upper limb anatomy

Question 1

Demonstrate dermatomes of upper limb on yourself

Answer 1

C4-T2

Question 2

Describe the cutaneous innervation of the hand?

Answer 2

median nerve
- thumb, Index finger, middle finger, ring finger (1/2), thenar side

ulnar nerve
- little finger, 1/2 ring finger, hypothenar side and dorsal

radial
- thumb, dorsal hand

Question 3

Describe the lymphatics of the superficial limb?

Answer 3

1. -superficial lymphatics originate from lymphatic plexus in the hand
2. -ascend with superficial veins (cephalic or basilic) and terminate in the apical axillary LNs

either -
- cephalic vein - lymph nodes enter the apical axillary LNs - but some enter deltopectoral LNs

• or basilic vein - lymph nodes enter the cubital LNs - humeral axillary LNs - central axillary LNs - apical axillary LNs

Question 4

Describe the drainage of the deep lymphatics of the upper limb?

Answer 4

Ascend with the major deep veins(radial and ulnar vein) in the upper limb and terminate in the humeral (lateral) axillary lymph nodes - drain central axillary LNs - apical axiallary LNs - supraclavicular LNs - R+L subclavian lymphatic trunks

Question 5

How does the right and left subclavian lymphatic trunks drain?

Answer 5

right subclavian lymphatic trunk
joined by right jugular trunk = right lymphatic duct - joins the right venous angle to enter the right subclavian vein

left subclavian trunk
joins the thoracic duct and enters the left brachiocephalic vein

Question 6

Describe the course of the median nerve in the forearm?

Answer 6

• emerges from cubital fossa - lateral crosses medial to brachial artery
• passes between 2 heads of pronator teres
• descends deep to flexor digitorum superficialis
• continues distally between flexor digitorum superficialis and flexor digitorum profundus
• more distally runs deep to palmaris longus
• passes deep to flexor retinaculum
• gives off palmar cutaneous branch before passing deep to flexor retinaculum

Question 7

What structures are supplied by the median nerve?

Answer 7

no branches in the arm
articular branches to the elbow joint
branches to proximal radioulnar joint

-muscular branches to forearm muscles:
pronator teres, 
flexor carpi radialis, 
palmaris longus, 
flexor digitorum superficialis

-anterior interosseous nerve:
pronator quadratus, 
flexor pollicus longus, 
flexor digitorum profundus (digits 2, 3)
branches to inferior radioulnar joint, wrist and carpal joints

-palmar cutaneous branch:
sensory innervation of lateral palm

-recurrent branch to thumb muscles:
opponens pollicis,
abductor pollicis brevis,
flexor pollicis brevis

-palmar digital branch to: divides into 2 (medial and lateral branch) (medial branch divides into 2)
= lumbricals 1, 2
= palmar surface
= fingertips of lateral 3.5 digits (thumb to half the ring finger)
= nail beds lateral 3.5 digits

Question 8

what are the branches of the median nerve distal to the flexor retinaculum and what do they supply?

Answer 8

1- recurrent branch to thumb muscles

• opponens pollicis
• abductor pollicis brevis
• flexor pollicis brevis

2. palmar digital branch
   then gives off

= medial branch - divides again into 2
- supplies the palm skin
the cleft and adjacent sides of the ring and middle fingers and the middle and index fingers
- supplies the second lumbrical

= lateral branch
supplies the palmer skin, radial side of index and the whole of thumb and its web on the palmer surface and the distal part of the dorsal surface
the branch of the index finger supples the first lumbrical

they both supply the nail beds and distal dorsal skin of the digits

Question 9

Identify the boundaries and contents of the cubital fossa?

Answer 9

boundaries -
superior = line connecting medial to lateral epicondyles medially = pronator teres (lateral border)
laterally = brachioradialis (medial border)
base = brachialis and supinator muscles
roof = skin, SC tissue, fascia - reinforced by bicipital aponeurosis, median cubital vein

-contents:
lateral to medial =
radial nerve, biceps tendon, brachial artery, median nerve

Question 10

Describe the course of the radial nerve in the upper limb?

Answer 10

• C5-C7 branch of posterior cord
• exits axilla
• passes through triangular interval (lower triangular space)
• crosses humerus obliquely over radial groove with profunda brachii artery
• pierces the intermuscular septum
• passes between brachialis and brachioradialis,
• then anterior to lateral epicondyle then divides into branches:
  1) deep branch pierces supinator, supplies it, emerges in posterior compartment as posterior interosseous nerve
  2) superficial (sensory) branch runs between pronator teres and brachioradialis to the anatomical snuffbox

Question 11

Major branches of the radial nerve?

