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Anatomy Made
Easy “MSS”
part #10
11 ‫هذا البارت يشمل التفريغ‬
Done By :Dina Naag
Edited by: Awn Academic team
In this part, we are going to
discuss :
1. The axilla boarders and
contents
2. The gaps which are located
within shoulder.
3. The definition and types of
joints.
4. The shoulder joint.
The Axilla = Armpit
• The axilla extends from the
root of the neck into the
upper aspect of the medial
surface of the humerus.
• Axilla is a place where most
of the structure that goes
from the thorax to the
upper extremities pass
through, such as arteries
and brachial plexus.
Axilla
• It located medial to the surgical neck of the humerus and
lateral to the lateral aspect of the thorax upper part (2nd,
3rd, 4th, 5th costal ribs).
• The axilla is pyramidal in shape , with :
1. The apex oriented toward the neck (small inlet)
2. The base practically is going down into the armpit and it is
mainly covered by the skin (large outlet)
• The base is called the axillary fossa, it is a depression within
the axillary region, and it is rectangular in shape
CONTENTS

AXILLARY LYMPH NODES

AXILLARY ARTERY & VEIN

BRACHIAL PLEXUS
BOUNDARIES

APEX  BETWEEN THE
CLAVICLE,SCAPULA AND 1ST RIB

BASE  AXILLARY FASCIA

ANTERIOR :
1.
PECTORALIS MAJOR
2.
Subclavius MUSCLE
3.
clavipectoral fascia

POSTERIOR
1.
SUBSCAPULARIS
2.
LATISSMUS DORSI
3.
TERES MAJOR

MEDIAL
1.
FIRST 4 RIBS
2.
SERRATUS ANTERIOR MUSCLE

1.
LATERAL
BICEPETAL GROOVE OF THE HUMERUS)
Apex
•
•
1.
2.
3.
Upper end of axilla or APEX is
directed into the root of neck
Its triangular in shape 
the clavicle participates
anteriorly
the upper border of the scapula
posteriorly
the first rib medially.
Base
•
Lower end or Base is bounded in
front by the anterior axillary fold
formed by pectoralis major muscle
• Behind by posterior axillary fold
(lateral border of pectoralis) formed
by the tendons of latissimus dorsi
and teres major muscles
• Medially by the chest wall
• Lateraly by the long head of triceps
Take a look at the transverse section of the shoulder,
what can you see?
1.
2.
3.
4.
The scapula
The first rib
The subscapularis that covers the scapula
The serratus anterior which inserts into the vertebral
border and the inferior angle of the scapula
•Anterior
wall:
•
By the pectoralis major,Subclavius, pectoralis
minor, small part of the deltoid and clavipectoral
fascia
New => the deltoid participates in forming the upper
part of the axilla. It has nothing to do with the base
•Posterior
•
By the subscapularis, Latissimus dorsi and
teres major muscles
•Medial
•
wall:
wall:
By the upper 4 or 5 ribs and intercostal spaces
covered by serratus anterior muscle
*note: the long thoracic nerve goes above the
serratus anterior
•Lateral
•
wall:
By the coracobrachialis and biceps muscles in
the bicipital groove of humerus
*note: The lateral wall is triangular in shape, and it’s
much smaller than the medial wall .
The lateral wall contain intertubercular sulcus, it usually
fused with medial wall so sometimes we don’t consider
it as a lateral wall because the intertubercular ligament
covers the intertubercular sulcus.
Contents of Axilla
•
Axillary artery and its
branches (the main
structure everything else is
arranged around it)
•
Axillary vein and its
tributaries
•
Lymph vessels and
lymph nodes
•
Important nerve plexus
the “Brachial Plexus”
which innervates the
upper limb
*note: subclavian
artery gives axillary
and after it exits the
axillary region it gives
the brachial artery
Axillary Artery
•
Is a continuation of subclavian artery
•
Begins at the lateral border of the 1st
rib
•
•
Ends at the lower border of teres
major
It continues as the brachial artery
• Closely related to brachial plexus
cords
• Enclosed with them in the axillary
sheath “”
• Axillary sheath is continuous with
the prevertebral fascia
• Pectoralis minor divides it into 3
parts
Axillary vein
Axillary vein is also covered
by the axillary sheath
The subclavian vein will
divide and give axillary
and cephalic (the axillary
will continue as basilic)
Now this division happens
at the level of the axilla
The cords of brachial
plexus are also covered by
