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The pectoralis major muscle is a fan-shaped muscle that is the most prominent and largest muscle of the anterior chest wall. It is a paired muscle that is divided into three parts: the clavicular part, the sternocostal part, and the abdominal part. The pectoralis major is innervated by the lateral and medial pectoral nerves, which stem from the brachial plexus. The lateral pectoral nerve is distributed over the deep surface of the pectoralis major, while the medial pectoral nerve innervates the sternocostal head. The muscle's primary functions include flexion, adduction, and internal rotation of the humerus, contributing to the thoracobrachial motion.
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What You'll Learn
- The lateral pectoral nerve innervates the pectoralis muscle
- The medial pectoral nerve innervates the pectoralis muscle
- The nerve supply of the pectoralis muscle is relevant to reconstructive surgery
- The dorsal branch of the MPN supplies the posterior limb of the pectoralis muscle tendon
- The nerve entry points of the pectoralis muscle can be visualised using Sihler's stain
The lateral pectoral nerve innervates the pectoralis muscle
The pectoralis major is a fan-shaped muscle that is the most prominent and largest muscle of the anterior chest wall. It is a thick muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. The pectoralis major has two heads, the clavicular and the sternalcostal, which reference their area of origin. The muscle is innervated by the lateral pectoral nerve, which arises directly from the lateral cord of the brachial plexus.
The lateral pectoral nerve provides innervation to the clavicular head of the pectoralis major. This head is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. When the arm is at an approximately 110-degree angle, the clavicular head contributes to the adduction of the humerus. The clavicular head receives its nerve supply from the C5 and C6 nerve roots via the upper trunk and lateral cord of the brachial plexus, which gives off the lateral pectoral nerve.
The medial pectoral nerve, which arises from the medial cord, innervates the sternocostal head of the pectoralis major. The sternal head receives innervation from the C7, C8, and T1 nerve roots via the lower trunk of the brachial plexus and the medial pectoral nerve. The sternocostal head is antagonistic to the clavicular head, contributing to the downward and forward movement of the arm and inward rotation when accompanied by adduction.
The pectoralis major as a whole is responsible for the adduction and internal rotation of the arm in the shoulder joint. It also has a role in keeping the arm attached to the trunk of the body. The muscle is involved in deep or forced inspiration, assisting the diaphragm and intercostal muscles in proper breathing.
The precise knowledge of the nerve supply of the pectoralis major is important in reconstructive surgery, especially for its safe and functional transfer.
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The medial pectoral nerve innervates the pectoralis muscle
The pectoralis major is a prominent chest muscle that acts mainly on the shoulder joint. 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 the superior-most and largest muscle of the anterior chest wall. It is also referred to as the
The pectoralis major has two heads: the clavicular head and the sternocostal head. The clavicular head is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. The sternocostal head is antagonistic to the clavicular head, contributing to the downward and forward movement of the arm and inward rotation during adduction.
The pectoralis major receives dual motor innervation by the medial pectoral nerve and the lateral pectoral nerve, also known as the lateral anterior thoracic nerve. The medial pectoral nerve innervates the pectoralis muscle, specifically the sternocostal head. The lateral pectoral nerve innervates the clavicular head.
The medial pectoral nerve arises from the medial cord, while the lateral pectoral nerve arises directly from the lateral cord of the brachial plexus. The brachial plexus is a network of nerves that originate from the spine and supply the chest, shoulder, and arm muscles. The medial and lateral pectoral nerves have different functions and distributions, providing innervation to different parts of the pectoralis major muscle.
The pectoralis major is a crucial muscle for shoulder joint movement and has four primary actions: flexion, adduction, internal rotation, and extension of the humerus. It is active during deep or forced inspiration, assisting in breathing when the diaphragm and intercostal muscles are insufficient.
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The nerve supply of the pectoralis muscle is relevant to reconstructive surgery
The pectoralis major muscle is a fan-shaped muscle that consists of three parts: the clavicular, sternocostal, and abdominal parts. It is a prominent chest muscle that acts mainly on the shoulder joint. The nerve supply of the pectoralis muscle is relevant to reconstructive surgery because the muscle is involved in the safe and functional transfer of the nerve supply.
The pectoralis major muscle is innervated by the lateral and medial pectoral nerves, which stem from the brachial plexus. The lateral pectoral nerve is the primary source of innervation, with the medial pectoral nerve providing supplementary innervation. The proximal and upper third of the distal segments of the muscle receive nerve supply from different branches of the lateral pectoral nerve and the medial pectoral nerve.
