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The pectoralis major is a thick, fan-shaped or triangular convergent muscle that makes up the bulk of the chest muscles. It is the largest and most superficial muscle in the chest area, lying underneath the breast tissue. The pectoralis major is one of the two muscles that connect the front walls of the chest with the bones of the upper arm and shoulder. It originates at the clavicle, the sternum, the ribs, and a tendinous extension of the external oblique abdominal muscle. The pectoralis major is responsible for the movement of the shoulder joint, as well as keeping the arm attached to the trunk of the body.
| Characteristics | Values |
|---|---|
| Muscle name | Pectoralis major |
| Muscle type | Voluntary |
| Muscle shape | Fan-shaped or triangular convergent |
| Muscle location | Anterior chest wall, underneath the breast tissue |
| Muscle size | Thick and large |
| Muscle parts | Clavicular, sternocostal, and abdominal |
| Muscle function | Adduction, internal rotation, and flexion of the humerus; assists in pulling the trunk forward or upward |
| Muscle innervation | Medial pectoral nerve, lateral pectoral nerve (or lateral anterior thoracic nerve), C5, C6, C7, C8, T1 nerve roots, brachial plexus |
| Muscle vascularization | Pectoral branches of thoracoacromial artery, perforating branches of internal thoracic artery |
| Muscle injury | Pectoralis major tendon rupture, Poland syndrome (congenital condition with absence of the muscle) |
| Muscle exercises | Bench press, dumbbell fly |
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What You'll Learn
- The pectoralis major is the thickest and largest muscle in the anterior chest wall
- It has two heads: the clavicular and the sternocostal
- The pectoralis major is involved in flexion, adduction, and internal rotation of the humerus
- It is also responsible for keeping the arm attached to the body's trunk
- The pectoralis major is commonly referred to as pecs or chest muscle
The pectoralis major is the thickest and largest muscle in the anterior chest wall
The muscle consists of two heads: the clavicular and the sternocostal. The sternocostal head is the larger of the two and originates from the anterior surface of the manubrium and body of the sternum, the anterior surface of the superior six costal cartilages, and the superior part of the aponeurosis of the external oblique muscle. The upper and lower fibres of the pectoralis major insert into the crest of the greater tubercle of the humerus.
The pectoralis major has several important functions. Firstly, it is responsible for flexion, adduction, and internal rotation of the humerus. This includes contributing to the flexion of the humerus, as seen in underhand throwing or lifting a child. Secondly, it assists in keeping the arm attached to the trunk of the body. Thirdly, it stabilises the scapula by drawing it anteroinferiorly against the thoracic wall.
The pectoralis major is susceptible to rare injuries, such as tendon rupture and tears, which are commonly seen in weight lifters and athletes involved in high-impact contact sports. These injuries can result in pain, weakness, and disability. Additionally, Poland syndrome is a rare congenital condition characterised by the absence of the pectoralis major, typically on one side of the body.
To strengthen the pectoralis major, exercises such as the flat barbell bench press and the flat dumbbell bench press are commonly performed. These exercises involve lying supine on a bench with feet flat on the ground and using weights to extend and lower the arms slowly towards the nipple line, bringing the weights up over the face at arm's length.
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It has two heads: the clavicular and the sternocostal
The pectoralis major is the largest muscle in the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue. It has two heads: the clavicular and the sternocostal. These names refer to the area from which each originates.
The clavicular head of the pectoralis major originates from the anterior surface of the medial half of the clavicle. The clavicle is commonly known as the collarbone. The clavicular head is close to the deltoid muscle and is responsible for flexion, horizontal adduction, and inward rotation of the humerus.
The sternocostal head is the larger of the two heads. It originates from the anterior surface of the manubrium and body of the sternum, the anterior surface of the superior six costal cartilages, and the superior part of the aponeurosis of the external oblique muscle. The sternocostal head is antagonistic to the clavicular head, contributing to the downward and forward movement of the arm and inward rotation when accompanied by adduction.
The pectoralis major is active in deep or forced inspiration, but not expiration. It assists in flexion of the arm via its clavicular head and in the extension of the arm via the sternocostal head at the glenohumeral joint. It also depresses the shoulder girdle at the acromioclavicular and sternoclavicular joints.
The pectoralis major is the most common site of muscle injury in weightlifters. This injury is most commonly seen during exercises such as the flat barbell bench press and the flat dumbbell bench press, where the arm under load is in extension and external rotation.
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The pectoralis major is involved in flexion, adduction, and internal rotation of the humerus
The pectoralis major is a thick, fan-shaped or triangular convergent muscle of the human chest. It is the largest and most superficial muscle in the chest area, lying underneath the breast tissue. The pectoralis major is involved in flexion, adduction, and internal rotation of the humerus.
The muscle has four actions that are primarily responsible for the movement of the shoulder joint. Firstly, flexion of the humerus, as seen when throwing a ball underhand or lifting a child. Secondly, it adducts the humerus, as when flapping the arms. Thirdly, it medially rotates the humerus, as occurs during arm-wrestling. Finally, the pectoralis major is responsible for keeping the arm attached to the trunk of the body. The muscle has two distinct parts, each responsible for different actions.
