Pectoral Region Anatomy PDF

Pectoral region Pectoralis major muscle: Origin: 2 heads Clavicular head: Front of medial half of the clavicle Sternocostal head: Front of the sternum and upper 6 ribs Insertion: Lateral lip of bicipital groove by U- shaped bilaminar tendon Nerve supply: Medial and lat...

Pectoral region Pectoralis major muscle: Origin: 2 heads Clavicular head: Front of medial half of the clavicle Sternocostal head: Front of the sternum and upper 6 ribs Insertion: Lateral lip of bicipital groove by U- shaped bilaminar tendon Nerve supply: Medial and lateral pectoral nerve Action: 1- Whole muscle adduction and medial rotation of the arm. 2- Clavicular head flex the arm anteromedially. 3- Sternocostal head return the fully flexed or extended arm to the resting position acts with latissimus dorsi if the arm raised and fixed to raise the trunk (latissimus dorsi) Pectoralis minor muscle: Origin: 3rd to 5th ribs near their costal cartilages Insertion: Medial border and superior surface of coracoid process of scapula Action: Stabilizes scapula by drawing it inferiorly and anteriorly against thoracic wall (Protraction of the scapula) Innervation: Medial pectoral nerves. Pectoralis minor syndrome: It compresses the brachial plexus over the coracoid process causing pain and numbness Subclavius muscles: Origin : Junction of 1st rib and Its costal cartilage ( 1st costochondral junction) Insertion : Groove of sublavius in the inferior Surface of the middle third of the clavicle. Action: Steadies the clavicle during Movements of shoulder girdle. Nerve supply: Nerve to subclavius Serratus anterior muscle: Origin: by 8 serratus anterior fleshy digitations from upper 8 ribs & fascia covering intercostal muscles Insertion: ventral aspect of medial border of scapula Superior angle: 1st digitation → superior angle of scapula Subscapular fossa and medial border : 2nd & 3rd digitations→ medial border of scapula Inferior angle: Lower 5 digitations into inferior angle Nerve supply: nerve to serratus anterior ( long thoracic nerve ) C5,6,7 from roots of brachial plexus Action:  1) Protraction & depression of the scapula  2) With trapezius, produces upward rotation of scapula during raising the arm above the head  3) Acting from its origin, it can elevate the ribs as in forced inspiration Applied Anatomy:  Injury of long thoracic nerve leads to paralysis of serratus anterior → winging of the scapula ( prominence of medial border of scapula i.e. it does not become in contact with the thoracic wall) PECTORAL FASCIA: thin membrane that invests the pectoralis major muscle. Attachments:  Superiorly: to the clavicle.  Inferiorly: continuous laterally with the axillary fascia and medially with the fibrous sheath of the rectus abdominis.  Medially: to the front of the sternum.  Laterally: continuous with fascia that covers the deltoid muscle (shoulder). The Clavipectoral fascia Medially: It blends with fascia over the first two intercostal spaces Laterally: it is thick and dense and is attached to the coracoid process Structures piercing the Clavipectoral fascia: 1. Thoracoacromial artery. 2. Cephalic vein to terminate into the axillary vein. 3. Lateral pectoral nerve. 4. Lymph vessels.