Week 3 Flashcards
Which two muscles form the floor of the cubital fossa?
The supinator and brachialis
Which structure lies between the two heads of the supinator?
The radial nerve
Which muscles produce the characteristic shape of the shoulder?
Deltoid and trapezius
Which level of the vertebrae does the trapezius origination extend down to?
T12
What is the motor and sensory innervation of the trapezius muscle?
Motor: accessory nerve; Sensory: ventral rami of 3rd and 4th cervical nerves
What is the action of the trapezius?
Upper fibres: elevate the scapula and rotate it during abduction of the arm
Middle fibres: retract the scapula Lower fibres: pull the scapula inferiorly
How can you test the accessory nerve?
Test how well the trapezius is functioning; get the patient to elevate the shoulder against resistance
Describe the latissimus dorsi muscle
Flat, wide, found laterally on the back of the trunk
What is the action of the latissimus dorsi?
It acts to extend the arm at the shoulder, adduction at the shoulder and medial rotation of the arm
What is the innervation of the latissimus dorsi?
Thoracodorsal nerve
Describe the location of the levator scapulae
Lies in the back and neck, deep to the trapezius and sternocleidomastoid muscles
What is the action of the levator scapulae?
Elevates the scapula, rotates the scapula, and tilts the glenohumeral joint inferiorly
What is the innervation of the levator scapulae?
Dorsal scapular nerve
What are the rhomboid muscles?
Pair of muscles, rhomboid major and rhomboid minor; they lie deep to the trapezius and have a rhomboid appearance
What is the difference in size between the rhomboids?
Major is twice the width of minor
What is the innervation of the rhomboid muscles?
Dorsal scapular nerve
What is the action of the rhomboids?
Retract the scapula, rotate the scapula to tilt the glenohumeral joint, and also fix the scapula to the thoracic wall
What are the divisions of the deltoid muscle?
Anterior, middle and posterior; each can act independently or together when required
What is the innervation of the deltoid?
Axillary nerve
What is the action of the anterior and posterior fibres of the deltoid?
Anterior fibres flex the arm at the shoulder, posterior fibres extend the arm at the shoulder
What is the action of the middle fibres of the deltoid?
Major abductor of the arm; they take over from the supraspinatus, which abducts the first 15 degrees
What is the quadrangular space?
A gap that the axillary artery and posterior circumflex humeral artery pass through to reach the posterior scapular region
What is the relevance of the teres major in regard to the quadrangular space?
Forms the inferior border
What is the innervation of the teres major?
Lower subscapular nerve
What is the action of the teres major?
Adduction of the shoulder, and medial rotation of the arm
How would you test the deltoid muscle?
Examiner resists patients abduction of the limb by the deltoid; if the deltoid is acting normally, contraction of the middle part of the muscle can be palpated
What are the four rotator cuff muscles?
Supraspinatus, infraspinatus, teres minor, and subscapularis
Which rotator cuff muscle attaches to the lesser tubercle?
Subscapularis
What purpose does the intertubecular sulcus serve?
Tendons of the pectoralis major, teres minor and latissiumus dorsi attach to the lips of the sulcus
What is the name of the landmark of the humerus where the deltoid muscle attaches? Where is it located?
Deltoid tuberosity; lateral side
What lies in the radial groove? Describe its location
The radial nerve and profunda brachii artery; runs diagonally down posterior surface of humerus, parallel to the deltoid tuberosity
Why is the lateral supraepicondylar ridge of the humerus roughened?
It is a place of attachment for many of the extensor muscles in the posterior forearm
Where can the ulnar nerve be palpated?
Posterior side of the medal epicondyle
What structures are of concern with a fracture to the surgical neck of the humerus?
The axillary nerve and the posterior circumflex artery
What will damage to the axillary nerve result in?
Axillary nerve damage will result in paralysis of the deltoid and teres minor muscles- patient unable to abduct. It also innervates the skin of the regimental badge region (loss of sensation)
What structures are at risk with a mid-shaft fracture of the humerus? Why?
The radial nerve and profunda brachii artery; they are tightly bound in the radial groove
What is a supraepicondylar fracture? How does it occur?
