Session 2: The Shoulder and Arm (07.01.2020) Flashcards
What are the important bones in the shoulder and arm area?
- scapula
- clavicle
- humerus
What is the arm?
- it is the region between the shoulder joint and the elbow joint
- the area between the elbow and wrist is the forearm
- now often referred to as upper arm and lower arm which is not fully correct anatomically
Scapula
- triangular, flattish bone
- has a spine that divides the scapula into a suoraspinous and infraspinous process
- glenoid cavity -> socket for the humerus (joint)
- acromion
- coracoid process
- three angles (lateral, superior, inferior)
- three borders (medial, superior and inferior)
- two surfaces (costal and posterior)
Glenoid cavity
- cup/socket for the shoulder joint
Clavicle
- small, long bone
- S- shaped
- the first bone to calcify in foetal development and one of the last bones to finish calcifying (age 20/22)
- flattened at the acromial end
- has a flattened facet at the sternal end where it articulates with the manubrium of the sternum
The Humerus
- long bone
- has an anatomical (true) and a surgical neck. Fractures are more common in the surgical neck.
- ends have articular features
- deltoid tuberosity where the muscle attaches
- condyles and epicondyles
Acromion
- bony process of the scapula
- anterolateral projection of the spine over the glenohumeral joint
- articulates (via small oval facet on its distal end) with the clavicle
Coracoid Process
- hook-like structure that projects anterolaterally
- positioned directly inferior to the lateral part of the clavicle
Muscle attachments terminology
- Old-fashioned terminology for muscle attachments is:
origins and insertions. Now considered inaccurate. - For Limbs, the correct terminology is: proximal attachment and distal attachment. The proximal attachment is at, or closer to, the trunk.
What are the muscular compartments in that region?
- anterior pectoral girdle muscles
- posterior pectoral girdle muscles
- intrinsic shoulder muscles
- anterior compartment of the upper arm
- posterior compartment of the upper arm
Name the Anterior Pectoral Girdle Muscles
- Pectoralis major
- Pectoralis minor
- Subclavius
- Serratus anterior* (runs between anterior and posterior)
=> chest muscles except for serrates anterior
Pectoralis major
- anterior pectoral girdle muscle
- broad attachment to medial 3rd of clavicle, sternum and some costal cartilages
- 3 parts: clavicular head, sternocostal head, abdominal part); according to Gray’s there are 2 heads: clavicular and sternocostal
- attaches to groove on lateral humerus (lateral lip of the inter tubercular sculls (groove))
- developed with push-ups and punching/boxing
- function: adducts and medially rotates the humerus, lesser actions on the scapula
- most superficial muscle of the anterior wall
- innervated by lateral and medial pectoral nerves (oroginating from brachial plexus, C5-T1)
Pectoralis minor
- attaches to coracoid process of scapula
- attaches to ribs 2,3,4 and 5
- pulls scapula down (pulls tip of shoulder down) and possibly forward (protracts scapula)
- innervated by medial pectoral nerve (C5,6,7,8, T1)
Innervation of Pec Major
Medial and lateral pectoral nerve
- clavicular head (C5,C6)
- sternocostal head (C6,7,8, T1)
Subclavius muscle
- Attachment:
Distally inferior part of the clavicle
Proximally Rib 1 at the costochondrial joint - Function: Pulls tip of shoulder down; pulls clavicle medially to stabilise the sternoclavicular joint)
- Innervation: Nerve to subclavius (C5,C6)
Serrates Anterior Muscle
Attachment:
- proximal: attaches to the lateral surfaces of the upper 8-9 ribs and deep fascia overlying the related intercostal spaces
- distal: costal surface of the medial border of scapula
Function:
- protraction and rotation of the scapula
- keeps medial border and inferior angle of the scapula opposed to the thoracic wall
Innervation:
- Long thoracic nerve (C5, C6,C7)
Name the posterior pectoral girdle muscles
- Trapezius
- Latissimus dorsi
- Levator scapulae
- the Rhomboids
Trapezius Muscle
Attachment:
- superior crest of the spine of the scapula, acromion, posterior border of the lateral one-third of clavicle
- superior nuchal line, external occipital proturbance, medial margin of the ligament nuchae
- spinous processes of C7 to T12 and related supraspinous ligaments
Innervation:
- motor: spinal part of accessory nerve (XI)
- sensory: (proprioception) anterior rami of C3 and C4
Function:
- powerful elevation of scapula
- rotates the scapula during abductionof humerus above horizontal
- middle fibres retract scapula
- lower fibres depress scapula
Other:
- there are 3 types of fibres: ascending (inferiorly), descending (superiorly) and middle fibres coming across
Latissimus dorsi muscle
Attachments:
- floor of the inter tubercular sulcus (groove) of humerus (strap like muscle and tendon that attaches to the groove)
- spinous processes of the lower 6 thoracic vertebrae and related interspinous ligaments; via the thoracolumbar fascia to the spinous processes of the lumbar vertebrae, related interspinous ligaments, and iliac crest; lower 3-4 ribs.