The nerve supply of the pectoralis muscle is relevant in reconstructive surgery, particularly in procedures involving the pectoral region. Surgeons need to be aware of anatomical variations in the nerve supply to plan and perform surgeries effectively. Knowledge of the nerve supply is crucial for safe and functional nerve transfers during reconstructive procedures.
Furthermore, understanding the nerve supply is essential for blocking muscle spasticity and managing conditions like hemiplegic shoulder pain. In subpectoral breast implant surgery, clarifying the anatomy and variations in innervation helps identify the preferred level for denervation, reducing the risk of animation deformity or breast distortion due to pectoralis muscle contraction.
Additionally, studies have investigated the nerve supply to the clavicular part of the pectoralis major muscle, which is relevant for plastic and reconstructive surgery procedures that isolate this specific part of the muscle.
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The dorsal branch of the MPN supplies the posterior limb of the pectoralis muscle tendon
The pectoralis major muscle is a fan-shaped muscle that is the most superficial muscle in the pectoral region. It is a thick muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. The pectoralis major is innervated by the lateral and medial pectoral nerves. The lateral pectoral nerve arises directly from the lateral cord of the brachial plexus, while the medial pectoral nerve arises from the medial cord.
The medial pectoral nerve (MPN) plays a crucial role in supplying the pectoralis major muscle. Specifically, the dorsal branch of the MPN is responsible for supplying the posterior limb of the pectoralis muscle tendon. This was observed in a study that examined the innervation patterns of the pectoralis major muscle. Out of 30 specimens analysed, 26 showed that the dorsal branch of the MPN supplied the posterior limb of the tendon.
The pectoralis major muscle has two heads: the clavicular head and the sternocostal head. These heads have different nerve supplies. The clavicular head, also known as the clavicular part, receives its nerve supply from the lateral pectoral nerve. This head is positioned close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus.
On the other hand, the sternocostal head, or the sternocostal part, is innervated by the medial pectoral nerve. This head arises from a different anatomical site compared to the clavicular head. It originates from the anterior surface of the sternum and the anterior aspects of the costal cartilages of ribs 1-6. The sternocostal head performs functions that are antagonistic to those of the clavicular head, contributing to the downward and forward movement of the arm and inward rotation during adduction.
The dorsal branch of the MPN plays a specific role in supplying the posterior limb of the pectoralis muscle tendon. This knowledge is particularly important in the field of reconstructive surgery, where a precise understanding of nerve supply is essential for safe and effective procedures involving the pectoralis major muscle.
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The nerve entry points of the pectoralis muscle can be visualised using Sihler's stain
The pectoralis major muscle is a prominent chest muscle that is fan-shaped and consists of three parts: the clavicular part, the sternocostal part, and the abdominal part. The nerve entry points of the pectoralis muscle can be visualised using Sihler's stain, a whole-mount nerve staining technique. Sihler's stain renders other soft tissue translucent or transparent, allowing for the clear visualisation of the nerves. This technique can be used to map the entire nerve supply patterns of muscles.
Sihler's stain is particularly useful for demonstrating the precise intramuscular branching and distribution patterns of skeletal muscles. This is important for anatomists, physiologists, and clinicians. For example, Sihler's stain has been used to visualise the detailed intramuscular distribution of certain nerve sub-branches in cadavers, where the fusion between the clavicular portion of the pectoralis major muscle and the deltoid muscle was observed.
In studies examining the innervation of the pectoralis major muscle, Sihler's stain was used to confirm the contribution of the intercostal nerves in pectoralis major innervation. This technique also allowed for the evaluation of a detailed intramuscular innervation pattern of the pectoralis major muscle. Specifically, distances from the margin of the sternum and the inferior border of the clavicle to the entry points of the neurovascular pedicles within the pectoralis major muscle were measured, and five randomly selected muscles were examined using Sihler's stain.
The visualisation of nerve entry points using Sihler's stain has applications in understanding muscle functions, performing electrophysiological experiments, and developing novel neurosurgical techniques. It is also useful in planning and conducting surgeries in the pectoral region, as it provides knowledge of the nerve supply to the pectoralis major muscle, which is important for its safe and functional transfer.
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Frequently asked questions
The pectoralis major muscle is innervated by the lateral and medial pectoral nerves.
The lateral pectoral nerve arises directly from the lateral cord of the brachial plexus. The medial pectoral nerve arises from the medial cord.
The pectoralis major is a prominent chest muscle that acts mainly on the shoulder joint. Its primary functions are flexion, adduction, and internal rotation of the humerus.
The pectoralis major has three parts: the clavicular part, the sternocostal part, and the abdominal part.
