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The pectoralis muscle is a group of skeletal muscles that connect the front walls of the chest with the bones of the upper arm and shoulder. There are two types of pectoralis muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor. The pectoralis major is the largest muscle of the anterior chest wall, lying underneath the breast tissue. The pectoralis minor lies underneath the pectoralis major, arising from the middle ribs and inserting into the scapula (shoulder blade).
| Characteristics | Values |
|---|---|
| Number of muscles in the pectoral region | 3 |
| Names of the muscles | Pectoralis major, pectoralis minor, serratus anterior |
| Location | Anterior chest wall |
| Muscle shape | Thick, fan-shaped |
| Muscle function | Adduction, or depression, of the arm; rotation of the arm forward about the axis of the body |
| Muscle activation | Dependent on which parts of the muscle are activated |
| Muscle origin | Anterior surface of the medial half of the clavicle, the anterior surface of the sternum, the first 7 costal cartilages, the sternal end of the sixth rib, and the aponeurosis of the external oblique of the anterior abdominal wall |
| Muscle insertion | Lateral lip of the bicipital groove of the humerus |
| Innervation | Medial pectoral nerve |
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What You'll Learn
- The pectoralis major is the largest muscle in the anterior chest wall
- The pectoralis minor lies underneath the pectoralis major
- The serratus anterior is located in the chest wall
- The subclavius is a small muscle located directly underneath the clavicle
- The pectoralis muscles are a group of skeletal muscles
The pectoralis major is the largest muscle in the anterior chest wall
The pectoralis major has two heads: the clavicular and the sternocostal.Head The clavicular head originates from the anterior surface of the medial half of the clavicle. The sternocostal head, which is larger, originates from the anterior surface of the manubrium and body 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.
The functions of the pectoralis major include flexion, adduction, and medial rotation of the arm at the glenohumeral joint. The clavicular head causes flexion of the extended arm, while the sternocostal head causes extension of the flexed arm. The pectoralis major is active in deep or forced inspiration, assisting in breathing when the diaphragm and intercostal muscles are insufficient.
The pectoralis major is one of four muscles in the pectoral region, along with the pectoralis minor, serratus anterior, and subclavius. These muscles exert a force on the upper limb and are responsible for a wide range of motions, including flexion, adduction, and internal rotation of the humerus, as well as stabilising the scapula.
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The pectoralis minor lies underneath the pectoralis major
The pectoralis minor lies underneath its larger counterpart muscle, the pectoralis major. Both muscles form part of the anterior wall of the axilla region. The pectoralis minor originates from the third to fifth ribs near the corresponding costal cartilages, as well as the fascia overlying the adjacent intercostal muscles found in the intercostal spaces. The muscle extends superolaterally to form a flat tendon, which inserts into the coracoid process of the scapula. The pectoralis minor is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. It is an anterior axioappendicular (thoracoappendicular) muscle, along with the pectoralis major, subclavius, and serratus anterior.
The pectoralis minor is thinner and triangular in shape compared to the pectoralis major. It pulls the scapula downward and anteriorly against the thoracic wall, contributing to its stabilisation. The pectoralis minor also aids in respiration by raising ribs 3-5 during inspiration and expanding the thoracic cavity. Additionally, it helps to protect the underlying neurovascular structures in cases of clavicular fracture or other trauma.
The primary nerve supply to the pectoralis minor comes from the medial pectoral nerve (C8, T1), a minor branch of the brachial plexus originating from the cervical portion of the spinal cord. It also receives innervation from the lateral pectoral nerve via the 'ansa pectoralis'. This results in the pectoralis minor receiving innervation from the spinal roots of C5-T1. The vascular supply to the pectoralis minor is provided by branches of the axillary artery, including the thoracoacromial artery and the superior thoracic artery.
The pectoralis muscles, including the pectoralis major and minor, are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. These muscles enable a wide range of motions in the upper extremities, such as flexion, adduction, and internal rotation of the humerus, as well as stabilisation of the scapula. The pectoralis major constitutes the bulk of the chest muscles, lying underneath the breast. It is thick and fan-shaped, originating from multiple places along the medial and superior chest, including the anterior sternum, clavicular head, and superior six costal cartilages.
