Victor Forge
The pectoralis major is the largest muscle in the chest, lying underneath the breast. It is thick and fan-shaped and constitutes the bulk of the chest muscles. The pectoralis minor lies underneath the pectoralis major and assists in key functions, including shoulder movement and rotation. The pectoralis 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. 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 elevation and depression of the bones of the thorax.
| Characteristics | Values |
|---|---|
| Definition | Group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls |
| Location | Anterior chest wall |
| Muscle composition | Pectoralis major, pectoralis minor, serratus anterior, and subclavius |
| Pectoralis major | Thick, fan-shaped muscle that lies underneath the breast tissue |
| Pectoralis minor | Lies underneath the pectoralis major; integral to shoulder movement, especially rotation |
| Serratus anterior | Located in the chest wall laterally and forms the medial border of the axilla region |
| Subclavius | Small, triangle-shaped muscle located directly underneath the clavicle |
| Functions | Moving the upper extremities in a wide range of motions, including flexion, adduction, internal rotation of the humerus, stabilization of the scapula, and elevation and depression of the bones of the thorax |
| Exercises | Flat barbell bench press, flat dumbbell bench press, and dumbbell fly |
| Injuries | Tendonitis, torn pectoralis major tendon, and pectoralis major tendon rupture |
Explore related products
Pectoralis major
The pectoralis major is the superior most and largest 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 insertion of the pectoralis major is at the lateral lip of the intertubercular sulcus of the humerus.
There are two heads of the pectoralis major, the clavicular and the sternocostal, which reference their area of origin. The sternocostal head is the larger of the two heads. 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. The upper and lower fibres of pectoralis major insert into the crest of the greater tubercle of the humerus. The two heads of the pectoralis major have different nervous supplies. The clavicular head derives its nerve supply from the lateral pectoral nerve, while the sternocostal head receives its nerve supply from the medial pectoral nerve.
The pectoralis major is responsible for flexion, adduction, and internal rotation of the humerus. The muscle fibres attaching to the clavicular head allow for the flexion of the humerus, as seen when lifting a glass in 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 major is also responsible for keeping the arm attached to the trunk of the body. The clavicular part contributes to flexion, horizontal adduction, and inward rotation of the humerus. The sternocostal part contributes to downward and forward movement of the arm and inward rotation when accompanied by adduction.
Poland syndrome is a rare congenital condition in which the whole pectoralis major muscle is missing, most commonly on one side of the body. This may be accompanied by the absence of the breast in females.
Muscle Tetanus: Uncommon Condition, Understand the Triggers and Risks
You may want to see also
Explore related products
Pectoralis minor
The pectoralis muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. The pectoralis major is the most superficial muscle in the pectoral region, lying underneath the breast. It is thick and fan-shaped. The pectoralis minor is the smaller of the two muscles and lies underneath the pectoralis major. Both muscles form part of the anterior wall of the axilla region. The pectoralis minor is triangular in shape and originates from the margins of the third to fifth ribs adjacent to the costochondral junction. The fibres pass upward and laterally to insert into the medial border and superior surface of the coracoid process of the scapula.
The pectoralis minor is clinically important and is used as a surgical landmark. It is also an accessory muscle of 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. The pectoralis minor also receives innervation from the lateral pectoral nerve via a communicating branch known as the 'ansa pectoralis'. This results in the pectoralis minor receiving innervation from the spinal roots of C5-T1.
The pectoralis minor can be activated through exercises such as the serratus punch exercise and the modified push-up plus exercise. Issues that can arise due to pectoralis minor dysfunctions include pain and/or restriction in neck movements, stiffness and pain in the upper back, and an increased risk of rotator cuff pathologies. Shortening of the pectoralis minor may produce impingement on the brachial plexus and axillary blood vessels, causing shoulder impingement and thoracic outlet syndrome.
Muscle Soreness: Normal or Not?
