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Transcript
Dissector Answers - Axilla, Posterior Shoulder, &
Arm
Learning Objectives:
Upon completion of this session, the student will be able to:
1. Describe the lymphatic drainage of the upper limb and the major lymphatic node
groups of the axilla.
2. Recall the concept of the axilla as a space, its boundaries and its contents.
3. Illustrate or describe the brachial plexus, including its parts, the nerves arising
from it, and their specific origins and areas of distribution.
4. Predict the functional and cutaneous loss that might result in the back, posterior
shoulder, pectoral region, or cutaneous upper limb, given an injury to a specific
site in the brachial plexus.
5. Predict where the brachial plexus might be injured, given a functional or
cutaneous loss in the back, posterior shoulder, pectoral region or cutaneous upper
limb.
6. Identify or describe the axillary artery and vein, their major branches, and their
relationships to each other, the brachial plexus, and the pectoralis minor muscle.
7. Identify the posterior shoulder muscles and associated rotator cuff muscles. Give
their general functions and nerve supply.
8. Identify and demonstrate the regional blood supply of the posterior shoulder.
9. Identify prominent features of the humerus, cubital fossa and associated
prominences of the scapula, radius and ulna as given in the lab manual.
10. Identify the contents of each of the three compartments of the arm and the
functional significance of the included muscles.
11. Correlate any fractures of the humerus with functional disruptions of associated
muscular and neurovascular structures.
12. Describe the movements of the shoulder and elbow joints.
13. Identify spatial relationships of all associated muscular and neurovascular
structures within the cubital fossa.
Learning Objectives and Explanations:
1. Describe the lymphatic drainage of the upper limb and the major lymphatic node groups of the
axilla. (W&B 106-107, 123, N184, N483, TG2-11)
As a general rule, the superficial lymphatic drainage of the upper limb follows the superficial
venous drainage. Most of the lymph ends up in the lateral and central axillary lymph nodes, with
some of it passing through the cubital lymph nodes along the way. Some of the lymph from the
posterior surface of the upper limb travels in vessels that accompany the cephalic vein, piercing
the clavipectoral fascia to end in the apical axillary lymph node. The deep lymphatic vessels of
the upper limb accompany the major arteries to also end in the lateral and central axillary lymph
nodes.
So what about these axillary lymph nodes? They are extremely important clinically, since they
drain the major portion of the breast. These lymph nodes are carefully palpated during any
thorough breast exam. There are five groups:





anterior axillary (pectoral) lymph nodes: along the lower border of the
pectoralis major muscle
lateral axillary (humeral) lymph nodes: distal along the axillary vein
posterior axillary (subscapular) lymph nodes: along the subscapular vein and
its tributaries
central axillary lymph nodes: centrally located along the axillary vein, deep to
the pectoralis minor insertion
apical axillary lymph node(s): at the apex of the axilla, receiving lymph from
all other groups
2. Recall the concept of the axilla as a space, its boundaries and its contents. (W&B 114-115,
N181, TG2-11, TG2-12, TG2-13)
The axillary space is shaped like a truncated pyramid. Its boundaries are:




anterior wall: pectoralis major and minor muscles. The lateral border of
pectoralis major muscle forms the anterior axillary fold.
posterior wall: scapula, subscapularis muscle, teres major muscle, and
latissimus dorsi muscle. The teres major muscle combines with latissimus
dorsi muscle to form the posterior axillary fold.
medial wall: serratus anterior muscle
lateral wall: the floor of the intertubercular groove of the humerus.
3. Illustrate or describe the brachial plexus, including its parts, the nerves arising from it, and
their specific origins and areas of distribution. (W&B 119-123, 708-714, N429, N430, TG2-13,
TG2-14)
Images from "Anatomy of the Human Body" by Henry Gray are provided by:
The brachial plexus consists of roots, trunks, divisions, cords, and branches. There is a classic
mnemonic to help with this one: Robert Taylor Drinks Cold Beer. The roots are mostly derived
from the ventral primary rami of C5 to T1. Three trunks, the superior, middle and inferior
trunks, are derived from those roots (C5-C6, C7, and C8-T1 respectively). Each trunk divides
into an anterior and posterior division. The posterior divisions of all three trunks unite to form
the posterior cord. The anterior divisions of the superior and middle trunks unite to form the
lateral cord. Finally, the anterior division of the inferior trunk forms the medial cord. (The
medial aspect of your arm when it is in the anatomical position is also the inferior aspect when
you stick your arm straight out, or, for that matter, when you are an embryo and your arm is
2mm long. In the same way, lateral is superior.) These cords then terminate as branches that
supply the skin and muscles of the upper limb.
