Muscles of the Pectoral Region

Question 1

How many muscles lie in the pectoral region?

Answer 1

4

Question 2

What do the muscles in the pectoral region do?

Answer 2

Exert a force on the upper limb

Question 3

What are the muscles of the pectoral region?

Answer 3

Pectoralis major
Pectoralis minor
Serratus anterior
Subclavius

Question 4

What is the most superficial of the muscles in the pectoral region?

Answer 4

Pectoralis major

Question 5

What shape is the pectoralis major?

Answer 5

Large, fan shaped

Question 6

What does the pectoralis major make up?

Answer 6

Most of the anterior wall of the axilla

Question 7

What does the pectoralis major have?

Answer 7

Two heads- a clavicular head, and a sternocostal head

Question 8

Where is the insertion of the pectoralis major?

Answer 8

The lateral lip of the intertubercular sulcus of humerus

Question 9

How can the two heads of the pectoralis major work?

Answer 9

Independently or synergistically

Question 10

What do the two heads of the pectoralis major produce when working together?

Answer 10

Adducts and medially rotates the humerus at the shoulder, and draws the scapula anteriorly and inferiorly

Question 11

What does the clavicular head of the pectoralis major do when acting alone?

Answer 11

Flexes humerus

Question 12

What does the sternocostal head of the pectoralis major do when acting alone?

Answer 12

Extends the humerus from the flexed position

Question 13

What innervates the pectoralis major?

Answer 13

Lateral and medial pectoral nerve, derived from the brachial plexus
The clavicular head by C5 and C6
The sternocostal head C7, C8 and T1

Question 14

What is the arterial supply of the pectoralis major?

Answer 14

Pectoral and deltoid branches of the thoracoacromial artery, anterior intercostal arteries and perforating branches of internal thoracic artery

Question 15

How does the pectoralis minor muscle differ from the pectoralis major?

Answer 15

It is much smaller, and more posterior

Question 16

What does the pectoralis form?

Answer 16

With the pectoralis major, forms part of the anterior wall of the axilla

Question 17

What shape is the pectoralis minor?

Answer 17

Triangular

Question 18

What does the attachment of the pectoralis minor to the scapula form?

Answer 18

A ‘bridge’, which vessels passing into the upper limb must travel underneath

Question 19

What is the function of the pectoralis minor?

Answer 19

Stabilises the scapula by drawing it inferiorly and anteriorly against the thoracic wall (depressing the shoulder)

Question 20

What is the pectoralis minor innervated by?

Answer 20

Medial pectoral nerve (C8, T1)

Question 21

What is the arterial supply of the pectoralis minor?

Answer 21

Pectoral and deltoid branches of thoracoacromial artery

Question 22

Where is the serratus anterior muscle found?

Answer 22

More laterally in the chest

Question 23

What does the serratus anterior muscle form?

Answer 23

The medial wall of the axilla

Question 24

What does the serratus anterior consist of?

Answer 24

Several strips

Question 25

What is the innervation of the serratus anterior?

Answer 25

Long thoracic nerve

Question 26

What is the main function of the serratus anterior?

Answer 26

Rotate the scapula, allowing the arm to be held above 90º

Protracts the scapula and hold it against the thoracic wall

Question 27

What is the arterial supply of the serratus anterior?

Answer 27

Lateral thoracic artery

Question 28

What happens if damage to the long thoracic nerve occurs?

Answer 28

The serratus anterior muscle will become paralysed

Question 29

What is the result of paralysation of the serratus anterior?

Answer 29

When pushing with the affected limb, the scapula is no longer held against the rib cage, and protrudes out of the back- it is said to have a winged appearance

Question 30

When can the long thoracic nerve become damaged?

Answer 30

By trauma to the shoulder, repetitive movements involving the shoulder, or by structures becoming inflamed and pressing on the nerve

Question 31

What is the innervation of the subclavius?

Answer 31

Nerve to subclavius

Question 32

What is the main action of the subclavius?

Answer 32

Anchors and depresses clavicle

Question 33

What is the arterial supply to the subclavius?

Answer 33

Clavicular branch of the thoracoacromial artery