You may want to see also
Explore related products
Serratus anterior
The pectoralis region is located on the anterior chest wall and contains four muscles: the pectoralis major, pectoralis minor, serratus anterior, and subclavius. 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: upper/superior, middle/intermedius, and lower/inferior. The muscle wraps around the ribcage, passing beneath the scapula to insert on its underside along its superior angle, medial border, and inferior angle.
The serratus anterior acts on the scapula and is the prime mover in scapular protraction and upward rotation. It is a key scapular stabiliser, working with the upper and lower fibres of the trapezius muscle to keep the shoulder blades against the ribcage during rest and movement. This allows for overhead lifting. The serratus anterior 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 serratus anterior is supplied with oxygenated blood by the lateral thoracic artery, which originates from the axillary artery. The superior thoracic artery and the thoracodorsal artery also supply the serratus anterior. The long thoracic nerve, which arises from the C5 to C7 nerve roots of the brachial plexus, is responsible for the innervation of the serratus anterior. Damage to this nerve is the most common cause of winged scapula.
The serratus anterior is important in respiration, as it lifts the ribcage and supports breathing. It is also involved in climbing, where it supports the scapula against the reaction forces of the free limb and exerts high bending forces on the ribs.
Eyeballs and Muscles: What's the Connection?
You may want to see also
Explore related products
Subclavius
The pectoralis region is a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. The four muscles that make up the pectoralis region are the pectoralis major, pectoralis minor, serratus anterior, and subclavius.
The subclavius is a small, triangular muscle in the anterior thorax located between the clavicle and the first rib. It is enveloped in the clavipectoral fascia along with the pectoralis minor, coracobrachialis, and short head of the biceps. The subclavius originates at the junction of the first rib and its costal cartilage and inserts onto the inferior surface of the middle third of the clavicle in a bony groove.
The subclavius is innervated by the nerve to the subclavius, a branch of the brachial plexus. The nerve to the subclavius originates from the C5-C6 nerve roots. The subclavius is supplied by the clavicular branch of the thoracoacromial trunk.
The subclavius depresses and anchors the clavicle, helping to stabilize the sternoclavicular joint. This muscle affords some protection to the underlying neurovascular structures, such as in the case of a clavicular fracture. It also contributes to the control of the position of the scapula in relation to the thorax.
Myofascial pain or muscle strain of the subclavius can result in pain along the clavicle, sternoclavicular joint, shoulder, or arm. This pain may result from heavy lifting, chronic forward shoulder positioning, using a heavy backpack, or sleeping with the arm positioned overhead.
Glycogenolysis: Muscle's Energy Source and Performance Enhancer
You may want to see also
Explore related products
Skeletal muscles
The development of skeletal muscles begins with the differentiation of the para-axial mesoderm into somites, stimulated by myogenic regulatory factors such as Wnt, Shh, and BMP4 proteins. The somites then differentiate into the dermomyotome and sclerotome. The myotome, receiving signals from the Sonic Hedgehog (Shh) molecule, forms the skeletal muscles in the body. The dorsomedial aspect of the myotome gives rise to back muscles, while the ventrolateral aspect forms muscles of the body wall. Embryonic myoblasts undergo differentiation to create primary muscle fibres and eventually secondary myofibers through the fusion of myoblasts in the fetus. After birth, satellite cells act as stem cells, contributing to the growth and development of skeletal muscles.
Roundworms' Muscular System: A Complex Network of Contractions
You may want to see also
Frequently asked questions
The pectoral muscles are a group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. They are responsible for a wide range of movements of the upper extremities.
The pectoral region contains four muscles: the pectoralis major, pectoralis minor, serratus anterior, and subclavius.
The pectoralis major is the largest muscle in the pectoral region and lies underneath the breast. It is responsible for flexion of the humerus, such as when lifting a glass for a toast. It also permits the horizontal and vertical adduction, extension, and internal rotation of the upper extremity.
