The shoulder and arm

Question 1

What is the difference between the arm and the forearm

Answer 1

Arm- part between shoulder and elbow (often called upper arm in clinical practice)
Forearm- between the elbow and the wrist

Question 2

What are the 3 key bones in the shoulder and arm region

Answer 2

The Scapula
The Clavicle
The Humerus

Question 3

Summarise the key features of the scapula

Answer 3

The scapula is a large, flat triangular bone with:
▪
three angles (lateral, superior, and inferior),
▪
three borders (superior, lateral, and medial),
▪
two surfaces (costal and posterior), and
▪
three processes (acromion, spine, and coracoid process)

Question 4

What does the spine of the scapula divide the posterior surface of the scapula into

Answer 4

A prominent spine subdivides the posterior surface of the scapula into a small, superior supraspinous fossa and a much larger, inferior infraspinous fossa

Question 5

What is the lateral angle of the scapula marked by

Answer 5

The lateral angle of the scapula is marked by a shallow, somewhat comma-shaped glenoid cavity, which articulates with the head of the humerus to form the glenohumeral joint

Question 6

Describe the greater scapular notch

Answer 6

The region between the lateral angle of the scapula and the attachment of the spine to the posterior surface of the scapula is the greater scapular notch (spinoglenoid notch)

Question 7

Describe the costal surface of the scapula

Answer 7

Unlike the posterior surface, the costal surface of the scapula is unremarkable, being characterized by a shallow concave subscapular fossa over much of its extent (Fig. 7.21B). The costal surface and margins provide for muscle attachment, and the costal surface, together with its related muscle (subscapularis), moves freely over the underlying thoracic wall.

Question 8

Describe the acromian and coracoid processes of the scapula

Answer 8

The acromion, which is an anterolateral projection of the spine, arches over the glenohumeral joint and articulates, via a small oval facet on its distal end, with the clavicle.

the coracoid process, a hook-like structure that pro­jects anterolaterally and is positioned directly inferior to the lateral part of the clavicle (on its superior border)

Question 9

Describe the suprascapular notch

Answer 9

▪

the small but distinct suprascapular notch, which lies immediately medial to the root of the coracoid process.

Question 10

Compare the lateral border of the scapula to the medial border

Answer 10

The lateral border of the scapula is strong and thick for muscle attachment, whereas the medial border and much of the superior border is thin and sharp

Question 11

Describe the tubercles of the scapula

Answer 11

A less distinct supraglenoid tubercle is located superior to the glenoid cavity and is the site of attachment for the long head of the biceps brachii muscle.

A large triangular-shaped roughening (the infraglenoid tubercle) inferior to the glenoid cavity is the site of attachment for the long head of the triceps brachii muscle.

Deltoid tubercle on spine of the scapula

Question 12

Summarise the clavicle

Answer 12

The clavicle is the only bony attachment between the trunk and the upper limb. It is palpable along its entire length and has a gentle S-shaped contour, with the forward-facing convex part medial and the forward-facing concave part lateral. The acromial (lateral) end of the clavicle is flat, whereas the sternal (medial) end is more robust and somewhat quadrangular in shape

Question 13

Compare the acromial end of the clavicle to the sternal end

Answer 13

The acromial end of the clavicle has a small oval facet on its surface for articulation with a similar facet on the medial surface of the acromion of the scapula.
The sternal end has a much larger facet for articulation mainly with the manubrium of the sternum, and to a lesser extent, with the first costal cartilage.

Question 14

Describe the inferior surface of the lateral 1/3rd of the clavicle

Answer 14

Conoid tubercle (distinct tuberosity)
Trapezoid line (lateral roughening)
They are the point of attachment of the conoid ligament and trapezoid ligament (both part of the coracoclavicular ligament)
The coracoclavicular ligament is responsible for vertically attaching the scapula to the clavicle.

