45. Fascia, efferent vessels, cutaneous innervation and myotomes of upper limb Flashcards
(118 cards)
1
Q
Discuss the principles of fascial layers in the upper limb
A
Deep to the skin is
1) subcutaneous tissue (superficial fascia) that contains fat, and
2) deep fascia that compartmentalises and invests the muscles.
If no structure (no muscle, tendon, or bursa) intervenes between the skin and the bone, the deep fascia is usually attached to bone.
2
Q
Discuss the principles of fascial layers in the upper limb
A
Deep to the skin is
1) subcutaneous tissue (superficial fascia) that contains fat, and
2) deep fascia that compartmentalises and invests the muscles.
If no structure (no muscle, tendon, or bursa) intervenes between the skin and the bone, the deep fascia is usually attached to bone.
3
Q
Fascia of the pectoral region include
A
- Pectoral fascia which invests the pectoralis major and is continuous inferiorly with the fascia of the anterior abdominal wall.
- Axillary fascia is formed from lateral border of the pectoralis major. Deep to the pectoral fascia and the pectoralis major is another fascial layer the clavipectoral fascia.
- The clavipectoral fascia desends from the clavicle, enclosing the subclavius and then the pectoralis minor, becoming continuous inferiorly with the axillary fascia.
4
Q
Where is the costocoracoid membrane located and what is it’s significance?
A
The costocoracoid membrane is part of the clavipectoral fascia and is located between the pectoralis minor and the subclavius. It is pierced by the lateral pectoral nerve which primarily supplies the pectoralis major.
5
Q
What forms the suspensory ligament of the axilla and what is it’s role?
A
The suspensory ligament is part of the clavipectoral fascia inferior to the pectoralis minor and it supports the axillary fascia and pulls it and the skin inferior to it upwards during abduction of the arm, thus forming the axillary fossa.
6
Q
What is the fascia that covers the scapulohumeral muscles and where does it descend from?
A
The deltoid fascia descends over the superficial surface of the deltoid from the clavicle, acromion and scapular spine
7
Q
What three (3) structures are created by the septa that penetrate between the fascicles (bundles) of muscles that originate from the deltoid fascia and what is achieved by their attachments to overlying fascia?
A
The three structures are the osseofibrous subscapular, supraspinous and infraspinous compartments. By attaching to the overlying fascia it allows the muscle to have greater bulk than would be the case if only bony attachments occurred.
8
Q
What is significant about the supraspinous and infraspinous fascia that overlie the supraspinatus and infraspinatus muscles?
A
The are both so dense at the posterior aspect of the scapula that they must be removed during dissection to view the muscles
9
Q
Describe key aspects of the brachial fascia
A
- The brachial fascia is a sheath of deep fascia that encloses the arm like a snug sleeve deep to the skin and subcutaneous tissue.
- It is continuous superiorly with the deltoid, pectoral, axillary and infraspinous fascial
- Inferiorly it is attached to the epicondyles of the humerus and the olectranon of the ulna and is continuous with the antebrachial fascia, the deep fascia of the forearm.
10
Q
The upper arm is divided by two intermuscular septa, where are they located and what do they divide?
A
- The intermuscular septa of the upper arm are identified as the medial and lateral intermuscular septa. The extend from the deep surface of the brachial fascia to the central shaft, and medial and lateral supraepicondylar riges of the humerus.
- These intermuscular septa divide the arm into anterior (flexor) and posterior (extensor) fascial compartments, with each containing muscles serving similar functions and sharing common innervation.
11
Q
TEST YOURSELF Fig. 6.13 p. 688
A
TEST YOURSELF Fig. 6.13 p. 688
12
Q
How are fascial compartments organised in the forearm?
A
Similar to the upper arm, the fascial comparments are surrounded by the antebrachial fascia and are separated by the interosseous membrane connecting the radius and ulna.
13
Q
The distal ends of the antebrachial fascia forms what?
A
The distal end of the antebrachial fascia forms the palmar carpal ligament anteriorly, which is continuous with the extensor retinaculum posteriorly which retains the extensor tendons in position.