Innervation:
- thoracodorsal nerve (C6,C7, C8)
Function:
- Adduction, medial rotation and extension of the arm at the glenohumeral joint
Rhomboid muscles
Attachment:
- Rhomboid minor: lower end of ligaments nuchae and spinous process of C7 and T1 vertebrae; posterior surface of medial border of the scapula at the root of the spine of the scapula
- Rhomboid major: spinous processes of T2-T5 vertebrae and intervening supraspibous ligaments; posterior surface of medial border of the scapula at the root of the spine of the scapula to the inferior angle
[=medial border of scapula and spinous processes between C7 and T5]
Innervation: dorsal scapular nerve (C4,C5)
Function: Elevation and retraction of the scapula (retracts, rotates and fixes the scapula)
Levator Scapulae
Attachment:
- transverse processes of C1 and C2 vertebrae and posterior tubercles of transverse processes of C3 and C4 vertebrae
- posterior surface of medial border of scapula from superior angle to root of spine of the scapula
Innervation:
- branches directly form the anterior rami of C3 and C4 spinal nerves and by branches (C5) from dorsal scapular nerve
Function: elevates the scapula (duh) + rotation
Name the intrinsic shoulder muscles
- Deltoid
- Teres Major
- The rotator cuff muscles
- supraspinatus
- infraspinatus
- teres minor
- subscapularis
Deltoid muscle
Attachements:
- inferior edge of the crest of the spine of the scapula, lateral margin of the acromion, anterior border of the lateral 3rd of the clavicle
- deltoid tuberosity of humerus
Innervation:
- axillary nerve (C5, C6)
Function:
- major abductor of the arm
- clavicular fibers assist in flexing the arm
- posterior fibers assis in extending the arm
Other: there is a spinal (posterior) and a clavicular (anterior) part of the deltoid -> fibers can act separately but together they act as the major abductor of the shoulder joint
Which muscle is the major abductor of the arm?
Deltoid
The rotator cuff
- Rotator cuff group acts to fix the head of humerus in the glenoid fossa.
- attach at superior head of the humerus
- Their main activity is to act as a group to hold the head of the humerus inside the fossa, one of the main stabilising factors of the shoulfer joint
- supraspinatus, infraspinatus, teres minor, subscapularis
- Subscapularis = broad muscle
- Supraspinatus important in initiating abduction of arm for first 15°, then deltoid takes over.
- teres major is NOT one of the rotator cup muscles
innervation mainly C5,C6? suprascapular nerve for sup and infraspinatus and axillary nerve for teres minor)
Teres latin
smooth, rounded
Teres Major
- NOT a rotator cuff muscle
Attachments:
- elongate oval area of posterior surface of the inferior angle of the scapula
- medial lip of the intertubercular sulcus on the anterior surface of the humerus
- attaches at almost the same place as latissimus doors
Innervation: Inferior subscapular nerve (C5,C6.C7)
Function:
- Medial rotation and extension of the arm at the glenohumeral joint;
- stabilisation of the glenohumeral joint
What are the muscles in the anterior compartment of the arm?
- bicpes brachii
- brachialis
- coracobrachialis
=> all supplied by the musculocutaneous nerve
Biceps brachii muscle
Attachments:
- long head: supraglenoid tubercle of scapula; short head: apex of coracoid process.
- insertion/proximal: tuberosity of radius
Innervation: Musculocutaneous nerve (C5,C6)
Function:
- powerful flexor of the forearm at the elbow joint and supinator of the forearm; accessory flexor of the arm at the glenohumeral joint
Other: Biceps means 2 heads
Coracobrachialis Muscle
Attachments:
- apex of the coracoid process
- linear roughening of the humerus on medial side
Innervation: musculocutaneous nerve (C5,C6, C7)
Function:
- Flexor of the arm at the glenohumeral joint
- adducts arm
Brachialis muscle
Attachments:
- anterior aspect of humerus (medial and lateral surfaces) and adjacent intermuscular septae
- tuberosity of the ulna
Innervation:
- musculocutaneous nerve (C5, C6)
- small contribution by the radial nerve (C7) to lateral part of muscle
Function: powerful flexor of the forearm at the elbow joint
Other: beneath the biceps brachia muscle; flattens to form a tendon which attaches to the ulna.
What are the muscles of the posterior compartment of the arm?
