S6) Pectoral Region, Axilla and Brachial Plexus Flashcards
What is the pectoral region?
The pectoral region is a region located on the anterior chest wall and contains four muscles that exert a force on the upper limb
Identify the 4 muscles in the pectoral region
- Pectoralis major
- Pectoralis minor
- Serratus anterior
- Subclavius
State the structure and function of pectoralis major
- Structure: most superficial muscle in the pectoral region, composed of a sternal head and a clavicular head
- Function: adduction, medial rotation, flexion (clavicular head)
State the origin and attachments of pectoralis major
- Origins:
I. Clavicular head – anterior surface of medial clavicle
II. Sternocostal head – anterior surface of sternum, superior six costal cartilages and aponeurosis of external oblique muscle
- Attachments: intertubercular sulcus of the humerus
Which nerve(s) innervate pectoralis major?
- Lateral pectoral nerve
- Medial pectoral nerve
State the structure and function of pectoralis minor
- Structure: lies deep to pectoralis major, forms part of the anterior wall of the axilla region
- Function: stabilises the scapula by drawing it anteroinferiorly against the thoracic wall
State the origins and attachments of pectoralis minor
- Origins: 3rd-5th ribs
- Attachments: coracoid process of the scapula
Which nerve(s) innervates pectoralis minor?
Medial pectoral nerve
State the structure and function of serratus anterior
- Structure: located laterally in the chest wall, forming the medial border of the axilla region
- Function: rotates the scapula, allowing the arm to be raised over 90o
State the origins and attachments of the serratus anterior
- Origins: lateral aspects of ribs 1-8
- Attachments: costal surface of the medial border of the scapula
Which nerve(s) innervate serratus anterior?
Long thoracic nerve
State the structure and function of the subclavius
- Structure: small muscle, located directly deep to the clavicle
- Function: anchors and depresses the clavicle
State the origins and attachments of subclavius
- Origins: junction of the 1st rib and its costal cartilage
- Attachments: inferior surface of the middle 1/3 of the clavicle
Which nerve(s) innervate subclavius?
Nerve to subclavius
What is the axilla region?
The axilla region is an area that lies underneath the shoulder joint, at the junction of the upper limb and the thorax, acting as a passageway for neurovascular and muscular structures
What are the 6 borders of the axilla region?
Which structures form the apex and base of the axilla region?
- Apex – lateral border of the first rib, superior border of scapula, and the posterior border of the clavicle
- Base – axillary fascia and skin
Which structures form the lateral and medial walls of the axilla region?
- Lateral wall – intertubercular groove of the humerus
- Medial wall – serratus anterior and thoracic wall (ribs and intercostal muscles)
Which structures form the anterior and posterior walls of the axilla region?
- Anterior wall – pectoralis major, pectoralis minor, subclavius muscles
- Posterior wall – subscapularis, teres major and latissimus dorsi
Identify the three main routes by which structures leave the axilla
- Inferiorly and laterally, into the upper limb (main route)
- Through the quadrangular space
- Through the clavipectoral triangle
What is the quadrangular space?
The quadrangular space is a gap in the posterior wall of the axilla, allowing access to the posterior arm and shoulder area
Identify 2 structures which pass through the quadrangular space
What is the clavipectoral triangle?
The clavipectoral triangle is an opening in the anterior wall of the axilla which is bound by the pectoralis major, deltoid, and clavicle
Identify 3 structures which pass through the clavipectoral triangle
- Cephalic vein (enter)
- Medial pectoral nerve (exit)
- Lateral pectoral nerve (exit)