The Pecs are the main chest muscles. The chest is made up of 2 muscles, the pectoralis major and pectoralis minor. This page has a brief overview of the anatomy of the chest muscles.
The pectoral region is the region on the front of the shoulder. The pectoralis major is the larger of the 2 chest muscles and it covers up the pec minor.
When most people refer to the chest they are referring to the pectoralis major since it forms the bulk of the chest region. The pec major is one muscle but it has 2 portions-- a clavicular head and a sternal head.
The clavicular head is sometimes referred to as the upper pec, but the sternal head makes up the bulk of this chest muscle and is the middle and lower portion of the pectorals.
Origination/ Starting Point:
The clavicular head (upper pec) starts of the medial half of the clavicle, and the sternal head (middle and lower pec) starts on the anterior surface of the clavicle, costal cartilage of the first 6 ribs, and the aponeurosis of the external oblique muscle.
Insertion/ Ending Point:
Both portions of the pectoralis major insert on the lateral lip of the bicipital groove of the humerus
Both parts of the pectoralis major will move the arm back towards the side (adduction), pull the arm across the chest (horizontal adduction) and turn the shoulder inwards (internal rotation).
When the upper portion works by itself it can assist with bringing the shoulder straight forwards (shoulder flexion).
The pectorals will also help to stabilize the shoulder joint during dynamic movements or isometric exercises.
And lastly, the pectoral may also be an accessory breathing muscle. When the arm is fixed the pecs can pull on the ribs to slightly expand the rib cage to increase lung volume.
The pectoralis major is innervated by the medial and lateral pectoral nerves and get some contribution from the nerve roots at C5-T1.
The pectoralis minor is located underneath the pectoralis major, so you cannot see the pec minor when you are looking at someone who is in really good shape.
The Pectoralis Minor starts on the 3rd, 4th, and 5th ribs.
The Pec Minor inserts on the coracoid process of the scapula.
The Pec Minor is innervated by the medial pectoral nerve.
The pec minor stabilizes the scapula by holding it against the back of the thoracic cavity.
It also pulls the scapula forwards (protraction of the scapula).
Tight chest muscles can affect the position of the shoulders, limit shoulder range of motion, and increase the likelihood of developing shoulder injuries.
The pec major and minor work together to move the scapula and the shoulder as a unit.
Compound exercises like the barbell bench press or dumbbell bench press work the pecs, shoulders, and triceps all at the same time.
The pectorals will also work during chest flyes, push ups, and dips.
Choose a variety of chest exercises, and mix up your workout to keep it fun and challenging.
Yours in health,
Dr. Charles PT/PT
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