the axillary sheath
(enveloped by the
fascia??)
Brachial plexus
• comes out from the cervical region, then it goes all the way into the arm
and split to give :
1) Radial nerve ‘radial side’
2) Ulnar nerve ‘ulnar side’
3) Median nerve ‘posterior aspect
• The Brachial plexus is a lesser complex plexus of nerves that comes from the
anterior rami of the intervertebral nerves.
The Axillary lymph nodes:
•
are the lymphatics distribution in the axilla, all of
them will drain into main subclavian nodes.
•
That’s why when we have an over-exercise in our
hands, the subclavian nodes will be enlarged and
we’ll be able to palpate them.
•
Practically we have the Pectoral nodes which are
lateral and anterior, they will drain into the
subscapular nodes. Then the
subscapular nodes will drain into the central nodes
that are located within the axilla.
• There’s a connection between the central nodes
and the apical nodes, these apical nodes drain the
breast. Most of the time when we have breast
cancer in a female or in a male, these nodes will be
palpated.
• The central nodes are deep, where the apical and
the subscapular nodes are superficial and can be
visualized and palpated from the armpit
immediately under the skin by holding the hand in
an adduction position.
• In the middle of the axilla we
have a neurovascular bundle.
This bundle is held into a sheath
called the axillary sheath.
• Inside it we have the medial,
lateral and posterior cords of the
brachial plexus in addition to
axillary artery
• More anterior and toward the
medial aspect we have the
axillary vein.
• the Basalic vein and the cephalic
vein join together at the level of
superior aspect of the axillary
region to form the axillary vein
which will continue as the
subclavian vein
the clavipectoral fascia
•
It is a strong sheet of connective tissue that
comes down from the inferior surface of the
clavicle, it Splits above to enclose the subclavius
muscle. Below it splits to enclose the pectoralis
minor muscle, then continues downward as the
suspensory ligament of the axilla which joins the
fascial floor of armpit.
•
So the clavipectoral fascia begins at the clavicle
and ends down into the skin
• It is pierced by 4 important structures which are
found in the anterior wall of the apex; 2
inwards and 2 outwards.
The 2 inwards are: 1) Lymphatics
2) Cephalic vein: penetrates the axilla from
superior and anterior aspect.
The 2 outwards are: 1) Lateral pectoral nerve 2)
Thoracoacromial artery or its branches:
a- Pectoral b- Acromial c- Deltoid d- Clavicular
• deep cervical fascia that covers the
omohyoid and wind around the
lateral aspect of scalenus anterior
and scalenus medius.
• pectoralis fascia that covers the
pectoralis major
• clavipectoral fascia that covers the
Pectoralis minor and the posterior
part of Pectoralis major
• The continuation of the
clavipectoral fascia is axillary fascia.
 In the muscles of the shoulder there are many gaps. These gaps are
Important:
1. Quadrangular space
2. Triangular space.
3. Triangular interval.
Triangular space
Quadrangular space:
•
•
•
•
Is made laterally by the surgical neck of the humerus
superiorly by the inferior margin of the subscapularis muscle
inferiorly by the superior margin of teres major
medially by the long head of the triceps brachii
• The structures passing through the quadrangular space are:
1. axillary nerve
2. Posterior circumflex humeral artery and vein.
Triangular space:
1. The medial margin of the long head of the triceps brachii muscle
2. The superior margin of the teres major muscle.
3. The inferior margin of the subscapularis muscle or teres minor.
• Structures passing through it:
Circumflex scapular artery and vein.
Triangular interval
1) The inferior margin of the teres major muscle
2) The shaft of the humerus
3) The lateral margin of the long head of the Triceps brachii
• Structures passing through it  radial nerve
The Joints:
The Joints:
• A joint is the point where two or more bones meet.
• There are 3 types of the joints:
1) Fibrous (immoveable): found in the sutures.
2) Cartilaginous (partially moveable): in which the end of a bone is