14
Q
What sits immediately distal and at a deeper level to the palmar carpal ligament and what is its function?
A
Immediately distal and at a deeper level to the palmar carpal ligament and continuous with the antebrachial fascia is the flexor retinaculum (transverse carpal ligament).
15
Q
Where are the points of attachment for the flexor retinaculum (transverse carpal ligament)?
A
It extends between the anterior prominences of the outer carpal bones and convert the anterior concavity of the carpus into the carpal tunnel, through which the flexor tendons and median nerve pass.
16
Q
Discuss the anatomy of the palmar fascia.
A
- The palmar fascia is an extension of the deep fascia of the upper limb that extends beyond the extensor and flexor retinacula and is teathered to the skin by innumerable minute, strong skin ligaments to stop sliding movement of the skin.
- Its central part is a thick, tendious triangular structure, the palmar aponeurosis that overlies the central compartment of the palm. Its apex is located proximally and is continuous with the tendon of the Palmaris longus (when present)
- The base forms four distinct thickenings that radiate to the bases of the fingers and become continuous with the fibrous tendon sheaths of the digits.
- The base of the palmar aponeurosis is formed by the superficial transverse metacarpal ligament.
17
Q
TEST YOURSELF Fig. 6.14 p.688
A
TEST YOURSELF Fig. 6.14 p.688
18
Q
What are the superficial veins of the upper limb?
A
The cephalic (lateral) and basilic (medial) veins that originate in the subcutaneous tissue on the dorsum of the hand from the dorsal venous network
19
Q
What is the function of the perforating veins?
A
They form communications between the superficial and deep veins
20
Q
Describe the cephalic vein.
A
- It ascends in the subcutaneous tissue from the lateral aspect of the dorsal venous network, proceeding along the lateral border of the writ and the anterolateral surface of the proximal forearm and arm.
- Anterior to the elbow it communicates with the median cubital vein which passes obliquely across the anterior aspect of the elbow in the cubital fossa and joins the basilic vein.
21
Q
Describe the basilic vein
A
- It ascends in the subcutaneous tissue from the medial end of the dorsal venous network along the medial side of the forearm and the inferior part of the arm.
- Near the junction of the middle and inferior thirds of the arm, it passes deeply piercing the brachial facia and running superiorly parallel to the brachial artery and the medial cutaneous nerve of the forarm to the axilla, where it merges with the accompanying veins of the axillary artery to form the axillary vein.
22
Q
Describe the median antebrachial vein (median vein of the forearm).
A
- It is highly variable.
- It begins at the base of the dorsum of the thumb and curves around the lateral side of the wrist, and ascends in the middle of the anterior aspect of the forearm between the cephalic and the basilic vein
- It sometimes divides into a median basilica vein and joins the basilica vein or a median cephalic vein, which joins the cephalic vein.
23
Q
List the key differences between the superficial and deep veins of the upper limb.
A
- Deep veins lie internal to the deep fascial
- Deep veins usually occur as paired (continually interanastomosing) accompanying veins that travel with, and bear the same name as the major arteries of the limb.
24
Q
TEST YOURSELF fig 6.15 p.690
A
TEST YOURSELF fig 6.15 p. 690
25
List the deep veins of the forearm from the deep palmar arch
* The ulnar and radial veins
* The anterior interoseous vein and posterior interoseous veins
* The radial and ulnar recurrent veins (at the level of the elbow)
* The collateral veins of the elbow joint
* The brachial veins and deep brachial vein which anastomose with the basilic vein
26
TEST YOURSELF fig 6.16 p. 691
TEST YOURSELF fig 6.16 p. 691
27
Where do the superficial lymphatic vessels of the upper limb arise from?
Superficial lymphatic vessels arise from lymphatic plexuses in the skin of the fingers, palm, and dorsum of the hand to ascend mostly with the superficial veins, such as the cephalic and basilic veins.
28
Discuss the key points of the cubital lymph nodes.
* Some vessels accompanying the basiclic vein enter the cubital lymph nodes, located proximal to the medial epicondyle and medial to the basilic vein.
