Sem 1 - S - Axilla and brachial plexus - Boundaries/Contents (vessels, lymph, nerves, fat, muscle) of axilla - and brachial plexus

Question 1

What runs in the groove between the deltoid and pectoralis major? What is this groove known as?

Answer 1

Bteween the pec major and deltoid is the deltopectoral groove The cephalic veins runs in this groove to drain into the axillary vein

Question 2

What is the sheet of connective tissue which is the deep layer of fascia in the pectoral region? Can see it when reflecting the pectoralis major What is its purpose?

Answer 2

This is the clavipectoral fascia It acts to supsend the floor of the axilla

Question 3

What are the attachments of the pectoralis minor and subclavius? State both their functions and nerve supply

Answer 3

Pectoralis minor - Attaches from ribs 3 to 5 to the coracoid process of the scapula

• * Stabilises the scapula by pulling it anteroinferiorly against the body wall (can also elevate the ribs if the shoulders are fixed)
• * Supplied by the Medial pectoral nerve - C8,T1

Subclavius - Attaches from the sternal end of the 1st rib to the underside of the clavicle

• * Stabilises the clavicle by pulling it down and slightly forward during shoulder abduction
• * Supplied by the nerve to the subclavius (C5,6)

Question 4

The clavipectoral fascia encloses the pec minor and subclavius muscle and acts as a suspensory ligament of the axilla inferiorly Superiorly, between the 1st rib and coracoid process, the fascia is thickened to form what?

Answer 4

Superiorly, between the 1st rib and coracoid process the clavipectoral fascia thickens (like it does inferiorly to form the supsensory ligament of the axilla) to form the Costocoracoid membrane

Question 5

The clavipectoral fascia lies below the clavicular head of the pectoralis major. It fills in the space between the clavicle and the pectoralis minor. Again state what the clavipectoral fascia acts as? What two muscles does it enclose?

Answer 5

Clavicpectoral fascia acts as the suspensory ligament to the fascial floor of the axilla (suspends the floor of the axilla) It enclose the pectoralis minor and subclavius minor

Question 6

Which structures pierce through the clavipectoral fascia? What are they piercing to reach?

Answer 6

This would be the: Thoracoacromial artery - to supply the clavicle, acromion, deltoid and pectoral muscles via its terminal branches Cephalic vein to reach the axillary vein Lateral pectoral nerve - to supply the pectoralis major (C5,6,7)

Question 7

The axilla has different boundaries The roof, floor, anterior wall, posterior wall, medial and lateral walls What shape is the axilla said to be?

Answer 7

The axilla is said to be pyramidal in shape

Question 8

What forms the roof and floor of the axilla? (roof and floor are called apex and base respectively in some texts)

Answer 8

Roof of the axilla is formed by the clavicle, 1st rib and the scapula The floor is formed by the skin and into the arm

Question 9

What forms the anterior wall of the axilla?

Answer 9

The pectoralis minor and major The subclavius and fascia

Question 10

What forms the posterior wall of the scapula?

Answer 10

The subscapularis, teres major, lattismus dorsi and the long head of the triceps brachii

Question 11

What forms the medial and lateral walls of the axilla?

Answer 11

Medial wall - serratus anterior and wall of thorax Lateral wall - humerus

Question 12

State the boundaries of the axilla

Answer 12

Roof- Rib 1, Clavicle and the scapula Floor -skin and into arm Anterior wall - pec minor & major, subclavius & fascia Posterior wall - subscapularis, teres major, lattismus dorsi and long head of triceps brachii Medial wall - serratus anterior &wall of the thorax Lateral wall - Humerus

Question 13

What are the contents of the axilla? (lloking for 5 things)

Answer 13

* Axillary artery and veins * Brachial plexus * Lymphatics * Adipose tissue * Short head of biceps brachii & coracobrachialis

Question 14

What vein is the basilic vein continous with and when does it become this? What does the basicilic vein drain?

Answer 14

The basilic vein is continous with the axillary vein - it becomes the axillary vein at the inferior border of the teres major The basilic vein drains the posteromedial surface of the hand and forearm

Question 15

The basilic vein becomes the axillary vein at the inferior border of the teres major (the basilic becomes axillary as the brachial vein also drains into the axillary) (brachial vein is a deep vein) When does the axillary vein become known as the subclavian vein? Does the axillary vein or artery lie anterior?

Answer 15

The axillary vein becomes the subclavian vein at the lateral border of rib 1 The axillary vein lies anterior to the axillary artery in the axilla (axillary artery is wound up in the brachial plexus)

Question 16

When does the cepahlic vein drain into the axillary vein?

Answer 16

The cepalic vein runs in the deltopectoral groove before piercing the clavipectoral fascia to enter into the axillary vein in the axilla

Question 17

Immediately posterior to the axillary vein is the axillary artery When does the subclavian artery become the axillary artery? When does the axillary artery become the brachial artery?

