Session 6: Pectoral Region and Axilla

Question 1

What muscles can be found in the pectoral region?

Answer 1

Pectoralis Major
Pectoralis Minor
Serratus Anterior
Coracobrachialis
Subclavius
Deltoid

Question 2

Location and structure of pectoralis major

Answer 2

Most superficial muscle in the pectoral region.
Triangular shape
Sternocostal head and a clavicular

Question 3

Origination of the pectorals major and insertion. (Several originations)

Answer 3

Clavicular head originates from anterior surface of medial clavicle.

Sternocostal head originates from the anterior surface of the sternum, upper six costal cartilages and aponeurosis of external oblique muscle.

Inserts into intertubercular sulcus of the humerus.

Question 4

Actions of the pectoralis major

Answer 4

If arm is abducted at shoulder join, contraction of sternocostal head pulls the humeral insertion towards the fixed sternocostal origin, and therefore adducts the arm.

If upper limb starts in the anatomical position contraction of clavicular head will flex the arm at the shoulder joint

If the humerus is already laterally rotated at the shoulder joint, contraction of pectoralis major will medially rotate it.

Question 5

Innervation of pectoralis major

Answer 5

Medial pectoral nerve (C8-T1)

Lateral pectoral nerve (C5-C7)

Question 6

Location and structure of pectoralis minor.

Origination and insertion.

Answer 6

Lies deep to pectoralis major
Originates from 3rd to 5th rib
Inserts into coracoid process of the scapula

Question 7

Action of pectoralis minor

Answer 7

Stabilises the scapula by drawing it anteroinferiorly against the thoracic wall.

Question 8

Innervation of pectoralis minor

Answer 8

Medial pectoral nerve (C8-T1)

Question 9

Location of serratus anterior

Answer 9

More laterally on the chest wall

Question 10

Origination and insertion of serratus anterior.

Answer 10

Originates as separate parts from the lateral aspect of ribs 1-8, or 1-9.
Inserts into the costal surface (rib-facing) of its medial border.

Question 11

Action of serratus anterior.

Answer 11

Protracts (pulls back) the scapula

Rotates the medial border of the scapula anteroinferiorly causing the glenoid cavity to rotate upwards.

Question 12

Why is the rotation of the medial border of the scapula important?

Answer 12

It enables the upper limb to be abducted above 90 degrees at the shoulder

Question 13

Innervation of serratus anterior.

Answer 13

Long thoracic nerve (C5-C7)

Question 14

Location of coracobrachialis.

Answer 14

Lies deep to the biceps brachii in arm.

Question 15

Origination and insertion of coracobrachialis.

Answer 15

Originates from the coracoid process of the scapula.

Inserts onto the medial side of the humeral shaft.

Question 16

Action of coracobrachialis.

Innervation of coracobrachialis.

Answer 16

Action: flexes arm at the shoulder and a weak adductor
Innervation: Musculocutaneous nerve (C5-C7)

Question 17

Location of subclavius.

Answer 17

Located directly underneath the clavicle and runs parallel (horizontal).

Question 18

Origination and insertion of subclavius.

Answer 18

Originates from the junction of the first rib and its costal cartilage and inserts onto the inferior surface of the middle third of the clavicle.

Question 19

Action and innervation of subclavius.

Answer 19

Anchors and depresses the clavicle.

Innervation from nerve to subclavius.

Question 20

Location of deltoid and features.

Answer 20

Triangular muscle. Divided into anterior, middle and posterior part.

Question 21

Origination and insertion of deltoid.

Answer 21

Originates from the anterior border and upper surface of the lateral third of the clavicle, but also from the acromion and spine of scapula.

Inserts into the deltoid tuberosity on the lateral surface of the humerus.

Question 22

Actions of each fibres of deltoid.

Answer 22

Anterior fibres: Flex and medially rotate arm at shoulder
Middle fibres: Abducts the arm from 15 degrees to 90 degrees.
Posterior fibres: Extend and laterally rotate the arm at the shoulder

Question 23

The middle fibres of the deltoid abducts the arm from 15 to 90 degrees. Which muscle abducts the arm from 0-15 degrees?

Answer 23

Supraspinatus

Question 24

Innervation of deltoid.

Answer 24

Axillary nerve (C5-C6)

Question 25

What is the axilla? Why is it important?

Answer 25

A pyramidal space at the junction of the upper limb and the thorax. It's a landmark and provides a passageway by which neuromuscular and muscular structures can enter and leave the upper limb.

Question 26

What borders of the axilla exist?

Answer 26

Anterior, lateral, posterior and medial wall. | Apex and base.