* Efferent vessels from these lymph nodes ascend in the arm and terminate in the humeral (lateral) axillary lymph nodes.
29
Where do most superficial lymphatic vessels of the upper limbs travel?
Most superficial lymphatic vessels of the upper limb accompany the cephalic vein and cross the proximal part of the arm and the anterior aspect of the shoulder to enter the apical axillary lymph nodes, however some may previously enter the more superficial deltopectoral lymph nodes.
30
What is the course of the lymphatic vessels and where possible draw comparison with the superficial vessels
Deep lymphatic vessels are less numerous than superficial vessels and accompany the major deep veins in the upper limb (radial, ulnar and brachial) to terminate in the humeral axillary lymph nodes. In fact there are very few deep lymph nodes occurring along their course.
31
What structures do deep lymphatic vessels drain?
They drain lymph from the joint capsules, periosteum, tendons, nerves, and muscles
32
Where are the axillary lymph nodes drained?
The axillary lymph nodes are drained by the subclavian lymphatic trunk.
33
TEST YOURSELF fig 6.17 p.692
TEST YOURSELF fig 6.17 p. 692
34
TEST YOURSELF fig 6.18 p.693
TEST YOURSELF fig 6.18 p.693
35
```
Identify the dermatome regions associated with these spinal segments
• C3, C4
• C5
• C6
• C7
• C8
• T1
• T2
```
* C3,C4 – Region at the base of the neck, extending laterally over the shoulder
* C5 – Lateral aspect of the arm (i.e. superior aspect of the abducted arm)
* C6 – Lateral forearm and thumb
* C7 – Middle and ring fingers and centre of posterior aspect of the forearm
* C8 – Little finger, medial side of hand and forearm (i.e. inferior aspect of abducted arm)
* T1 – Medial aspect of forearm and inferior arm
* T2 – medial aspect of uperior arm and skin of axilla
36
The pain sensation experienced with myocardial ischaemia may be felt radiating down the medial side of the left arm, what dermatome is this?
• T1 & T2
37
Where are the nerves of the upper limb derived from?
The brachial plexus, a major nerve network formed by the anterior rami of the C5-T1 pinal nerves.
38
Where are the nerves of the shoulder derived from.
The cervical plexus, a nerve network consisting of a series of nerve loops formed between adjacent anterior rami of the first four cervical nerves.
39
Where is the cervical plexus located?
The cervical plexus lies deep to the sternocleidomastoid muscle on the anterolateral aspect of the neck.
40
TEST YOURSELF fig 6.19 p.696
TEST YOURSELF fig 6.19 p. 696
41
Why are there no anterior cutaneous nerves of the arm and forearm?
Because this pattern corresponds to that of the cords of the brachial plexus
42
Where do the supraclavicular nerves originate, what is their contributing spinal nerve and describe their course and distribution
* The supraclavicular nerves originate from the cervical plexus and their contributing spinal nerves are C3 & C4.
* They pass anterior to the clavicle, immediately deep to the platyma, and supply skin over the clavicle and superiolateral aspects of pectoralis major
43
Where does the superior lateral cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The superior lateral cutaneous nerve of the arm is the terminal branch of the axillary nerve and its contributing spinal nerve is C5 & C6
* It emerge from beneath the posterior margin of the deltoid and supplies skin over the lower part of this muscle, and on the lateral side of the midarm
44
Where does the inferior lateral cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The inferior lateral cutaneous nerve originates from the radial nerve (or posterior cutaneous nerve of the arm), from C5 & C6.
