Logan Steele
The pectoral muscles, commonly referred to as pecs, are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. They are a vital component of the upper body and play a crucial role in various movements, including pushing, lifting, and stabilizing the shoulders and arms. The pectoralis major is the largest muscle of the chest and lies underneath the breast tissue. It is thick and fan-shaped, originating from multiple places along the medial and superior chest. The pectoralis minor lies underneath the pectoralis major and assists in key functions, including shoulder movement and rotation. The serratus anterior, also known as the boxer muscle, extends from the lower shoulder to the ribs and enables a long and strong reach. The subclavius is a small, triangle-shaped muscle that elevates the clavicle bone during inhalation.
| Characteristics | Values |
|---|---|
| Location | Anterior chest wall |
| Muscle group | Pectoralis major, pectoralis minor, serratus anterior, subclavius |
| Pectoralis major origin | Anterior surface of the medial clavicle, sternum, superior six/seven costal cartilages, aponeurosis of the external oblique muscle |
| Pectoralis major insertion | Ends in a flat tendon, inserting into the lateral lip of the bicipital groove of the humerus |
| Pectoralis major function | Flexion, adduction, and internal rotation of the humerus, stabilization of the scapula, elevation and depression of the bones of the thorax |
| Pectoralis minor origin | 3rd-5th ribs |
| Pectoralis minor insertion | Coracoid process of the scapula |
| Pectoralis minor function | Stabilises the scapula, drawing it anteroinferiorly against the thoracic wall |
| Serratus anterior location | Laterally in the chest wall, forming the medial border of the axilla region |
| Serratus anterior origin | Lateral aspects of ribs 1-8 |
| Serratus anterior insertion | Costal (rib facing) surface of the medial border of the scapula |
| Serratus anterior function | Rotates the scapula, allowing the arm to be raised over 90 degrees, protracts the scapula, holding it against the ribcage |
| Subclavius location | Directly underneath the clavicle |
| Subclavius origin | Junction of the 1st rib and its costal cartilage |
| Subclavius insertion | Inferior surface of the middle third of the clavicle |
| Subclavius function | Anchors and depresses the clavicle, affording minor protection to underlying neurovascular structures |
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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 and forms the medial border of the axilla region
- The subclavius is a small, triangle-shaped muscle that elevates the clavicle bone
- Pectoral muscles are important for upper body strength and function
The pectoralis major is the largest muscle in the anterior chest wall
The pectoral muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. The pectoralis major is the largest muscle in the anterior chest wall. It is thick and fan-shaped, lying underneath the breast tissue. The pectoralis major constitutes the bulk of the chest muscles.
The pectoralis major has two heads: the clavicular head and the sternocostal head. The clavicular head originates from the clavicle, while the sternocostal head originates from the sternum and the upper ribs. Both heads converge to form the bulk of the muscle, inserting into the humerus (upper arm bone). The pectoralis major is primarily responsible for movements such as horizontal adduction (bringing the arms across the chest) and internal rotation of the shoulder. The muscle fibres attaching to the clavicular head allow for the flexion of the humerus, for example, when lifting a glass for 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 major is the most superficial muscle in the pectoral region. It is composed of the sternal head and the clavicular head. The clavicular head originates from the anterior surface of the medial clavicle. The sternocostal head originates from the anterior surface of the sternum, the superior six costal cartilages, and the aponeurosis of the external oblique muscle. All the fibres converge and end in a flat tendon, inserting into the lateral lip of the bicipital groove of the humerus.
The pectoralis major plays a crucial role in various movements, including pushing, lifting, and stabilising the shoulders and arms. It is also important for upper body strength and function, providing stability during activities such as carrying objects. Well-developed pectoralis major muscles help support good posture by promoting proper alignment of the shoulders and upper back. This can reduce the risk of orthopedic problems related to poor posture, such as kyphosis or rounded shoulders.
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The pectoralis minor lies underneath the pectoralis major
The pectoralis minor is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. It is one of the anterior axioappendicular (thoracoappendicular) muscles, along with the pectoralis major, subclavius, and serratus anterior. The pectoralis minor is also important clinically and as a surgical landmark, due to the structures that lie below or deep to the muscle and its tendon. For instance, nerve compression can occur in the subcoracoid space underneath the pectoralis minor muscle, requiring a pectoralis minor tenotomy. This procedure involves the detachment of the pectoralis minor tendon to relieve symptoms.
The primary nerve supply to the pectoralis minor muscle 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. Innervation to the pectoralis minor is also received from the lateral pectoral nerve, via a communicating branch known as the 'ansa pectoralis', which is usually found anterior to the first part of the axillary artery. This results in the pectoralis minor receiving innervation from the spinal roots of C5-T1. The vascular supply to the pectoralis minor comes from several sources, including the thoracoacromial artery and the superior thoracic artery.
Medial or downward rotation of the scapula against resistance is achieved by the pectoralis minor exerting force on the coracoid process, which pulls the lateral aspect of the scapula inferiorly. When the scapula is fixed, the pectoralis minor can be considered an accessory muscle of respiration, as it helps raise ribs 3-5 during inspiration and aids in expanding the thoracic cavity.
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The serratus anterior is located in the chest wall and forms the medial border of the axilla region
The pectoral muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. They are vital for upper body strength and function, providing stability during activities such as lifting, pushing, and carrying objects. The pectoralis major and pectoralis minor are the two main muscles in the pectoral region, with the serratus anterior and subclavius also included.
The serratus anterior is a fan-shaped muscle located in the lateral wall of the thorax, underneath the scapula and the pectoral muscles. It is positioned more laterally in the chest wall and forms the medial border of the axilla region. The axilla, or armpit, is a small anatomical space located between the upper thoracic wall and the arm. The serratus anterior muscle originates from the first to eighth or ninth ribs and inserts at the anterior surface of the medial border of the scapula.
