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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. The primary muscles in the chest include the pectoralis major, pectoralis minor, serratus anterior, and subclavius. The pectoralis major is the most superior and largest muscle of the anterior chest wall, lying underneath the breast. It is thick and fan-shaped, stretching from the armpit up to the collarbone and down across the lower chest region on both sides of the chest. The pectoralis minor lies underneath the pectoralis major and assists in key functions.
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What You'll Learn
The pectoralis major is the main chest muscle
The pectoralis major is a paired, superficial muscle found in the anterior chest wall. It is composed of a sternal head and a clavicular head. The clavicular head originates from the anterior surface of the medial clavicle, 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 pectoralis major has a broad origin, which is divided into three parts: the clavicular part, the sternocostal part, and the abdominal part. All three parts converge laterally and insert onto the greater tubercle of the humerus.
The main function of the pectoralis major as a whole is the adduction and internal rotation of the arm in the shoulder joint. The clavicular part helps to flex the extended arm up to 90 degrees, while the sternocostal part facilitates the extension of the flexed arm by pulling it downwards. In addition, the pectoralis major assists in forced breathing during physical distress by facilitating the act of inspiration when acting from the humeral attachment.
The pectoralis major is also of significant interest in surgical situations due to its extensive vascularity. It has been effectively used in maxillofacial defects, skull base defects, pharyngoesophageal abnormalities, and the reconstruction of other systems.
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The pectoralis minor lies underneath the pectoralis major
The chest muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. The pectoral region is located on the anterior chest wall and contains four muscles that exert a force on the upper limb: the pectoralis major, pectoralis minor, serratus anterior, and subclavius.
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 3rd, 4th, and 5th ribs and inserts into the coracoid process of the scapula. It is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. The pectoralis minor is also one of the anterior axioappendicular (thoracoappendicular) muscles, along with the pectoralis major, subclavius, and serratus anterior.
The pectoralis minor has several important functions. It helps to stabilise the scapula by drawing it anteroinferiorly against the thoracic wall. Additionally, it can be considered an accessory muscle of respiration, aiding in expanding the thoracic cavity during deep and forced inspiration. The pectoralis minor also works together with other muscles of the region, such as the serratus anterior, to produce various movements of the scapula.
The pectoralis minor receives its nerve supply from the medial pectoral nerve (C8, T1), a minor branch of the brachial plexus that arises from the cervical portion of the spinal cord. It also receives innervation from the lateral pectoral nerve via a communicating branch called 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 comes from the thoracoacromial artery and the superior thoracic artery.
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The sternalis muscle is a strip of muscle lateral to the pectoralis major
The chest muscles, or pectoral muscles, are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. The pectoral region is located on the anterior chest wall and contains four muscles: the pectoralis major, pectoralis minor, serratus anterior, and subclavius.
The pectoralis major is the largest and most superior muscle of the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. Its origin lies 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.
The pectoralis minor is a smaller muscle that lies underneath the pectoralis major. It originates from the 3rd to 5th ribs and inserts into the coracoid process of the scapula. The pectoralis minor stabilizes the scapula by drawing it anteroinferiorly against the thoracic wall.
The sternalis muscle is a strip of muscle located anterior and lateral to the sternum, and lateral to the pectoralis major. It is inserted at the level of the manubriosternal junction and arises from the sternal handlebar, with myofascial continuity with the sternocleidomastoid muscle. The sternalis muscle can be about 9 centimetres long and may be present unilaterally or bilaterally. Its origin and insertion are variable, and there is disagreement about its innervation and embryonic origin. Some sources suggest innervation by the external or internal thoracic nerves, while others report innervation by the intercostal nerves or the pectoral nerves. Cadaveric studies have shown that the sternalis muscle has a mean prevalence of around 7.8% in the population, with a higher incidence in females and a higher incidence of unilateral presentation.
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The subclavius is a small muscle underneath the clavicle
The chest muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. The pectoralis major is the main muscle associated with the chest and is the largest and strongest of the chest muscles. The pectoralis minor lies underneath the pectoralis major and assists in key functions.
The subclavius is a small muscle located directly underneath the clavicle, running horizontally. It is a short, triangular muscle of the thoracic wall. It originates from the first rib and courses laterally to insert on the undersurface of the middle third of the clavicle. Its main function is to stabilize the clavicle during movements of the shoulder girdle and arm.
The subclavius also plays a role in preventing injuries to the adjacent neurovascular structures, such as the subclavian blood vessels and the superior trunk of the brachial plexus, in the event of a fractured clavicle. This protective function is particularly important as the clavicle is the most frequently broken long bone.
The subclavius muscle can be absent from one side of the body, and it may also occur supernumerary. The subclavius posticus muscle is a variation of the subclavius muscle that arises from the first rib and moves towards the scapula (upper edge), passing under the clavicle.
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The serratus anterior is located in the rib cage
The serratus anterior is a fan-shaped muscle that is located in the rib cage. It is one of the four muscles in the pectoral region, along with the pectoralis major, pectoralis minor, and subclavius. The serratus anterior originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax and inserts along the superior angle, medial border, and inferior angle of the scapula. Its main part lies deep under the scapula and the pectoral muscles.
The serratus anterior has a "serrated" or "saw-toothed" appearance due to its course. It is easily palpable between the pectoralis major and latissimus dorsi muscles. In athletic bodies, the muscle may even be visible to the naked eye along the ribs underneath the axilla. The serratus anterior is responsible for rotating the scapula, allowing the arm to be raised over 90 degrees. It also protracts the scapula, holding it against the rib cage. This muscle is also known as the "boxer's muscle" because it is largely responsible for the protraction of the scapula that occurs when throwing a punch.
The serratus anterior is a key scapular stabilizer, keeping the shoulder blades against the rib cage when at rest and during movement. When the shoulder blade is in a fixed position, the serratus anterior lifts the rib cage and supports breathing. This muscle is very thin and covers the side of the rib cage. It can be felt by putting your hand just below the armpit.
The serratus anterior is susceptible to pain and injury due to tension, stress, and overuse, especially in sports with repetitive motions such as swimming, tennis, or weightlifting. Injury to the long thoracic nerve, which supplies innervation to the serratus anterior, can lead to a functional loss of the muscle and a clinical phenomenon known as a winged scapula, where the scapula is no longer held against the chest wall.
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Frequently asked questions
The chest muscles are located on the anterior chest wall.
The pectoralis major is the main muscle associated with the chest. It is the largest and strongest of the chest muscles and is located underneath the breast tissue.
The pectoralis major has three functions: flexion, adduction, and medial rotation of the arm at the glenohumeral joint.
The pectoralis minor is a thin, triangular muscle that lies underneath the pectoralis major. It assists in key chest functions.
Other muscles located in the chest include the serratus anterior, subclavius, sternalis, and chondrocoracoideus.
