Logan Steele
The chest is made up of several muscles, including the pectoralis major and minor, the serratus anterior, and the subclavius. Together, these muscles are responsible for moving the upper extremities in a wide range of motions, including flexion, adduction, and internal rotation of the humerus, stabilization of the scapula, and elevating and depressing the bones of the thorax. The pectoralis major is the largest and most superficial muscle in the chest area, spanning from the armpit up to the collarbone and down to the lower chest region on both sides. It is thick and fan-shaped, originating from multiple places along the medial and superior chest, including the anterior sternum, clavicular head, and sternal end of rib 6. The pectoralis minor lies beneath the pectoralis major and assists in key functions, including shoulder movement and rotation.
| Characteristics | Values |
|---|---|
| Number of chest muscles | 2 |
| Names of the chest muscles | Pectoralis Major, Pectoralis Minor |
| Other names for Pectoralis Major | Pec Major, Pecs, Pectoral Muscle, Chest Muscle |
| Largest muscle | Pectoralis Major |
| Shape of Pectoralis Major | Fan-shaped, Triangular |
| Location of Pectoralis Major | Upper chest, underneath the breast |
| Functions of Pectoralis Major | Flexion, Adduction, Internal rotation of the humerus, Moving the shoulder joint |
| Functions of Pectoralis Minor | Shoulder movement, especially shoulder rotation, Assists in breathing |
| Location of Pectoralis Minor | Underneath the Pectoralis Major |
| Shape of Pectoralis Minor | Triangular |
| Other chest muscles | Serratus Anterior, Subclavius |
| Functions of Serratus Anterior | Moves the scapula forward around the torso, e.g. during a punch |
| Functions of Subclavius | Elevates the clavicle bone during breathing, Helps in depressing the shoulder, Elevates the first rib |
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What You'll Learn
- The pectoralis major is the largest chest muscle
- The pectoralis minor is a small, triangular muscle that lies beneath the pectoralis major
- The serratus anterior is a fan-shaped muscle that enables a long and strong reach
- The subclavius is a small, triangle-shaped muscle that elevates the clavicle bone when breathing in
- Chest muscles help bring your arms closer to your body with strength and control
The pectoralis major is the largest chest muscle
The chest is made up of several muscles, including the pectoralis major, pectoralis minor, serratus anterior, and subclavius. Of these, 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 and forms the anterior wall of the axilla. The pectoralis major is responsible for moving the upper extremities in a wide range of motions, including flexion, adduction, and internal rotation of the humerus, stabilization of the scapula, and elevation and depression of the bones of the thorax.
The pectoralis major has two heads: the clavicular head and the sternocostal head. The clavicular head originates from the anterior surface of the medial half of the clavicle, while the sternocostal head originates from the anterior surface of the manubrium and body of the sternum, as well as the superior six costal cartilages. The upper and lower fibers of the pectoralis major insert into the crest of the greater tubercle of the humerus. The actions of the pectoralis major depend on which parts of the muscle are activated. For example, the muscle fibers 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 fibers attaching to the sternocostal head permit horizontal and vertical adduction, extension, and internal rotation of the upper extremity.
The pectoralis major is a crucial muscle for many activities and exercises. For example, pressing exercises like the flat barbell bench press and the flat dumbbell bench press involve utilizing the pectoralis major. In these exercises, the individual lies supine on a bench with their feet flat on the ground and uses either a barbell or a pair of dumbbells to extend their arms, lowering them slowly towards the nipple line and then bringing the weights up to arm's length. The pectoralis major is also active during deep or forced inspiration, assisting in breathing when the diaphragm and intercostal muscles are insufficient.
Injuries to the pectoralis major are relatively rare but can occur in high-impact contact sports such as powerlifting or weight-lifting, particularly during bench press maneuvers. These injuries can result in pain, weakness, and disability, and may require surgery and physical therapy for recovery. In some cases, congenital abnormalities can also lead to the absence of the pectoralis major, as seen in Poland Syndrome or Moebius Syndrome. However, the absence of this muscle may not always result in functional loss, as in the case of a 22-year-old marine who was able to perform daily activities without difficulty despite having only one pectoralis major muscle.
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The pectoralis minor is a small, triangular muscle that lies beneath the pectoralis major
The chest is made up of several muscles, including the pectoralis major and the pectoralis minor. The pectoralis minor is a small, triangular muscle that lies beneath the pectoralis major. It is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. It is located deep to the pectoralis major and its covering fascia, which is a connective tissue layer called the clavicopectoral fascia. Together, the pectoralis major and minor form the anterior wall of the axilla.
The pectoralis minor is crucial in stabilising the scapula by pulling it downward and anteriorly against the thoracic wall. It works with the serratus anterior muscle to create a full range of movement for the scapula. This movement is important in reaching the arm forward. The pectoralis minor also acts as an accessory muscle of respiration, helping to raise ribs 3-5 during deep inspiration.
The primary nerve supply to the pectoralis minor comes via 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'. The vascular supply to the pectoralis minor comes from the thoracoacromial artery and the superior thoracic artery.