Question 15

What are the surfaces and margins of the clavicle roughened by

Answer 15

In addition, the surfaces and margins of the clavicle are roughened by the attachment of muscles that connect the clavicle to the thorax, neck, and upper limb. The superior surface is smoother than the inferior surface.

Question 16

What is important to remember about the clavicle

Answer 16

§ First long bone to ossify in the body (5th week) and does so by intramembranous ossification rather than endochondral which is most common to long bones.
§ Orientate via the “flat” lateral end at the acromion of the scapula and the circular sternal end at the sternum/1st CC (superior smooth).
§ Identify – conoid tubercle, trapezoid line, subclavian and costo-clavicular ligament groove (sternal end of posterior surface- can see a groove)

Question 17

Which structures are at risk if the fractured clavicle is displaced

Answer 17

Structures that may be injured are the subclavian vessels, axillary artery, elements of the brachial plexus, and internal jugular vein, and the lung, causing a pneumothorax.

Question 18

How are fractures of the clavicle commonly classified

Answer 18

Fractures of the clavicle are classified on which third is fractured. The middle one-third of the clavicle is most commonly fractured (80%), with lateral one-third fractures accounting for 15%, and medial one-third fractures being the least frequent (5%).

Question 19

What is the key role of the clavicle and what can happen in a fracture

Answer 19

The clavicle serves as an osseous strut that braces the shoulder against the sternum to force the upper extremity away from the trunk so that movement of the upper limb clears the trunk. As an osseous strut, the clavicle is buttressed by strong ligaments that connect it horizontally and vertically to adjacent structures.

In this clinical case, the fracture occurred medial to the coracoclavicular ligament (see Figure 94). Consequently, the weight of the upper limb caused the scapula and its attachment to the distal clavicle to move downward and the muscles bridging the glenohumeral joint pulled the upper limb medially.

Question 20

Preservation of the arterial supply to the clavicle is essential to the repair process. What is the arterial supply to the clavicle?

Answer 20

The nutrient artery to the clavicle is a branch of the suprascapular artery. The nutrient foramen is located in the lateral end of the subclavian groove, which serves as the insertion for the subclavius muscle.

Question 21

What does the proximal end of the humerus consist of

Answer 21

The proximal end of the humerus consists of the head, the anatomical neck, the greater and lesser tubercles, the surgical neck, and the superior half of the shaft of the humerus

Question 22

Describe the head of the proximal humerus

Answer 22

The head is half-spherical in shape and projects medially and somewhat superiorly to articulate with the much smaller glenoid cavity of the scapula.

Question 23

Describe the anatomical neck of the proximal humerus

Answer 23

The anatomical neck is very short and is formed by a narrow constriction immediately distal to the head. It lies between the head and the greater and lesser tubercles laterally, and between the head and the shaft more medially.

Question 24

Describe the surgical neck and its clinical importance

Answer 24

One of the most important features of the proximal end of the humerus is the surgical neck (Fig. 7.22). This region is oriented in the horizontal plane between the expanded proximal part of the humerus (head, anatomical neck, and tubercles) and the narrower shaft. The axillary nerve and the posterior circumflex humeral artery, which pass into the deltoid region from the axilla, do so immediately posterior to the surgical neck. Because the surgical neck is weaker than more proximal regions of the bone, it is one of the sites where the humerus commonly fractures. The associated nerve (axillary) and artery (posterior circumflex humeral) can be damaged by fractures in this region.

Fractures occur here more commonly than the anatomical neck

Question 25

Summarise fractures of the proximal humerus

Answer 25

It is extremely rare for fractures to occur across the anatomical neck of the humerus because the obliquity of such a fracture would have to traverse the thickest region of bone. Typically fractures occur around the surgical neck of the humerus. Although the axillary nerve and posterior circumflex humeral artery may be damaged with this type of fracture, this rarely happens. It is important that the axillary nerve is tested before relocation to be sure that the injury has not damaged the nerve and that the treatment itself does not cause a neurological deficit.