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The serratus anterior is located in the chest wall
The serratus anterior is a key scapular stabiliser, keeping the shoulder blades against the rib cage at rest and during movement. It acts to rotate the scapula and hold it against the thoracic wall, allowing the arm to be raised over 90 degrees. This muscle is also responsible for scapular protraction, or the pulling of the scapula forward and around the rib cage, which occurs when throwing a punch. For this reason, the serratus anterior is sometimes called the "big swing muscle" or the "boxer's muscle".
The serratus anterior is innervated by the long thoracic nerve, a branch of the brachial plexus. Injury to this nerve can result in a winged scapula, where the scapula is no longer held against the chest wall. The serratus anterior is also associated with certain exercises, such as anterior deltoid exercises and chest exercises that involve scapular protraction, like planks and straight-arm planks.
The serratus anterior is easily palpable between the pectoralis major and latissimus dorsi muscles. It lies deep to the scapula and the pectoral muscles, and is separated from the rib by the scapulothoracic (infraserratus) bursa. The serratus anterior is divided into three parts according to the points of insertion: the serratus anterior superior, intermediate, and inferior. These parts correspond to the superior angle, medial border, and inferior angle of the scapula, respectively.
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The subclavius is a small muscle located directly underneath the clavicle
The pectoralis major, pectoralis minor, and the serratus anterior are the three muscles that lie in the pectoral region. The pectoralis major constitutes the bulk of the chest muscles, lying underneath the breast. It is thick and fan-shaped, originating from multiple places along the medial and superior chest.
The pectoralis minor lies underneath its larger counterpart muscle, the pectoralis major. Both muscles form part of the anterior wall of the axilla region.
The serratus anterior is located more laterally in the chest wall and forms the medial border of the axilla region. The muscle consists of several strips, which originate from the lateral aspects of ribs 1-8.
The subclavius is a small, triangular muscle located directly underneath the clavicle. It originates from the first rib and courses laterally to insert on the undersurface of the middle third of the clavicle. The subclavius muscle is enclosed by the clavipectoral fascia, a fibrous connective tissue that spans the interval between the clavicle and pectoralis minor muscle.
The main function of the subclavius muscle is the active stabilization of the clavicle at the sternoclavicular joint during movements of the shoulder and arm. Its contraction leads to a depression of the sternal end of the clavicle and a subsequent elevation of the first rib. This movement helps prevent dislocation of the clavicle at the sternoclavicular joint during certain types of activity.
Additionally, the subclavius is important in preventing injuries to the adjacent neurovascular structures in cases of clavicular fracture or other trauma. It protects the underlying brachial plexus and subclavian blood vessels from damage in case of a broken clavicle, the most frequently broken long bone.
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The pectoralis muscles are a group of skeletal muscles
There are two pectoralis muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor. The pectoralis major is the largest and most superior muscle of the anterior chest wall. It is thick and fan-shaped, lying underneath the breast tissue and forming the anterior wall of the axilla. The muscle fibres of the pectoralis major have different functions depending on which parts of the muscle are activated. For example, the fibres attaching to the clavicular head allow for the flexion of the humerus, such as when lifting a glass in a toast. On the other hand, the muscle fibres attaching to the sternocostal head permit the horizontal and vertical adduction, extension, and internal rotation of the upper extremity.
The pectoralis minor lies underneath the pectoralis major, originating from the middle ribs and inserting into the scapula (shoulder blade). It aids in drawing the shoulder forward and downward. The serratus anterior is another muscle located in the pectoral region, situated more laterally in the chest wall. It forms the medial border of the axilla region and is responsible for rotating the scapula, allowing the arm to be raised over 90 degrees.
The knowledge of the anatomy of the pectoralis muscles is important, especially in the context of breast surgery, as procedures such as breast reconstruction and augmentation can pose risks to the nervous supply of the pectoralis major. Additionally, various exercises can be performed to strengthen the pectoralis muscles, such as the flat barbell bench press and the flat dumbbell bench press. These exercises involve utilising the pectoralis major muscle to extend and lower weights slowly towards the nipple line.
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Frequently asked questions
Pec muscles, or pectoralis muscles, are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls.
The pec muscles are located in the pectoral region, or anterior chest wall.
Yes, there are three muscles in the pectoral region: pectoralis major, pectoralis minor, and serratus anterior.
The pectoralis major is the largest and most superficial muscle in the chest area. It is a thick, fan-shaped muscle that lies underneath the breast tissue.
The pectoralis minor is a smaller muscle that lies underneath the pectoralis major. It helps to stabilise the scapula by drawing it anteroinferiorly against the thoracic wall.
