Download MUSCLES OF THE PECTORAL GIRDLE

MUSCLES OF THE PECTORAL GIRDLE
LEARNING OBJECTIVES
At the end of this lecture the student should be able to:
• Know the role of muscles of pectoral region in stabilizing the
pectoral girdle.
• Enumerate the muscle of pectoral girdle .
• Describe the attachments of muscle of pectoral girdle, nerve
supply and actions ( Pectoralis Major and minor,
• Subclavius,Trapezius,Latissimus Dorsi,Rhomboid major and
minor,Levator Scapulae and Serratus anterior).
• Discuss the clavi-pectoral fascia.
• Know the triangle of auscultation.
• Mention the nerves and blood vessels of this region.
PECTORAL GIRDLE
• The pectoral girdle or shoulder girdle is the set of bones
which connects the upper limb to the axial skeleton on each
side.
• Consists of the clavicle and scapula
PECTORAL GIRDLE
• The only joints between the shoulder girdle and axial skeleton are
the sternoclavicular joints on each side.
• No joint exists between each scapula and the rib cage; instead the
muscular connection between the two permits relatively great
mobility of the shoulder girdle in relation to the pelvic girdle.
PERCTORAL GIRDLE MUSCLES:
• Muscles of the pectoral girdle broadly are divided into
• Anterior axioappendicular group
• Posterior axioappendicular group
ANTERIOR AXIOAPPENDICULAR MUSCLES
Also called
Thoracoappendicular or
pectoral muscles
• Four muscles
– Pectoralis major
– Pectoralis minor
– Subclavius
– Serratus anterior
PECTORALIS MAJOR
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Large fan shaped
Covers superior part of thorax
Has clavicular and sternocostal heads
Its inferior border forms Ant. Axillary fold
Pectoralis major and adjacent deltoid forms the narrow
deltopectoral groove in which cephalic vein runs
• Pectoralis major along with clavicle forms clavipectoral or
deltopectoral triangle
PECTORALIS MINOR
• Lies beneath Pectoralis major
• An imp.landmark for structures in axilla
• With coracoid process makes a bridge beneath which vessels and
nerves pass
SUBCLAVIUS
• Lies almost horizontally when the arm is in anatomical position
• Located inferior to clavicle and affords some protection to the
subclavian vessels and the superior trunk of brachial plexus if
clavicle fractures
SERRATUS ANTERIOR
• Saw toothed appearance, also called boxer’s muscle
• Overlies lateral part of thorax and forms medial wall
of axilla
• Holds scapula against thoracic wall while doing pushups
Attachments of muscles of ant.axioappendicular
group
Posterior Axioappendicular Muscles
• Also called scapulohumeral muscles
• Divided into 3 groups
• Superficial posterior Appendicular (extrinsic shoulder) muscles
– Trapezius
– Latissimus dorsi
• Deep posterior Appendicular (extrinsic shoulder) muscles
– Levator scapulae or rhomboids
• Scapulohumeral (intrinsicshoulder) muscles;
– Deltoid
– Teres major
– 4 rotator cuff muscles (supraspinatus, infraspinatus, teres
minor and subscapularis)
TRAPEZIUS
• Large, triangular muscle, covers the posterior aspect of neck
and superior half of trunk
• Have 3 types of fibres
• Superior fibres; elevate scapula
• Middle fibres; retract scapula
• Inferior fibres; depress scapula
• Origin
Medial third superior nuchal line
– External occipital protuberance
– Nuchal ligament
– Spinous processess of C7-C12 vertebrae
Insertion
– Lateral third of clavicle;
– Acromion
– Spine of scapula
Innervation
Motor
– Accessory nerve (CN XI)
Sensory
– C3, C4 spinal nerves
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LATISSIMUS DORSI
• Widest muscle of the back
• Climbing muscle
• Large fan shaped muscle passes from trunk to
humerus
• Origin
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Spinous processes of inferior 6 thoracic vertebrae
Thoracolumbar fascia
Iliac crest
Inferior 3 or 4 ribs
• Insertion
– Floor of intertubercular groove of humerus
• Innervation
– Thoracodorsal nerve (C6,C7,C8)
LEVATOR SCAPULAE
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• Superior third lies deep to sternocleidomastoid,while inferior
third lies deep to trapezius.
• Function
– Elevates scapula
– Tilts its glenoid cavity inferiorly by rotating scapula
• Origin
– Posterior tubercle of transverse processes of C1-C4 vertebrae
• Insertion
– Medial border of scapula superior to root of spine
• Innervation
– Dorsal scapula (C5)
– Cervical nerve (C3,C4)
RHOMBOIDS
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Major and minor
Forms oblique equilateral parrallelogram
Lies deep to trapezius
Innervation
– Dorsal scapular nerve (C4,C5)
• Function
– Retract scapula and fix scapula to thoracic wall
• Rhomboid minor
• Origin
– Nuchal ligament
– Spinous processes of C7-T1
• Insertion
– Scapular spine
• Rhomboids major
• Origin
– Spinous processes of T2-T5
• Insertion
– Medial border of scapula from spine to inferior angle
SCAPULOHUMERAL (INTRINSIC SHOULDER) MUSCLES
Deltoid
Teres major
Rotator cuff
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
• Thick ,powerful, coarse textured forming rounded contour
of the shoulder
• Shaped like delta
• Has unipennate anterior and posterior parts
• Multipennate middle part
• Origin
– Clavicle
– Acromion
– Spine of scapula
• Insertion
– Deltoid tuberosity of humerus
• Function
– Flexor and medial rotator of arm
– Abducts and laterally rotates arm
• Innervation
– Axillary nerve (C5,C6)
SUPRASPINATUS
• Origin
– Scapular supraspinator fossa
• Insertion
– Greater tubercle of humerus
• Function
– Abductor of arm
• Innervation
– Suprascapular nerve (C4,C5,C6)
INFRASPINATUS
• Origin
– Scapular infraspinator fossa
• Insertion
– Greater tubercle of humerus
• Function
– External or lateral rotator
– Upper posterior border of musculotendinous cuff
TERES MINOR AND MAJOR
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Teres minor
Origin
– Lateral border of scapula
Insertion
– Greater tubercle of humerus
Function
– External or lateral rotator
– Lower posterior border of musculotendinous cuff
Innervation
– Axillary nerve (C5,C6)
Teres Major
Origin
– Inferior angle of scapula
Insertion
– Intertubercular groove of humerus
Function
– Adducts and medially rotates arm
Innervation
– Lower subscapular nerve (C5,C6)
SUBSCAPULARIS
• Origin
– Scapular subscapular fossa
• Insertion
– Lesser tubercle of humerus
• Function
– Chief internal and medial rotator
– Anterior border of musculotendinous cuff
• Innervation
– Upper and lower subscapular nerves (C5,C6,C7)
REFERENCES
• Gray’s textbook of anatomy
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