the scapula from the superior angle to the root of the spine.
Nerve supply
1) Dorsal scapular nerve.
2) Anterior rami of the C3 and C4 spinal nerves.
Actions
Elevation of the scapula.
Rhomboid minor
Origin
1) Ligamentum nucahe.
2) Spines of the 7th cervical and the 1st thoracic vertebrae.
Insertion
At the dorsum of the medial border of the scapula opposite the root of the spine.
Nerve supply
Dorsal scapular nerve
Actions
1) Retract the scapula
2) Elevate the scapulae
1) Ligamentum nucahe.
2) Spines of the 7th cervical and the 1st thoracic vertebrae.
Insertion
At the dorsum of the medial border of the scapula opposite the root of the spine.
Nerve supply
Dorsal scapular nerve
Actions
1) Retract the scapula
2) Elevate the scapulae
Rhomboid major
Origin
From the 2nd to 5th thoracic spines and the supraspinous ligament.
Insertion
At the dorsum of the medial border of the scapula from the root of the spine to the inferior angle.
Nerve supply
Dorsal scapular nerve.
Actions
1) Retract the scapula
2) Elevate the scapulae
From the 2nd to 5th thoracic spines and the supraspinous ligament.
Insertion
At the dorsum of the medial border of the scapula from the root of the spine to the inferior angle.
Nerve supply
Dorsal scapular nerve.
Actions
1) Retract the scapula
2) Elevate the scapulae
Figure3:Rhomboid major and minor and levator scapulae.
The muscles connecting the scapula to the humerus are as follows, the:
1) Deltoid,
2) Supraspinatus,
3) Infraspinatus,
4) Teres minor,
5) Teres major, and
6) Subscapularis.
2) Supraspinatus,
3) Infraspinatus,
4) Teres minor,
5) Teres major, and
6) Subscapularis.
Figure4: Deltoid.
Deltoid
Origin
Corresponds to the insertion of trapezius.
1) The anterior fibres originate from the anterior border of the lateral 1/3 of the clavicle,
2) The lateral fibres originate from the lateral border of the acromion, and
3) The posterior fibres originate from the lower lip of the crest of the spine of the scapula.
Insertion
To the deltoid tuberosity of the humerus.
Nerve supply
Axillary nerve.
Actions
1) The lateral fibres abduct the arm from 15 degrees,
2) The anterior fibres flexion and medial rotation of the arm, and
3) The posterior fibres extend and laterally rotate the arm.
Corresponds to the insertion of trapezius.
1) The anterior fibres originate from the anterior border of the lateral 1/3 of the clavicle,
2) The lateral fibres originate from the lateral border of the acromion, and
3) The posterior fibres originate from the lower lip of the crest of the spine of the scapula.
Insertion
To the deltoid tuberosity of the humerus.
Nerve supply
Axillary nerve.
Actions
1) The lateral fibres abduct the arm from 15 degrees,
2) The anterior fibres flexion and medial rotation of the arm, and
3) The posterior fibres extend and laterally rotate the arm.
Figure5: Deltoid.
Supraspinatus
Origin
Medial two thirds of the supraspinous fossa of the scapula.
Insertion
To the superior impression on the greater tuberosity of the humerus.
Nerve supply
Suprascapular nerve.
Action
Initiates the abduction of the arm up to 15 degrees.
Medial two thirds of the supraspinous fossa of the scapula.
Insertion
To the superior impression on the greater tuberosity of the humerus.
Nerve supply
Suprascapular nerve.
Action
Initiates the abduction of the arm up to 15 degrees.
Figure6: Supraspinatus & teres minor.
Infraspinatus
Origin
Medial 2/3 of the infraspinous fossa of the scapula.
Insertion
To the middle impression on the greater tuberosity of the humerus.
Nerve supply
Suprascapular nerve.
Action
Main lateral rotator of the arm.
Medial 2/3 of the infraspinous fossa of the scapula.
Insertion
To the middle impression on the greater tuberosity of the humerus.
Nerve supply
Suprascapular nerve.
Action
Main lateral rotator of the arm.
Figure7: Teres major and minor and infraspinatus.
Teres minor
Origin
Upper two-thirds of the dorsal surface of the lateral border of the scapula.
Insertion
To the lowest impression on the greater tuberosity of the humerus.
Nerve supply
Axillary nerve.