For the rest, we will rely on the tables:
Nerve
Source
Branches
Motor
Sensory
nerves from the
roots:
dorsal scapular
brachial
plexus
(C5)
rhomboid major & minor;
levator scapulae
long thoracic
brachial
plexus
(C5-C7)
serratus anterior
to subclavius
superior
trunk of
brachial
plexus
subclavius
suprascapular
superior
trunk of
brachial
plexus
(C5-C6)
supraspinatus,
infraspinatus
lateral pectoral
lateral
cord of
brachial
plexus
pectoralis major
musculocutaneous
lateral
cord of
brachial
plexus
(C5,6)
medial pectoral
medial
cord of the
brachial
plexus
medial brachial
cutaneous
medial
cord of
brachial
plexus
nerves from the
trunks:
terminal branches
(i.e., from the
cords):
lateral
antebrachial
cutaneous
coracobrachialis, biceps
brachii, brachialis
skin of
lateral side
of forearm
pectoralis minor & major
skin of the
medial side
of the arm
skin of
medial side
of forearm
medial
antebrachial
cutaneous
medial
cord of
brachial
plexus
median
lateral &
medial
cords of
brachial
plexus
anterior
interosseous,
palmar br.,
recurrent (motor)
Br, common
palmar digital ns.
(1st-3rd)
pronator teres, flexor carpi
radialis, palmaris longus,
flexor digitorum
superficialis, flexor
digitorum profundus
(radial half), flexor pollicis
longus, pronator quadratus,
abductor pollicis brevis,
flexor pollicis brevis,
opponens pollicis, radial 2
lumbricals
skin of
radial half
of palm &
palmar side
of radial 3
1/2 digits
(and nail
bed for
these digits)
ulnar
medial
cord of the
brachial
plexus
palmar cutaneous
Br, dorsal Br,
superficial &
deep Br
flexor carpi ulnaris, flexor
digitorum profundus (ulnar
half), abductor digiti
minimi, flexor digiti
minimi brevis, opponens
digiti minimi, ulnar 2
lumbricals, palmar &
dorsal interossei
skin of
medial side
of wrist &
hand &
ulnar 1 1/2
digits
upper subscapular
posterior
cord of
brachial
plexus
subscapularis
thoracodorsal
(middle
subscapular)
posterior
cord of
brachial
plexus
latissimus dorsi
lower subscapular
posterior
cord of
brachial
plexus
subscapularis, teres major
radial
posterior
cord of
brachial
plexus
posterior brachial
cutaneous,
inferior lateral
brachial
cutaneous,
posterior
antebrachial
triceps brachii, anconeus,
brachioradialis, extensor
carpi ulnaris, extensor
carpi radialis longus &
brevis, extensor digitorum,
extensor digiti minimi,
supinator, abductor pollicis
skin of
posterior
arm,
forearm &
hand
axillary
posterior
cord of
brachial
plexus
cutaneous,
superficial &
deep br
longus, extensor pollicis
longus & brevis, extensor
indicis
superior lateral
brachial
cutaneous n.
deltoid, teres minor
skin of
upper lateral
arm
4. Predict the functional and cutaneous loss that might result in the back, posterior shoulder,
pectoral region, or cutaneous upper limb, given an injury to a specific site in the brachial plexus.