The pectoralis minor is prone to painful tightness, which can disrupt posture and cause issues such as stiffness and pain in the upper back. This tightness can be prevented by maintaining proper posture and incorporating a well-rounded strength-training routine into one's exercise regimen. Stretches such as the "field goal" stretch and the "myofascial chest stretch" can help to alleviate tightness in the pectoralis minor and other chest muscles.
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The serratus anterior is a fan-shaped muscle that enables a long and strong reach
The chest is made up of several muscles, including the pectoralis major, pectoralis minor, serratus anterior, and subclavius. These muscles are responsible for moving the upper extremities in a wide range of motions, including flexion, adduction, and internal rotation of the humerus, as well as stabilising the scapula and lifting and depressing the bones of the thorax.
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. Its main part lies deep under the scapula and the pectoral muscles, and it is easily palpable between the pectoralis major and latissimus dorsi muscles. The serratus anterior is a thin muscle that covers the side of the ribcage.
The serratus anterior muscle is responsible for the protraction of the scapula, a movement that occurs when throwing a punch. It also acts with the upper and lower fibres of the trapezius muscle to sustain upward rotation of the scapula, allowing for overhead lifting. This muscle is often referred to as the "boxer's muscle" because it enables a long and strong reach.
The contraction of the entire serratus anterior leads to an anterolateral movement of the scapula along the ribs. The inferior part of the muscle pulls the lower scapula, shifting the shoulder joint superiorly and enabling the arm to lift above 90 degrees. In contrast, the superior part depresses the scapula. The serratus anterior also actively stabilises the scapula within the shoulder and, when the shoulder girdle is fixed, lifts the ribs and assists with respiration.
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The subclavius is a small, triangle-shaped muscle that elevates the clavicle bone when breathing in
The chest is made up of several muscles, including the pectoralis major, pectoralis minor, serratus anterior, and the subclavius. The subclavius is a small, triangle-shaped muscle located in the anterior thorax, between the clavicle and the first rib. It originates from the upper border of the first rib and its cartilage, and inserts into the subclavian groove of the clavicle, specifically the inferior surface of the middle third of the bone.
The subclavius is responsible for depressing the clavicle and elevating the first rib when breathing in. This movement helps to stabilize the sternoclavicular joint and prevent dislocation of the clavicle during certain activities. Additionally, the subclavius plays a role in protecting the neurovascular structures beneath it, such as the subclavian vessels and the brachial plexus, in the event of a clavicular fracture.
The subclavius is enclosed by the clavipectoral fascia, a fibrous connective tissue that spans the interval between the clavicle and pectoralis minor muscle. It is innervated by the subclavian nerve, which arises from the junction of the fifth and sixth cervical nerves of the superior trunk of the brachial plexus.
Due to its location, the subclavius can be prone to tightness and strain. It is situated in an area where some people hold tension, and it can be overused through repetitive movements or excessive force or resistance. As a result, the subclavius may contribute to compression or pain along the clavicle, sternoclavicular joint, or shoulder.
In summary, the subclavius is a small, triangle-shaped muscle that plays a crucial role in stabilizing the clavicle and preventing injuries to adjacent neurovascular structures. Its contraction leads to the elevation of the first rib and the clavicle bone when breathing in, contributing to the overall function and movement of the chest and shoulder.
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Chest muscles help bring your arms closer to your body with strength and control
The chest is made up of several muscles, including the pectoralis major, pectoralis minor, serratus anterior, and subclavius. These muscles are responsible for a wide range of movements, including bringing the arms closer to the body with strength and control.
The pectoralis major is the largest and most prominent chest muscle, situated on the anterior chest. It is thick and fan-shaped, with fibres converging into a flat tendon that inserts into the lateral lip of the bicipital groove of the humerus. The pectoralis major assists in bringing the arms closer to the body, but it also helps with moving the shoulders and rotating the arms. Its two heads, the clavicular head and the sternocostal head, work antagonistically, allowing for a range of motions.
The pectoralis minor, located beneath the pectoralis major, is also crucial for shoulder movement, especially shoulder rotation. It stabilises the shoulder blade by pulling it forward and down against the rib cage. The serratus anterior, also known as the "boxer muscle," extends from the lower shoulder to the ribs, enabling a long and strong reach. The subclavius, a small, triangular muscle, elevates the clavicle bone during inhalation and helps depress the shoulder.
To maintain the health and functionality of these chest muscles, it is essential to incorporate a well-rounded strength-training routine into your exercise regimen. This includes exercises such as push-ups, modified push-ups, and various stretches that target the chest muscles. By strengthening the chest muscles, individuals can improve their ability to perform everyday activities, enhance their performance in sports, and reduce the risk of injuries related to muscle tightness and overuse.
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Frequently asked questions
The two chest muscles are the pectoralis major and the pectoralis minor. The pectoralis major is the larger of the two and lies on top of the pectoralis minor.
The pectoralis major is responsible for moving the shoulder joint and keeping the arms attached to the body. It also helps with flexion, adduction, and internal rotation of the humerus.
The pectoralis minor is integral to shoulder movement, especially shoulder rotation. It also assists with breathing.
Some exercises to strengthen the chest muscles include push-ups, inclined presses, decline presses, and dumbbell pull-overs.