Answer 11

main branch of radial nerve:
triceps, 
anconeus, 
brachioradialis, 
extensor carpi radialis longus

elbow joint
runs between the brachilais and brachioradialis = then
splits into deep branch and the superficial branch

1) deep branch of radial nerve: 
gives off the supinator and extensor carpi radialis brevis (becomes the posterior interosseous branch after it gives off the supinator) 
extensor carpi ulnaris
extensor digiti minimi
extensor digitorum

= posterior interosseous branch of radial nerve:

• abductor pollicis longus,
• extensor pollicis brevis
• extensor pollicis longus,
• extensor indicis

2) superficial sensory branch of radial nerve runs between pronator teres and brachioradialis to the anatomical snuffbox

Question 12

Functional deficits from radial nerve injury in mid arm?

Answer 12

1. -elbow extension would be preserved due to action of long head and lateral head of triceps
2. -wrist drop would be present - inability to extend wrist and MCP joints of fingers and thumb
3. interphalangeal joints maintained due to lumbericals and interossei
4. -sensory loss over radial 2/3 dorsum of hand

Question 13

Describe the course of the ulnar nerve at the elbow?

Answer 13

passes posterior to the medial epicondyle of the humerus and medial to the olecranon. It lies in the grooved surface of the posterior band of the ulnar collateral ligament at the elbow.

Question 14

What clinical findings would be present if the ulnar nerve is injured at the elbow?

Answer 14

• sensory loss
  1. of medial half of palmar aspect of hand (palmer cutaneous branch)
  2. medial half of dorsal aspect hand and medial 1.5 fingers (dorsal cutaneous branch)
  3. medial 1.5 fingers on palmer surface (superficial branch)

-motor loss
1. flexor carpi ulnaris = flex and adduct
2. medial 2 FDP (III and IV) = flex interphalangeal joints 4th and 5th digits
3. hypothenar muscles (Abductor digiti minimi, opponens digiti minimi, flexor digiti minimi) = flex and abducts 5th MCPJ
4. adductor pollicis + 1/2 flexor pollicis brevis = adducts thumb
5. interosseous, 3/4 lumbrical = abducts and adducts 3rd and 4th fingers
paralysis of almost all intrinsic hand muscles apart from 2 radial lumbricals and thenar compartment = causes claw hand

Question 15

How would you differentiate an ulnar nerve lesion at the elbow from one at the wrist?

Answer 15

more pronounced claw hand if lesion is more distal as flexor digitorum profundus and flexor carpi ulnaris are preserved

Question 16

Demonstrate where sensation changes may occur if the ulnar nerve is injured in the forearm?

Answer 16

• sensory loss
  1. of medial half of palmar aspect of hand (palmer cutaneous branch)
  2. medial half of dorsal aspect hand and medial 1.5 fingers (dorsal cutaneous branch)
  3. medial 1.5 fingers on palmer surface (superficial branch)
  4. ulnar aspect of the wrist

Question 17

Describe the superficial drainage of the upper limb?

Answer 17

-dorsal and palmar networks drain to
cephalic (anterolateral)
AND
basilic (posteromedial) veins

palm drains dorsally

• connected in cubital fossa by median cubital vein
• basilic vein goes deep (drains middle and distal 1/3 arm) and joins brachial vein to form axillary vein
• cephalic begins in roof of anatomic snuff box and pierces clavipectoral fascia (runs in deltopectoral groove) to join axillary vein, runs inferior to the clavicle

Question 18

Can you describe the venous drainage of the upper limb?

Answer 18

superficial + deep

superficial - 
-dorsal and palmar networks drain to 
cephalic (anterolateral) 
AND
basilic (posteromedial) veins 

palm drains dorsally

• connected in cubital fossa by median cubital vein
• basilic vein goes deep (drains middle and distal 1/3 arm) and joins brachial vein to form axillary vein
• cephalic begins in roof of anatomic snuff box and pierces clavipectoral fascia (runs in deltopectoral groove) to join axillary vein, runs inferior to the clavicle

deep -
palmar venous arch
radial and ulnar veins corresponds to the arteries
starts at the venous comitantes - join to form the brachial vein that joins with the basilic vein to form the axillary vein

Question 19

What are the boundaries of the axilla?

