Anatomy - Back/Shoulder

Question 1

What nerve supplies the Latissimus Dorsi?

Answer 1

Thoracodorsal nerve.

Question 2

What is the function of the Latissimus Dorsi?

Answer 2

Extends, adducts, and medially rotates the humerus at the shoulder joint.

Question 3

What nerve innervates the trapezius?

Answer 3

Accessory nerve (CN XI) and C3 & C4 (spinal nerves)

Question 4

What is the function of trapezius?

Answer 4

Upper fibers: Elevate scapula
Middle fibers: Retract scapula
Lower fibers: Depress scapula

The upper part of the trapezius, in rotating the scapula, helps the serratus anterior in making possible abduction of the humerus of more than 90°. Paralysis of the trapezius muscle results in a ‘droopy’ shoulder. The nerve supply may be injured in surgical dissections of the posterior triangle of the neck

Question 5

What nerve innervates the levator scapulae?

Answer 5

Dorsal scapular nerve

Question 6

What is the function of the levator scapulae?

Answer 6

Elevates and fixes the scapula

Question 7

What nerve innervates the rhomboidei major/minor?

Answer 7

Dorsal scapular nerve

Question 8

What is the function of the rhomboids?

Answer 8

Retracts and elevates the scapula

Question 9

What nerve supplies the serratus anterior?

Answer 9

Long thoracic nerve; injury to the nerve produces “winged scapula”

Question 10

What is the function of the serratus anterior?

Answer 10

Protracts the scapula and holds it against the thoracic wall. Positions the glenoid cavity.

Question 11

What nerve supplies the deltoid?

Answer 11

Axillary Nerve

Question 12

What is the function of the deltoid?

Answer 12

Anterior fibers: Flex and medially rotate the humerus
Middle fibers: Chief abductor of the humerus
Posterior fibers: Extend and laterally rotate the humerus

Question 13

What nerve supplies the teres major?

Answer 13

Lower subscapular nerve

Question 14

What is the function of the teres mjor?

Answer 14

Adducts and medially rotates the humerus

Question 15

What nerve supplies the supraspinatus?

Answer 15

Suprascapular nerve

Question 16

Function of supraspinatus?

Answer 16

Abducts the humerus

Question 17

What nerve supplies the infraspinatus?

Answer 17

Suprascapular nerve

Question 18

What is the function of the infraspinatus?

Answer 18

Laterally rotates the humerus

Question 19

What nerve supplies the Teres minor?

Answer 19

Axillary nerve

Question 20

What is the function of the teres minor?

Answer 20

Laterally rotates the humerus

Question 21

What nerve innevates the Subscapularis?

Answer 21

Upper and lower subscapular nerves

Question 22

What is the function of the Subscapularis?

Answer 22

Medially rotates the humerus

Question 23

What nerve supplies the Omohyoid muscle?

Answer 23

Cervical nerves 1,2 and 3

Question 24

What is the function of the Omohyoid muscle?

Answer 24

Depresses, retracts and steadies the hyoid bone

Question 25

What are symptoms/results of CN XI (accessory nerve) damage?

Answer 25

It will lead to a pasly. Ipslateral weakness.
Weakness and atrophy in the trapezius, and impaired neck movements.
Drooping of the shoulder!

Question 26

Symptoms/results of clavicle fracture

Answer 26

Sternocleidomastoid lifts the medial part of the fractured clavicle.
The trapezius isn’t strong enough to keep the lateral part of clavicle raised, so the shoulder will droop.
Medial part of clavicle may be pulled more medial by adductor muscles of arm (e.g. by pectoralis).

Question 27

What causes paralysis of the serratus anterior?

Answer 27

Damage to the long thoracic nerve.
The serratus anterior normally protracts the scapula.
When the nerve is damaged, the medial boarder of the scapula moves laterally and posterior, pushing out and giving the appearance known as “winged scapula”
Sometimes with this condition, arms cannot be abducted above horizontal position.

Question 28

What three structures make up the triangle of auscultation?

Answer 28

The trapezius, latissimus dorsi, and scapula.

Question 29

What results from thorcodorsal nerve injury?

Answer 29

The thorcodorsal nerve supplies the latissimus dorsi.

So paralysis results in an inability to climb - or inability to raise the trunk with the upper limbs.

Question 30

Axillary nerve injury?

Answer 30

Results in paralysis of deltoid. This will lead the deltoid to atrophy, making it so one cannot abduct the arm above horizontal level. This will also lead to a “flat shoulder”

Injury usually results from humeral fracture (at surgical neck) or incorrect use of crutches, or due to glenohumoral joint dislocation.

Question 31

Calcified supraspinatous tendonitis (aka subacromial bursitis)

Answer 31

This is when there is calcification and inflammation in the the subacromial bursa - leading to limited movement in the glenohumoral joint.
It results in pain when abducting the arm, this pain can go all the way through to the hand.
This usually results in older people after using the glenohumoral joint muscles extensively.

Question 32

Rotator cuff injury or muscolotendonitis injury

Answer 32

Can occur due to excessive use of the the rotator cuff, e.g. tennis, swimming, throwing etc… Leads to degenerative tendonitis, eventually leading to patient inability to abduct the upper limb.
One way to tell is to have patient lower arm and when it gets to 90 degree angle it will suddenly drop.

Question 33

Dislocation of Glenohumoral joint

Answer 33

Can happen anteriorly or inferiorly.
Anterior usually happens when the humerus is extended and then laterally rotated. Or it can also happen if the humerus is fully abducted, and is then stricken. This leads to head of humerus dislocated from the glenoid cavitiy.
Also the dislocation can occur inferiorly, in which case the greater tubercle is fractured.

A result of the dislocation is inability to use the arm, so it is usually held with the other hand.

Question 34

What is the posterior axillary fold comprised of?

Answer 34

It is the latissimus dorsi and the teres major.

Question 35

What three arteries make up the collateral circulation?

Answer 35

Subscapular artery, suprascapular artery, transverse cranial artery.