Answer 17

The subclavian artery becomes the axillary artery at the lateral border of rib 1 The axillary artery becomes the brachial artery at the inferior border of the teres major

Question 18

There are three parts to the axillary artery in relation to the pec minor. How is this so?

Answer 18

1st part of axillary artery - proximal (medial) to pec minor 2nd part of axillary artery - posterior to pec minor 3rd part of axillary artery - distal (lateral) to pec minor

Question 19

Each part of the axillary artery has arteries coming off it 1st part - 1 branch 2nd part - 2 branches 3rd part - 3 branches Name the branches from each of the parts

Answer 19

1st part of axillary artery - superior thoracic artery 2nd part of axillary artery - thoracoacromial artery and lateral thoracic artery 3rd part of axilllary artery - subscapular artery and anterior and posterior circumflex humeral arteries

Question 20

The superior thoracic artery comes off the 1st part just after it passes beneath the clavicle * Which branch from the 2nd part pierces the clavipectoral fascia? * Which branch from the 3rd part runs in the quadrangular space? * What is the biggest branch from the 3rd part of the axillary artery?

Answer 20

The thoracoacromial artery pierces the clavipectoral fascia to supply the clavicle, acromion, deltoid and pectoral muscles The posterior circumflex humeral artery branch of the 3rd part of the axillary artery runs in the quadrangular space with axillary nerve Subscapular artery is biggest of the third part branches

Question 21

Axillary nodes drain upper limb but also drain lateral mammillary tissues, upper back and shoulder, lower neck What tail of breast tissue creates the pathway for breast lymphatic drainage?

Answer 21

This would be the tail of spence - the extension of breast tissue that extends into the axilla

Question 22

How many axillary nodes are there and how many groups are they split into?

Answer 22

Have roughly 20-30 axillary nodes split into 5 groups

Question 23

In medicine got told about groups of axillary nodes Anterior, posterior, infraclavicular (only useful for the mnemonic), central, apical, lateral What are the 5 groups of axillary nodes in anatomy? Only anterior, posterior and lateral which have their names changed

Answer 23

Pectoral (was anterior) Subscapular (was posterior) Central Apical Humeral (was lateral)

Question 24

5 groups Pectoral, subscapular, central, apical and humeral Where are each of these groups of axillary nodes located and what do they drain?

Answer 24

• Pectoral axillary nodes - located at the inferior margin of the pectoralis minor draining the thorax and mammary tissue
• Subscapular axillary nodes - located at the posterior axillary wall on subscapularis draining back, shoulder and neck
• Central axillary nodes- located at the axilllary fat behind the pec minor communicating with other nodes
• Apical axillary nodes - located at the superior margin of the pec minor draining the other nodes and mammary tissue
• Humeral axillary nodes - posterior to axillary vein draining the upper limb

Question 25

One more time, state the 5 groups of axillary nodes, their location and where they drain

Answer 25

* \* Pectoral nodes - inferior margin of the pectoralis minor - draining thorax and mammary tissue * \* Subscapular - located at posterior axillary wall on the subscapularis- draining the back, shoulder&neck * \* Central - located behind the pec minor in xillary fat - communicates with the other nodes * \* Apical - located at the superior margin of pec minor - draining the other nodes and mammary tissue * \* Humeral - located posterior to the axillary vein - draining the upper limb

Question 26

What percentage of the breast drains to the axillary nodes? What percentage of the breast drains to the parasternal nodes?

Answer 26

75% of the breast drains to the axillary nodes ~25% of the breast drains to the parasternal nodes

Question 27

Now we have discussed the axilla - its boundaries and contents Time to discuss the brachial plexus What is the brachial plexus?

Answer 27

The brachial plexus is formed by the anterior rami of C5-T1 and supplies the upper limb with nerve innervation If you damage one nerve root, you will still have function in that nerve as each nerve is form multiple nerve roots

Question 28

The brachial plexus can split into different regions. What are these regions?

Answer 28

\* Roots (Ramsay) \* Trunks (Taylor) \* Divisions (Drinks) \* Cords (Cold) \* Branches (Beers)

Question 29

The anterior rami carry somatic motor, somatic sensory and sympathetic fibres to supply to the anterolateral body wall wand limbs (in this case upper limb) How does the sympathetics get from the sympathetic chain to the anterior rami?

Answer 29

The symapthetics will enter the sympathetic chain via white rami communicantes from T1 to L2 (they will have synapsed in the paravertebral ganglia) and then travel up the sympathetic chain and re-enter the spinal nerve via grey rami communicantes and travel into the anterior rami

Question 30

Where do the roots and trunks lie between?

Answer 30

The roots and trunks lie in the posterior triangle of the neck passing between the anterior and middle scalene muscles

Question 31

What are the three trunks and which roots form them?