Answer 19

• base = level of 4th rib, forms the armpit
• apex = first rib, clavicle, superior scapula
• anterior wall = pectoralis minor and major, clavipectoral fascia

-posterior wall =
scapula, subscapularis, (on surface)
teres major, latissimus dorsi (inferior)

• lateral wall = intertubercular sulcus of humerus
• medial wall = 1-4th rib and serratus anterior

Question 20

Contents of the axilla?

Answer 20

• axillary sheath (axillary artery, axillary vein(formed from basilic and brachiel veins + becomes the subclavian vein lateral border of the first rib, brachial plexus)
• axillary LNs - pectoral, subscapular, humeral, central, apical
• fat

Question 21

what is it and describe it - Brachial plexus formation/ relations?

Answer 21

It is a major nerve network supplying the upper limb extends from the neck to the axilla which results in the formation of multisegmental peripheral nerves

• union of anterior rami (root) of C5-T1
• roots: between anterior/middle scalene
• trunks: roots unit to form 3 trunks - form in lower part of posterior triangle - 1st part axillary artery = superior, middle, inferior
• divisions: form behind the clavicle = each trunk divides into anterior and posterior divisions

-cords: embrace the 2nd part of the axillary artery posterior to pectoralis minor - outer border of first rib
= form 3 cords - lateral, posterior, medial
posterior divisions of all 3 trunks forms posterior cord

-terminal branches: surround the 3rd part of the axillary artery inferior to pectoralis minor

major peripheral nerves supplying the upper limb form from these cords:

lateral cord C5-7
formed from super and middle trunks
1. lateral pectoral nerve
2. musculocutaneous nerve
3. lateral root - median nerve

posterior cord C5-T1
formed from the superior, middle and inferior trunks
1. upper and lower subscapularis
2. thoracodorsal nerve
3. axillary nerve
4. radial nerve

medial cord C8-T1
formed from inferior trunk
1. medial pectoral nerve
2. medial cutaneous nerve of arm
3. medial cutaneous nerve of forearm
4. medial root of median nerve
5. ulnar nerve

Question 22

Terminal branches of the medial cord?

Answer 22

1. ulnar nerve
2. medial pectoral nerve
3. medial cutaneous nerve of arm
4. medial cutaneous nerve of forearm
5. medial root of median nerve

Question 23

What are the nerve roots of the posterior cord?

Answer 23

C5, C6, C7, C8, T1

Question 24

What are the terminal branches of the posterior cord?

Answer 24

lateral cord: C5, C7
posterior cord: C5, C6, C7, C8, T1
medial cord: C8, T1

-Axillary nerve: (C5-6)
joint - glenohumeral (shoulder)
muscles - deltoid and teres minor
sensation - to skin over inferior aspect of deltoid

-Radial nerve: (C5 - T1)
muscles - all muscle of posterior compartment of arm and forearm
sensation - to posterior/inferolateral arm, posterior forearm, dorsum of hand lateral to ring finger

other branches - 
-upper subscapular: C5
muscle -  to subscapularis 
-lower subscapular : C6
muscle - inferior part of the subscapularis and teres major
-Thoracodorsal: C6,7,8
muscles - to lat dorsi

Question 25

Nerve most likely to be injured in brachial plexus?

Answer 25

radial nerve

Question 26

Apart from wrist extensor weakness, what other functions may be lost with a radial nerve lesion in the axilla?