- triceps brachii
- Anconeus
=> supplied by the radial nerve
Triceps brachii
Attachments:
- origin: long head: infraglenoid tubercle of scapula; medial head posterior surface of humerus; lateral head: posterior surface of humerus;
- insertion: olecranon
Innervation: radial nerve
Function:
- extension of the forearm at the elbow joint; long head can also extend and adduct the arm at the shoulder joint.
Other: triceps = 3 heads
Anconeus
Attachments:
- origin: lateral epicondyle of humerus
- insertion: olecranon and proximal posterior surface of ulna
Innervation:
- radial nerve (C6,7,8) via branch to medial head of triceps brachia
Funciton:
- abduction of the ulna in pronation
- accessory extensor of the elbow joint
What are the joints in that region?
- Sterno-clavicular joint
- Acromio-clavicular joint
- Gleno-Humeral joint (Shoulder joint)
- Scapulo-thoracic joint (sometimes referred to as a “virtual” or “physiological” joint)
- Elbow joint
- The pectoral girdle = SCJ + ACJ + GHJ + STJ
- GHJ is not truly in the pectoral girdle
In what direction is shoulder dislocation likely to occur?
- inferiorly
Shoulder joint
- Gleno-humeral joint
- Ball-and-socket synovial joint.
- The glenoid fossa (the socket) is shallow, but slightly deepened by a cartilaginous labrum. (it is not that deep)
- However, muscles required for joint stability. (eg. Rotator cuff group) -> many muscles and ligaments hold the head in.
- the joint is prone to dislocation (mainly inferiorly)
The rotator cuff and the shoulder joint
- Main function is to hold the humeral head within the glenoid
- The rotator cuff depresses the humeral head (depress =. hold it in the glenoid fossa)
What are the possible movements of the shoulder joint?
- abduction (deltoid, supraspinatus)
- adduction (pectoralis major, latissimus dorsi, teres major, triceps long head)
- flexion (pectoralis major, coracobrachialis, deltoid)
- extension (deltoid, teres major, latissimus dorsi, long head triceps)
- lateral rotation (deltoid, infraspinatus, teres minor)
- medial rotation (deltoid, pec major, teres major, subscapularis, latissimus dorsi)
Movements of the scapulothoracic joint
- Elevation / Depression of the scapula
- Protraction / Retraction of the scapula
- Rotation of the scapula
- The contact between the scapula and the thoracic wall, not a proper joint
Contents of the axilla
- Arteries – axillary artery and its branches
- Veins – axillary vein and its tributaries
- Lymphatic vessels and lymph nodes (important!) - also re breast cancer
- Nerves – the brachial plexus
Shape and function of the axilla
- pyramid
- goes down until the 5th rib
- The gateway for nerves and blood vessels to enter and leave the upper limb
- transition between shoulder and arm
Name the arteries of the region
Subclavian artery
- passes over the first rib to become…
Axillary artery
- at the lower border of teres major becomes the…
Brachial artery
- gives off a large branch in the arm – profunda brachii
Divides as the level of the elbow into…
Ulnar and Radial arteries
Name the veins of the region
- In limbs, venous return is via superficial and deep vessels
- Dorsal venous network on the hand -> forms to veins: cephalic and basilic
- Cephalic vein (superficial) runs up lateral border of arm
- Basilic vein (superficial) runs up the medial border of arm
- Basilic veins joins venae comitantes to form the axillary vein in the arm
- Cephalic vein joins axillary vein in the axilla
- Axillary vein becomes the subclavian vein at the level of the first rib
Lymphatic drainage of the region
- Superficial and deep systems, run with veins
- Cubital lymph nodes
- Delto-pectoral lymph nodes
- Axillary lymph nodes – important! (Axillary lymph nodes also very important in draining the breast; removing axillary lymph nodes in breast cancer treatment can lead to lymphedema of the arm, forearm and hand.)
- Subclavian lymph trunk
- Long thoracic nerve and thoraco-dorsal nerve!
- lots of nodes in the axilla including the ones draining the breast
Nerves of the region
- Brachial plexus
- nerve fibres to and from the spinal roots, more than 1 spinal root
Brachial Plexus
- passes under clavicle
- some terminal nerves branch off e.g. long thoracic nerve
What are the largest nerves of the brachial plexus?
- Axillary nerve (C56)
- Musculocutaneous nerve (C567)
- Ulnar nerve (C8T1)
- Median nerve (C678T1)
- Radial nerve (C5678T1)
Radial nerve
- supplies all posterior muscles of arm and forearm
Medial and ulnar nerve
Do not supply the arm
Profunda brachii A
= deep artery of the arm
- large vessel which arises from the lateral and posterior part of the brachial artery, just below the lower border of the teres major.