Question 26

Summarise the tubercles of the humerus

Answer 26

The greater and lesser tubercles are prominent landmarks on the proximal end of the humerus and serve as attachment sites for the four rotator cuff muscles of the glenohumeral joint.

Question 27

Describe the greater tubercle

Answer 27

The greater tubercle is lateral in position. Its superior surface and posterior surface are marked by three large smooth facets for muscle tendon attachments:
▪
The superior facet is for attachment of the supraspinatus muscle.
▪
The middle facet is for attachment of the infraspinatus.
▪
The inferior facet is for attachment of the teres minor.

Question 28

Describe the lesser tubercle

Answer 28

The lesser tubercle is anterior in position and its surface is marked by a large smooth impression for attachment of the subscapularis muscle.

Question 29

Describe the intertubecular sulcus

Answer 29

A deep intertubercular sulcus (bicipital groove) separates the lesser and greater tubercles and continues inferiorly onto the proximal shaft of the humerus (Fig. 7.22). The tendon of the long head of the biceps brachii passes through this sulcus.

Question 30

Describe the roughenings for attachments of muscles onto the intertubercular sulcus

Answer 30

Roughenings on the lateral and medial lips and on the floor of the intertubercular sulcus mark sites for the attachment of the pectoralis major, teres major, and latissimus dorsi muscles, respectively.

Question 31

Describe the deltoid tuberosity of the proximal humerus

Answer 31

The lateral lip of the intertubercular sulcus is continuous inferiorly with a large V-shaped deltoid tuberosity on the lateral surface of the humerus midway along its length (Fig. 7.22), which is where the deltoid muscle inserts onto the humerus.
In approximately the same position, but on the medial surface of the bone, there is a thin vertical roughening for attachment of the coracobrachialis muscle.

Question 32

Summarise the shaft of the humerus

Answer 32

In cross section, the shaft of the humerus is somewhat triangular with:
▪
anterior, lateral, and medial borders, and
▪
anterolateral, anteromedial, and posterior surfaces

Question 33

Describe the posterior surface of the humerus

Answer 33

The posterior surface of the humerus is marked on its superior aspect by a linear roughening for the attachment of the lateral head of the triceps brachii muscle, beginning just inferior to the surgical neck and passing diagonally across the bone to the deltoid tuberosity.

Question 34

Describe the radial groove

Answer 34

The middle part of the posterior surface and adjacent part of the anterolateral surface are marked by the shallow radial groove, which passes diagonally down the bone and parallel to the sloping posterior margin of the deltoid tuberosity. The radial nerve and the profunda brachii artery lie in this groove.

Question 35

Which structure is found in the middle of the shaft

Answer 35

Approximately in the middle of the shaft, the medial border is marked by thin elongate roughening for the attachment of the coracobrachialis muscle.

Question 36

Describe the lateral and medial intermuscular septa

Answer 36

Intermuscular septa, which separate the anterior compartment from the posterior compartment, attach to the medial and lateral borders

Question 37

Distally, what happens to the humerus

Answer 37

Distally, the bone becomes flattened, and these borders expand as the lateral supraepicondylar ridge (lateral supracondylar ridge) and the medial supraepicondylar ridge (medial supracondylar ridge). The lateral supraepicondylar ridge is more pronounced than the medial ridge and is roughened for the attachment of muscles found in the posterior compartment of the forearm.
The distal end of the humerus, which is flattened in the anteroposterior plane, bears a condyle, two epicondyles, and three fossae, as follows

Question 38

Compare the capitulum to the trochlea

Answer 38

The two articular parts of the condyle

The capitulum articulates with the radius of the forearm. Lateral in position and hemispherical in shape, it projects anteriorly and somewhat inferiorly and is not visible when the humerus is viewed from the posterior aspect.
The trochlea articulates with the ulna of the forearm. It is pulley shaped and lies medial to the capitulum. Its medial edge is more pronounced than its lateral edge and, unlike the capitulum, it extends onto the posterior surface of the bone.