Action
Lateral rotator of the arm.
Origin
Upper two-thirds of the dorsal surface of the lateral border of the scapula.
Insertion
To the lowest impression on the greater tuberosity of the humerus.
Nerve supply
Axillary nerve.
Action
Lateral rotator of the arm.
Teres major
Origin
Lower third of the dorsal surface of the lateral border of the scapula.
Insertion
To the medial lip of the bicipital groove of the humerus.
Nerve supply
Lower subscapular nerve.
Action
Adduction and medial rotator of the arm
Lower third of the dorsal surface of the lateral border of the scapula.
Insertion
To the medial lip of the bicipital groove of the humerus.
Nerve supply
Lower subscapular nerve.
Action
Adduction and medial rotator of the arm
Figure8: Infraspinatus and teres major.
Subscapularis
Origin
Medial two thirds of the subscapular fossa.
Insertion
To the lesser tuberosity of the humerus.
Nerve supply
Upper and lower subscapular.
Action
Medial rotator of the arm.
Medial two thirds of the subscapular fossa.
Insertion
To the lesser tuberosity of the humerus.
Nerve supply
Upper and lower subscapular.
Action
Medial rotator of the arm.
Figure9: Subscapularis.
Rotator cuff
The rotator cuff is formed by four tendons which blend with the capsule of the shoulder joint which it strengthens and holds the humeral head in position.
The rotator cuff is formed by the:
1) Subscapularis, which is located anterior to the capsule of the shoulder joint,
2) Supraspinatus, which is located superior to the capsule,
3) Infraspinatus, which is located posterior to the capsule, and
4) Teres minor, which is also located posterior to the capsule.
The rotator cuff is formed by the:
1) Subscapularis, which is located anterior to the capsule of the shoulder joint,
2) Supraspinatus, which is located superior to the capsule,
3) Infraspinatus, which is located posterior to the capsule, and
4) Teres minor, which is also located posterior to the capsule.
Clavipectoral fascia
The clavipectoral fascia is a thickened part of the deep fascia which fills the space between pectoralis minor and the clavicle and splits superiorly to enclose subclavius and inferiorly to enclose pectoralis minor.
Structures piercing the clavipectoral fascia include the:
1) Cephalic vein,
2) Thoracoacromial artery,
3) Lateral pectoral nerve, and
4) Lymphatics.
Structures piercing the clavipectoral fascia include the:
1) Cephalic vein,
2) Thoracoacromial artery,
3) Lateral pectoral nerve, and
4) Lymphatics.
Figure10: Clavipectoral triangle and fascia.
Deltopectoral triangle
The deltopectoral triangle is the triangular space between pectoralis major, deltoid, and the clavicle.
Quadrangular space
The quadrangular space is a space for the passage of the axillary nerve and posterior circumflex humeral vessels, which is bounded by the surgical neck laterally, lower margin of teres minor superiorly, long head of triceps medially, and upper margin of teres major inferiorly.
Quadrangular space
The quadrangular space is a space for the passage of the axillary nerve and posterior circumflex humeral vessels, which is bounded by the surgical neck laterally, lower margin of teres minor superiorly, long head of triceps medially, and upper margin of teres major inferiorly.
The triangular space
The triangular space is a space for the passage of the circumflex scapular blood vessels between the axilla and the posterior region of the scapula. This space is bounded by teres minor superiorly, teres major inferiorly, and long head of triceps laterally.
The triangular interval
This is a space for the passage of the radial nerve and profunda brachii blood vessels to the radial groove at the posterior surface of the humerus. This space is bounded by the long head of triceps medially, the medial border of the humerus laterally and teres major superiorly
The triangular interval
This is a space for the passage of the radial nerve and profunda brachii blood vessels to the radial groove at the posterior surface of the humerus. This space is bounded by the long head of triceps medially, the medial border of the humerus laterally and teres major superiorly
Arterial Anastomoses Around the Scapula
Arterial anastomoses around the scapula are important in carrying blood to the upper limb in the event of one of the arteries becoming blocked between the first part of the subclavian and the third part of the axillary arteries. It is formed by two arterial branches from the subclavian artery, the transverse cervical artery, and the suprascapular artery anastomosing with the circumflex scapular artery,and the anterior and posterior circumflex humeral arteries, which are branches from the axillary artery.