The serratus anterior has several important functions. Firstly, it rotates the scapula, allowing the arm to be raised over 90 degrees. This movement is made possible by the contraction of the entire serratus anterior, which leads to an anterolateral movement of the scapula along the ribs. Secondly, it protracts the scapula, holding it against the ribcage. This action is controlled by the long thoracic nerve, and damage to this nerve can result in a functional loss of the serratus anterior, causing the scapula to protrude out of the back, creating a "winged" appearance. Thirdly, the serratus anterior actively stabilizes the scapula within the shoulder. Finally, when the scapula is fixed, the serratus anterior lifts the ribs and acts as an accessory inspiratory muscle.
The serratus anterior is a crucial muscle for shoulder movement and stability, working in conjunction with the pectoralis major and minor to enable a wide range of motions in the upper extremities. Its location in the chest wall and its role in forming the medial border of the axilla region contribute to its functional significance in the pectoral region.
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The subclavius is a small, triangle-shaped muscle that elevates the clavicle bone
The pectoral muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. These muscles are responsible for a wide range of movements of the upper extremities, including flexion, adduction, and internal rotation of the humerus, as well as the elevation and depression of the bones of the thorax. The pectoralis major and pectoralis minor are the two main muscles that make up the pectoral region.
The pectoralis major is the larger and more superficial muscle of the two, lying underneath the breast and forming the bulk of the chest muscles. 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. All the fibers of the pectoralis major converge and end in a flat tendon, inserting into the lateral lip of the bicipital groove of the humerus.
The pectoralis minor lies underneath the pectoralis major and forms part of the anterior wall of the axilla region. It originates from the 3rd to 5th ribs and inserts into the coracoid process of the scapula. The pectoralis minor helps to stabilize the scapula by drawing it against the thoracic wall.
In addition to the pectoralis major and minor, there are two other muscles in the pectoral region: the serratus anterior and the subclavius. The subclavius is a small, triangle-shaped muscle that plays an important role in the function of the pectoral region. It is located directly underneath the clavicle, running horizontally between the clavicle and the first rib. The subclavius originates from the junction of the first rib and its costal cartilage and inserts onto the inferior surface of the middle third of the clavicle.
The main function of the subclavius is to stabilize the clavicle, or collarbone, during movements of the shoulder and arm. It helps to prevent dislocation of the clavicle at the sternoclavicular joint and protects the neurovascular structures beneath it in the event of a clavicular fracture. The contraction of the subclavius leads to a depression of the sternal end of the clavicle and a subsequent elevation of the first rib. This movement helps to prevent injuries to the adjacent subclavian blood vessels and the superior trunk of the brachial plexus in the event of a fractured clavicle.
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Pectoral muscles are important for upper body strength and function
The pectoral muscles, commonly referred to as pecs, are a vital component of the upper body musculature. They 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. These muscles work together to provide strength, stability, and a wide range of motion to the upper extremities.
The pectoralis major is the largest and strongest muscle in the pectoral region. It is thick, fan-shaped, and constitutes the bulk of the chest muscles, lying underneath the breast. The pectoralis major has two heads: the clavicular head and the sternal head. The clavicular head originates from the clavicle, while the sternal head originates from the sternum and the upper ribs. Both heads converge to form a strong tendon that inserts into the upper arm bone (humerus). The main function of the pectoralis major is to bring the arms across the body (horizontal adduction) and rotate the arms internally. It also assists with lifting objects and shoulder movements.
The pectoralis minor is a smaller muscle situated beneath the pectoralis major. It originates from the 3rd to 5th ribs and inserts into the scapula. The pectoralis minor stabilises the scapula by drawing it against the thoracic wall. This muscle is integral to shoulder movement, especially shoulder rotation. The serratus anterior is located laterally in the chest wall and forms the medial border of the axilla region. It consists of several strips of muscle that originate from the lower ribs and attach to the scapula. The serratus anterior rotates the scapula, allowing the arm to be raised above 90 degrees. It also helps to hold the scapula against the ribcage.
The subclavius is a small muscle located directly underneath the clavicle. It originates from the first rib and inserts onto the middle third of the clavicle. The subclavius anchors and depresses the clavicle, providing minor protection to the underlying neurovascular structures. Together, the pectoralis minor, serratus anterior, and subclavius muscles play a crucial role in stabilising the scapula and allowing for a wide range of motion in the upper extremities.
Strong pectoral muscles are essential for upper body strength and function. They provide stability during activities such as lifting, pushing, and carrying objects. The pectoral muscles work in conjunction with other muscles around the shoulder joint to maintain stability and proper alignment. Well-developed pectoral muscles also support good posture by promoting proper alignment of the shoulders and upper back. This can help prevent orthopedic problems related to poor posture, such as kyphosis or rounded shoulders. By incorporating targeted exercises for the pectoral muscles into a workout routine, individuals can enhance their upper body strength, improve shoulder stability, and promote better posture.
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Frequently asked questions
The pectoral muscles, commonly known as pecs, are a vital component of the upper body musculature. They are skeletal muscles that connect the front walls of the chest with the bones of the upper arm and shoulder.
The pectoral muscles are located on the anterior chest wall.
There are two pectoral 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. It is thick and fan-shaped, lying underneath the breast tissue. It is responsible for movements such as flexion, adduction, and internal rotation of the humerus.
The pectoralis minor lies underneath the pectoralis major, arising from the middle ribs and attaching to the scapula (shoulder blade). It aids in drawing the shoulder forward and downward.