* It perforates the lateral head of the tricep, passing clos to the cephalic vein to supply skin over the inferolateral aspect of the arm
45
Where does the posterior cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The posterior cutaneous nerve of the arm has it’s source in the radial nerve (in the axilla) and it’s contributing spinal nerves are C5-C8
* It crosses posterior to and communicates with the intercostobrachial nerve and supplies skin on the posterior arm as far as the olecranon
46
Where does the posterior cutaneous nerve of the forearm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The posterior cutaneous nerve of the forearm also has it’s source with the radial nerve (with the inferior lateral cutaneous nerve of the arm) and its contributing spinal nerve is C5 – C8
* It perforates the lateral head of the triceps descends laterally in the arm, then rungs along and supplies the posterior forearm to the wrist
47
Where does the lateral cutaneous nerve of the forearm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The lateral cutaneous nerve of the forearm originates from the musclocutaneous nerve (terminal branch) and it’s contributing spinal nerves are C6&C7
* It emerge lateral to the biceps tendon deep to the cephalic vein, supplying the skin of anterolateral forearm to the wrist.
48
Where does the medial cutaneous nerve of the forearm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The medial cutaneous nerve of the forearm originates from the medial cord of the brachial plexus (in the axilla) and it’s contributing spinal nerves are C8 & T1
* It descends medial to the brachial artery, pierces the deep fascia with the basilic vein in the midarm, dividing into anterior and posterior branches that enter the forearm and supply skin of the anteromedial aspect of the wrist
49
Where does the medial cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The medial cutaneou nerve of the arm also has its origins in the medial cord of the brachial plexus (in the axilla) but it’s contributing nerves are C8 – T2
* It communicates with the intercostobrachial nerve, continuing to supply the skin of the medial aspect of the distal arm
50
Where does the intercostobrachial nerve originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The intercostobrachial nerve originates from the second intercostal nerve (as it’s lateral cutaneous branch) from the spinal nerve T2.
* It extends laterally, communicating with posterior and medial cutaneous nerves of the arm, supplying skin of the axilla and medial aspect of the proximal arm
51
How do somatic motor fibres travel in the upper limb?
• Somatic motor (general somatic efferent) fibres that travel in the same mixed peripheral nerves convey sensory fibres to the cutaneous nerves that transmit the impulses to the voluntary muscles of the upper limb.
52
Define a myotome
* It is the unilateral embryological muscle mass that receives innervation from a single spinal cord segment or spinal nerve.
* Most upper limb muscles usually receive motor fibres from several spinal cord segments or nerves, thus most muscles are made up of more than one myotome, and multiple spinal cord segments are usually involved in producing the movement of the upper limb.
53
TEST YOURSELF 6.20 p. 696
TEST YOURSELF 6.20 p.696
54
Key points about fascia the upper limb
* The firm deep fascia of the upper limb surrounds and contains the structures of the upper limb as an expansion-limiting membrane deep to the skin and subcutaneous tissue.
* The deep surface of the fascia, which occasionally serves to extend the surface area available for muscular origin, is attached directly or via intermuscular septa to enclosed bones
* The deep fascia thus forms fascial compartments containing individual muscles or muscle groups of similar function and innervation
* The compartment also contain or direct the spread of infection or haemorrhage
55
Key points about superficial veins of the upper limb
* The cephalic vein courses along the cranial (cephalic) margin of the limb, while the basilic vein courses along the caudal (basic) margin of the limb
* Both veins come from the dorsal venous network on the dorsum of the hand and terminate by draining into the beginning (basilic vein) and end (cephalic vein) of the axillary vein.
56
Key points about deep veins of the upper limb
• Deep veins in the limbs usually take the form of paired accompanying veins, bearing the same name as the artery they accompany
57
Key points about lymphatic vessels of the upper limb
* The superficial lymphatic vessels generally converge on and follow the superficial veins, and the deep lymphatics follow the deep veins
* The lymph collected from the upper limb by both superficial and eep lymphatics drains into the axillary lymph nodes
58
Key points about dermatomes of the upper limb
• As a consequence of plexus formation, two patterns of cutaneous innervation occur in the upper limb (1) segmental innervation (dermatomes) by spinal nerves and (2) innervation by multisegmental peripheral (named) nerves
59
Key points about cutaneous innervation of the upper limb
* Like the brachial plexus, which forms posterior, lateral and medial (but no anterior) cords, the arm and forearm have posterior, lateral and medial (but no anterior) cutaneous nerves
* The medial cutaneous nerves are branches of the medial cord of the brachial plexus
* The posterior cutaneous nerves are branches of the radial nerve
* Each of the lateral cutaneous nerves arise from a separate source (axillary, radial and musculocutaneous nerves).