cartilaginous and attached to another cartilaginous surface of another bone
ex. The Ribs, the Vertebrae and symphysis pubis.
3) Synovial (freely moveable) joint
• All of them contain a thin layer of hyaline cartilage and consist of
two ends of bones covered by this layer of hyaline cartilage.
• The movement depends on the amount of cartilage, in which the
fibrous joints contain minimal amount of cartilage compared to the
other types.
• Most of the body joints are Synovial (movable) joints
Synovial Joint:
The bursae are pockets of
synovial fluid located between
the ligaments and the bones
or between the muscles and
the bone.
This will reduce the friction
between them.
So you can see the bursae
underneath the tendon, and
you can see it located
between two bones as in the
shoulder joint. Also you can
see the bursae covering the
capsule to protect it.
Note =>The bursitis is the inflammation of the bursa
Synovial Joints:
• Two bones that come along the side of each other and they have to be covered
•
•
•
•
•
•
by joint cartilage which is Hyaline cartilage “Articular cartilage”.
There’s a distance in the middle of the joint to allow the joint to move, and this
distance is a very sterile space called “synovial cavity” . The sterility comes
from a membrane called “synovial membrane”
The synovial cavity contains a fluid which allow a free movement of the joint,
reduce the pressure and reduce the friction and erosion of the articular
cartilage.
Outer to the synovial membrane, we find a tougher structure called the
Capsule. The capsule could be tight or loose. When a joint is greatly movable,
its capsule will be loose and vice versa.
Outer to the capsule there are Ligaments. These ligaments will hold the joint
together and limit its movement
In addition, there are muscles that act upon the joint and allow certain
movements (flexion, extension, abduction, adduction ...).
The Articular disc(meniscus) is made of hyaline cartilage and located within the
synovial cavity. It’s found in particular joints in the body such as the Knee, the
TMJ and the sternoclavicular joint. In those joints the synovial membrane is
splitted, so we’ll find a complex synovial distribution there
Notes
Certain
structures pass through the joint,
such as the cruciate ligament in the knee ,
or the long head of the biceps femoris
muscle.
The synovial cavity contains nothing other
than the synovial fluid, it's a sterile part of
the joint, nothing penetrates it. Inflammation
of this liquid that exists inside the synovial
cavity is called synovialitis "or it could be
due to inflammation of the membrane".
 When
some people have pain in the knee joint,
they may go to the doctor and inject cortisone
there ,cortisone is very bad for the knee, you
shouldn't inject cortisone inside the joint!
Cortisone is a magical treatment ,it will reduce
the inflammation and the infection in a certain
part, but it'll never give you a cure.You get the
cure by exercising, always by exercise, that will
strengthen the joint itself and reduce the amount
of fluid that's secreted inside the synovial joint,
reduce the inflammation and help the patients to
cope with the pain.
Bursae
 Bursae
are nothing but synovial membranes; pockets.They
are found at the level where there is friction between a
tendon and a bone, or between a ligament and a capsule or a
muscle and a capsule..
1- Small pockets of gelatinous structure
2- sterile
3- very tightly packed
** the connective tissue layer is a very tough membrane ,it
could burst ,it could be inflated ,and inflammation and
infection may occur at this level.
 It separate certain parts that are located around the
joints mainly or between ligaments and bones and
will reduce the friction between the two structures.
**Subacromial bursa is located underneath
the acromion, below the coracoacromial
ligament.
**If It's inflamed you won't be able to elevate
your shoulder, it'll be very painful.
Acromion
of scapula
Coracoacromial
ligament
Subacromial
bursa
Fibrous
articular capsule
Coracoacromial
ligament
Subacromial
bursa
Cavity in
bursa containing
Glenoid cavity synovial fluid
containing
synovial fluid
Hyaline
cartilage
Tendon
sheath
(b)
Synovial membrane
