Shoulder, pectoral and axilla anatomy Flashcards
Name the 4 muscles of the pectoral region.
Pectoralis major
Pectroalis minor
Serratus anterior
Subclavius
What is the most superficial muscle in the pectoral region?
Pectoralis major
What are the functions of the pectoralis major?
Adducts and medially rotates upper limb.
Draws scapula anteroinferiorly.
Flexes the upper limb (clavicular head).
What is the innervation of pectoralis major?
Lateral and medial pectoral nerves.
What muscle lies underneath pectoralis major?
Pectoralis minor.
What is the function of the pectoralis minor?
Stabilises scapula (pulls it anteroinferiorly against thoracic wall).
What is the innervation of the pectorals minor?
Medial pectoral nerve.
What border of the axilla does the serrates anterior form?
Medial border.
What border of the axilla do the pectorals major and minor form?
Anterior border.
What is the function of the serratus anterior?
Rotates the scapula, allowing arm to be raised >90 degrees.
Holds scapula against rib cage.
What is the innervation of the serrates anterior?
Long thoracic nerve.
What is the function of the subclavius?
Anchors and depresses clavicle.
What is the innervation of the subclavius?
Nerve to subclavius.
What does the subclavius afford minor protection to?
The neuromuscular structures underlying the clavicle.
If the long thoracic nerve is damaged, what does this cause?
Winging of the scapula, as the serrates anterior cannot hold the scapula against the rib cage.
What is the most common cause of long thoracic nerve palsy?
Traction injuries (where the upper limb is stretched violently).
What are the actions of the latissimus dorsi?
Extends, adducts and medially rotates the upper limb.
What is the innervation of the latissimus dorsi?
Thoracodorsal nerve.
Which 2 bones articulate to form the sternoclavicular joint?
Sternum and clavicle.
What type of joint is the sternoclavicular joint?
Saddle-type synovial joint.
What provide the majority of the stability of the sternoclavicular joint?
Ligaments (particularly the costoclavicular ligament).
Which movements do the sternoclavicular and acromioclavicular joints aid in?
Pectoral movements.
Which 2 bones articulate to form the acromioclavicular joint?
Clavicle and acromion of the scapula.
What type of joint is the acromioclavicular joint?
A plane type synovial joint.
What provides the majority of stability for the acromioclavicular joint?
Ligaments.
What are the 2 main causes of acromioclavicular joint dislocation?
FOOSH
Direct blow to the joint
Which muscle is responsible for abducting the shoulder past 90 degrees?
Serratus anterior.
Which bones articulate to form the shoulder joint?
The scapula and the humerus.
What type of joint is the shoulder joint?
Ball and socket synovial joint.
Why is the shoulder joint so unstable?
The head of the humerus is much larger than the glenoid fossa.
Name the 4 ligaments which provide stabilisation to the shoulder joint.
Glenohumeral ligaments
Coracohumeral ligament
Transverse humeral ligament
Coracoacromial ligament
Where is the coracoacromial ligament in relation to the shoulder joint?
Forms an arch-like structure superiorly over the shoulder joint.
What is the function of the coracoacromial ligament?
Resists superior displacement of the humeral head.
Where is the transverse humeral ligament in relation to the shoulder joint?
Between the two tubercles of the humerus.
What is the function of the transverse humeral ligament?
Holds the tendon of the long head of the biceps in the inter tubercular groove.
Where is the coracohumeral ligament in relation to the shoulder joint?
Extends from the base of the coracoid process to the greater tubercle of the humerus.
What is the function of the coracohumeral ligament?
Supports the superior part of the joint capsule.
Where is the glenohumeral ligament in relation to the shoulder joint?
Extends from humerus to glenoid fossa.
What is the function of the glenohumeral ligament?
Stabilises the anterior aspect of the joint.
Which muscle provides the first 15 degrees of abduction at the shoulder?
Supraspinatus
What muscle provides 15-90 degrees of abduction at the shoulder?
Middle fibres of the deltoid ligament.
How does the glenoid labrum provide stability to the shoulder joint?
Deepens the glenoid cavity and creates a seal with the head of the humerus.
How do the rotator cuff muscles contribute to stability of the shoulder joint?
When they are relaxed, they act to compress the humeral head into the glenoid cavity.
What is the coracoacromial arch?
A group of bones and ligaments that forms the superior border of the supraspinatus outlet.
Name the 4 structures that form the coracocacromial arch.
Coracoid process
Coracoacromial ligament
Acromioclavicular joint
Acromion
Name the 6 intrinsic muscles of the shoulder joint.
Deltoid
Teres major
Teres minor
Subscapularis
Supraspinatus
Infraspinatus
Name the 4 rotator cuff muscles.
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
What is the innervation of the supraspinatus?
Suprascapular nerve.
What is the action of the supraspinatus?
Abducts the arm to 15 degrees.
Assist the deltoid to abduct the arm 15-90 degrees.
What is the innervation of the infraspinatus?
Suprascapular nerve
What is the function of the infraspinatus?
Laterally rotates the arm.
What is the action of the subscapularis?
Medially rotates the arm.
What is the innervation of the subscapularis?
Upper and lower subscapular nerves.
What is the innervation of the Teres minor muscle?
Axillary nerve.
What is the function of Teres minor?
Laterally rotates the arm.
What is the innervation of the deltoid?
Axillary nerve.
What is the function of the anterior deltoid fibres?
Flexion + medial rotation.
What is the function of the middle deltoid fibres?
Abducts the arm between 15 and 90 degrees.
What is the function of the posterior deltoid fibres?
Extension and lateral rotation.
What is the innervation of the Teres major muscle?
Lower sub scapular nerve.
What is the function of the Teres major muscle?
Adducts and extends at the shoulder
Medially rotates the arm.
Which important nerve structure is transmitted through the axilla?
Brachial plexus.
The axilla transmits what from the neck to the upper limb?
Neurovascular bundle:
Axillary artery
Axillary vein
Brachial plexus
Axillary lymph nodes
Biceps brachii (short head)
Coracobrachialis
Which artery supplies the circumflex humeral arteries?
Axillary artery