Answer 26

finger extension | sensory loss over radial 2/3 dorsum. of hand

Question 27

Identify the components of the brachial plexus

Answer 27

``` lateral cord C5-7 formed from super and middle trunks 1. lateral pectoral nerve 2. musculocutaneous nerve 3. lateral root - median nerve ``` ``` posterior cord C5-T1 formed from the superior, middle and inferior trunks 1. upper and lower subscapularis 2. thoracodorsal nerve 3. axillary nerve 4. radial nerve ``` ``` medial cord C8-T1 formed from inferior trunk 1. medial pectoral nerve 2. medial cutaneous nerve of arm 3. medial cutaneous nerve of forearm 4. medial root of median nerve 5. ulnar nerve ```

Question 28

Identify and describe the features of clavicle

Answer 28

- medial end articulates with manubrium of the sternum (sternal end) - lateral end articulates with acromion - inferior/laterally contains conoid tubercle and trapezoid line for conoid ligament - inferiorly contains subclavian groove and impression for costoclavicular ligament

Question 29

what structures stabilise the AC joint?

Answer 29

1. acromioclavicular ligament 2. coracoclavicular ligament 3. coracoacromial ligament

Question 30

What are the muscle attachments to the clavicle?

Answer 30

- deltoid = lateral 1/3 anterior - trapezius = lateral 1/3 posterior - pectoralis major = medial 1/3 anterior and inferior - sternocleidomastoid = clavicular head, medial 1/3 superior - subclavius = inferior, middle 1/3

Question 31

What are anatomical relations of medial third of clavicle?

Answer 31

-medial = sternoclavicular joint, manubrial notch -posterior = first rib, brachiocephalic vein (medial to scalenus anterior), internal jugular vein, subclavian vein (over scalenus anterior), subclavius, phrenic nerve (more posterior) anterior/superior/inferior = SC tissue skin apical pleura thoracic duct - on left side

Question 32

What is the course of the subclavian vein?

Answer 32

- becomes subclavian vein from axillary vein medial to outer border of the first rib - moves medial posterior to the clavicle, superior to first rib (flat section - groove) - lies anterior to scalene anterior, which separates it from the subclavian artery - becomes the brachiocephalic vein at the medial border of scalenus anterior when it joins the IJV

Question 33

What are the rotator cuff muscles - demonstrate origin and insertion on a model

Answer 33

-supraspinatus = origin - medial 2/3 supraspinous fossa of scapula insertion - to upper part of greater tuberosity of humerus (suprascapular nerve - c5,6) do - helps deltoid by initiating abduction -infraspinatus = origin - medial 2/3 infraspinous fossa of scapula and deep surface infraspinous fascia which covers muscle insertion - to central facet of greater tuberosity of humerus (suprascapular nerve c5,6) do - lateral rotation of humerus -subscapularis = origin - medial 2/3 costal surface subscapular fossa of scapula insertion - fuses with capsule of shoulder joint and into lesser tuberosity of humerus (subscapular nerve) do - medial rotation of humerus -teres minor = origin - dorsal surface of axillary border of scapula insertion - to lower facet of greater tuberosity of humerus (axillary nerve - posterior branch) do - lateral rotation of humerus All muscles stabilise the shoulder joint by bracing humeral head against the glenoid (tendons fuse with capsule)

Question 34

Identify the main features of the scapular

Answer 34

-glenoid cavity, spine, supraspinous and infraspinous fossae, subscapular fossae, acromion, coracoid process suprascapular notch, supra and infraglenoid tubercles, deltoid tubercle, inferior angle, med and lateral border, tubercle for long head of biceps, tubercle for long head of triceps

Question 35

Demonstrate the attachment of scapulohumeral muscles?

Answer 35

- deltoid = acromion and spine of scapula (also attaches lateral 1/3 clavicle) - supraspinatus = supraspinous fossae (medial 2/3) - infraspinatus = infraspinous fossae (medial 2/3) and deep surface of infraspinous fascia which covers muscle - subscapularis = subscapular fossa (medial 2/3 costal surface) - teres minor = middle part of lateral border - teres major = posterior surface of inferior angle

Question 36

Demonstrate muscular attachments on posterior surface?

Answer 36

superior = levator scapular inferior bellyomohyoid biceps medial = levator scapular rhomboid major and minor latissimus dorsi lateral = long head of triceps teres minor and major latissimus dorsi spine = trapezius (sup) deltoid (inferior)

Question 37

what muscles are involved in abduction of the shoulder ?

Answer 37

initiated by supraspinatus | then deltoid

Question 38

What stabilises the shoulder joint?

Answer 38

1. rotator cuff muscles 2. glenoid labrum - fibrocartiaginous 3. coraco-humeral ligament 4. long head of biceps in transverse humeral ligament 5. long head of triceps 6. anterior glenohumeral ligament (does not really help with reinforcement) 7. coraco-acromial arch

Question 39

What muscles are responsible for abduction and adduction of the shoulder joint?

Answer 39

abduction = deltoid, supraspinatus (initially) + upward movement scapular adduction = pectoralis major and lat dorsi (act in concert) teres major and long head of triceps (synergists)

Question 40

What muscles are responsible for the other movements of the shoulder ?

Answer 40

flexion = pec major (clav head) deltoid (clav and anterior acromial parts) coracobrachialis (synergist) ``` extension = spinal part of deltoid lat dorsi teres major long head of triceps (synergist) ``` ``` med rotation = subscapularis pec major teres major deltoid - clavicular part (synergist) ``` lat rotation = infraspinatus teres minor deltoid - spinal part (synergist) circumduction

Question 41

Outline bursa of shoulder joint?

Answer 41

subscapular bursa - located neck of scapular and subscapular tendon - protects the tendon subacromial (deltoid) bursa - between acromion, coraco-acromial ligament and deltoid superiorly AND supraspinatus tendon and joint capsule inferiorly

Question 42

ligaments of the shoulder joint?

Answer 42

1. glenohumeral ligament - 3 bands (superior, middle and inferior), which run withg joint capsule from glenoid fossa to anatomical neck humerus = stabilise anterior aspect of the joint 2. coracohumeral ligament - attaches to the base of the coracoid process to greater tubercle of humerus = supports superior part of the joint capsule 3. transverse humeral ligament - spans difference between the 2 tubercle of humerus = holds tendon of long head biceps in the intertubecular groove 4. coracoacromial ligament - runs between the acromion and corocoid process of scapula forming the coraco-acromial arch - this overlies the shoulder joint = prevents superior dislocation of the humeral head