Occurs by falling on a flexed elbow. It is a transverse fracture, spanning between the two epicondyles
Which vascular structure is at risk with a supraepicondylar fracture? What can interference of its supply cause?
Brachial artery; the resulting ischaemia can cause Volkmann’s ischaemic contracture - uncontrolled flexion of the hand, as flexors become fibrotic and short
Which nervous structures are at risk with a supraepicondylar fracture?
There can be damage to all 3 nerves (median, radial, ulnar)
Which nervous structure can a fracture to the medial epicondyle of the humerus damage? What will result?
Damage to the ulnar nerve, resulting in a deformity known as ulnar claw, and loss of sensation over the medial 1 and ½ fingers if the hand, on both the dorsal and palmar surfaces
What is the rotator cuff?
A group of 4 muscles, originating from the scapula which attach to the humeral head, pulling it into the glenoid fossa, providing extra stability
What is the action of the supraspinatus muscle? What is its innervation?
It is responsible for the first 15 degrees of abduction at the shoulder, assisting the deltoid for the rest; suprascapular nerve
What is the action of the infraspinatus muscle? What is its innervation?
Acts to laterally rotate the arm; suprascapular nerve
What is the action of the subscapularis muscle? What is its innervation?
Acts to medially rotate the arm; upper and lower subscapular nerves
What is the action of the teres minor? What is its innervation?
Acts to laterally rotate the arm; axillary nerve
What is the function of the subacromial bursa?
Reduces friction between the supraspinatus tendon and the coracoacromial arch during abduction of the arm
Which degenerative changes result in painful arc? What is painful arc?
Pain in the middle of abduction; under repetitive use, there are degenerative changes in the subacromial bursa and supraspinatus tendon
How is the coraco-acromial arch related to rotator cuff tendonitis?
Repetitive use of the rotator cuff muscles can cause the head of the humerus and the tendons of the muscles to irritate the coraco-acromial arch, which in turn causes greater inflammation of the rotator cuff tendons
What articulations form the shoulder joint? What is its anatomical name?
The glenoid cavity of the scapula with the head of the humerus; the glenohumeral joint
Why does the glenohumeral joint have inherent stability?
The glenoid cavity is relatively shallow, and the humeral head is large, and it is this disproportion that gives the inherent instability
What reduces the disproportion in size between the glenoid cavity and the humeral head?
The glenoid fossa is deepened by a fibrocartilaginous rim, called the glenoid labrum
Which nerves supply the glenohumeral joint? Where are they derived from?
The axillary, suprascapular and subscapular nerves; they are derived from C5 and C6
What is the blood supply of the glenohumeral joint?
Circumflex humeral arteries and suprascapular arteries
Where does the joint capsule of the glenohumeral joint attach? What property of it adds to mobility at the joint?
To the anatomical neck of the humerus and the border of the glenoid fossa; it is lax, although this adds to instability
What is the function of the inner surface of the joint capsule of the shoulder?
Synovial membrane; produces synovial fluid to reduce friction between structures at the joint
What occurs at holes in the joint capsule of the shoulder?
Synovial membrane protrudes to form bursae; they act to reduce rubbing between the structures around the joint during movement
What are the 3 clinically important bursae at the shoulder joint that do not form holes in the joint capsule?
Subacromial, subscapular, subdeltoid
What is the location of the subacromial bursa? What is its function?
Between the acromion of the scapula and the joint capsule and supraspinatus tendon; it allows relatively friction free movement of the tendon under the coracoacromial arch and deltoid
What is the location of the subscapular bursa?
Between the tendon of the subscapularis muscle and the joint capsule
What is the location of the subdeltoid bursa?
Between the deltoid and the joint capsule
What are the ligaments of the shoulder joint?
Superior, middle and inferior glenohumeral ligaments (they appear as one ligament), the coracohumeral ligament, and the transverse humeral ligament
Describe the location of the coracohumeral ligament
Between the base of the coracoid process and the greater tubercle of the humerus
Describe the location of the transverse humeral ligament
Between the two tubercles of the humerus, holding the tendon of the long head of the biceps in the intertubecular groove
Describe the location and function of the coracoacromial ligament
Joins the acromion and coracoid process of the scapula in a protective arch, that lies over the humeral head; this prevents superior displacement of the humeral head
Which muscles perform extension at the shoulder joint?