Question 39

Describe the medial epicondyle

Answer 39

The medial epicondyle, a large bony protuberance, is the major palpable landmark on the medial side of the elbow, and projects medially from the distal end of the humerus. On its surface, it bears a large oval impression for the attachment of muscles in the anterior compartment of the forearm. The ulnar nerve passes from the arm into the forearm around the posterior surface of the medial epicondyle and can be palpated against the bone in this location.

Question 40

Describe the lateral epicondyle

Answer 40

The lateral epicondyle is much less pronounced than the medial epicondyle. It is lateral to the capitulum and has a large irregular impression for the attachment of muscles in the posterior compartment of the forearm.

Question 41

Describe the fossae of the distal humerus

Answer 41

The radial fossa is the least distinct of the fossae and occurs immediately superior to the capitulum on the anterior surface of the humerus.
The coronoid fossa is adjacent to the radial fossa and is superior to the trochlea.
The largest of the fossae, the olecranon fossa, occurs immediately superior to the trochlea on the posterior surface of the distal end of the humerus.
These three fossae accommodate projections from the bones in the forearm during movements of the elbow joint.

Question 42

What is the difference between a tubercle and a tuberosity

Answer 42

Tubercle- round

Tuberosity- irregular lump

Question 43

Ultimately, what is the main purpose of the upper limbs

Answer 43

Musculoskeletal

To get your hand where you want it to be to perform a task

Question 44

What is important to remember about the nomenclature of the muscle attachments in the upper limb

Answer 44

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.

Question 45

What are the muscular compartments for the shoulder and arm region

Answer 45

Anterior pectoral girdle muscles
Posterior pectoral girdle muscles
Intrinsic shoulder muscles
Anterior compartment of the upper arm
Posterior compartment of the upper arm

Question 46

List the anterior pectoral girdle muscles

Answer 46

Pectoralis major
Pectoralis minor
Subclavius
Serratus anterior* (runs between anterior and posterior pectoral girdle)

Question 47

What are the proximal and medial attachments of the pectoralis major muscle

Answer 47

Proximal: Medial half of clavicle and anterior surface of sternum, first seven costal cartilages, aponeurosis of external oblique

Distal: Lateral lip of intertubercular sulcus of humerus

Question 48

Describe the actions of the pectoralis major and its innervation

Answer 48

Flexion, adduction, and medial rotation of arm at glenohumeral joint; clavicular head—flexion of extended arm; sternocostal head—extension of flexed arm

Medial and lateral pectoral nerves; clavicular head (C5, C6); sternocostal head (C6, C7, C8, T1)

Question 49

Describe the features of the pectoralis major muscle

Answer 49

The pectoralis major muscle is the largest and most superficial of the pectoral region muscles. It directly underlies the breast and is separated from it by deep fascia and the loose connective tissue of the retromammary space.

3 parts:
clavicular head
sternal head
abdominal part

Question 50

Describe the proximal and distal attachments of the pectoralis minor muscle

Answer 50

Proximal: Anterior surfaces of the third, fourth, and fifth ribs, and deep fascia overlying the related intercostal spaces (fans out to have digital- finger like parts)

Distal: Coracoid process of scapula (medial border and upper surface)

Question 51

Describe the innervation and actions of the pectoralis minor muscle

Answer 51

Depresses tip of shoulder; protracts scapula, pulls scapula down

Medial pectoral nerve (C5, C6, C7, C8, T1)

Question 52

What are the proximal and distal attachments for the subclavius

Answer 52

Proximal- Rib I at junction between rib and costal cartilage

Distal- Groove on inferior surface of middle third of clavicle

Question 53

Describe the innervation and function of the subclavius

Answer 53

Pulls clavicle medially to stabilize sternoclavicular joint; depresses tip of shoulder

Nerve to subclavius (subclavian nerve)- C5,C6- small branch from superior trunk of brachial plexus

