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The pectoralis muscles are 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 pectoralis muscles on each side of the sternum (breastbone): the pectoralis major and the pectoralis minor. The pectoralis major constitutes the bulk of the chest muscles, lying underneath the breast. It is thick and fan-shaped, with two heads: the clavicular and the sternocostal. The pectoralis minor lies underneath the pectoralis major, originating from the middle ribs and inserting into the scapula (shoulder blade). These muscles are responsible for a wide range of movements in the upper extremities, including flexion, adduction, and internal rotation of the humerus, as well as stabilisation of the scapula.
| Characteristics | Values |
|---|---|
| Number of Pectoral Muscles | 3 |
| Names of Pectoral Muscles | Pectoralis Major, Pectoralis Minor, Serratus Anterior |
| Pectoralis Major Characteristics | Thick, fan-shaped muscle that lies underneath the breast tissue |
| Pectoralis Major Location | Anterior wall of the axilla |
| Pectoralis Minor Characteristics | Lies underneath the Pectoralis Major |
| Pectoralis Minor Location | Originates from the 3rd-5th ribs and inserts into the coracoid process of the scapula |
| Serratus Anterior Characteristics | Located in the chest wall |
| Serratus Anterior Location | Forms the medial border of the axilla region |
| Functions | Moving the upper extremities in a wide range of motion, flexion, adduction, internal rotation of the humerus, stabilization of the scapula, elevating and depressing the bones of the thorax, drawing the shoulder forward and downward |
| Exercises | Flat barbell bench press, flat dumbbell bench press, dumbbell fly |
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What You'll Learn
Pectoralis major and minor
The pectoral muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. The three muscles in the pectoral region that exert a force on the upper limb are the pectoralis major, pectoralis minor, and the serratus anterior.
The pectoralis major is the most superficial muscle in the pectoral region. It is thick, fan-shaped, and composed of a sternal head and a clavicular head. The sternal head originates from the anterior surface of the sternum, the superior six costal cartilages, and the aponeurosis of the external oblique muscle. The clavicular head originates from the anterior surface of the medial clavicle. All the fibres converge and end in a flat tendon, inserting into the lateral lip of the bicipital groove of the humerus. The actions of the pectoralis major depend on which parts of the muscle are activated. The fibres attaching to the clavicular head allow for the flexion of the humerus, such as lifting a glass for a toast. 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 is a muscle of the upper chest and lies underneath the pectoralis major. The pectoralis minor originates from the third, fourth, and fifth ribs, specifically from the margins adjacent to their costochondral junctions. These are the points where the bony part of the rib meets the cartilage that connects the ribs to the breastbone, or sternum. From this origin, the fibres of the pectoralis minor ascend superolaterally, angling upward and sideways towards the shoulder. The fibres eventually converge to form a flat tendon that inserts into the coracoid process of the scapula. The pectoralis minor primarily contributes to movements of the shoulder girdle and it also aids in the process of respiration as a secondary action.
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Serratus anterior
The pectoralis muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. There are three muscles in the pectoral region: pectoralis major, pectoralis minor, and serratus anterior.
The serratus anterior (SA) 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. It wraps posteromedially around the ribcage, passing beneath the scapula to insert on the underside of the scapula on its medial border.
The serratus anterior is divided into three parts: upper/superior, middle/intermedius, and lower/inferior. The upper part originates from the first to second rib and inserts into the superior angle of the scapula. The middle part originates from the second to third rib and inserts into the medial border of the scapula. The lower part originates from the fourth to ninth rib and inserts into the medial border and inferior angle of the scapula. This is the most powerful and prominent part of the muscle.
The serratus anterior acts on the scapula and is the prime mover in scapular protraction and upward rotation. It is a key scapular stabiliser, keeping the shoulder blades against the ribcage when at rest and during movement. It is also known as the "boxer's muscle" because it is responsible for the protraction of the scapula, or the pulling of the scapula forward and around the rib cage, which occurs when throwing a punch.
The long thoracic nerve supplies the serratus anterior muscle. This nerve is vulnerable during certain types of surgery, such as lymph node clearance for breast cancer. Damage to this nerve is the most common cause of winged scapula.
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Subclavius
The pectoralis 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 in the upper extremities, 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 constitutes the bulk of the chest muscles, lying underneath the breast, while the pectoralis minor lies underneath the pectoralis major.
One of the muscles in the pectoral region is the subclavius. The subclavius is a small, triangular muscle in the anterior thorax located directly underneath the clavicle, running horizontally. It 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 subclavius is enveloped in the clavipectoral fascia, a fibrous connective tissue that spans the interval between the clavicle and the pectoralis minor muscle.
