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The chest muscles, also known as pecs, are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. There are two main chest muscles: the pectoralis major and the pectoralis minor. The pectoralis major is the main muscle associated with the chest and is the largest and strongest of the two. It is responsible for bringing the arms closer to the body and moving the shoulders and rotating the arms. The pectoralis minor lies underneath the pectoralis major and assists in key functions. In addition to these two main chest muscles, there are also other muscles that assist the pecs in action, such as the serratus anterior and the subclavius. These muscles are important for daily activities and injury prevention, and they can be strengthened through various exercises such as presses and flyes.
| Characteristics | Values |
|---|---|
| Number of chest muscles | 2 |
| Names of the chest muscles | Pectoralis major, Pectoralis minor |
| Location of the pectoralis major | Anterior chest wall |
| Location of the pectoralis minor | Underneath the pectoralis major |
| Functions of the pectoralis major | Bring the arms closer to the body, move the shoulders, rotate the arms |
| Functions of the pectoralis minor | Assists the pectoralis major, helps with breathing |
| Types of exercises for the chest muscles | Presses, Flyes |
| Common chest injuries | Tendonitis, Torn pectoralis major tendon |
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Pectoralis major
The pectoralis major is the main muscle associated with the chest. It is the largest and strongest of the chest muscles, and therefore the most important. It is a thick, fan-shaped or triangular convergent muscle that makes up the bulk of the chest muscles. It lies underneath the breast and forms the anterior wall of the axilla. The pectoralis minor lies underneath the pectoralis major.
The pectoralis major has its origin on the 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. It has two heads, the clavicular and the sternocostal, which reference their area of origin. The sternocostal head is the larger of the two, originating 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 upper fibres are more anterior and caudal on the crest, while the posterior fibres twist on themselves and are more posterior and cranial than the upper fibres.
The pectoralis major has three primary functions, which are dependent on which heads of muscles are involved. These are flexion, adduction, and internal rotation of the humerus. The clavicular head originates from the anterior surface of the medial clavicle and assists in flexion of the arm at the glenohumeral joint. The sternocostal head, meanwhile, assists in the extension of the arm at the glenohumeral joint. The muscle is also responsible for keeping the arm attached to the trunk of the body.
The pectoralis major is highly vascularised via the thoracoacromial artery, which lowers the chances of necrosis in flap formation. It receives dual motor innervation from the medial pectoral nerve and the lateral pectoral nerve, also known as the lateral anterior thoracic nerve. The muscle is used in flap repairs in neck surgery and can be targeted with exercises such as the barbell bench press, dumbbell bench press, and machine bench press.
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Pectoralis minor
The pectoralis minor is a small, triangular-shaped muscle that lies underneath the pectoralis major in the pectoral region of the chest. It is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. The pectoralis major and minor muscles form the anterior wall of the axilla. The pectoralis minor originates from the third, fourth, and fifth ribs and inserts into the coracoid process of the scapula. It is innervated by the medial pectoral nerve, which pierces the muscle, and receives innervation from the spinal roots of C5-T1. The vascular supply to the pectoralis minor comes from the thoracoacromial artery, the superior thoracic artery, and the lateral thoracic artery.
The pectoralis minor has several functions, mostly related to the movement of the scapula. It helps to stabilise the scapula by drawing it downward and anteriorly against the thoracic wall. This movement depresses the point of the shoulder and pulls the scapula towards the thorax, throwing its inferior angle posteriorly. The pectoralis minor also acts as an accessory muscle of respiration, assisting with breathing. In addition, it can be used as a surgical landmark due to the structures that lie below or deep to the muscle and its tendon.
The pectoralis minor is associated with several clinical issues. Shortening of the pectoralis minor can cause impingement on the brachial plexus and axillary blood vessels, leading to shoulder impingement and
To target the pectoralis minor in exercise, specific movements that isolate this small muscle are required as it is not a prime mover. The serratus punch exercise and the modified push-up plus exercise are examples of movements that can help activate the serratus anterior while minimising the work of the pectoralis minor.
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Serratus anterior
The serratus anterior is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax. It is divided into three parts: the serratus anterior superior, serratus anterior intermediate, and serratus anterior inferior. The serratus anterior is located laterally in the chest wall and forms the medial border of the axilla region.