Question 54

Where do the lateral and medial pectoral nerves originate from

Answer 54

The brachial plexus in the axilla

Question 55

Describe the proximal and medial attachments of the serratus anterior

Answer 55

Proximal: Lateral surfaces of upper 8–9 ribs and deep fascia overlying the related intercostal spaces

Distal: Costal surface of medial border of scapula

Question 56

Describe the innervation and actions of the serratus anterior

Answer 56

Protraction and rotation of the scapula; keeps medial border and inferior angle of scapula opposed to thoracic wall

Long thoracic nerve (C5, C6, C7)

Question 57

Describe winging of the scapula

Answer 57

Because the long thoracic nerve passes down the lateral thoracic wall on the external surface of the serratus anterior muscle, just deep to skin and subcutaneous fascia, it is vulnerable to damage. Loss of function of this muscle causes the medial border, and particularly the inferior angle, of the scapula to elevate away from the thoracic wall, resulting in characteristic “winging” of the scapula, on pushing forward with the arm. Furthermore, normal elevation at the arm is no longer possible.

Question 58

List the posterior pectoral girdle muscles

Answer 58

Trapezius, Latissimus dorsi, Levator scapulae, the Rhomboids

Question 59

What are the proximal and distal attachments of the trapezius

Answer 59

Proximal- Superior nuchal line, external occipital protuberance, medial margin of the ligamentum nuchae, spinous processes of CVII to TXII and the related supraspinous ligaments

Distal- Superior edge of the crest of the spine of the scapula, acromion, posterior border of lateral one-third of clavicle

Question 60

Describe the actions and innervation of the trapezius muscle

Answer 60

Innervation- Motor spinal part of accessory nerve (XI). Sensory (proprioception) anterior rami of C3 and C4

Actions- Powerful elevator of the scapula; rotates the scapula during abduction of humerus above horizontal; middle fibers retract scapula; lower fibers depress scapula

The accessory nerve can be evaluated by testing the function of the trapezius muscle. This is most easily done by asking patients to shrug their shoulders against resistance.

Question 61

Describe the different parts of the trapezius muscle

Answer 61

Inferior fibres- ascending(C7-T12)
Middle fibres- horizontal
Superior fibres- descending.- nuchal ligament (C1-C6) AND SKULL

Question 62

What is important to remember about the scapula

Answer 62

Hub for muscles to attach- often there to stabilise it and hold it in position

Question 63

Describe the proximal and distal attachments of the latissimus dorsi

Answer 63

Distal- Floor of intertubercular sulcus of humerus

Proximal- Spinous processes of TVII to LV and sacrum, iliac crest, ribs X to XII (attached to iliac crest and sacrum via thoracolumbar fascia)

Thoracolumbar fascia and posterior 1/3 of the iliac crest
Floor of the intertubercular sulcus

Broad attachment proximally- fibres converge as a tendon to its distal attachment on the intertubecular groove.

Question 64

Describe the innervation and actions of the latissimus dorsi

Answer 64

Innervation- Thoracodorsal nerve (C6 to C8)

Actions- Extends, adducts, and medially rotates humerus (at the gleno-humeral joint)

pulls the body up to the arms during climbing. Also important in rowing.

Question 65

Describe the proximal and distal attachments of the rhomboid minor

Answer 65

Proximal- Lower end of ligamentum nuchae and spinous processes of CVII and TI vertebrae

Distal- Posterior surface of medial border of scapula at the root of the spine of the scapula

Question 66

Describe the innervation and actions of the rhomboid minor

Answer 66

Innervation- Dorsal scapular nerve (C4, C5)

Actions- Elevates and retracts the scapula

Question 67

Describe the proximal and distal attachments of the rhomboid major

Answer 67

Proximal- Spinous processes of TII–TV vertebrae and intervening supraspinous ligaments

Distal- Posterior surface of medial border of scapula from the root of the spine of the scapula to the inferior angle

Question 68

Describe the innervation and actions of the rhomboid major muscle

Answer 68

Innervation- Dorsal scapular nerve (C4, C5)