60
Key points about the myotomes of the upper limb
* Most upper limb muscles include components of more than one myotome and thus receive motor fibres from several spinal cord segments or spinal nerves.
* Thus multiple spinal cord segments are involved in producing the movements of the upper limb
* The intrinsic muscles of the hand constitute a single myotome (T1).
61
Fascia of the pectoral region include
1. Pectoral fascia which invests the pectoralis major and is continuous inferiorly with the fascia of the anterior abdominal wall.
2. Axillary fascia is formed from lateral border of the pectoralis major. Deep to the pectoral fascia and the pectoralis major is another fascial layer the clavipectoral fascia.
3. The clavipectoral fascia desends from the clavicle, enclosing the subclavius and then the pectoralis minor, becoming continuous inferiorly with the axillary fascia.
62
Where is the costocoracoid membrane located and what is it’s significance?
The costocoracoid membrane is part of the clavipectoral fascia and is located between the pectoralis minor and the subclavius. It is pierced by the lateral pectoral nerve which primarily supplies the pectoralis major.
63
What forms the suspensory ligament of the axilla and what is it’s role?
The suspensory ligament is part of the clavipectoral fascia inferior to the pectoralis minor and it supports the axillary fascia and pulls it and the skin inferior to it upwards during abduction of the arm, thus forming the axillary fossa.
64
What is the fascia that covers the scapulohumeral muscles and where does it descend from?
The deltoid fascia descends over the superficial surface of the deltoid from the clavicle, acromion and scapular spine
65
What three (3) structures are created by the septa that penetrate between the fascicles (bundles) of muscles that originate from the deltoid fascia and what is achieved by their attachments to overlying fascia?
The three structures are the osseofibrous subscapular, supraspinous and infraspinous compartments. By attaching to the overlying fascia it allows the muscle to have greater bulk than would be the case if only bony attachments occurred.
66
What is significant about the supraspinous and infraspinous fascia that overlie the supraspinatus and infraspinatus muscles?
The are both so dense at the posterior aspect of the scapula that they must be removed during dissection to view the muscles
67
Describe key aspects of the brachial fascia
* The brachial fascia is a sheath of deep fascia that encloses the arm like a snug sleeve deep to the skin and subcutaneous tissue.
* It is continuous superiorly with the deltoid, pectoral, axillary and infraspinous fascial
* Inferiorly it is attached to the epicondyles of the humerus and the olectranon of the ulna and is continuous with the antebrachial fascia, the deep fascia of the forearm.
68
The upper arm is divided by two intermuscular septa, where are they located and what do they divide?
* The intermuscular septa of the upper arm are identified as the medial and lateral intermuscular septa. The extend from the deep surface of the brachial fascia to the central shaft, and medial and lateral supraepicondylar riges of the humerus.
* These intermuscular septa divide the arm into anterior (flexor) and posterior (extensor) fascial compartments, with each containing muscles serving similar functions and sharing common innervation.
69
TEST YOURSELF Fig. 6.13 p. 688
TEST YOURSELF Fig. 6.13 p. 688
70
How are fascial compartments organised in the forearm?
Similar to the upper arm, the fascial comparments are surrounded by the antebrachial fascia and are separated by the interosseous membrane connecting the radius and ulna.
71
The distal ends of the antebrachial fascia forms what?
The distal end of the antebrachial fascia forms the palmar carpal ligament anteriorly, which is continuous with the extensor retinaculum posteriorly which retains the extensor tendons in position.
72
What sits immediately distal and at a deeper level to the palmar carpal ligament and what is its function?
Immediately distal and at a deeper level to the palmar carpal ligament and continuous with the antebrachial fascia is the flexor retinaculum (transverse carpal ligament).
73
Where are the points of attachment for the flexor retinaculum (transverse carpal ligament)?
It extends between the anterior prominences of the outer carpal bones and convert the anterior concavity of the carpus into the carpal tunnel, through which the flexor tendons and median nerve pass.