Fibrous capsule
Tendon of
long head
of biceps
brachii muscle
(a)
Humerus
 If you look
over here, you'll be able to see that the
long head of the biceps of the humerus enters inside
the cavity of the shoulder and reaches the upper
portion of the glenoid cavity (it originates from here)
Acromion
of scapula
Coracoacromial
ligament
Subacromial
bursa
Fibrous
articular capsule
Coracoacromial
ligament
Subacromial
bursa
Cavity in
bursa containing
Glenoid cavity synovial fluid
containing
synovial fluid
Hyaline
cartilage
Tendon
sheath
(b)
Synovial membrane
Fibrous capsule
Tendon of
long head
of biceps
brachii muscle
(a)
Humerus
Types of synovial joints:
1) Hinge joint: it produces flexion and extension.
2) Pivot joint: it exists between a head and a fossa.
We can find it at the proximal ends of the radius
and the ulna that’s where the supination and
pronation. In this joint, one bone will wind around
itself and it’ll be held by the Annular ligament
which will fix the joint and allow only the movable
bone to move.
3) Ball-and-socket joint wide-range movement
joint. It exists between a head of a bone and a
depression of another bone.
Ex : the head of the femur and the acetabulum.
• These joints are complex, with few ligaments,
large amount of muscles and loose capsule
4) The condyloid joint: exists within the carpal
bone allow movement on two axes: flexion
and extension; it can also be tilted sideways
(toward the radius and ulna).
5) The gliding joint: Surfaces of these joints are
relatively flat and not very mobile; they allow
only a narrow gliding range (e.g., vertebrae,
certain bones of the carpus).
6) The saddle joint: between the carpal and
metacarpal. It’s like riding on a horse’s back
and only movable in 2 directions (abductionadduction). Resembles the condyloid joint but
allows a wider range of motion; this type of
joint is rare
•
These are synovial joints that exists in the
upper and lower extremities (the hand and
the foot).
TMJ
• In the TMJ we have two synovial cavities, one above
the disc and the other below, but these synovial cavities
adhere at the lateral border of the disc and it appears that
the disc is inside the synovial cavity but actually it’s not. So
the articular disc is usually inter-capsular but not intersynovial.
• The articular discs have different shapes. They could be
rounded or semilunar
The temporomandibular
(jaw) joint
 it occurs
between the articular lower anterior surface
of the temporal bone (mandibular fossa) and the head
of the mandible (mandibular condyle).
 Both the fossa and the condyle are covered by hyaline
cartilage
The Shoulder joint
Shoulder Joint
it's a complex and a simple joint at the
same time..it's complex because of the
muscles that surround the joint and affect
its movement, and because of the wide
range of movement that occurs at this
level. It's simple because it has few
ligaments and a bigger capsule and
because its synovial membrane is
straightforward.
 but this joint occurs
between two parts, one part
coming from the humerus ,which is the
incomplete/half-a-ball part and the very shallow
glenoid cavity which belongs to the lateral upper
part of the scapula.
The cavity is very shallow
(not deep) ,so we need to
deepen this cavity in order
for the head to fit ,we need
to have a cartilaginous
structure that makes this
cavity deeper, and that's what
we call "the glenoid labrum"
triangular shaped
The
glenoid fossa of the scapula is a
depression on the head of the scapula,
between the acromion and coracoid
processes. It joins with the head of the
humerus.
The glenohumeral joint is a
multiaxial synovial ball and socket joint.
The glenoid labrum is a fibrocartilaginous rim
attached around the margin of the glenoid
cavity in the scapula.
It is continuous above with the tendonof
the long head of the Biceps brachii.
It deepens the articular cavity,and
protects the edges of the bone.
goes outside in a triangular way.
Due
to the very limitedinterface of the
humerus and scapula, it is the most
mobile joint of the human body.H O W ?
When
we have a ball that fits in one socket
which is big such as the acetabulum (in the
hip joint) ,the movement will be limited ,