(W&B 185-186, N430, TG2-14)
Symptoms of brachial plexus injury may include a limp or paralyzed arm, lack of muscle control
in the arm, hand, or wrist, and lack of feeling or sensation in the arm or hand. Although injuries
can occur at any time, many brachial plexus injuries happen during birth: the baby's shoulders
may become impacted during the birth process causing the brachial plexus nerves to stretch or
tear. There are four types of brachial plexus injuries: avulsion, the most severe type, in which the
nerve is torn from the spine; rupture, in which the nerve is torn but not at the spinal attachment;
neuroma, in which the nerve has tried to heal itself but scar tissue has grown around the injury,
putting pressure on the injured nerve and preventing the nerve from conducting signals to the
muscles; and neuropraxia or stretch, in which the nerve has been damaged but not torn.
Neuropraxia is the most common type of brachial plexus injury.
These injuries usually occur at the roots. The upper roots of the brachial plexus supply the more
proximal muscles, while the lower roots supply the more distal. The segmental innervation of the
skin does not correlate with the supply of the muscles beneath.
Injury to the upper roots, C5 and C6, are the most common type. This results in Erb-Duchenne
Palsy, or "Waiter's Tip". It affects the suprascapular nerve especially and frequently also
involves the musculocutaneous and axillary nerves, which results in paralysis of the rotator cuff
muscles, in addition to the biceps, brachialis, coracobrachialis, and deltoid muscles.
Subscapularis may also be affected. The upper limb hangs limply, medially rotated by
unopposed pectoralis major, latissimus dorsi, and teres major muscles and pronated due to loss of
biceps.
Injury to the lower roots, C8 and T1, results in Klumpke's Palsy. The ulnar and median nerves
are affected, paralyzing all of the intrinsic muscles of hand. Patients present with a "clawed
hand" due to hyperextension of MP joints and flexion of digits by forearm flexors unopposed by
interossei.
As for related cutaneous losses, check out a diagram of the cutaneous nerves of the upper limb.
5. Predict where the brachial plexus might be injured, given a functional or cutaneous loss in the
back, posterior shoulder, pectoral region or cutaneous upper limb. (N430, TG2-14)
If you know where the nerves go and what they innervate, then you will be able to work
backwards:



"Hey Doc, my shoulder blade is sticking out of my back like an angel's wing."
"Well, Hank, you must have injured your long thoracic nerve."
"Yeah, come to think of it, I fell off my bike and stretched my neck to the right
the other day."
The possibilities are numerous. See #3 and #4 above.
6. Identify or describe the axillary artery and vein, their major branches, and their relationships to
each other, the brachial plexus, and the pectoralis minor muscle. (W&B 115-119, N427, N429,
N256, TG2-19, TG2-15A, TG2-15B)
Images from "Anatomy of the Human Body" by Henry Gray are provided by:
The axillary artery is the second portion of the upper limb's main arterial stem. (This arterial
stem changes names regionally, even though it is all really the same vessel. It is like the external
iliac, femoral, and popliteal arteries in the lower limb.) The axillary artery is defined to be the
distal continuation of the subclavian artery, after that artery passes over the first rib. It
continues to the inferior border of teres major where its name changes to the brachial artery.
The axillary artery is divided into three parts, numbered proximally to distally as parts 1, 2 and 3.
Each part is defined in relation to the pectoralis minor muscle, which, by definition, covers the
2nd portion of the axillary artery. (The portion proximal to pectoralis minor is therefore the1st
part of the axillary artery, while the portion distal to pectoralis minor is the 3rd portion of the
axillary artery.
The 1st part has one branch, the superior thoracic artery, which supplies the intercostal
muscles of the 1st and 2nd intercostal spaces and the upper portion of serratus anterior muscle.
The 2nd part has two branches, the thoracoacromial and lateral thoracic arteries. The
thoracoacromial artery is a short trunk arising anteriorly and passing medial to the pectoralis
minor muscle. It divides into four branches distributing according to their regional names:
acromial, deltoid, pectoral and clavicular. The lateral thoracic artery is a variable artery that,
in 65% of us, is a direct branch of the axillary artery, but can also arise from the thoracoacromial
or subscapular arteries. It passes below the inferolateral border of pectoralis minor muscle to
distribute most significantly to serratus anterior and the pectoral muscles.