74
Discuss the anatomy of the palmar fascia.
* The palmar fascia is an extension of the deep fascia of the upper limb that extends beyond the extensor and flexor retinacula and is teathered to the skin by innumerable minute, strong skin ligaments to stop sliding movement of the skin.
* Its central part is a thick, tendious triangular structure, the palmar aponeurosis that overlies the central compartment of the palm. Its apex is located proximally and is continuous with the tendon of the Palmaris longus (when present)
* The base forms four distinct thickenings that radiate to the bases of the fingers and become continuous with the fibrous tendon sheaths of the digits.
* The base of the palmar aponeurosis is formed by the superficial transverse metacarpal ligament.
75
TEST YOURSELF Fig. 6.14 p.688
TEST YOURSELF Fig. 6.14 p.688
76
What are the superficial veins of the upper limb?
The cephalic (lateral) and basilic (medial) veins that originate in the subcutaneous tissue on the dorsum of the hand from the dorsal venous network
77
What is the function of the perforating veins?
They form communications between the superficial and deep veins
78
Describe the cephalic vein.
* It ascends in the subcutaneous tissue from the lateral aspect of the dorsal venous network, proceeding along the lateral border of the writ and the anterolateral surface of the proximal forearm and arm.
* Anterior to the elbow it communicates with the median cubital vein which passes obliquely across the anterior aspect of the elbow in the cubital fossa and joins the basilic vein.
79
Describe the basilic vein
* It ascends in the subcutaneous tissue from the medial end of the dorsal venous network along the medial side of the forearm and the inferior part of the arm.
* Near the junction of the middle and inferior thirds of the arm, it passes deeply piercing the brachial facia and running superiorly parallel to the brachial artery and the medial cutaneous nerve of the forarm to the axilla, where it merges with the accompanying veins of the axillary artery to form the axillary vein.
80
Describe the median antebrachial vein (median vein of the forearm).
* It is highly variable.
* It begins at the base of the dorsum of the thumb and curves around the lateral side of the wrist, and ascends in the middle of the anterior aspect of the forearm between the cephalic and the basilic vein
* It sometimes divides into a median basilica vein and joins the basilica vein or a median cephalic vein, which joins the cephalic vein.
81
List the key differences between the superficial and deep veins of the upper limb.
* Deep veins lie internal to the deep fascial
* Deep veins usually occur as paired (continually interanastomosing) accompanying veins that travel with, and bear the same name as the major arteries of the limb.
82
TEST YOURSELF fig 6.15 p.690
TEST YOURSELF fig 6.15 p. 690
83
List the deep veins of the forearm from the deep palmar arch
* The ulnar and radial veins
* The anterior interoseous vein and posterior interoseous veins
* The radial and ulnar recurrent veins (at the level of the elbow)
* The collateral veins of the elbow joint
* The brachial veins and deep brachial vein which anastomose with the basilic vein
84
TEST YOURSELF fig 6.16 p. 691
TEST YOURSELF fig 6.16 p. 691
85
Where do the superficial lymphatic vessels of the upper limb arise from?
Superficial lymphatic vessels arise from lymphatic plexuses in the skin of the fingers, palm, and dorsum of the hand to ascend mostly with the superficial veins, such as the cephalic and basilic veins.
86
Discuss the key points of the cubital lymph nodes.
* Some vessels accompanying the basiclic vein enter the cubital lymph nodes, located proximal to the medial epicondyle and medial to the basilic vein.
* Efferent vessels from these lymph nodes ascend in the arm and terminate in the humeral (lateral) axillary lymph nodes.
87
Where do most superficial lymphatic vessels of the upper limbs travel?
Most superficial lymphatic vessels of the upper limb accompany the cephalic vein and cross the proximal part of the arm and the anterior aspect of the shoulder to enter the apical axillary lymph nodes, however some may previously enter the more superficial deltopectoral lymph nodes.