The main function of the subclavius is to actively stabilize 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 subsequent elevation of the first rib. This helps to prevent dislocation of the clavicle at the sternoclavicular joint. Additionally, the subclavius protects the neurovascular structures beneath it, such as the brachial plexus and subclavian vessels, in the event of a clavicular fracture.
The subclavius is innervated by the nerve to the subclavius, also known as the subclavian nerve (C5-6), which is a small branch arising from the superior trunk of the brachial plexus. The muscle receives arterial blood from the clavicular branch of the thoracoacromial artery, with contributions from the suprascapular artery. While the subclavius typically contributes to the stabilization and protection of the clavicle, its contraction is hypothesized to increase tension at the tendinous border and the aponeurosis, potentially regulating the output of kinetic energy during the movement of the upper extremity.
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Chest wall and axilla
The chest wall and axilla (armpit) are areas of the body where the pec muscles are prominent and have important functional roles. The chest wall, also known as the thoracic wall, consists of the bones, muscles, and other structures that enclose and protect the thoracic cavity, which contains vital organs such as the heart and lungs. The axilla, or armpit, is the hollow beneath the junction of the arm and shoulder, and it is an important anatomical region that provides passage for nerves, blood vessels, and lymphatics.
The pec muscles, namely the pectoralis major and pectoralis minor, play a key role in the function and movement of the chest wall and axilla. The pectoralis major is a large, fan-shaped muscle that originates from the clavicle (collarbone), sternum (breastbone), and ribs, and inserts into the humerus (upper arm bone). It is responsible for movements of the shoulder joint, including adduction (bringing the arm across the body), internal rotation (turning the palm inward), and flexion (lifting the arm forward). The pectoralis major also contributes to respiratory movements by assisting in deep inspiration, particularly during forceful or labored breathing.
The pectoralis minor, as the name suggests, is a smaller muscle located beneath the pectoralis major. It originates from the third, fourth, and fifth ribs near the sternum and inserts into the coracoid process, a small projection on the scapula (shoulder blade). The pectoralis minor has a crucial role in stabilizing the scapula and is responsible for movements such as drawing the scapula forward and downward, and elevating the rib cage, which can assist in forced exhalation.
Together, the pec muscles contribute to the structural integrity and movement of the chest wall and axilla. They provide protection to the underlying organs and help maintain the normal respiratory movements of the thorax. Additionally, these muscles play a role in upper body strength and are important for activities that require pushing or pulling movements, such as weightlifting, swimming, and climbing. A strong and well-developed pectoralis muscle group contributes to functional movements and can help prevent injuries in the shoulder and chest region.
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Common exercises
The pectoral muscles, or 'pecs', are the group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. There are three muscles that lie in the pectoral region: pectoralis major, pectoralis minor, and the serratus anterior. The pectoralis major constitutes the bulk of the chest muscles, lying underneath the breast. It is thick and fan-shaped, and originates from multiple places along the medial and superior chest.
There are several exercises that can be done to target the pec muscles. Here are some common exercises to target each region of the pec muscles:
Upper Pecs
To target the upper pecs, you can perform the Incline Bench Press. This exercise is perfect for activating those upper chest fibres.
Middle Pecs
The traditional Bench Press is the optimal choice for targeting the mid-chest area with substantial weights.
Lower Pecs
Some of the best exercises to target the lower pecs include the Decline Barbell Bench Press and Incline Pushups. To activate the lower pecs, overload the muscle with Weighted Dips and cross the midline with High to Low Cable Crossover.
Overall Pec Development
To develop the pecs overall, it is important to move the arm across various ranges of motion, targeting the middle, upper, and lower parts of the major chest muscle. This can be done by performing exercises such as Single-Arm Cable Crossover, which takes your hand across the centre of the body. Another exercise is the Dumbbell Press, where you lie on a flat bench with a dumbbell in one hand and press it upwards until your arm is extended. This exercise provides constant tension throughout the movement.
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Frequently asked questions
The pec muscles, or pectoralis muscles, are the 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 pec muscles: 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).
The pectoralis major is involved in movements such as flexion, adduction, and internal rotation of the humerus, as well as stabilisation of the scapula. The pectoralis minor aids in drawing the shoulder forward and downward.
Common exercises to strengthen the pec muscles include pressing exercises such as the flat barbell bench press and the flat dumbbell bench press. These exercises involve utilising the pectoralis major muscle by extending and lowering weights towards the nipple line.