The posterior deltoid, latissimus dorsi, and teres major
Which muscles perform flexion at the shoulder joint?
Biceps brachii (both heads), pectoralis major, anterior deltoid and coracobrachialis
Which muscles perform abduction at the shoulder joint?
Initially, by the supraspinatus, then the middle fibres of the deltoid take over; past 90 degrees, the scapula is rotated by the trapezius and serratus anterior
Which muscles perform adduction at the shoulder joint?
Pectoralis major, latissimus dorsi, teres major and anterior deltoid
Which muscles perform medial rotation at the shoulder joint?
Subscapularis, pectoralis major, latissimus dorsi, teres major and anterior deltoid
Which muscles perform lateral rotation at the shoulder joint?
Infraspinatus and teres minor
What factors contribute to mobility at the shoulder joint?
It is a ball and socket joint; the disproportion of size between the glenoid cavity and humeral head
What factors contribute to stability at the shoulder joint?
Rotator cuff muscles (attach to tubercles of the humerus, pulling the humeral head into the glenoid cavity), the glenoid labrum (deepens cavity, reducing risk of dislocation), and the ligaments
How is an anterior dislocation of the shoulder joint usually caused?
Trauma to a fully abducted arm usually from a posterior direction
Which nerves may be damaged with an anterior dislocation of the shoulder?
Axillary nerve as it runs in close proximity to the joint (causes paralysis of deltoid, regimental badge), and radial nerve damage can also occur, as it is tightly bound in the radial groove
Which structures, other than nerves, may tear during an anterior dislocation of the shoulder?
Rotator cuff muscles and joint capsule
How many muscles are in the anatomical arm? What are they (anterior and posterior)?
4; Anterior: biceps brachii, brachialis, coracobrachialis Posterior: triceps brachii
What is the action of the biceps brachii?
Supination of the forearm; flexion of the arm at the shoulder and elbow
What is the innervation of the biceps brachii?
Musculotaneous nerve
Which spinal cord segment is tested by tapping the biceps tendon?
C6
What is the bicipital aponeurosis?
A connective tissue sheath given off the biceps tendon as it enters the forearm
What is the significance of the bicipital aponeurosis?
Forms the roof of the cubital fossa, blending with the deep fascia of the forearm
What is a popeye sign? What is it suggestive of?
Bulge of upper arm during flexion at the elbow; rupture of the tendon of the long head of the biceps brachii
Why would a patient not notice much weakness in the upper limb with a rupture of the tendon of the long head of the biceps brachii?
Action of brachialis and supinator compensate
What is the action of the coracobrachialis? What is its innervation?
Flexion of the arm at the shoulder; musculotaneous nerve
What forms the base of the cubital fossa?
The brachialis muscle
Which muscle is the main flexor of the elbow?
The brachialis
What is the action of the brachialis muscle?
Flexion at the elbow
What is the innervation of the brachialis muscle?
Musculotaneous nerve (small lateral portion is innervated by the radial nerve)
What are the three heads of the triceps brachii? Which one lies deeper than the other two?
Medial, lateral, and long; the medial head is deeper than the other two
What is the action of the triceps brachii?
Perform extension of the arm at the elbow
What is the innervation of the triceps brachii?
Radial nerve
Which spinal segment does a tap on the triceps tendon test?
C7
How does Erbs palsy usually occur?
Difficult birth or blow to the shoulder
Which nerves are affected with Erbs Palsy?
Those derived from solely C5 or C6 roots; musculotaneous, axillary, suprascapular and nerve to subclavius
Which muscles are paralysed with Erbs palsy?
Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, corachobrachialis, deltoid and teres minor
Which movements are lost or greatly weakened in people with Erbs palsy?
Abduction at the shoulder, lateral rotation of the arm, supination of the forearm, and flexion at the shoulder
What are the characteristic signs of Erbs palsy?
Affected limb hangs limply medially rotated by unopposed action of the pectoralis major, forearm pronated due to loss of biceps brachii; known as waiters tip
Which muscles does the musculotaneous nerve innervate? What actions does it hence control?
Biceps brachii, brachialis, coracobrachialis; flexion of the upper arm at the shoulder and elbow, and the biceps brachii also performs supination of the forearm
How would damage to the musculotaneous nerve likely occur?