88
What is the course of the lymphatic vessels and where possible draw comparison with the superficial vessels
Deep lymphatic vessels are less numerous than superficial vessels and accompany the major deep veins in the upper limb (radial, ulnar and brachial) to terminate in the humeral axillary lymph nodes. In fact there are very few deep lymph nodes occurring along their course.
89
What structures do deep lymphatic vessels drain?
They drain lymph from the joint capsules, periosteum, tendons, nerves, and muscles
90
Where are the axillary lymph nodes drained?
The axillary lymph nodes are drained by the subclavian lymphatic trunk.
91
TEST YOURSELF fig 6.17 p.692
TEST YOURSELF fig 6.17 p. 692
92
TEST YOURSELF fig 6.18 p.693
TEST YOURSELF fig 6.18 p.693
93
```
Identify the dermatome regions associated with these spinal segments
• C3, C4
• C5
• C6
• C7
• C8
• T1
• T2
```
* C3,C4 – Region at the base of the neck, extending laterally over the shoulder
* C5 – Lateral aspect of the arm (i.e. superior aspect of the abducted arm)
* C6 – Lateral forearm and thumb
* C7 – Middle and ring fingers and centre of posterior aspect of the forearm
* C8 – Little finger, medial side of hand and forearm (i.e. inferior aspect of abducted arm)
* T1 – Medial aspect of forearm and inferior arm
* T2 – medial aspect of uperior arm and skin of axilla
94
The pain sensation experienced with myocardial ischaemia may be felt radiating down the medial side of the left arm, what dermatome is this?
• T1 & T2
95
Where are the nerves of the upper limb derived from?
The brachial plexus, a major nerve network formed by the anterior rami of the C5-T1 pinal nerves.
96
Where are the nerves of the shoulder derived from.
The cervical plexus, a nerve network consisting of a series of nerve loops formed between adjacent anterior rami of the first four cervical nerves.
97
Where is the cervical plexus located?
The cervical plexus lies deep to the sternocleidomastoid muscle on the anterolateral aspect of the neck.
98
TEST YOURSELF fig 6.19 p.696
TEST YOURSELF fig 6.19 p. 696
99
Why are there no anterior cutaneous nerves of the arm and forearm?
Because this pattern corresponds to that of the cords of the brachial plexus
100
Where do the supraclavicular nerves originate, what is their contributing spinal nerve and describe their course and distribution
* The supraclavicular nerves originate from the cervical plexus and their contributing spinal nerves are C3 & C4.
* They pass anterior to the clavicle, immediately deep to the platyma, and supply skin over the clavicle and superiolateral aspects of pectoralis major
101
Where does the superior lateral cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The superior lateral cutaneous nerve of the arm is the terminal branch of the axillary nerve and its contributing spinal nerve is C5 & C6
* It emerge from beneath the posterior margin of the deltoid and supplies skin over the lower part of this muscle, and on the lateral side of the midarm
102
Where does the inferior lateral cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The inferior lateral cutaneous nerve originates from the radial nerve (or posterior cutaneous nerve of the arm), from C5 & C6.
* It perforates the lateral head of the tricep, passing clos to the cephalic vein to supply skin over the inferolateral aspect of the arm
103
Where does the posterior cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The posterior cutaneous nerve of the arm has it’s source in the radial nerve (in the axilla) and it’s contributing spinal nerves are C5-C8
* It crosses posterior to and communicates with the intercostobrachial nerve and supplies skin on the posterior arm as far as the olecranon
104
Where does the posterior cutaneous nerve of the forearm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The posterior cutaneous nerve of the forearm also has it’s source with the radial nerve (with the inferior lateral cutaneous nerve of the arm) and its contributing spinal nerve is C5 – C8
* It perforates the lateral head of the triceps descends laterally in the arm, then rungs along and supplies the posterior forearm to the wrist
105
Where does the lateral cutaneous nerve of the forearm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The lateral cutaneous nerve of the forearm originates from the musclocutaneous nerve (terminal branch) and it’s contributing spinal nerves are C6&C7
* It emerge lateral to the biceps tendon deep to the cephalic vein, supplying the skin of anterolateral forearm to the wrist.