The 3rd part has three branches. The subscapular artery is the largest branch of the axillary
artery. It divides into the circumflex scapular and thoracodorsal branches three or four
centimeters from its origin. The circumflex scapular artery passes through the triangular space
and supplies the infraspinatous, subscapular, teres major, and teres minor muscles. It also
anastomoses with the infraspinatous branch of the suprascapular artery in the infraspinatus
fossa. The thoracodorsal artery is the principal supply to the latissimus dorsi muscle and is
accompanied by the thoracodorsal nerve. The next branch of the 3rd part of the axillary artery is
the anterior circumflex humeral artery. It runs anteriorly around the surgical neck of the
humerus and anastomoses with the posterior circumflex humeral artery, which is the final
branch of the 3rd part of the axillary artery. This is larger than its anterior partner, and passes
through the quadrangular space with the axillary nerve.
As for the axillary vein, it begins as the union of the brachial veins with the basilic vein. It
continues through the axilla, medial to the axillary artery, until it changes its name to the
subclavian vein at the lateral border of the first rib. The axillary vein receives the cephalic vein
and numerous other tributaries that roughly correspond to the branches of the axillary artery,
though things are of course somewhat variable (See #15 below). (One thing to note is that the
vein receives one or more thoracoepigastric veins, which represent anastomoses of veins from
the superficial inguinal region with one or more axillary tributaries. This represents a possible
route of collateral drainage if the inferior vena cava is obstructed for some reason.)
7. Identify and demonstrate the posterior shoulder muscles and associated rotator cuff muscles.
Give their general functions and nerve supply. (N425, N426, N427, TG2-08A, TG2-08B, TG216A, TG2-16B, TG2-16C)
Muscle
Origin
Insertion
Action
Innervation
deltoid
lateral one-third of
clavicle, acromion,
lower lip of the crest
of the spine of the
scapula
deltoid
tuberosity of
the humerus
abducts arm; anterior
fibers flex & medially
rotate arm; posterior
fibers extend &
laterally rotate arm
axillary nerve (C5,6)
from posterior cord of
brachial plexus
teres
major
dorsum of the
inferior angle of
scapula
crest of lesser adducts arm, medially
tubercle of
rotates arm, assists in
humerus
arm extension
lower subscapular
nerve (C5,6) from the
posterior cord of the
brachial plexus
Rotator Cuff:
Muscle
Origin
Insertion
Action
Innervation
supraspinatus supraspinatus fossa
greater
tubercle of
humerus
(highest facet)
abduct arm
(initiate
abduction)
suprascapular nerve
(C5,6) from superior
trunk of brachial
plexus
infraspinatus
infraspinatus fossa
greater
tubercle of
humerus
(middle facet)
laterally rotate
arm
suprascapular nerve
teres minor
upper 2/3 of the
lateral border of the
scapula
greater
tubercle of
humerus
(lowest facet)
laterally rotates
arm
axillary
lesser tubercle
of humerus
medially rotates upper and lower
arm; assists
subscapular nerves
extension of
(C5,6)
arm
subscapularis medial two-thirds of
costal surface of
scapula (subscapular
fossa)
The rotator cuff is a musculotendinous cuff around the glenohumeral joint. To remember the
muscles that participate in it, use the mnemonic "SITS": Supraspinatus, Infraspinatus, Teres
minor, Subscapularis. The tendons of these muscles reinforce the articular capsule of this joint.
Their main purpose is to hold the head of the humerus in the glenoid cavity during movement of
the arm. (The rotator cuff's vulnerable aspect is that it does not effectively prevent dislocations of
the shoulder if the arm is pulled straight down, since it is incomplete inferiorly. Otherwise, the
most common way to damage the cuff is seen in the example of a hockey player who collides
into a wall with her arm stuck straight out in front of her to absorb the shock.)
8. Identify and demonstrate the regional blood supply to the shoulder. (W&B 115-118, N426,
N427, TG2-08B, TG2-09A)
The axillary artery is the primary source of blood to the region. (It continues as the brachial
artery, which supplies the upper limb.) The artery proper, including all of its branches, will be
given complete treatment with the axilla. For now, there are a few important concepts to begin
thinking about.
