Pectoralis Major muscle origin insertion nerve supply and actions
Pectoralis major derives from the Latin word “pectus,” meaning breast is a broad, fan-shaped convergent muscle in the pectoral region and the most exterior ones. Pectoralis major is a paired muscle located at the fore surface of the thoracic cage. Bodybuilders call pectoral muscle pecs muscle. According to its origin, it is categorized into three types; clavicular, sternocostal, and abdominal. The pectoralis major is responsible for deep enforced breathing inspiration but not expiration.
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Pectoralis Major Origin and Insertion:
The pectoral muscle is made of two heads, the clavicular and the sternocostal head. The former originates from the fore surface of the medial half of the clavicle, and the latter is larger of the two. Sternocostal head originates from the anterior surface of manubrium, superior six costal cartilages, the body of the sternum, and from the outside part of the external oblique muscle. All three parts of pectoral muscle laterally coverage and pectoralis major insertion to the greater the tubercle of the humerus (the largest and longest bone of the upper limb). Pectoralis major origin from the medial half of the clavicle and from upper costal cartilages (1-6) and the aponeurosis of the external oblique.
Functions:
Pectoralis major muscle overall function is adduction and internal rotation of the arm on the shoulder joint. The movement of adduction is closely associated with the median plane. This movement usually occurs on the anterior plane around an anteroposterior axis. Legs and arm movements are classic examples of adduction and abduction movements. The arm and leg move relative to the shoulder and hip, respectively. The clavicular part of the Pectoralis major muscle helps the arm to flex up to 90 degrees, and the sternocostal part aids the extension of the flexed arm pulling down. Pectoralis major functions are internal arm rotation, arm adduction around the shoulder joint, and arm flexion and extension.
Nerve and Blood Supply
Pectoralis major nerve supply comes from the brachial plexus. C5, C6, C7 are lateral pectoral nerves to the clavicular head, and C8, T1 medial pectoral nerve to the sternocostal head, which stems from the brachial plexus. The brachial plexus is a network of nerves from where all motor and sensory nerves of the upper extremity derive. The pectoral branches of the thoracoacromial artery supply blood to the Pectoralis major muscle. The perforating branches of the internal thoracic artery also vascularize the pectoral muscle. The thoracoacromial artery is a short artery arising from the axillary artery.
Pectoralis Minor
The Pectoralis minor lies below the Pectoralis major muscle and both constitute the anterior part of the axilla region. The pectoralis minor originates from the third to fifth ribs and inserts into the scapula; it stabilizes the scapula by drawing it anteroinferior against the thoracic wall.
Pectoralis Major Pain
Pectoralis major pain occurs when an individual pushes a heavy object away from his chest. This phenomenon can occur while weight training or bench press exercises. During bench press exercise, the muscle requires a substantial amount of strength to lift the lower part of the bar coupled with overstretching of the muscle. The combined effects insert too much pressure on the pectoralis major, which can result in muscle tear or scar. The first symptom of pectoralis major muscle tear is abrupt pain. The pain generally starts from the armpit region and is sometimes experienced across the chest. At the same time, the person experiences something tearing inside the chest.
In Pectoralis major pain, the person may continue with the activity with minor pain experience. The pain may gradually increase as the muscle cools down with bleeding and swelling around the wounded muscle. The pectoralis major becomes stiff and taut. These other symptoms may arise, such as reduced range of movement, rigidity, weakness, swelling/inflammation, and numbness in that area.
Pectoralis major stretch is beneficial for pectoralis major/minor muscle. A person should stretch his arm and put his palm on the wall, and rotate his body, ten to fifteen seconds on each side; this exercise is for pectoralis major. A person must stand in the doorway with one foot before the other. Then the person must bend the elbow to 90 degrees and place each forearm on each side of the entrance. A shift of weight on the extended leg will insert stretch on the chest muscle; ten to fifteen seconds is recommended for each leg. This stretch exercise is for pectoralis minor.
Hopefully, this article has helped you understand all about Pectoralis Major in detail.
FAQs on Pectoralis Major Muscle Anatomy and Function
1. What is the pectoralis major?
The pectoralis major is a large, fan-shaped muscle located on the front of the chest that is responsible for major movements of the shoulder joint. It is a superficial chest muscle that:
- Forms the bulk of the anterior chest wall
- Attaches from the clavicle, sternum, and ribs to the humerus
- Plays a key role in arm movement and upper body strength
It is commonly targeted in exercises like push-ups and bench presses.
2. What is the function of the pectoralis major muscle?
The primary function of the pectoralis major is to move the arm at the shoulder joint, especially in flexion, adduction, and medial rotation. Its main actions include:
- Adduction – bringing the arm toward the body
- Medial (internal) rotation – rotating the arm inward
- Flexion – lifting the arm forward
These movements are essential for pushing, lifting, and hugging actions.
3. Where is the pectoralis major located?
The pectoralis major is located on the anterior (front) surface of the chest, covering the upper ribs and extending to the upper arm. Specifically, it:
- Originates from the medial clavicle, sternum, and costal cartilages of the upper ribs
- Inserts into the lateral lip of the intertubercular sulcus of the humerus
It lies superficial to the pectoralis minor muscle.
4. What are the parts of the pectoralis major?
The pectoralis major has two main heads: the clavicular head and the sternocostal head. These parts include:
- Clavicular head – originates from the medial half of the clavicle and assists mainly in shoulder flexion
- Sternocostal head – originates from the sternum and upper ribs and is mainly involved in adduction and medial rotation
Both heads converge to insert into the humerus.
5. What is the difference between pectoralis major and pectoralis minor?
The pectoralis major is a large superficial chest muscle that moves the arm, while the pectoralis minor is a smaller, deeper muscle that stabilizes the scapula. Key differences include:
- Size: Major is larger; minor is smaller
- Location: Major is superficial; minor lies underneath
- Function: Major moves the humerus; minor stabilizes and protracts the scapula
They work together during shoulder and upper limb movements.
6. What nerve innervates the pectoralis major?
The pectoralis major is innervated by the medial and lateral pectoral nerves, which arise from the brachial plexus. Specifically:
- The lateral pectoral nerve mainly supplies the clavicular head
- The medial pectoral nerve mainly supplies the sternocostal head
These nerves originate from spinal nerve roots C5–T1.
7. What happens if the pectoralis major is injured?
An injury to the pectoralis major can cause pain, weakness, and difficulty moving the arm, especially during pushing movements. Common features include:
- Sudden chest or upper arm pain
- Bruising and swelling
- Reduced strength in adduction and medial rotation
Severe tears may require surgical repair to restore full shoulder function.
8. How does the pectoralis major help in breathing?
The pectoralis major can assist in forced inspiration by elevating the rib cage when the arms are fixed. During deep or labored breathing:
- The muscle pulls on the ribs if the upper limbs are stabilized
- This increases thoracic volume
It acts as an accessory muscle of respiration, especially during exercise or respiratory distress.
9. Is the pectoralis major a skeletal muscle?
Yes, the pectoralis major is a voluntary skeletal muscle attached to bones and controlled by the somatic nervous system. It has the typical features of skeletal muscle:
- Striated muscle fibers
- Multinucleated cells
- Voluntary control
It enables conscious movements of the upper limb.
10. What type of movements require the pectoralis major?
Movements that involve pushing, lifting, or bringing the arm toward the body require the pectoralis major. Examples include:
- Push-ups and bench presses
- Throwing or punching motions
- Hugging or clasping actions
These actions depend on shoulder adduction, flexion, and medial rotation.