Actions- Elevates and retracts scapula

Same as minor

Forms parallelogram

Question 69

Describe the proximal and distal attachments of the levator scapulae muscle

Answer 69

Proximal- Transverse processes of CI and CII vertebrae and posterior tubercles of transverse processes of CIII and CIV vertebrae

Distal- Posterior surface of medial border of scapula from superior angle to root of spine of the scapula

Question 70

Describe the innervations and actions of the levator scapulae muscle

Answer 70

Innervation- Branches directly from anterior rami of C3 and C4 spinal nerves and by branches (C5) from the dorsal scapular nerve

Actions- Elevates and rotates the scapula

Question 71

Which muscles make up the intrinsic shoulder compartment

Answer 71

Rotator cuff muscles (supraspinatus, infraspinatus, teres minor and subscapularis)
Teres major
Deltoid

Question 72

Describe the proximal and distal attachments of the deltoid

Answer 72

Proximal- Inferior edge of the crest of the spine of the scapula, lateral margin of the acromion, anterior border of lateral one-third of clavicle

Distal- Deltoid tuberosity of humerus

Question 73

Describe the innervation and actions of the deltoid

Answer 73

Innervation- Axillary nerve (C5, C6)
The axillary nerve and associated blood vessels (the posterior circumflex humeral artery and vein) enter the deltoid by passing posteriorly around the surgical neck of the humerus.

Actions- Major abductor of arm (abducts arm beyond initial 15° done by supraspinatus); clavicular fibers assist in flexing the arm; posterior fibers assist in extending the arm (at GHJ)

Question 74

Describe the different parts of the deltoid muscle

Answer 74

Clavicular part (anterior)
Spinal part (posterior)
Middle part 

The deltoid covers the shoulder joint- giving it a rounded appearance- broad attachment
Fibres can act separately to aid a particular movement- but most act together to contribute the movements of the shoulder joint.

Question 75

Summarise the rotator cuff muscle

Answer 75

Rotator cuff group acts to fix the head of humerus in the glenoid fossa.

Supraspinatus important in initiating abduction of arm for first 15°, then deltoid takes over.

Question 76

Describe the proximal and distal attachments of the supraspinatous muscle

Answer 76

Proximal- Medial two-thirds of the supraspinous fossa of the scapula and the deep fascia that covers the muscle

Distal- Most superior facet on the greater tubercle of the humerus

Question 77

Describe the innervation and actions of the supraspinatous muscle

Answer 77

innervation- Suprascapular nerve (C5, C6)

Actions- Rotator cuff muscle; initiation of abduction of arm to 15° at glenohumeral joint

Question 78

Describe the proximal and distal attachments of the infraspinatous muscle

Answer 78

Proximal- Medial two-thirds of the infraspinous fossa of the scapula and the deep fascia that covers the muscle

Distal- Middle facet on posterior surface of the greater tubercle of the humerus

Question 79

Describe the innervation and actions of the infraspinatous muscle

Answer 79

Innervation- Suprascapular nerve (C5, C6)

Actions- Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint

Question 80

Describe the proximal and distal attachments of the teres minor

Answer 80

proximal- Upper two-thirds of a flattened strip of bone on the posterior surface of the scapula immediately adjacent to the lateral border of the scapula

Distal- Inferior facet on the posterior surface of the greater tubercle of the humerus

Question 81

Describe the innervation and actions of the teres minor

Answer 81

Innervation- Axillary nerve (C5, C6)

Action- Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint

Question 82

Describe the proximal and distal attachments of the subscapularis muscle

Answer 82

Proximal- Medial two-thirds of subscapular fossa

Distal- Lesser tubercle of humerus

Question 83

Describe the innervation and actions of the subscapularis muscle

Answer 83

Innervation- Upper and lower subscapular nerves (C5, C6, (C7))

Action- Rotator cuff muscle; medial rotation of the arm at the glenohumeral joint

Question 84

Describe the proximal and distal attachments of the teres major muscle

Answer 84

Proximal- Elongate oval area on the posterior surface of the inferior angle of the scapula

Distal- Medial lip of the intertubercular sulcus on the anterior surface of the humerus

Question 85

Describe the innervation and actions of the teres major muscle

Answer 85

Innervation- Lower subscapular nerve (C5, C6, C7)

Actions- Medial rotation and extension of the arm at the glenohumeral joint

Question 86

Which muscles make up the anterior compartment of the arm and which nerve innervates them?