Two branches of the third part of the axillary artery are the anterior and the posterior
circumflex humoral arteries. These form a circle of blood flow around the surgical neck of the
humerus. The posterior is larger than the anterior, and accompanies the axillary nerve through
the quadrangular space.
The important arteries that form anastomoses around the scapula are the dorsal scapular,
suprascapular and subscapular, and, one of its branches, the circumflex scapular artery. A
visual must be consulted to truly get the picture, however, the significance of the anastamoses of
the shoulder is that if one of these arteries is occluded there are other routes through which the
blood supply can reach the area, thereby avoiding ischemia. Also, surgical ligatures can be
placed on the suprascapular, axillary or subscapular arteries without damaging the muscles of the
shoulder.
9. Identify prominent features of the humerus, cubital fossa and associated prominences of the
scapula, radius and ulna as given in the lab manual. (N420, N421, N436, N439, TG2-03A, TG203B, TG2-04)
The only prominent feature of the humerus that we are worried about here is the radial groove,
which spirals around the posterior surface of the shaft of the humerus, containing the radial nerve
and the deep brachial vessels. See the next session for prominent features of the bones of the
forearm.
10. Identify the contents of each of the three compartments of the arm and the functional
significance of the included muscles. (W&B 124-127, N184, N420, N421, N426, N429, N431,
N433, N434, N435, N447, N473, N474, N475, N476, N477, N479, N480, TG2-17A, TG2-17B,
TG2-18A, TG2-18B, TG2-19A, TG2-19B, TG2-20A, TG2-20B)
The medial and lateral intermuscular septa divide the arm into an anterior (flexor)
compartment and a posterior (extensor) compartment. Furthermore, the medial intermuscular
septum consists of two laminae, and the space between them is the neurovascular
compartment. The contents of each compartment are listed below:
anterior (flexor) compartment:
Muscle
Origin
Insertion
Action
Innervation
biceps brachii
short head: tip of
coracoid process; long
head: supraglenoid
tubercule of scapula
tuberosity of flexes forearm, musculocutaneous
radius
flexes arm
nerve (C5,6)
(long head),
supinates
brachialis
anterior surface of
lower one-half of
humerus and
intermuscular septa
coronoid
process of
ulna
flexes forearm
musculocutaneous
nerve (C5,6)
medial
humerus at
mid-shaft
flexes and
adducts arm
musculocutaneous
nerve (C5,6)
coracobrachialis coracoid process of
scapula
posterior (extensor) compartment:
Muscle
Origin
Insertion
Action
Innervation
triceps
brachii
long head: infraglenoid tubercle
of scapula; lateral head:
posterolateral humerus & lateral
intermuscular septum; medial
head: posteromedial surface of
inferior 1/2 of humerus
olecranon
process of the
ulna
extends
radial nerve
forearm; long
head extends
and adducts
arm
anconeus
lateral epicondyle
lateral side of
olecranon and
upper onefourth of ulna
extends
forearm
Neurovascular
structure
ulnar nerve
nerve to
anconeus from
radial nerve
Source
Branches
Supply to:
medial cord
of the
brachial
plexus
palmar cutaneous
Br, dorsal Br,
superficial &
deep Br
motor: flexor carpi ulnaris, flexor
digitorum profundus (ulnar half), abductor
digiti minimi, flexor digiti minimi brevis,
opponens digiti minimi, ulnar 2
lumbricals, palmar & dorsal interossei
sensory: skin of medial side of wrist &
hand & ulnar 1 1/2 digits
neurovascular compartment:
Neurovascular
structure
Source
brachial artery axillary
(continuation
distal to teres
major m.)
median nerve
Branches
deep brachial, sup.
ulnar collateral,
nutrient, inf. ulnar
collateral; terminal
branches are the
radial & ulnar
anterior interosseous,
lateral &
medial cords of palmar br, recurrent
brachial plexus (motor) br, common
palmar digital nn
(1st-3rd)
Supply to:
arm, forearm & hand
motor: pronator teres, flexor carpi
radialis, palmaris longus, flexor
digitorum superficialis, flexor
digitorum profundus (radial half),
flexor pollicis longus, pronator
quadratus, abductor pollicis brevis,
flexor pollicis brevis, opponens
pollicis, radial 2 lumbricals
sensory: skin of radial half of palm
& palmar side of radial 3 1/2 digits
(and nail bed for these digits)
The compartment also contains the basilic vein and several brachial veins.
