Muscles of the Pectoral & Shoulder region

Dr. Sama-ul-Haque Dr. Rania Jabr

Objectives• Identify the bony components of the shoulder.

girdle including the Clavicle, Scapula and

Humerus.

• Describe how primary muscles are responsible

for the following shoulder motion: adduction,

abduction, flexion, extension.

Bony Skeleton

1-Bones of the Pectoral Girdle: Clavicle and Scapula2- Arm : Humerus. 3-Forearm : Radius & Ulna.4-Wrist : Carpal bones 5-Hand: Metacarpals & Phalanges

Bones of the Upper Limb

Clavicle

It is considered as a long bone but it has no medullary (bone marrow) cavity.

Clavicle

Scapula (anterior)

Scapula (posterior)

Articulations of clavicle• Clavicle articulates

Medially with the manubrium of the Sternum at the Sternoclavicular joint .

• Laterally with the Scapula at the Acromioclavicular joint

• Inferiorly with the 1st rib at the Costoclavicular Joint

Pectoral (Shoulder) Girdle

• connects the upper limb to the axial skeleton

• formed of two bones: Clavicle and Scapula.• formed of two joints1. Sternoclacvicular joint2. Acromioclavicular joint

SA

Humerus

Anterior

Posterior

Movements of the shoulder joint:

Abduction / adductionFlexion / extension

Rotation – internal (medial) -external (lateral)

Movements of the shoulder girdle: (increase range of movement of upper limb)

Protraction / RetractionElevation / Depression

Rotation:Superior / Inferior

Circumduction

Muscles of the (Pectoral) Region

• muscles of the pectoral region.Pectoralis major.Pectoralis minor.Subclavius.Serratus anterior.

Pectoralis Major

Clavicular head:Medial ½ of front of the clavicle.

Sternocostal head:Sternum.Upper 6 costal cartilages.

Lateral lip of bicipital groove.

• Nerve supply: medial & lateral pectoral nerve

• Action : Adduction and medial rotation of the arm. Clavicular head helps in flexion of arm (shoulder).

Pectoralis Minor

3

4

5

Coracoid process.

Nerve supply: medial pectoral nerveAction:• Depression & protraction

of the shoulder.• Elevate the ribs during

deep inspiration.

Subclavius

Nerve supply:• Nerve to subclaviusAction: • Fixes the clavicle during movement of

shoulder joint.

1st ribSubclavian groove in the inferior surface of clavicle.

Nerve supply: • Long thoracic nerve.Action:• Depression & protraction of

the scapula (boxing) • Raising the arm above 90

degree (climbing).• Accessory muscle of

respiration

Serratus anterior

Upp

er 8

ribs

Front of the medial border of scapula.

Injury of long thoracic nerve: Winged Scapula:

Subscapularis

Cause; Paralysis of serratus anterior as it is "big swing muscle" or "boxer's muscle”Antagonist of Rhomboids

Injury of long thoracic nerve

Deltoid

Nerve supply:Axillary nerve

Action:Anterior fibers : Flexion, medial rotation Middle fibers: abduct arm from 15°- 90°.Posterior fibers : Extension, lateral rotation

Lateral third of clavicle, acromion, spine of scapula

Deltoid tuberosity of humerus

D

DELTOID MUSCLE

Axillary nerve injury

Deformity: flat shoulderCause: fracture surgical neck of humerus.Clinical signs: 1. Paralysis of deltoid

and teres minor.2. Loss of abduction

from 15-90.

TRAPEZIUS External occipital protuberance.Ligamentum nuchae.Spine of C7Spine of T1-T12

Clavicle, acromion and spine of scapula

Nerve supply: Spinal part of accessory (11th cranial) nerve.

Action:Abduction > 90 (climbing)Upper fibers: elevate scapula.

Middle fibers: retract scapulaLower fibers: depress scapula.

• Both deltoid and Trapezius muscles give the shoulder its characteristic shape.

Poland Syndrome

CongenitalAbsence of

Pectoralis Major,Partial or complete

absence