The clavicular part is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. At an angle of roughly 110 degrees, it also contributes to adduction of the humerus. The sternocostal part, on the other hand, opposes the clavicular part, facilitating the downward and forward movement of the arm and inward rotation when accompanied by adduction. The sternal fibres can also contribute to extension, but not beyond the anatomical position.
The pectoralis major muscle is a broad, superficial muscle found in the anterior chest wall. It is covered by the deep layer of fascia, subcutaneous tissue, and adjacent skin in males. In females, it is covered by the breast. The deep surface of the muscle covers the pectoralis minor and serratus anterior muscles, as well as the anterior surface of the upper six ribs. The muscle fibres from all three parts of the pectoralis major converge laterally, attaching to the proximal humerus.
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It is also responsible for keeping the arm attached to the body's trunk
The pectoralis major is a thick, fan-shaped or triangular convergent muscle of the human chest. It is the largest and most superficial muscle in the chest area, making up the bulk of the chest muscles. The pectoralis major arises from parts of the clavicle and sternum, costal cartilages of the true ribs, and the aponeurosis of the abdominal external oblique muscle. It is attached to a ridge at the rear of the humerus, which is the upper arm bone.
The pectoralis major has four actions that are primarily responsible for the movement of the shoulder joint. The first action is flexion of the humerus, as seen in throwing a ball underhand or lifting a child. The second action is adduction of the humerus, as when flapping the arms. The third action is internal rotation of the humerus. The fourth action is the depression of the arm, which is in opposition to the action of the deltoideus muscle.
The pectoralis major also assists in the extension of the arm via the sternocostal head at the glenohumeral joint. It depresses the shoulder girdle at the acromioclavicular and sternoclavicular joints. Additionally, it assists in elevating the thorax during forced inspiration. In crutch-walking or parallel-bar work, the pectoralis major helps support the weight of the body.
The pectoralis major is responsible for keeping the arm attached to the body's trunk through its actions of adduction and depression of the arm. Adduction is the movement of bringing the arm towards the body, and the pectoralis major achieves this by pulling the arm across the chest. This action of the pectoralis major counteracts the force of gravity that acts on the arm, preventing it from falling downwards and keeping it attached to the trunk. The depression of the arm by the pectoralis major also helps to lower the arm towards the body, further contributing to keeping the arm attached to the trunk.
The two parts of the pectoralis major, the clavicular and sternocostal heads, work together to facilitate these movements. The clavicular part contributes to flexion, horizontal adduction, and inward rotation of the humerus. Meanwhile, the sternocostal part contributes to the downward and forward movement of the arm, along with inward rotation during adduction.
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The pectoralis major is commonly referred to as pecs or chest muscle
The pectoralis major is a thick, fan-shaped or triangular convergent muscle of the human chest. It is the largest and most superficial muscle in the chest area, and it makes up the bulk of the chest muscles. The pectoralis major is commonly referred to as "pecs", "pectoral muscle", or "chest muscle". It is located underneath the breast tissue and forms the anterior wall of the axilla.
The pectoralis major has two heads: the clavicular and the sternocostal. The clavicular head originates from the anterior surface of the medial half of the clavicle (collarbone), while the sternocostal head originates from the anterior surface of the sternum, the superior six costal cartilages, and the aponeurosis of the external oblique muscle. The upper and lower fibres of the pectoralis major insert into the crest of the greater tubercle of the humerus, with the upper fibres being more anterior and caudal, and the posterior fibres being more posterior and cranial.
The pectoralis major is responsible for several important functions. Its primary actions are flexion, adduction, and internal rotation of the humerus, contributing to movements such as throwing a ball underhand or lifting a child. It also assists in pulling the trunk forward or upward when its humeral attachment is fixed, which is crucial in activities like climbing. Additionally, the pectoralis major plays a role in deep or forced inspiration during physical distress.
The pectoralis major receives dual motor innervation from the medial pectoral nerve and the lateral pectoral nerve, also known as the lateral anterior thoracic nerve. It is a paired muscle, with a broad origin that divides it into three parts: the clavicular part, the sternocostal part, and the abdominal part. These parts converge laterally and insert onto the greater tubercle of the humerus.
In summary, the pectoralis major is a significant muscle in the chest region, commonly known as "pecs" or "chest muscle". It plays a crucial role in shoulder and arm movements and is essential for various physical activities.
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Frequently asked questions
The pectoralis major is a thick, fan-shaped or triangular convergent muscle of the human chest. It is the largest and most superficial muscle in the chest area.
The pectoralis major is located on the anterior surface of the thoracic cage, underneath the breast tissue.
The pectoralis major's primary functions are flexion, adduction, and internal rotation of the humerus or arm at the shoulder joint. It also assists in pulling the trunk upwards, which is important in activities such as climbing.
The pectoralis major consists of two heads: the clavicular and sternocostal.
The clavicular head of the pectoralis major can be tested by transversely adducting the arm at the glenohumeral joint against resistance. The sternocostal head can be tested by adducting the arm at the same joint, also against resistance.