11. Correlate any fractures of the humerus with functional disruptions of associated muscular and
neurovascular structures. (N426, N434, N477, TG2-19B, TG2-20B)
The humerus can break just about anywhere along its length. The three most common places,
due to relative weakness, are the surgical neck, the distal end of the middle 1/3 of the bone, and
the supracondylar region. With surgical neck fractures, laceration of the axillary nerve and one or
both circumflex humeral arteries could cause a significant problem. In the case of a fracture more
distal along the shaft, the structure most in danger is the radial nerve, which is wrapping around
the bone in the radial groove. According to Wheeless's Textbook of Orthopaedics, radial nerve
palsy of some degree occurs with 18% of humeral shaft fractures.
12. Describe the movements of the shoulder and elbow joints.
The shoulder joint is a ball and socket joint. Movements there include flexion, extension,
abduction, adduction, and circumduction, as well as medial and lateral rotation of the arm. The
elbow joint is a hinge, permitting only flexion and extension.
13. Identify spatial relationships of all associated muscular and neurovascular structures within
the cubital fossa. (W&B 132-134, N447, N479, TG2-23, TG2-24)
The floor of the cubital fossa is the brachialis and supinator muscles, so all of the contents of the
space lie superficial to those two structures. The tendon of the biceps brachii runs through the
middle of the cubital fossa. Medial to it we find the brachial artery (which splits into radial and
ulnar arteries near the inferior border of the cubital fossa). The median nerve lies medial to the
brachial artery as they both enter the forearm. More superficially we find the median cubital
vein, the lateral antebrachial cutaneous nerve, and branches of the medial antebrachial
cutaneous nerve.
Cultural enrichment: Check out these sections from the 1918 version of Gray's Anatomy of the
Human Body! Some of the terms are (of course) out-of-date, but the illustrations are timeless.
The Anterior Divisions (nerves) - The Veins of the Upper Extremity and Thorax - The Axillary
Artery - The Brachial Artery - The Muscles and Fascia¾ of the Shoulder - The Muscles and
Fascia of the Arm - Surface Anatomy of the Upper Extremity - Surface Markings of the Upper
Extremity
Questions and Answers:
14. Define the boundaries of the axillary space.
See #2 above. (N181, TG2-12)
15. How is the axillary vein formed?
It's formed by the union of the brachial veins (which accompany the brachial artery) and the
basilic vein at the inferior border of teres major. (N184, TG2-53)
16. Is the axillary vein a single, paired or plexiform vein?
The axillary is normally a single vein.
17. Do the tributaries of the axillary vein correspond to the axillary arterial branches?
Yes, with the exception of the thoracoacromial vein, whose branches join the axillary vein
independently and the cephalic vein which has no corresponding artery. (N427, N256, TG2-19,
TG2-53)
18. Are the axillary vein's tributaries paired?
Some, such as the brachial veins, are paired. Others, such as cephalic vein, are not. (N184, TG253)
19. Can you see any valves in the veins?
There are valves within the axillary vein, and valves are also located in tributaries where they
join the axillary vein.
20. Establish relationships of axillary artery and vein within the axilla.
At its source, the vein lies on the medial side of the artery, partly overlapping it. Thereafter, in
the upper part of the axilla, the vein lies anterior and inferior to the artery. (N429, N479, TG211)
21. Do you see a separate medial brachial cutaneous n.?
The medial brachial cutaneous nerve is much smaller than the medial antebrachial cutaneous
nerve, and, once the skin of the axilla is removed, it may be difficult to find. It branches from the
medial cord, just proximal to the medial antebrachial cutaneous nerve. It may make a nerve
anastomosis with the intercostobrachial nerve. (TG2-13)
22. What artery accompanies the axillary nerve?
The posterior circumflex humeral artery, a branch of the 3rd part of the axillary artery,
accompanies the axillary nerve through the quadrangular space. (N426, N432, TG2-18, TG219, TG2-20)
23. What does lower subscapular nerve accompany?
Lower subscapular nerve accompanies circumflex scapular artery into the triangular space.