now in this case the movement is wider
because an "incomplete" head will fit in
the glenoid cavity even though we have the
labrum.
Note
 The labrum will act in a different way
with the
long head of the biceps brachi which originates
from the supraglenoid tubercle " a small tubercle
superior to the glenoid cavity" ,when it comes
to the joint, this tendon will spread laterally and
inferiorly to be part of what we call "the glenoid
labrum" so it'll help the labrum to be stable and
will drag it somehow to prevent the head (of the
humerus) from dislocation In case of flexion and
extension of the shoulder joint.
 Capsule
surrounds the joint and is attached
◦ medially to the margin of the glenoid cavity
outside the labruum
◦ laterally it is attached to the anatomic neck of the
humerus.
the capsule will run from
the edges of the glenoid
surface more lateral to
the anatomical neck of
the humerus reaching
the two elevations on
the lateral aspects of the
humerus.
 The
capsule is thin and lax, allowing a wide
range of movement.
 It is strengthened by fibrous slips from the
tendons of the the rotator cuff muscles.
Note
The loosest part of this capsule is the inferior part,
the inferior part is like a pocket, it'll allow the
abduction and the extension of the arm at the
shoulder level .if it was tight and runs obliquely
from the inferior aspect of the anatomical neck of
the humerus to the lower part of the glenoid
cavity ,the movement will be limited ,that's why
the capsule is lax and big.
Synovial membrane :
 This lines the
capsule and is attached to the
margins of the cartilage covering the articular
surfaces. It forms a tubular sheath around the
tendon of the long head ofthe biceps brachii
 This
is the synovial membrane, encircling the
inside, this synovial membrane on the anterior
aspect will expand and form a small bursa and
that will reduce the friction between the
subscapularis muscle and joint capsule.
There are three glenohumeral ligaments (between
the glenoid cavity and the humerus)  in the
glenohumeral joint.
(1)The superior glenohumeral ligament
(SGHL).This ligament resists inferior
translation of the humeral head in the
adducted shoulder.
(2)The middle glenohumeral ligament
(MGHL).This ligament resists inferior
translation in the adducted and externally
rotated shoulder.
(3)The inferior glenohumeral ligament (IGHL).
This resists humeral head anterior and
posterior translation.
Coracoacromial
ligament (in the coracoacromial join)
prevents the superior dislocation of the joint
Coracoclavicular ligament
 which Is composed of Trapezoid and
Conoid ligaments
 The shoulder
is made of
three joints
practically,
but the most
important is
the
glenohumeral
joint.
The capsule of the shoulder is
reinforced by the
coracohumeral ligament
The transverse humeral
ligament is another ligament
into which the tunnel between
the two elevations on the
lateral aspect of the humerus,
allow the synovial sheet that
covers the long head of the
biceps to pass through to the
inside of the capsule but not
inside the synovial membrane.
The coracoclavicular ligament is
made of two bands that connect
the inferior surface of the clavicle
with the superior surface of the
coracoid process.
 The
transverse humeral ligament strengthens the
capsule and bridges the gap between the two tuberosities.
 The coracohumeral ligament strengthens the capsule
above and stretches from the root of the coracoid
process to the greater tuberosity of the humerus.
Remember :
bursae in the capsule that aid mobility:
Subacromial bursa (between joint capsule and
acromion of scapula).
Subscapular bursa (between joint capsule and
tendon of subscapularis muscle)
The movements of this joint
are:
•
•
•
•
Flexion , Extension
Abduction , Adduction
Lateral Rotation , Medial Rotation
Circumduction .
Clinical aspect
• A subglenoid displacement of the head of the
humerus into the quadrangular space can
cause damage to the axillary nerve. This is
indicated by paralysis of the deltoid muscle
and loss of skin sensation over the lower half
of the deltoid.
• Downward displacement of the humerus can
also stretch and damage the radial nerve.