Transcript deltoid muscles

Region of upper limb attachment to the trunk.
Proximal segment of limb that overlaps parts of the trunk
(thorax and back) and lower lateral neck.
Shoulder
includes
Pectoral
Scapular
Deltoid regions of the upper limb
lateral part (greater supraclavicular fossa) of lateral cervical region.
Overlies half of the pectoral girdle.
The pectoral (shoulder) girdle is a bony ring, incomplete
posteriorly, formed by:
Scapulae and clavicles
completed anteriorly by the manubrium of the sternum
(part of the axial skeleton).
Bone framework of the shoulder
Clavicle & scapula [form pectoral girdle-shoulder girdle-]
&
Proximal end of humerus
The superficial muscles of the
shoulder
trapezius & deltoid muscles
together form the smooth
muscular contour over the
lateral part of the shoulder.
Connect scapula to trunk &
clavicle to arm.
.
The 3 joints in the shoulder complex :
Sternoclavicular joint
Acromioclavicular joint
Glenohumeral joint
Muscles
The two most superficial muscles of the shoulder are the
trapezius and deltoid muscles. Together, they provide the
characteristic contour of the shoulder:
Trapezius attaches scapula & clavicle to the trunk
Deltoid attaches scapula & clavicle to the humerus
Both the trapezius and deltoid are attached to opposing
surfaces and margins of the spine of the scapula,
acromion, and clavicle.
The scapula, acromion, and clavicle can be palpated
between the attachments of trapezius and deltoid.
SUPERFICIAL POSTERIOR AXIOAPPENDICULAR
MUSCLES
EXTRINSIC SHOULDER MUSCLES
Trapezius & latissimus dorsi
• Descending (superior) fibers elevate the scapula (e.g.,
when squaring the shoulders).
• Middle fibers retract the scapula (i.e., pull it posteriorly).
• Ascending (inferior) fibers depress the scapula and
lower the shoulder.
Movement to 180 degrees (elevation) is brought about by
rotation of the scapula upwards by the trapezius and
serratus anterior.
 Passes from the trunk to the humerus and acts directly
on the glenohumeral joint and indirectly on the pectoral
girdle (scapulothoracic joint).
 In combination with the pectoralis major, the
latissimus dorsi is a powerful adductor of the humerus
and plays a major role in downward rotation of the
scapula in association with this movement.
Levator scapulae & rhomboids
Provide direct attachment of
appendicular skeleton to the axial skeleton
SCAPULOHUMERAL
(INSTRINSIC SHOULDER) MUSCLES
6 scapulohumeral muscles
Deltoid, teres major, supraspinatus, infraspinatus,
subscapularis, and teres minor
pass from scapula to humerus
Act on the glenohumeral joint.
All the intrinsic muscles but the deltoid and the
subscapularis are muscles of the posterior scapular region.
Large and triangular in shape
Base attached to the scapula and clavicle
Apex attached to the humerus
Originates along a continuous
U-shaped line of attachment to clavicle & scapula
mirroring the adjacent insertion sites of the trapezius muscle.
Inserts into deltoid tuberosity on the lateral surface of
the shaft of the humerus.
Major function:
Abduction of the arm
beyond the initial 15° accomplished by supraspinatus
Innervation:
Axillary nerve
branch of the posterior cord of the brachial plexus
 Thick, triangular muscle
 Lies on the costal surface of the scapula
 Originates from the
subscapular fossa on the
anterior surface of the
scapula
 Attaches to the lesser
tubercle of the humerus
Primary medial rotator of the arm
Adducts the arm.
Joins the other rotator cuff muscles in holding the head
of the humerus in the glenoid cavity during all
movements of the glenohumeral joint (i.e., it helps
stabilize this joint during movements of the elbow, wrist,
and hand).
Innervation: Superior and inferior subscapular nerves
The posterior scapular region occupies the posterior aspect of
the scapula and is located deep to the trapezius and deltoid
muscles.
Contains 4 muscles
pass between the scapula and proximal end of humerus:
supraspinatus, infraspinatus, teres minor, teres major
The posterior scapular region also contains part of one
additional muscle, the long head of the triceps brachii,
which passes between the scapula and the proximal end
of the forearm.
This muscle, along with other muscles of the region and
the humerus, participates in forming a number of spaces
through which nerves and vessels enter and leave the
region.
 Originate from 2 large fossae, 1 above and 1 below the
spine, on the posterior surface of the scapula.
 Insert on greater tubercle of the humerus.
 Supraspinatus initiates abduction of the arm.
 Infraspinatus laterally rotates the humerus.