Answer 86

Biceps brachii
Brachialis
Coracobrachialis
Innervated by: musculocutaneous nerv

Question 87

Describe the proximal and distal attachments of the biceps brachii

Answer 87

proximal- Long head—supraglenoid tubercle of scapula (goes through intertubecular groove held in place by transverse humeral ligament); short head—apex of coracoid process
Distal- Radial tuberosity
The long and short heads converge to form a single tendon, which inserts onto the radial tuberosity.
As the tendon enters the forearm, a flat sheet of connective tissue (the bicipital aponeurosis) fans out from the medial side of the tendon to blend with deep fascia covering the anterior compartment of the forearm.

Question 88

Describe the innervation and actions of the biceps brachii

Answer 88

Innervation- Musculocutaneous nerve (C5, C6)
Actions- Powerful flexor of the forearm at the elbow joint and supinator of the forearm; accessory flexor of the arm at the glenohumeral joint

Question 89

Describe the proximal and distal attachments of the coracobrachalis muscle

Answer 89

Proximal -Apex of coracoid process

Distal- Linear roughening on midshaft of humerus on medial side

Question 90

Describe the innervation and actions of the coracobrachialis muscle

Answer 90

Innervation- Musculocutaneous nerve (C5, C6, C7)

Action- Flexor of the arm at the glenohumeral joint

Question 91

Describe the proximal and distal attachments of the brachialis muscle

Answer 91

Proximal- Anterior aspect of humerus (medial and lateral surfaces) and adjacent intermuscular septae- shaft of humerus

Distal- Tuberosity of the ulna (coranoid process)

Question 92

Describe the innervation and actions of the brachialis muscle

Answer 92

Innervation- Musculocutaneous nerve (C5, C6); small contribution by the radial nerve (C7) to lateral part of muscle
Actions- Powerful flexor of the forearm at the elbow joint

Question 93

List the muscles of the posterior arm compartment

Answer 93

Triceps

Anconeus

Question 94

Describe the proximal and distal attachments of the triceps brachii muscle

Answer 94

proximal- Long head—infraglenoid tubercle of scapula; medial head—posterior surface of humerus; lateral head—posterior surface of humerus

Distal- The three heads converge to form a large tendon, which inserts on the superior surface of the olecranon of the ulna.

Question 95

Describe the innervation and actions of the triceps brachii muscle

Answer 95

Innervation- Radial nerve (C6, C7, C8)
Innervation of the triceps brachii is by branches of the radial nerve. A tap on the tendon of the triceps brachii tests predominantly spinal cord segment C7

Actions- Extension of the forearm at the elbow joint; long head can also extend and adduct the arm at the shoulder joint

Question 96

Describe the proximal and distal attachments of the anconeus muscle

Answer 96

Proximal- Lateral epicondyle of humerus

Distal- Olecranon and proximal posterior surface (shaft) of ulna

Question 97

Describe the innervation and actions of the anconeus muscle

Answer 97

Innervation- Radial nerve (C6, C7, C8) (via branch to medial head of triceps brachii)

Actions- Abduction of the ulna in pronation; accessory extensor of the elbow joint (stabilises the joint in pronation and supination_

Question 98

What is important to remember about the rotator cuff muscles

Answer 98

All head to the head of the humerus and cross the shoulder joint to attach around the head of the humerus

Main activity is to hold head of humerus into the glenoid cavity- although each muscle can act individually.