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

Bones of the Upper Limb 1-Bones of the Pectoral Girdle: Clavicle and Scapula 2- Arm : Humerus. 3-Forearm : Radius & Ulna. 4-Wrist : Carpal bones 5-Hand: Metacarpals & Phalanges

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 joints Sternoclacvicular joint Acromioclavicular joint A S

Humerus

Anterior acromion anatomical neck coracoid process Lesser tubercule glenoid cavity surgical neck anatomical neck Greater tubercule Lesser tubercule bicipital groove

Posterior Acromioclavicular joint Supraspinous Fossa anatomical neck Spine Supraspinous Fossa Infraspinous Fossa Radial Groove Deltoid Tuberosity surgical neck anatomical neck Acromioclavicular joint

Movements of the shoulder joint : Abduction / adduction Flexion / extension Rotation – internal (medial) - external (lateral) Movements of the shoulder girdle : (increase range of movement of upper limb) Protraction / Retraction Elevation / Depression Rotation: Superior / Inferior Circumduction

Muscles of the (Pectoral) Region Pectoralis major. Pectoralis minor. Subclavius. Serratus anterior.

Pectoralis Major Clavicular head: Lateral lip of bicipital groove. 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 Coracoid process. 3 4 5 Nerve supply: medial pectoral nerve Action: Depression & protraction of the shoulder. Elevate the ribs during deep inspiration.

Subclavius Subclavian groove in the inferior surface of clavicle. 1st rib Nerve supply: Nerve to subclavius Action: Fixes the clavicle during movement of shoulder joint.

Serratus anterior Upper 8 ribs Nerve supply: Action: Front of the medial border of scapula. Upper 8 ribs Nerve supply: Long thoracic nerve. Action: Depression & protraction of the scapula (boxing) Raising the arm above 90 degree (climbing). Accessory muscle of respiration

Injury of long thoracic nerve Subscapularis en.wikipedia.org/wiki/Serratus_anterior_muscle Injury of long thoracic nerve: Winged Scapula: Cause; Paralysis of serratus anterior as it is "big swing muscle" or "boxer's muscle” Antagonist of Rhomboids

Deltoid Action: Nerve supply: Lateral third of clavicle, acromion, spine of scapula Deltoid tuberosity of humerus Nerve supply: Axillary nerve Action: Anterior fibers : Flexion, medial rotation Middle fibers: abduct arm from 15°- 90°. Posterior fibers : Extension, lateral rotation

D

DELTOID MUSCLE

Axillary nerve injury Deformity: flat shoulder Cause: fracture surgical neck of humerus. Clinical signs: Paralysis of deltoid and teres minor. Loss of abduction from 15-90.

TRAPEZIUS External occipital protuberance. Ligamentum nuchae. Spine of C7 Spine 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 scapula Lower fibers: depress scapula.

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

Poland Syndrome Congenital Absence of Pectoralis Major, Partial or complete absence