The serratus anterior is a key scapular stabiliser, keeping the shoulder blades against the ribcage when at rest and during movement. It acts in concert with the upper and lower fibres of the trapezius muscle to sustain upward rotation of the scapula, allowing for overhead lifting. The serratus anterior is also known as the "boxer's muscle" or the "big swing muscle" because it is largely responsible for the protraction of the scapula, a movement that occurs when throwing a punch.
The serratus anterior is easily palpated between the pectoralis major and latissimus dorsi muscles. The muscle is supplied with oxygenated blood by the lateral thoracic artery, also known as the external mammary artery. The long thoracic nerve, which arises from C5 to C7 nerve roots of the brachial plexus, is responsible for the innervation of the serratus anterior.
The most common causes of serratus anterior muscle pain include tension, stress, and overuse. This pain may also result from serratus anterior myofascial pain syndrome (SAMPS), a rare myofascial pain syndrome.
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Subclavius
The subclavius muscle is a small, triangular muscle of the anterior thoracic wall, underneath the collarbone or 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's primary function is to actively stabilise the clavicle at the sternoclavicular joint during movements of the shoulder and arm. When the muscle contracts, it depresses the sternal end of the clavicle, which causes the first rib to elevate. This movement is rather insignificant under normal circumstances, but it helps with forced breathing, such as during an asthma attack, and prevents dislocation of the clavicle at the sternoclavicular joint during certain activities.
Additionally, the subclavius plays a crucial role in preventing injuries to the adjacent neurovascular structures in the event of a fractured clavicle. Specifically, it shields the superior trunk of the brachial plexus and the subclavian blood vessels from potential damage. The subclavian nerve is a small branch of the brachial plexus. The muscle has another minor source of blood supply from the suprascapular artery, a branch of the thyrocervical trunk, which in turn branches off from the subclavian artery.
The subclavius lies deep to the pectoralis major muscle, along with the clavipectoral fascia. This fascia is the connective tissue between the clavicle and the pectoralis minor muscle and surrounds the subclavius.
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Chest muscle injuries
The chest muscles, also known as pecs, are made up of two muscles: the pectoralis major and the pectoralis minor. The pectoralis major is the bigger and stronger of the two and is the main muscle associated with the chest. The pectoralis minor lies underneath the pectoralis major and assists in key functions. The pectoral region also contains two other muscles: the serratus anterior and the subclavius.
The treatment for a chest muscle injury depends on the severity of the injury and the patient's health and activity level. Minor injuries can often be treated at home with rest, pain relievers, and cold therapy. For more severe injuries, a doctor may prescribe stronger painkillers, muscle relaxants, or surgery to reattach the muscle.
To diagnose a chest muscle injury, a doctor will ask about the patient's symptoms and medical history, as well as any activities that may have caused the pain. They may also perform a physical examination to assess the patient's strength and range of motion. Imaging techniques such as X-rays, CT scans, ultrasounds, and MRIs can also be used to determine the presence and extent of the injury.
To prevent chest muscle injuries, it is important to focus on maintaining good posture during daily activities, exercise, and when lifting things.
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Frequently asked questions
The chest is made up of two main muscles: the pectoralis major and the pectoralis minor, known collectively as your pecs. The pectoralis major is the larger and stronger of the two and is the main muscle associated with the chest. The pectoralis minor lies underneath the pectoralis major and assists in key functions.
The pectoralis major is responsible for bringing the arms closer to the body, as well as assisting with moving the shoulders and rotating the arms. It is composed of two heads: the sternal head and the clavicular head, each with distinct functions. The sternal head accounts for 80% of the pectoralis major's total size and powers most of its actions. The clavicular head helps with the above actions but also works to flex the humerus (raising your arm forward).
The pectoralis minor helps to stabilise the scapula by drawing it against the thoracic wall. It also assists with breathing. Despite sitting at the front of the body, it controls structures associated with the backside.
The serratus anterior, the subclavius, and the anterior deltoid are also commonly associated with the chest. The serratus anterior is located in the chest wall and works as an auxiliary muscle during certain chest movements, particularly when the shoulders are allowed to protract freely. The subclavius is part of the anterior chest wall and helps to hold the scapula against the ribcage. The anterior deltoid helps to raise the arm in front of the torso.