Question 43

identify the main features of the humerus?

Answer 43

proximal: head, anatomical and surgical neck, greater and lesser tuberosity (attachment for rotator cuff and deltoid) intertubercular groove (long head biceps) radial groove on shaft deltoid tuberosity ``` distal : medial and lateral supracondylar ridge lateral (ext origin) and medial (flex origin) epicondyle, anteriorly: coronoid fossa radial fossa capitulum trochlea posteriorly: trochlea olecranon fossa ```

Question 44

How does humerus articulate with the scapula?

Answer 44

glenohumeral joint = ball and socket | humeral head articular surface in contact with surface of glenoid cavity (deepened by glenoid labrum)

Question 45

Attachments of the rotator cuff muscles on the humerus

Answer 45

supraspinatus - insertion - to upper part of greater tuberosity of humerus infraspinatus - insertion - to central facet of greater tuberosity of humerus teres minor - insertion - lower facet of of greater tubersity of humerus subscapularis -insertion - fuses with capsule of shoulder joint and into lesser tuberosity of humerus

Question 46

what are the common sites of fracture and what nerve at risk?

Answer 46

1. surgical neck of humerus axillary nerve and brachial plexus 2. midshaft of humerus radial nerve, wrist drop, sensory deficit

Question 47

what are the major muscles of shoulder abduction - where do they insert humerus?

Answer 47

supraspinatus - greater tuberosity | deltoid - deltoid tuberosity

Question 48

what structures lie deep to flexor retinaculum at wrist/ what passes through carpal tunnel?

Answer 48

FDS FDP FPL median nerve

Question 49

tendons at the wrist?

Answer 49

FCU, Palmaris longus, FCU FDS FPL, FDP brachioradialis

Question 50

veins in venepuncture?

Answer 50

median cubital vein, basilic vein and cephalic vein

Question 51

Describe the path of the brachial artery?

Answer 51

-continuation of axillary artery at lower border of teres major, run to neck of radius -lies medial to humerus, posterior to biceps and anterior to triceps medial head -lies on brachialis and descends in cubital fossa, median nerve crosses anteriorly -division over proximal radius into radial and ulnar artery (ulnar N is a posterior relation in upper arm)

Question 52

Describe the ulna

Answer 52

- olecranon, coronoid process, trochlear notch | - radial notch, supinator crest, ulna tuberosity, interosseous border, supinator fossa

Question 53

How does ulna articulate with other bones of the elbow?

Answer 53

-olecranon and coronoid process forms walls of trochlear notch -trochlear notch articulates with trochlea of humerus = this allows flexion and extension -on lateral side of coronoid process - radial notch articulates with radial head

Question 54

What contributes to stability of elbow joint?

Answer 54

1. joint capsule 2. collateral ligaments: radial collateral ligament = humerus lateral epicondyle, fan-like, blends with annular ligament of radius ulnar ulnar collateral ligament = humerus medial epicondyle - anterior band - medial epicondyle to medial edge of coronoid (strongest) - posterior band - medial coronoid to medial olecranon (weakest) - oblique band - between anterior and posterior bands 3. muscles - biceps, triceps, brachialis 4. annular ligament

Question 55

Demonstrate the bony features of elbow joint

Answer 55

humerus = medial epicondyle - trochlear below - lateral capitulum - with the lateral epicondyle above, coronoid fossa medially and radial fossa laterally posteriorly olecranon fossa anteriorly ulna = olecranon and coronoid process with the trochlear notch in the middle the radial notch, tuberosity of ulna below, further down - supinator fossa, and crest then below this interosseous border radial head and neck and tubercle

Question 56

Demonstrate the capsular attachments of the elbow?

Answer 56

-fibrous layer surrounds the whole joint = proximally above the coronoid and olecranon fossa = distally across the neck of radius and adjacent ulna excludes epicondyles -synovial layer lines the internal surface of the fibrous layer and non articular parts of the humerus is continuous distally with synovial membrane of proximal radioulnar joint

Question 57

movements of elbow joint?

Answer 57

flexion and extension | not supination/pronation - proximal radio-ulnar joint does this

Question 58

What is the common extensor tendon?

Answer 58

tendon that attaches to the lateral epicondyle of the humerus muscles arise from it = 1. extensor carpi radialis brevis - 3rd metacarpal 2. aconeus 3. supinator - proximal 3rd radius 4. extensor carpi ulnaris - (lateral - dorsal base 5th metacarpal) 5. extensor digiti minimi - next in - extensor expansion of 5th digit 6. extensor digitorum - extensor expansion

Question 59

Demonstrate the bony features of the elbow

Answer 59

humerus = medial epicondyle - trochlear below - lateral capitulum - with the lateral epicondyle above, coronoid fossa medially and radial fossa laterally posteriorly olecranon fossa anteriorly ulna = olecranon and coronoid process with the trochlear notch in the middle the radial notch, tuberosity of ulna below, further down - supinator fossa, and crest then below this interosseous border radial head and neck and tubercle

Question 60

outline the capsular attachments of the humerus

Answer 60

medial and lateral margins capitellum and trochlea above the coronoid and olecranon fossa excludes the epicondyles

Question 61

describe the movements of supination and pronation and what muscles are involved

Answer 61

proximally - rotation of head of radius in annular ligament distally - radius rotates laterally around its axis muscles = pronation - 1. pronator teres 2. pronatar quadratus median nerve ``` supination - 1.biceps - musculocutanous nerve 2. supinator 3. Extensor carpi radialis longus 4. Extensor pollicis longus rest supplied by radial nerve ```

Question 62

describe the ulnar collateral ligament and its attachments

Answer 62

ulnar collateral ligament = humerus medial epicondyle - anterior band - medial epicondyle to medial edge of coronoid (strongest) - posterior band - medial coronoid to medial olecranon (weakest) - oblique band - between anterior and posterior bands

Question 63

muscles involved with flexion at the elbow

Answer 63

