Upper Limb Chapter 4: Muscles Of The Shoulder Region

Question 1

Muscles of the shoulder region (scapular muscles)

Answer 1

1. Deltoid
2. Supraspinatus
3. Infraspinatus
4. Teres minor
5. Teres minor
6. Subscapularis

Question 2

Deltoid

Answer 2

A triangular thick muscle which forms the rounded contour of the shoulder.

Question 3

Deltoid origin

Answer 3

A V shaped origin:
1. Anterior fibers: anterior border of the lateral one third of the clavicle.
2. Middle fibers: lateral border of the acromion.
3. Posterior fibers: Lower lip of crest of the spine of the scapula.

Question 4

Deltoid insertion

Answer 4

Inserted in the deltoid tuberosity at the middle of the lateral surface of the shaft of the humerus.

Question 5

Deltoid nerve supply

Answer 5

Circumflex (Axillary) nerve (C5, C6)

Question 6

Deltoid action

Answer 6

1. Anterior fibers: felx and medially rotates the arm.
2. Posterior fibers: extends and laterally rotates the arm.
3. Middle fibers: abducts the arm from 15 degrees to 90 degrees.

Question 7

Deltoid clinical importance

Answer 7

Paralysis of the deltoid muscle results in flattening of the shoulder and loss of abduction of the shoulder joint from 15 degrees to 90 degrees.

Question 8

Deltopectoral groove

Answer 8

A groove between the contiguous borders of the Pectoralis major and deltoid and ends above, just below the clavicle, in the infraclavicular fossa. It lodges the following structures:
1. Uppermost part of the cephalic vein.
2. Deltoid branch of the thoraco-acromial artery.
3. Deltopectoral lymph nodes.

Question 9

Supraspinatus origin

Answer 9

From the medial two third of the supraspinous fossa.

Question 10

Infraspinatus origin

Answer 10

Medial two thirds of the Infraspinous fossa.

Question 11

Subscapularis origin

Answer 11

Medial two thirds of the subscapular fossa.

Question 12

Supraspinatus insertion

Answer 12

Highest impression of the greater tuberosity.

Question 13

Infraspinatus insertion

Answer 13

Middle impression on the back of the greater tuberosity.

Question 14

Teres minor insertion

Answer 14

Lower impression on the back of the greater tuberosity.

Question 15

Supraspinatus nerve supply

Answer 15

Suprascapular nerve (C5, C6)

Question 16

Infraspinatus nerve supply

Answer 16

Suprascapular nerve (C5, C6)

Question 17

Subscapularis nerve supply

Answer 17

Upper and lower subscapular nerves (C5, C6)

Question 18

Teres major nerve supply

Answer 18

Lower subscapular nerve (C5, C6).

Question 19

Supraspinatus action

Answer 19

1. Steadies the head of the humerus in the glenoid cavity.
2. Abducts 0-15 degrees, thus initiates abduction.

Question 20

Infraspinatus action

Answer 20

1. Steadies the head of the humerus in the glenoid cavity.
2. Rotates the arm laterally.

Question 21

Teres minor action

Answer 21

1. Steadies the head of the humerus in the glenoid cavity.
2. Adducts and laterally rotates the arm.

Question 22

Teres major action

Answer 22

1. Adduction, medial rotation, and extension of the arm.

Question 23

Subscapularis action

Answer 23

1. Stabilization of the anterior aspect of the shoulder joint.
2. Medial rotation and adduction of the arm.

Question 24

Subscapularis insertion

Answer 24

Lesser tuberosity of the humerus.

Question 25

Teres major origin

Answer 25

Lower third of the dorsal surface of the lateral border of scapula.

Question 26

Teres major insertion

Answer 26

Medial lip of bicipital groove of the humerus.

Question 27

Teres minor nerve supply

Answer 27

Axillary (circumflex) nerve.

Question 28

Teres minor origin

Answer 28

Upper two third of the dorsal surface of the lateral border of the scapula.

Question 29

Subscapularis

Answer 29

Fits the subscapular fossa on the front of the scapula.

Question 30

Clinical importance of the scapular muscles

Answer 30

Subscapularis together with the Supraspinatus, infraspinatus, and teres minor steady the head of the humerus in the glenoid cavity during the movements of the arm. Tendons of these 4 muscles blend with the capsule of the shoulder joint and are called rotator cuff muscles.

Question 31

Serratus anterior

Answer 31

A large flat muscle which covers the upper part of the side of the chest.

Question 32

Serratus anterior origin

Answer 32

1. Arises by 8 digitations from the outer surfaces of the upper 8 ribs midway between their angles and their coastal cartilages.
2. The 1st digitation is the largest and arises from the 1st and 2nd rib.

Question 33

Serratus anterior insertion

Answer 33

Ventral surface of the medial border of the scapula:
1. 1st digitation is inserted into the superior angle.
2. 2nd and 3rd digitations fan out to be inserted into the whole length of the medial border.
3. The lower 5 digitations converge to be inserted into the inferior angle.

Question 34

Serratus anterior nerve supply

Answer 34

Nerve to Serratus anterior ( long thoracic nerve, C5,C6, C7). The nerve arises from the root of the brachial plexus and descends vertically on the outer surface of the serratus anterior, in the middle Axillary line.

Question 35

Serratus anterior action

Answer 35

1. The muscle as a whole a main protractor of the shoulder (powerful protractor) assisted by the pectoralis minor muscle.
2. Acting with the upper and lower fibers of the trapezius, the lower five digitations of the Serratus anterior rotate the scapula so the glenoid cavity looks upwards.
3. Helps fix the scapula to the chest wall.
4. When the scapula is fixed, the muscle pulls on the ribs informed inspiration.

Question 36

Muscles connecting the upper limb with the thoracic wall

Answer 36

1. Pectoralis major
2. Pectoralis minor
3. Subclavius
4. Serratus anterior

Question 37

Serratus anterior applied anatomy

Answer 37

Because the muscle fixes the scapula against a chest wall, paralysis of the Serratus anterior muscle results In the projection of the inferior angle and medial border of the scapula backwards, in cases of pushing against resistance. This condition is called the winging of the scapula.

Question 38

Quandrangular and triangular spaces

Answer 38

Intermuscular spaces lying just below the shoulder joint.

Question 39

Quadrangular space (laterally) boundries

Answer 39

1. Above: teres minor (behind), the Subscapularis (front), and the capsule of the shoulder joint.
2. Below: teres major.
3. Medially: long head of triceps.
4. Laterally: Surgical neck of humerus.

Question 40

Quadrangular space (laterally) contents

Answer 40

1. Posterior circumflex humoral vessels.
2. Axillary (circumflex) nerve.

Question 41

Upper triangular space (medially) boundries

Answer 41

1. Above: teres minor (behind) Subscapularis (front).
2. Below: teres major.
3. Laterally: long head of triceps.

Question 42

Upper triangular space (medially) contents

Answer 42

Transmits only the circumflex scapular artery.

Question 43

Lower triangular space (triangular interval)

Answer 43

Just lateral to the long head of triceps and is separated from the Quadrangular space by the teres major muscle.

Question 44

Lower triangular space (triangular interval) boundries

Answer 44

1. Above: teres major
2. Medially: long head of triceps
3. Laterally: lateral head of triceps and the shaft of the humerus.

Question 45

Lower triangular space (triangular interval) contents

Answer 45

Radial nerve and profunda brachii vessels.