106
Where does the medial cutaneous nerve of the forearm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The medial cutaneous nerve of the forearm originates from the medial cord of the brachial plexus (in the axilla) and it’s contributing spinal nerves are C8 & T1
* It descends medial to the brachial artery, pierces the deep fascia with the basilic vein in the midarm, dividing into anterior and posterior branches that enter the forearm and supply skin of the anteromedial aspect of the wrist
107
Where does the medial cutaneous nerve of the arm originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The medial cutaneou nerve of the arm also has its origins in the medial cord of the brachial plexus (in the axilla) but it’s contributing nerves are C8 – T2
* It communicates with the intercostobrachial nerve, continuing to supply the skin of the medial aspect of the distal arm
108
Where does the intercostobrachial nerve originate, what is it’s contributing spinal nerve and describe it’s course and distribution
* The intercostobrachial nerve originates from the second intercostal nerve (as it’s lateral cutaneous branch) from the spinal nerve T2.
* It extends laterally, communicating with posterior and medial cutaneous nerves of the arm, supplying skin of the axilla and medial aspect of the proximal arm
109
How do somatic motor fibres travel in the upper limb?
• Somatic motor (general somatic efferent) fibres that travel in the same mixed peripheral nerves convey sensory fibres to the cutaneous nerves that transmit the impulses to the voluntary muscles of the upper limb.
110
Define a myotome
* It is the unilateral embryological muscle mass that receives innervation from a single spinal cord segment or spinal nerve.
* Most upper limb muscles usually receive motor fibres from several spinal cord segments or nerves, thus most muscles are made up of more than one myotome, and multiple spinal cord segments are usually involved in producing the movement of the upper limb.
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TEST YOURSELF 6.20 p. 696
TEST YOURSELF 6.20 p.696
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Key points about fascia the upper limb
* The firm deep fascia of the upper limb surrounds and contains the structures of the upper limb as an expansion-limiting membrane deep to the skin and subcutaneous tissue.
* The deep surface of the fascia, which occasionally serves to extend the surface area available for muscular origin, is attached directly or via intermuscular septa to enclosed bones
* The deep fascia thus forms fascial compartments containing individual muscles or muscle groups of similar function and innervation
* The compartment also contain or direct the spread of infection or haemorrhage
113
Key points about superficial veins of the upper limb
* The cephalic vein courses along the cranial (cephalic) margin of the limb, while the basilic vein courses along the caudal (basic) margin of the limb
* Both veins come from the dorsal venous network on the dorsum of the hand and terminate by draining into the beginning (basilic vein) and end (cephalic vein) of the axillary vein.
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Key points about deep veins of the upper limb
• Deep veins in the limbs usually take the form of paired accompanying veins, bearing the same name as the artery they accompany
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Key points about lymphatic vessels of the upper limb
* The superficial lymphatic vessels generally converge on and follow the superficial veins, and the deep lymphatics follow the deep veins
* The lymph collected from the upper limb by both superficial and eep lymphatics drains into the axillary lymph nodes
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Key points about dermatomes of the upper limb
• As a consequence of plexus formation, two patterns of cutaneous innervation occur in the upper limb (1) segmental innervation (dermatomes) by spinal nerves and (2) innervation by multisegmental peripheral (named) nerves
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Key points about cutaneous innervation of the upper limb
* Like the brachial plexus, which forms posterior, lateral and medial (but no anterior) cords, the arm and forearm have posterior, lateral and medial (but no anterior) cutaneous nerves
* The medial cutaneous nerves are branches of the medial cord of the brachial plexus
* The posterior cutaneous nerves are branches of the radial nerve
* Each of the lateral cutaneous nerves arise from a separate source (axillary, radial and musculocutaneous nerves).
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Key points about the myotomes of the upper limb
* Most upper limb muscles include components of more than one myotome and thus receive motor fibres from several spinal cord segments or spinal nerves.
* Thus multiple spinal cord segments are involved in producing the movements of the upper limb
* The intrinsic muscles of the hand constitute a single myotome (T1).