 A cord-like muscle
 Originates from a flattened area of the scapula
immediately adjacent to its lateral border below the
infraglenoid tubercle.
 Inserts on inferior facet of greater tubercle of humerus.
 Laterally rotates the humerus and is a component of the
rotator cuff.
 Originates from a large oval region on the posterior
surface of the inferior angle of the scapula.
 Attaches to the medial lip of the intertubercular sulcus
on the anterior surface of the humerus.
 Medially rotates and extends the humerus.
4 intrinsic shoulder muscles
1) Supraspinatus
(SITS muscles)
2) Infraspinatus
3) Teres minor
4) Subscapularis
Form a musculotendinous
rotator cuff around the
glenohumeral joint.
Insertion exception:
Supraspinatus
Infraspinatus
Teres minor
greater tubercle
Subscapularis
lesser tubercle
Functional exception:
All except supraspinatus are rotators of the humerus
Supraspinatus, besides being part of the rotator cuff,
initiates and assists the deltoid in the first 15° of abduction
of the arm.
Suprascapular foramen
The route through which structures pass between the
base of the neck and the posterior scapular region.
Formed by
suprascapular notch
of scapula
&
superior transverse
scapular
(suprascapular)
ligament,
which converts the
notch into a foramen.
The suprascapular nerve passes through the
suprascapular foramen;
Suprascapular artery & suprascapular vein follow the same course as
the nerve, but normally pass immediately superior to the superior
transverse scapular ligament and not through the foramen.
Quadrangular space
Triangular space
Triangular interval
The two major nerves of the posterior scapular region:
Suprascapular & Axillary nerves
originate from the brachial plexus in the axilla.
Originates where?
Base of the neck from superior trunk of brachial plexus
Reach where through which space?
Posterior scapular region through suprascapular foramen
Which muscles innervates ?
Supraspinatus muscle & infraspinatus
Originates where?
Posterior cord of brachial plexus
Reach where through which space?
From the posterior wall of axilla to posterior scapular
region through quadrangular space
Which muscles innervates ?
Deltoid & teres minor
Cutaneous branch?
Superior lateral cutaneous nerve of the arm
carries general sensation from the skin over the
inferior part of the deltoid muscle.
3 major arteries in the posterior scapular region
 Suprascapular artery
 Posterior circumflex humeral artery
 Circumflex scapular artery
These arteries
contribute to an
interconnected
vascular network
around the scapula.
Posterior circumflex humeral artery anastomoses with anterior
circumflex humeral artery and also with branches from:
profunda brachii
(brachial artery)
suprascapular
.
(subclavian
artery)
thoracoacromial
(axillary artery)
arteries
A system connecting each subclavian artery and the
corresponding axillary artery, forming an anastomosis around the
scapula.
It allows blood to flow past the joint regardless of the position of the arm.
It includes:
transverse
cervical artery
.
(subclavian artery)
transverse scapular artery
(subclavian artery)
subscapular artery
(axillary artery)
branches of thoracic aorta
This collateral circulation allows for
blood to continue circulating if the
subclavian is obstructed.
Testing the deltoid muscle
 To test the deltoid (or the function of the axillary nerve that
supplies it), the arm is abducted, starting from approximately
15°, against resistance.
 If acting normally, the deltoid can easily be seen and palpated.
A clinical syndrome resulting from compression of the axillary nerve
and posterior circumflex humeral artery in the quadrilateral space
The passage of the axillary nerve backward from the
axilla through the quadrangular space makes it particularly
vulnerable here to downward displacement of the humeral
head in shoulder dislocations or fractures of the surgical
neck of the humerus.
Paralysis of the deltoid and teres minor
Cutaneous branches of the axillary nerve, including the
upper lateral cutaneous nerve of the arm
a loss of skin sensation over the lower half of the deltoid
muscle.
Movements of the shoulder girdle
Abduction of the shoulder is initiated by the supraspinatus; the
deltoid can then abduct to 90 degrees.
Further movement to 180 degrees (elevation) is brought about
by rotation of the scapula upwards by the trapezius and
serratus anterior.
As soon as abduction commences at the shoulder joint, so the
rotation of the scapula begins.
Principal muscles acting on the shoulder joint
Abductors
Supraspinatus
Deltoid
Adductors
Pectoralis major
Lattisimus dorsi
Extensors
Teres major
Lattisimus dorsi
Deltoid (posterior fibres)
Flexors
Pectorali major
Coracobrachialis
Deltoid (anterior fibres)
Medial rotators
Pecroralis major
Lattisimus dorsi
Teres major
Deltoid (anterior fibres)
Subscapularis
Lateral rotators
Infraspinatus
Teres minor
Deltoid (posterior
fibres)