(N426, TG2-13, TG2-15)
24. Note how the three cords of the brachial plexus are derived from the trunks.
See #3 above. (N430, TG2-14)
25. Note course, relations and parts of the axillary artery.
See #6 above. (N427, N429, TG2-15)
26. Note the area of distribution of the axillary artery's branches as well as any accompanying
nerves:
See #6 above. (N427, N429, N430, TG2-13, TG2-15)
27. What is the source of the long thoracic nerve and what is "winged scapula"?
The long thoracic nerve arises from the anterior rami of C5-C7. Winged scapula is a condition in
which the scapula protrudes from the back because it is not held in place by the counterbalancing
forces of the serratus anterior and trapezius muscles. It results from injury to the long thoracic
nerve. See #5 above. (N191, N429, TG2-14)
28. Does the supraspinatus muscle use the fascia spanning the area from the spine to the superior
border of the scapula?
Yes, it arises from the dense fascia covering the muscle. It arises from the medial 2/3 of the walls
of the fossa.
29. Does the subacromial bursa continue laterally deep to the deltoid muscle? Significance?
The subacromial bursa is a "synovial bursa" situated directly under the deltoid muscle, between it
and the supraspinatus tendon and the joint capsule. It has an extension which runs deep to the
acromion and the coracoacromial ligament. The bursa facilitates the movement of the deltoid
muscle over the joint capsule and tendons. (N423, TG2-42)
30. To how much of the supraspinous fossa does the supraspinatus muscle attach?
Although the supraspinatus muscle fills the supraspinous fossa, it arises primarily from the
medial aspects of this fossa. (N426, TG2-06)
31. How are the suprascapular artery, vein, and nerve related to the scapular notch?
The suprascapular notch is bridged by the superior transverse scapular ligament. The
suprascapular nerve passes under the ligament. The suprascapular artery and vein pass over it.
(The navy goes under the bridge, the army goes over.) (N426,N427, TG2-08)
32. How much of the fossa is used for the infraspinatus muscle attachment?
The infraspinatus muscle arises from the whole of the infraspinatus fossa except its lateral 1/4,
and from the overlying infraspinatus fascia and the intermuscular septa. (N425, N426, TG2-06)
33. Trace the nerve, artery, and vein from the supraspinatus to the infraspinatus fossa around the
notch of the neck of the scapula. Does the artery terminate in the infraspinatus muscle?
Semantically, the artery comes to an end, but really it enters into the anastomoses of the shoulder
region, specifically with the circumflex scapular artery. (N426,N427, TG2-08)
34. Is the teres minor muscle separated or fused with the lateral border of the infraspinatus?
The teres minor muscle is often totally fused with the lateral border of the infraspinatus muscle.
(N425, TG2-08)
35. For the question about the rotator cuff, see the treatment of the theme above under the lab
objectives.
See #7 above. (N421,N426,N429,N430, TG2-16Aa>, TG2-16Ba>, TG2-16C)
36. What are the boundaries of the quadrangular space? What does it transmit?
The borders of the quadrangular space are:




inferior: teres major muscle
lateral: humerus
superior: teres minor muscle
medial: the long head of the triceps muscle.
The space transmits the axillary nerve and the posterior circumflex humeral artery. (N426, TG208)
37. Find the circumflex scapular artery in the triangular space. Is there an open anastomosis
between it and the suprascapular artery?
There is usually an open anastomosis between the circumflex scapular artery and the
suprascapular artery. (N426,N427, TG2-08)
38. Identify the circumflex scapular artery. What does it supply? Does it anastomose with the
suprascapular artery?
The triangular space transmits the circumflex scapular artery. This vessel feeds the muscles of
the dorsum of the scapula and participates in the anastomoses described above. It certainly does
anastomose with the suprascapular artery. (N426,N427, TG2-08)
39. Do muscles use the intermuscular septa as attachments?
The lateral and medial heads of triceps brachii and brachialis all use intermuscular septae as part
of their origins.