``` biceps (musculocutaneus N) brachioradialis (radial N) brachialis (radial N) supinator (radial N) flexor digitorum superficialis (median N) ```

Question 64

whats the nerve supply for the extensor group of muscles of forearm

Answer 64

radial N

Question 65

how do muscles produce movement at the thumb

Answer 65

-APL = abduction and extension at carpometacarpal joint -EPL = extension at IP joint -EPB = extension at MCP joint radial nerve - posterior interosseous nerve -thenar muscles: flexor pollicis brevis (both median and ulnar N), opponens pollicis, abductor pollicis brevis - rest median nerve

Question 66

Flexor muscles of the forearm

Answer 66

``` superficial compartment: pronator teres flexor carpi radialis flexor digitorum superficialis palmaris longus flexor carpi ulnaris ``` deep compartment: flexor digitorum profundus flexor pollicis longus pronator quadratus

Question 67

not a viva question - for learning - boundaries of spaces in axilla =

Answer 67

Triangular space Boundaries Inferior: superior border of teres major Lateral: long head of triceps Superior: teres minor (or subscapularis) Contents: Scapular circumflex vessels Unlike the quadrangular space or the triangular interval, NO major nerve passes through the triangular space Quadrangular space Boundaries ``` Superior: teres minor (inferior margin) Inferior: teres major (superior margin) Medially: long head triceps brachii (lateral margin) Laterally: Surgical neck of the humerus Anteriorly: subscapularis Contents: ``` Axillary nerve and posterior circumflex humeral vessels (artery and vein) Triangular interval Boundaries Superior: teres major Medial: long head of triceps (brachii) Lateral: humerus (some sources say lateral head of triceps) Contents Radial nerve passes through on its way to the posterior compartment of the arm. Profunda brachii also passes from anterior to posterior.