It is uncommon as relatively protected, but a stab wound could damage it
Which muscles would be paralysed by a lesion to musculotaneous nerve?
Biceps brachii, brachialis, coracobrachialis
What actions would be compromised by a lesion to the musculotaneous nerve?
Flexion at shoulder weakened but still performed by the pectoralis major; flexion at the elbow affected but still performed by the brachioradialis; supination greatly weakened, but still produced by the supinator
Which muscles and hence which actions does the axillary nerve contribute to?
Deltoid; flexion and extension of the arm at the shoulder, major abductor of the arm past 15 degrees; Teres minor; lateral rotation of arm
How is the axillary nerve commonly injured?
Anterior dislocation of the humerus at the glenohumeral joint, or a fracture of the surgical neck
What functional loss will occur with an injury to the axillary nerve?
Paralysis of the deltoid and teres minor; patient will be unable to abduct the affected limb
What can be palpated in long standing cases of axillary nerve damage? Why?
Greater tuberosity of the humerus; deltoid rapidly atrophies
Describe how the radial nerve could be damaged in the axilla
Dislocation of humerus at glenohumeral joint, or fractures of proximal humerus; can also happen via excessive pressure on the axilla
What is the cubital fossa?
Area of transition between the anatomical arm and forearm, on the anterior surface if the elbow
What are the lateral, medial, and superior borders of the cubital fossa?
Lateral: medial border of the brachioradialisMedial: lateral border of pronator teresSuperior: imaginary line between condyles of humerus
What is the floor and roof of the cubital fossa?
Floor: brachialis, and more distally the supinatorRoof: skin, fascia, reinforced by bicipital aponeurosis
What are the contents of the cubital fossa? (lateral to medial)
Radial nerve, biceps tendon, brachial artery, median nerve
Which pulse can be palpated in the cubital fossa?
Brachial pulse; palpate medial to biceps tendon
What important structure runs superficial to the cubital fossa?
Median cubital vein, common site for venepuncture
Which arteries arise at the level of the humeral surgical neck from the axillary artery?
Posterior and anterior circumflex humeral arteries, and the subscapular artery
What does the brachial artery give rise to immediately distal to the teres major?
Profunda brachii artery; runs in radial groove, supplies triceps brachii
Describe the location of the brachial artery relative to the median nerve as it descends down the arm
Immediately posterior
Where does the brachial artery bifurcate to give the radial and ulnar nerves?
As it crosses the cubital fossa, under the brachialis muscle
What is a possible clinical manifestation of an occluded brachial artery?
Volkmanns contracture; necrosis and paralysis of muscles makes them fibrotic and contractious, causing the flexion deformity
What are then two main veins of the upper limb?
Cephalic (antero-lateral) and basilica (medial)
Which vessel connects the basilic and cephalic veins, superficial to the cubital fossa?
The median cubital vein (venepuncture)
Which muscles perform scapular retraction?
Both rhomboids, middle trapezius
Which muscles perform scapular protraction?
Serratus anterior, pectoralis minor
Which muscles perform scapular elevation?
Upper trapezius, levator scapulae
Which muscles perform scapular depression?
Lower trapezius, pectoralis minor, subclavius, latissimus dorsi
Which muscles perform scapular lateral rotation (upward)?
Lower and upper trapezius, serratus anterior
Which muscles perform medial scapular rotation? (downward)
Pectoralis minor, rhomboids, levator scapulae
Describe the location of the brachial artery in relation to the median nerve in the upper arm and cubital fossa
Upper arm it is medial to the median nerve; in the cubital fossa it lies lateral
What lies immediately anterior to the brachial artery and median nerve in the cubital fossa?
Bicipital aponeurosis; collagen from distal radial tendon, passing obliquely across cubital fossa and merging with fascia of flexors
What is the most common direction of humeral dislocation at the glenohumeral joint?
Weakest at inferior aspect, so dislocates in this direction but ends up anterior due to pull of muscles
What would be seen in clinical examination as a result or a torn supraspinatus tendon?
Failure of abduction in first 15 degrees, when lowering fully abducted arm slowly and smoothly, the limb suddenly drops