40. Where do branches of the musculocutaneous nerve enter anterior compartment muscles?
The musculocutaneous nerve is the continuation of the lateral cord of the brachial plexus after
that cord's contribution to the median nerve. The musculocutaneous nerve gives off branches to
the coracobrachialis as it pierces that muscle. It continues downward in the interval between the
brachialis muscle and biceps brachii muscle, giving branches to each. (TG2-17)
41. How does the musculocutaneous nerve terminate, where does it change its name, and does it
have any accompanying arteries?
The musculocutaneous nerve terminates by piercing the brachial fascia lateral to the biceps
tendon a short distance above the elbow. It continues as the lateral antebrachial cutaneous nerve.
It has no accompanying arteries. (N474, TG2-17)
42. How is the neurovascular compartment of the arm formed?
The medial intermuscular septum is divided into two laminae, which, with the overlying brachial
fascia, form the neurovascular compartment. (N435)
43. What are the relations and branches of the median nerve in the arm?
The median nerve has no muscular branches in the arm. Initially it rests atop the brachial artery
in the neurovascular compartment, then comes to lie anterolateral to the brachial artery and is
overlapped laterally by the coracobrachialis muscle. The nerve eventually becomes medial to the
brachial artery, crossing over it at the midarm level. (N435, N475, TG2-17)
44. Where does the ulnar nerve leave the neurovascular compartment?
At approximately mid-arm, the ulnar nerve pierces the posterior layer of the intermuscular
septum to enter the posterior compartment. (N433, N435, N473, N476)
45. Does the ulnar nerve have any branches in the arm?
No, it does not.
46. Is the ulnar nerve accompanied by any vessels in the arm? (N434)
The superior ulnar collateral artery, one of the arteries of the elbow collateral circulation,
accompanies ulnar nerve posterior to the medial epicondyle.
47. Is the brachial vein paired? How is it formed? What does it continue as? Where does the
basilic vein join it?
The brachial vein is a paired set accompanying the brachial artery. It is formed at the elbow by
the union of venae comitantes of the radial and ulnar arteries. It continues as the single axillary
vein, after the two veins join at about the lower border of teres major muscle. (N434, N256,
TG2-53)
48. What are the collateral branches of the brachial artery around the elbow?
The brachial artery gives off two collateral branches for the elbow anastomosis: the superior
ulnar collateral artery at mid-arm, that accompanies the ulnar nerve, and the inferior ulnar
collateral artery, that passes anterior to the medial epicondyle. (N434, TG2-46)
49. Locate the brachial artery and median nerve. What are their relative positions?
Remember TAN - in the cubital fossa, the biceps Tendon lies lateral, the brachial Artery is
intermediate, and the median Nerve is most medial. (N433, TG2-17)
50. Where does the brachial artery divide?
Within the cubital fossa, the brachial artery divides into the radial and ulnar arteries. (N447,
TG2-24)
51. What happens to the median nerve?
The median nerve passes into the forearm through the two heads of pronator teres. (N448, N475,
TG2-24, TG2-25)
52. Separate the brachialis from the brachioradialis muscle along the intermuscular septum
between them and identify the radial nerve. Is it accompanied by vessels? What are they?
The radial nerve is accompanied above the elbow by the radial collateral artery, a terminal
branch of the deep brachial artery. Below the elbow, radial nerve is accompanied by the radial
recurrent artery, that anastomoses with the radial collateral. (N447, N448, TG2-24)
53. What structures in the superficial fascia overlie the cubital fossa? What is their importance?
Danger?
Branches of the medial antebrachial cutaneous nerve cross the medial portion of the cubital
fossa, while the lateral antebrachial cutaneous nerve emerges from beneath the biceps on the
lateral side of the cubital fossa. The median cubital vein also crosses the fossa obliquely,
shunting blood from the cephalic vein up to join the basilic vein. This is a common site for
phlebotomy, and cutaneous nerves may be in danger here. (N480, TG2-02)
54. What nerve is given off to the forearm by the radial nerve as it enters the anterior
compartment?
As the radial nerve pierces the lateral intermuscular septum it gives off the posterior antebrachial
cutaneous nerve, which supplies the skin of the back of the forearm. (N477, TG2-18)