Answer 31

Superior trunk - formed by C5 and 6 roots Middle trunk - formed by C7 roots Inferior trunk - formed by C8 and T1 roots

Question 32

What do the trunks then pass over to become cords?

Answer 32

The trunks pass over rib 1 and enter the axilla where they will now divide to become cords

Question 33

There are some branches that arise from the roots and trunks of the brachial plexus before they divide What are the branches from the roots? State what the branches will be supply?

Answer 33

Root branches \* C5 root to the phrenic nerve (motor to diaphragm, sensory to fibrous pericardium, mediastinal pleura and diaphargmatic peritoneum) and dorsal scapular nerve (Rhomboid minor, major & levator scapulae) \* C5,6,7 roots to the long thoracic nerve which goes to supply the serratus anterior muscle \* T1 root gives off the 1st intercostal nerve

Question 34

Which trunk gives off branches and what are the branches going to supply what? What are the nerve roots of these branches?

Answer 34

Only the superior trunk gives off any branches with nerve roots from C5 and 6 Suprascapular nerve (C5,6) - to supraspinatus and infraspinatus muscles Nerve to subclavius (C5,6) - to subclavius muscle

Question 35

Each trunk divides into an anterior and posterior division What can be said about the dvisions and the compartments off the arms?

Answer 35

The three anterior divisions ultimately are the pathways for fibres associated with the anterior compartments of the arm and forearm The three posterior divisions ultimately are the pathways for fibres associated with the posterior compartments of the arm and forearm

Question 36

Which divisions make up which cords? What branches come from the divisions?

Answer 36

Anterior divisions of the superior and middle trunks make the lateral cord Anterior division of the inferior trunk makes the medial cord Posterior divisions of the superior, middle and lateral trunks make the posterior cord No peripheral nerves direct from divisions

Question 37

What are the cords named in relation to?

Answer 37

The cords are named in relation to the axillary artery

Question 38

Which fibres are present in the cords?

Answer 38

Lateral cord unites anterior divisions off the superior & middle trunks, therefore has fibres from C5,6,7 Posterior cord unites all posterior divisions of trunks, therefore fibres from C5-T1 are present Medial cord is a continuation of anterior division and therefore has fibres from C,8, T1

Question 39

In total there are 7 branches from the cords What are these branches?

Answer 39

The lateral cord gives: lateral pectoral nerve The posterior cord gives : Upper subscapular Lower subscapular Thoracodorsal nerves The medial cord gives: Medial pectoral nerve Medial cutaneous nerve of the arm Medial cutaneous nerve of the forearm

Question 40

What is the nerve root of the lateral pectoral nerve and what does it supply? What does the upper and lower subscapular nerves supply? What is the nerve root of the thoracodorsal nerve and what does it supply? What is the nerve root of the median pectoral nerve and what does it supply? What do the median cutaneous nerve of the arm and forearm supply?

Answer 40

Lateral pectoral nerve (C5,6,7) - pec major Upper subscapular nerve - subscapularis Lower subscapular nerve - subscapularis and teres major Thoracodorsal nerve (C6,7,8) - lattisimus dorsi Median pectoral nerve - C8,T1 Median cutaneous nerve of the arm - skin on arm Median cutaneous nerve of the forearm - skin on forearm

Question 41

The three anterior divisions were said to supply the anterior arm and forearm with the three posterior divisions supply the posterior arm and forearm Which cords supply the anterior and posterior arm and forearm?

Answer 41

Anterior compartments of arm and forearm - supplied by the medial and lateral cords Posterior compartments of arm and forearm - supplied by the posterior cord

Question 42

What does the lateral cord end in? (state the roots)

Answer 42

The musculocutaneous nerve - roots - C5,6,7 and gives off a lateral root of the median nerve

Question 43

What does the posterior cord end in? State the nerve roots

Answer 43

The axillary nerve (C5,6) and the radial nerve (C5-T1)

Question 44

What does the medial cord end in? What are its nerve roots?

Answer 44

The ulnar nerve (C(7),8,T1) and the medial root of the median nerve

Question 45

The lateral root of the median nerve from the lateral cord and the medial root of the median nerve from the medial cord form the MEDIAN NERVE WHat are its nerve roots?

Answer 45

Median nerve roots - C6-T1

Question 46

On dissection look for the M shape in the brachial plexus What forms this?

Answer 46

The M shape is formed by the medial and lateral roots uniting to form the median nerve anteiror to the axillary artery Blue thing next to the ulnar nerve is the axillary vein

Question 47

When will the radial and axillary nerves disappear?

Answer 47

Axillary nerve will disappear as it enters the quadrangular space along with the posterior circumflex humeral arteries Radial nerve will disappear as it enters the triangular hiatusalong with the profunda brachii

Question 48

What do the axillary and radial nerves wrap around once they pass through the quadrangular space and triangular hiatus respectively?

Answer 48

Axillary nerve wraps around the neck of the humerus Radial nerve wraps around the shaft of the humerus