Question 27

What structures make up the apex of the axilla?

Answer 27

Lateral border of first rib Superior border of scapula Posterior border of the clavicle

Question 28

What structures make up the lateral wall of the axilla?

Answer 28

Intertubercular sulcus of the humerus

Question 29

What structures make up the medial wall of the axilla?

Answer 29

Serratus anterior, ribs and intercostal muscles.

Question 30

What structures make up the posterior wall of the axilla?

Answer 30

Subscapularis, teres major and latissimus dorsi.

Question 31

What structures make up the base of the axilla?

Answer 31

Axillary fascia.

Question 32

How does the size and shape of the axilla change?

Answer 32

By the degree of arm abduction.

Question 33

What passes through the axilla? (Long list)

Answer 33

``` Axillary artery Axillary vein Cords of brachial plexus Branches of brachial plexus Intercostobrachial nerve Axillary lymph nodes Biceps brachii (short head) ```

Question 34

Why is the intercostobrachial nerve (T2) important?

Answer 34

Because it is a cutaneous nerve supplying the upper medial arm and part of the floor of the axilla. This means it can be a source of referred cardiac pain.

Question 35

What are the three main routes by which the structures mentioned previously leave the axilla?

Answer 35

Inferiorly and lateral into upper limb Via the quadrangular space (To posterior arm and shoulder area) Via the clavipectoral triangle (opening in anterior wall of axilla)

Question 36

Mnemonic for the lymph nodes of the axilla.

Answer 36

``` APICAL Anterior pectoral group Posterior subscapular group Infraclavicular (deltopectoral) group Central group Apical group Lateral group ```

Question 37

One lymph node group receives the efferent vessels of all the other groups. Which?

Answer 37

Apical axillary nodes.

Question 38

Where does the apical axillary nodes' efferent vessels go?

Answer 38

They converge to form the subclavian lymphatic trunk.

Question 39

What happens to the right subclavian lymphatic trunk?

Answer 39

It continues to form the right lymphatic duct and drains into the right venous angle.

Question 40

What does the left subclavian lymphatic trunk drain into?

Answer 40

Directly into the thoracic duct and then into the left venous angle.

Question 41

What are the five main artery vessels of the upper limb? | Name them proximal to distal.

Answer 41

``` Subclavian artery Axillary artery Brachial artery Radial artery Ulnar artery ```

Question 42

Explain how the subclavian artery becomes the axillary artery.

Answer 42

It enters the axilla at the lateral border of the first rib and is then renamed the axillary artery.

Question 43

The axillary artery can be divided into three parts. Which?

Answer 43

First part which is proximal to pectoralis minor. Second part which is posterior to pectoralis minor Third part which is distal to pectoralis minor

Question 44

What are the main branches of the axillary artery?

Answer 44

First part: (1) Superior thoracic artery Second part: (2) Thoracoacromial artery Lateral thoracic artery Third part: (3) Subscapular artery Anterior circumflex humeral artery Posterior circumflex humeral artery

Question 45

Why is it common to get avascular necrosis of the head of the humerus? How does it happen?

Answer 45

In case of a fracture at the surgical neck of the humerus avascular necrosis can occur. This is due to the anterior and posterior circumflex humeral arteries which form an anastomotic network around the neck. If you then get a fracture in this region you are likely to damage these arteries and then the neck of the humerus won't get blood supply causing necrosis.

Question 46

Explain the axillary vein.

Answer 46

Formed at lower border of teres major from brachial veins and basilic veins. The cephalic vein also drains to the axillary vein and axillary vein also gets blood from superolateral chest wall. Commences at inferior border of teres major and ascends through the axilla anteromedially to the axillary artery. It becomes the subclavian vein at lateral border of first rib.

Question 47

What are the major superficial veins of the upper limb?

Answer 47

Cephalic and basilic veins.

Question 48

Where can the cephalic and basilic veins be found?

Answer 48

Cephalic: Runs along the pre-axial border of the upper limb Basilic: Runs along the post-axial border of the upper limb

Question 49

Origination and ascension of cephalic vein.

Answer 49

Dorsal venous network of the hand. Ascends anterolateral aspect of upper limb and anteriorly to elbow. At the shoulder the cephalic vein travels between the deltoid and pectoralis major muscles and enters the axilla via the clavipectoral triangle. In the axilla the cephalic vein will drain into the first part of the axillary vein.

Question 50

Origination and ascension of basilic vein.

Answer 50

Dorsal venous network of the hand an ascends medial aspect of upper limb. At the Inferior border of teres major the basilic vein will move deep into the arm and pair with brachial veins from deep venous system to form axillary vein.